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# 1.1: Introduction to Nanoscience

Difficulty Level: At Grade Created by: CK-12

## Unit Overview

Contents

• For Anyone Planning to Teach Nanoscience...Read This First!
• Size Matters Overview and Learning Goals
• Unit at a Glance: Suggested Sequencing of Activities by Day for the Full Set of Size Matters Curriculum Materials
• Alignment of Unit Activities with Learning Goals
• Alignment of Unit Activities with Curriculum Topics
• Alignment Chart: Key Knowledge and Skills
• (Optional) Size Matters Pretest/Posttest: Teacher Answer Sheet

### For Anyone Planning to Teach Nanoscience... Read This First!

Nanoscience Defined

Nanoscience is the name given to the wide range of interdisciplinary science that is exploring the special phenomena that occur when objects are of a size between \begin{align*}1\end{align*} and \begin{align*}100\;\mathrm{nanometers} (10^{-9}\;\mathrm{m})\end{align*} in at least one dimension. This work is on the cutting edge of scientific research and is expanding the limits of our collective scientific knowledge.

Nanoscience is “Science-in-the-Making”

Introducing students to nanoscience is an exciting opportunity to help them experience science in the making and deepen their understanding of the nature of science. Teaching nanoscience provides opportunities for teachers to:

• Model the process scientists use when confronted with new phenomena
• Address the use of models and concepts as scientific tools for describing and predicting chemical behavior
• Involve students in exploring the nature of knowing: how we know what we know, the process of generating scientific explanations, and its inherent limitations
• Engage and value our student knowledge beyond the area of chemistry, creating interdisciplinary connections

One of the keys to helping students experience science in action as an empowering and energizing experience and not an exercise in frustration is to take what may seem like challenges of teaching nanoscience and turn them into constructive opportunities to model the scientific process. We can also create an active student-teacher learning community to model the important process of working collaboratively in an emerging area of science.

This document outlines some of the challenges you may face as a teacher of nanoscience and describes strategies for turning these challenges into opportunities to help students learn about and experience science in action. The final page is a summary chart for quick reference.

Challenges & Opportunities

1. You will not be able to know all the answers to student (and possibly your own) questions ahead of time...

Nanoscience is new to all of us as science teachers. We can (and definitely should) prepare ahead of time using the resources provided in this curriculum as well as any others we can find on our own. However, it would be an impossible task to expect any of us to become experts in a new area in such a short period of time or to anticipate and prepare for all of the questions that students will ask.

...This provides an opportunity to model the process scientists use when confronted with new phenomena.

Since there is no way for us to become all-knowing experts in this new area, our role is analogous to the “lead explorer” in a team working to understand a very new area of science. This means that it is okay (and necessary) to acknowledge that we don’t have all the answers. We can then embrace this situation to help all of our students get involved in generating and researching their own questions. This is a very important part of the scientific process that needs to occur before anyone steps foot in a lab. Each time we teach nanoscience, we will know more, feel more comfortable with the process for investigating what we don’t know, and find that there is always more to learn.

One strategy that we can use in the classroom is to create a dedicated space for collecting questions. This can be a space on the board, on butcher paper on the wall, a question “box” or even an online space if we are so inclined. When students have questions, or questions arise during class, we can add them to the list. Students can be invited to choose questions to research and share with the group, we can research some questions ourselves, and the class can even try to contact a nanoscientist to help us address some of the questions. This can help students learn that conducting a literature review to find out what is already known is an important part of the scientific process.

2. Traditional chemistry and physics concepts may not be applicable at the nanoscale level...

One way in which both students and teachers try to deal with phenomena we don’t understand is to go back to basic principles and use them to try to figure out what is going on. This is a great strategy as long as we are using principles and concepts that are appropriate for the given situation.

However, an exciting but challenging aspect of nanoscience is that matter acts differently when the particles are nanosized. This means that many of the macro-level chemistry and physics concepts that we are used to using (and upon which our instincts are based) may not apply. For example, students often want to apply principles of classical physics to describe the motion of nanosized objects, but at this level, we know that quantum mechanical descriptions are needed. In other situations it may not even be clear if the macroscale-level explanations are or are not applicable. For example, scientists are still exploring whether the models used to describe friction at the macroscale are useful in predicting behavior at the nanoscale (Luan & Robbins, 2005).

Because students don’t have an extensive set of conceptual frameworks to draw from to explain nanophenomena, there is a tendency to rely on the set of concepts and models that they do have. Therefore, there is a potential for students to incorrectly apply macroscale-level understandings at the nanoscale level and thus inadvertently develop misconceptions.

...This provides an opportunity to explicitly address the use of models and concepts as scientific tools for describing and predicting chemical behavior.

Very often, concepts and models use a set of assumptions to simplify their descriptions. Before applying any macroscale-level concept at the nanoscale level, we should have the students identify the assumptions it is based on and the situations that it aims to describe. For example, when students learn that quantum dots fluoresce different colors based on their size, they often want to explain this using their knowledge of atomic emission. However, the standard model of atomic emission is based on the assumption that the atoms are in a gaseous form and thus so far apart that we can think about their energy levels independently. Since quantum dots are very small crystalline solids, we have to use different models that think about the energy levels of the atoms together as a group.

By helping students to examine the assumptions a model makes and the conditions under which it can be applied, we not only help students avoid incorrect application of concepts, but also guide them to become aware of the advantages and limitations of conceptual models in science. In addition, as we encounter new concepts at the nanoscale level, we can model the way in which scientists are constantly confronted with new data and need to adjust (or discard) their previous understanding to accommodate the new information. Scientists are lifelong learners and guiding students as they experience this process can help them see that it is an integral and necessary part of doing science.

3. Some questions may go beyond the boundary of our current understanding as a scientific community...

Traditional chemistry curricula primarily deal with phenomena that we have studied for many years and are relatively well understood by the scientific community. Even when a student has a particularly deep or difficult question, if we dig enough we can usually find ways to explain an answer using existing concepts. This is not so with nanoscience! Many questions involving nanoscience do not yet have commonly agreed upon answers because scientists are still in the process of developing conceptual systems and theories to explain these phenomena. For example, we have not yet reached a consensus on the level of health risk associated with applying powders of nanoparticles to human skin or using nanotubes as carriers to deliver drugs to different parts of the human body.

...This provides an opportunity to involve students in exploring the nature of knowing: how we know what we know, the process of generating scientific explanations, and its inherent limitations.

While this may make students uncomfortable, not knowing a scientific answer to why something happens or how something works is a great opportunity to help them see science as a living and evolving field. Highlighting the uncertainties of scientific information can also be a great opportunity to engage students in a discussion of how scientific knowledge is generated. The ensuing discussion can be a chance to talk about science in action and the limitations on scientific research. Some examples that we can use to begin this discussion are: Why do we not fully understand this phenomenon? What (if any) tools limit our ability to investigate it? Is the phenomenon currently under study? Why or why not? Do different scientists have different explanations for the same phenomena? If so, how do they compare?

4. Nanoscience is a multidisciplinary field and draws on areas outside of chemistry, such as biology, physics, and computer science...

Because of its multidisciplinary nature, nanoscience can require us to draw on knowledge in potentially unfamiliar academic fields. One day we may be dealing with nanomembranes and drug delivery systems, and the next day we may be talking about nanocomputing and semiconductors. At least some of the many areas that intersect with nanoscience are bound to be outside our areas of training and expertise.

...This provides an opportunity to engage and value our student knowledge beyond the traditional areas of chemistry.

While we may not have taken a biology or physics class in many years, chances are that at least some of our students have. We can acknowledge students’ interest and expertise in these areas and take advantage of their knowledge. For example, ask a student with a strong interest in biology to connect drug delivery mechanisms to their knowledge about cell regulatory processes. In this way, we share the responsibility for learning and emphasize the value of collaborative investigation. Furthermore, this helps engage students whose primary area of interest isn’t chemistry and gives them a chance to contribute to the class discussion. It also helps all students begin to integrate their knowledge from the different scientific disciplines and presents wonderful opportunities for them to see the how the different disciplines interact to explain real world phenomena.

Final Words

Nanoscience provides an exciting and challenging opportunity to engage our students in cutting edge science and help them see the dynamic and evolving nature of scientific knowledge. By embracing these challenges and using them to engage students in meaningful discussions about science in the making and how we know what we know, we are helping our students not only in their study of nanoscience, but in developing a more sophisticated understanding of the scientific process.

References

• Luan, B., & Robbins, M. (2005, June). The breakdown of continuum models for mechanical contacts. Nature 435, 929-932.
Challenges of teaching nanoscience and strategies for turning these challenges into learning opportunities.
THE CHALLENGE... PROVIDES THE OPPORTUNITY TO...
1. You will not be able to know all the answers to student (and possibly your own) questions ahead of time

Model the process scientists use when confronted with new phenomena:

Identify and isolate questions to answer

Work collectively to search for information using available resources (textbooks, scientific journals, online resources, scientist interviews)

Incorporate new information and revise previous understanding as necessary

Generate further questions for investigation

2. Traditional chemistry and physics concepts may not be applicable at the nanoscale level

Address the use of models and concepts as scientific tools for describing and predicting chemical behavior:

Identify simplifying assumptions of the model and situations for intended use

Discuss the advantages and limitations of using conceptual models in science

Integrate new concepts with previous understandings

3. Some questions may go beyond the boundary of our current understanding as a scientific community

Involve students in exploring the nature of knowing:

How we know what we know

The limitations and uncertainties of scientific explanation

How science generates new information

How we use new information to change our understandings

4. Nanoscience is a multidisciplinary field and draws on areas outside of chemistry, such as biology and physics

Engage and value our student knowledge beyond the area of chemistry:

Help students create new connections to their existing knowledge from other disciplines

Highlight the relationship of different kinds of individual contributions to our collective knowledge about science

Explore how different disciplines interact to explain real world phenomena

### Size Matters: Overview and Learning Goals

Type of Courses: Chemistry, physics, biology, interdisciplinary science

Topic Area: The nanoscale perspective of physical properties

Key Words: Nanoscience, nanotechnology, nanometer, size and scale, properties

Time Frame: 5-7 class periods (assuming \begin{align*}50-\;\mathrm{minutes}\end{align*} classes), with extensions

Overview

This unit provides an introduction to nanoscience, focusing on concepts related to the size and scale, unusual properties of the nanoscale, and example applications of nanoscience.

Students will participate in learning activities that are designed to help them to establish an understanding of the nature of nanoscale science, the relative size of objects, unique properties of nanosized particles, and applications of nanoscience. They will read about these issues, complete worksheets, take quizzes, conduct laboratory investigations to understand properties of nanoscale objects, and create and present a poster comparing a current technology with a related nanotechnology.

As this is an introductory unit, many new terms will be introduced as students increase their understanding of the essential features of nanoscience. References to additional readings and curricular activities are provided so that the teacher can choose to include related topics as he or she determines is appropriate.

### Enduring Understandings (EU)

What enduring understandings are desired? Students will understand:

1. The study of unique phenomena at the nanoscale could vastly change our understanding of matter and lead to new questions and answers in many areas, including health care, the environment, and technology.
2. There are enormous scale differences in our universe, and at different scales, different forces dominate and different models better explain phenomena.
3. Nanosized materials exhibit some size-dependent effects that are not observed in bulk materials.
4. New tools for observing and manipulating matter increase our abilities to investigate and innovate.

Essential Questions (EQ)

What essential questions will guide this unit and focus teaching and learning?

1. How small is a nanometer, compared with a hair, a blood cell, a virus, or an atom?
2. Why are properties of nanoscale objects sometimes different than those of the same materials at the bulk scale?
3. Occasionally, there are advances in science and technology that have important and long-lasting effects on science and society. What scientific and engineering principles will be exploited to enable nanotechnology to be the next big thing?
4. How do we see and move things that are very small?
5. Why do our scientific models change over time?
6. What are some of the ways that the discovery of a new technology can impact our lives?

### Key Knowledge and Skills (KKS)

What key knowledge and skills will students acquire as a result of this unit? Students will be able to:

1. Describe, using the conventional language of science, the size of a nanometer. Make size comparisons of nanosized objects with other small objects.
2. Explain why properties of nanoscale objects sometimes differ from those of the same materials at the bulk scale.
3. Describe an application (or potential application) of nanoscience and its possible effects on society.
4. Compare a current technology solution with a related nanotechnology-enabled solution for the same problem.
5. Explain how an AFM and a STM work, and give an example of their use.

Prerequisite Knowledge

This unit assumes that students are familiar with the following concepts or topics:

1. Atoms, molecules, cells, cell organelles, and protein molecules.
2. Basic units of the metric system and knowledge of prefixes.
3. How to manipulate exponential and scientific notation.
4. Some knowledge and experience with a light microscope.

K-12 Unifying Concepts and Process Standard

As a result of activities in grades K-12, all students should develop understanding and abilities aligned with the following concepts and processes: (4 of the 5 categories apply)

• Systems, order, and organization
• Evidence, models and explanation
• Constancy, change, and measurement
• Form and function

Grades 9-12 Content Standard A: Science as Inquiry

• Scientists usually inquire about how physical, living, or designed systems function. Conceptual principles and knowledge guide scientific inquiries. Historical and current scientific knowledge influence the design and interpretation of investigations and the evaluation of proposed explanations made by other scientists. (12ASI2.1)
• Scientists rely on technology to enhance the gathering and manipulation of data. New techniques and tools provide new evidence to guide inquiry and new methods to gather data, thereby contributing to the advance of science. The accuracy and precision of the data, and therefore the quality of the exploration, depends on the technology used. (12ASI2.3)

Grades 9-12 Content Standard B: Physical Science

Chemical reactions

• Catalysts, such as metal surfaces, accelerate chemical reactions. Chemical reactions in living systems are catalyzed by protein molecules called enzymes. (12BPS3.5)

Motions and forces

• Between any two charged particles, electric force is vastly greater than the gravitational force. Most observable forces such as those exerted by a coiled spring or friction may be traced to electric forces acting between atoms and molecules. (12BPS4.3)

Grades 9-12 Content Standard E: Science and Technology

• Scientists in different disciplines ask different questions, use different methods of investigation, and accept different types of evidence to support their explanations. Many scientific investigations require the contributions of individuals from different disciplines, including engineering. New disciplines of science, such as geophysics and biochemistry often emerge at the interface of two older disciplines. (12EST2.1)
• Science often advances with the introduction of new technologies. Solving technological problems often results in new scientific knowledge. New technologies often extend the current levels of scientific understanding and introduce new areas of research. (12EST2.2)
• Science and technology are pursued for different purposes. Scientific inquiry is driven by the desire to understand the natural world, and technological design is driven by the need to meet human needs and solve human problems. Technology, by its nature, has a more direct effect on society than science because its purpose is to solve human problems, help humans adapt, and fulfill human inspirations.
Technological solutions may create new problems. Science, by its nature, answers questions that may or may not directly influence humans. Sometimes scientific advances challenge people’s beliefs and practical explanations concerning various aspects of the world. (12EST2.4)

Grades 9-12 Content Standard F: Science in Personal and Social Perspectives

Science and technology in local, national, and global challenges

• Understanding basic concepts and principles of science and technology should precede active debate about the economics, policies, politics, and ethics of various science - and technology - related challenges. However, understanding science alone will not resolve local, national or global challenges. (12FSPSP6.2)
• Individuals and society must decide on proposals involving new research and the introduction of new technologies into society. Decisions involve assessment of alternatives, risks, costs, and benefits and consideration of who benefits and who suffers, who pays and gains, and what the risks are and who bears them. Students should understand the appropriateness and value of basic questions - "What can happen?" - "What are the odds?" - and "How do scientists and engineers know what will happen? (12FSPSP6.4)

Grades 9-12 Content Standard G: History and Nature of Science

Historical perspectives

• Occasionally, there are advances in science and technology that have important and long lasting effects on science and society. Examples of such advances include the following: Copernican revolution, Newtonian mechanics, Relativity, Geologic time scale, Plate tectonics, Atomic theory, Nuclear physics, Biological evolution, Germ theory, Industrial revolution, Molecular biology, Information and communication, Quantum theory, Galactic universe, Medical and health technology. (12GHNS3.3)

AAAS Benchmark Standards

While some of the content of this unit does not map directly to the NSES, it does address the AAAS Benchmarks. Below we list the AAAS Benchmarks that this unit addresses that are not already addressed by the NSES.

Common Themes

• 11D Scale #1. Representing large numbers in terms of powers of ten makes it easier to think about them and to compare things that are greatly different.
• 11D Scale #2. Because different properties are not affected to the same degree by changes in scale, large changes in scale typically change the way that things work in physical, biological, or social systems.

### Unit at a Glance: Suggested Sequencing of Activities by Day for the Full Set of Size Matters Curriculum Materials

Lesson Teaching Day Main Activities and Materials Learning Goals Assessment Homework
(Prep Day) (Refer to individual lesson plans for detailed breakdown)

The Personal Touch: Student Reading and Worksheet

Introduction to Nanoscience 1 day

Class discussion on Personal Touch: Student Reading, Scale Diagram

Introduction to Nanoscience: PowerPoint and Student Worksheet

EU 1, 4;

EQ 1, 2, 4, 5, 6;

KKS 1, 3

Worksheets for The Personal Touch and Intro to Nanoscience Visualizing the Nanoscale: Student Reading
Scale of Objects 1 day

Number Line, Scale of Objects, or Cutting It Down Activity

Class discussion and Scale Diagram

EU 2;

EQ 1;

KKS 1

Scale Activity Worksheets

Scale of Small Objects Quiz

Unique

Properties at the Nanoscale

2 days: Day 1

Unique Properties at the Nanoscale: PowerPoint

Prepare for Unique Properties Lab

EU 2, 3;

EQ 2, 5;

KKS 2

Day 2 Unique Properties Lab Activities & Student Worksheet Lab Worksheet Seeing and Building Small Things: Student Reading
Tools of the Nanosciences 2 days: Day 1

Scanning Probe Microscopy: PowerPoint

Black Box Activity

EU 4;

EQ 4, 5;

KKS 5

Black Box Activity Worksheet
Day 2 Optional Extensions for Exploring Nanoscale Modeling

EU 4;

EQ 4, 5

Unique Properties Quiz
Applications of Nanoscience 4 days: Day 1 Applications of Nanoscience: PowerPoint

EU 1;

EQ 3, 6;

Prepare for What’s New Nanocat? Poster Session
Assign What’s New Nanocat Poster Session topics and groups KKS 3, 4
Applications of Nanoscience Days 2-4

Preparation for What’s New NanoCat Poster Session

Group presentations

Presentation Scoring Rubric and Peer Feedback Form
What enduring understandings (EU) are desired? Students will understand: What essential questions (EQ) will guide this unit and focus teaching and learning? What key knowledge and skills (KKS) will students acquire as a result of this unit? Students will be able to:
• The study of unique phenomena at the nanoscale could vastly change our understanding of matter and lead to new questions and answers in many areas, including health care, the environment, and technology.
• How small is a nanometer, compared with a hair, a blood cell, a virus, or an atom?
• Describe, using the conventional language of science, the size of a nanometer. Make size comparisons of nanosized objects with other small objects.
• There are enormous scale differences in our universe, and at different scales, different forces dominate and different models better explain phenomena.
• Why are properties of nanoscale objects sometimes different than those of the same materials at the bulk scale?
• Explain why properties of nanoscale objects sometimes differ from those of the same materials at the bulk scale.
• Nanosized materials exhibit some size-dependent effects that are not observed in bulk materials.
• Occasionally, there are advances in science and technology that have important and long-lasting effects on science and society. What scientific and engineering principles will be exploited to enable nanotechnology to be the next big thing?
• Describe an application (or potential application) of nanoscience and it’s possible effects on society.
• New tools for observing and manipulating matter increase our abilities to investigate and innovate.
• How do we see and move things that are very small?
• Compare a current technology solution with a related nanotechnology-enabled solution for the same problem.
• Why do our scientific models change over time?
• Explain how an AFM and a STM work; give an example of their use.
• What are some ways that the discovery of a new technology can impact our lives?

### Alignment of Unit Activities with Learning Goals

Learning Goals Lesson 1: Intro to Nanoscience Lesson 2: Scale of Objects Lesson 3: Unique Properties Lesson 4: Tools of the Nanosciences Lesson 5: Applic. of Nanoscience
Students will understand...
EU 1. The study of unique phenomena at the nanoscale could vastly change our understanding of matter and lead to new questions and answers in many areas, including health care, the environment, and technology. \begin{align*}\bullet\end{align*} \begin{align*}\bullet\end{align*}
EU 2. There are enormous scale differences in our universe, and at different scales, different forces dominate and different models better explain phenomena. \begin{align*}\bullet\end{align*} \begin{align*}\bullet\end{align*}
EU 3. Nanosized materials exhibit some size-dependent effects that are not observed in bulk materials. \begin{align*}\bullet\end{align*}
EU 4. New tools for observing and manipulating matter increase our abilities to investigate and innovate. \begin{align*}\bullet\end{align*} \begin{align*}\bullet\end{align*}
Students will be able to...
KKS1. Describe, using the conventional language of science, the size of a nanometer. Make size comparisons of nanosized objects with other small objects. \begin{align*}\bullet\end{align*} \begin{align*}\bullet\end{align*}
KKS2. Explain why properties of nanoscale objects sometimes differ from those of the same materials at the bulk scale. \begin{align*}\bullet\end{align*}
KKS3. Describe an application (or potential application) of nanoscience and its possible effects on society. \begin{align*}\bullet\end{align*} \begin{align*}\bullet\end{align*}
KKS4. Compare a current technology solution with a related nanotechnology-enabled solution for the same problem. \begin{align*}\bullet\end{align*}
KKS5. Explain how an AFM and a STM work; give an example of their use. \begin{align*}\bullet\end{align*}

### Alignment of Unit Activities with Curriculum Topics

Chemistry
Unit Topic Chapter Topic Subtopic Size Matters Lessons Specific Materials
Nature of Chemistry Tools of Science Units & Measurement (size & scale)
• Lesson 1 (L1): Intro to Nanoscience
• Lesson 2 (L2): Scale of Objects
• Lesson 6 (L6): One Day Introduction
Slides
• L1: 1-4
• L6: 1-8

Activity/Handout

• L1
• Student Reading: Intro to Nanoscience
• Worksheet: Intro to Nanoscience
• Handout: scale diagram
• L2
• Card Sort/Number Line Activity
• Scale of Objects Activity
• Cutting it down activity
• Quiz: Scale of small Objects
Structure of Matter Electron Configuration Quantum Theory
• Lesson 3 (L3): Unique

Properties at the nanoscale

Slides
• L3: 5, 6, 12, 14
Structure of Matter Atomic Interactions Chemical Reactions (precipitate formation, self-assembly)
• Lesson 1 (L1): Intro to Nanoscience
Slides
• L1: 17-19

Activity/Handout

• Worksheet: Intro to Nanoscience
Nature of Chemistry Tools of Science Units & Measurement (size & scale)
• Lesson 1 (L1): Intro to Nanoscience
• Lesson 2 (L2): Scale of Objects
• Lesson 6 (L6): One Day Introduction
Slides
• L1: 1-4
• L6: 1-8

Activity/Handout

• L1
• Worksheet: Intro to Nanoscience
• Handout: Scale Diagram
• L2
• Card Sort/Number Line Activity
• Scale of Objects Activity
• Cutting it down activity
• Quiz: Scale of Small Objects
Units & Measurement (Instruments)
• Lesson 1 (L1): Intro to Nanoscience
• Lesson 2 (L2): Scale of Objects
• Lesson 4 (L4): Tools of Nanoscience
• Lesson 6 (L6): One Day Introduction
Slides
• L1: 5-9
• L6: 11-14

Activity/Handout

• L1
• Student Reading: Intro to Nanoscience
• Worksheet: Intro to Nanoscience
• Handout: Scale Diagram
• L2
• Cutting it down activity
• L4
• Black Box Activity
• Reading: Seeing & Building Small Things
• Quiz
Biology
Unit Topic Chapter Topic Subtopic Size Matters Lessons Specific Materials
Nature of Life Science of Biology How Scientists Work
• Lesson 1 (L1): Introduction to Nanoscience
Slides
• L1: 1-4

Activity/Handout

• Scale Diagram: Discuss using question 1-2 from Intro to Nanoscience worksheet
Studying Life
• Lesson 2 (L2): Scale of Objects
Slides
• L1: 3

Activity/Handout

• Number Line
• Student Quiz
Tools and Procedure
• Lesson 4 (L4): Tools
Slides
• L4: 1-11, 12 (optional)

Activity/Handout

• Black Box Lab Activity
• Reading: Seeing and Building Small Things
• Quiz
Nature of Life The Chemistry of Life The Nature of Matter; Properties of Water; Carbon Compounds
• Lesson 3 (L3): Unique Properties at the Nanoscale
Slides
• L3: 1-17

Activity/Handout

• Unique Properties Labs
• Student Quiz
The Human Body Nervous System The Senses Drugs and the Nervous System
• Lesson 5 (L5): Applications of Nanoscience

Slides

L5: 1-2, 9

The Human Body Circulatory and Respiratory Systems The Circulatory System
• Lesson 5 (L5): Applications of Nanoscience

Slides

L5: 1-2, 11

The Immune System and Disease Infectious Disease

Slides

L5: 1-2, 12

Cancer

Slides

L5: 1-2, 10

Extensions Bioethics Use of Nanotechnology in the Human Arena Size Matters
• Lesson 5 (L5): Applications of Nanoscience
Any topics covered in L5 or any students may have considered
Physics
Unit Topic Chapter Topic Subtopic Size Matters Lessons Specific Materials
Mechanics Measurement

Length/mass/time

Units/order of magnitude

• Lesson 1 (L1): Intro to Nano
• Lesson 2 (L2): Scale of Objects
• Lesson 6 (L6): One Day Introduction
Slides
• L1: 2-3
• L6: 2-3

Activity/Handout

• L2
• Card Sort/Number Line
• Scale Diagram
• Cutting it Down
Electrostatic forces
• Lesson 4 (L4): Tools of the Nanosciences
• Lesson 6 (L6): One Day Introduction
Slides
• L4: 2, 8
• L6: 24
Electricity and Magnetism Current and Resistance Classical vs. Modern Physics (e.g., different dominant forces, different “rules” at nano/atomic scale)
• Lesson 3 (L3): Unique Properties at the Nanoscale
Slides
• L3: (most)
Environmental Science
Unit Topic Chapter Topic Subtopic Size Matters Lessons Specific Materials
Water Using Science to Solve Environmental Problems What is Science
• Lesson 1 (L1): Intro to Nanoscience
• Lesson 2 (L2): Scale of Objects
• Lesson 3 (L3): Unique Properties at the Nanoscale
Slides
• L1: 1-4
• L3: 1-17

Activity/Handout

• L1
• Scale Diagram
• Have students discuss and question diagram using questions 1-2 from student worksheet
• L2
• Number Line
• Student Quiz
• Student Quiz
• L3
• Labs A-H, any combination of labs as instructor sees fit
• Student Quiz

### Size Matters Pretest/Posttest: Teacher Answer Sheet

20 points total

1. How big is a nanometer compared to a meter? List one object that is nanosized, one that is smaller, and one that is larger but still not visible to the naked eye. (1 point each, total of 4 points)

A nanometer is one billionth of a meter (or \begin{align*}10^{-9}\;\mathrm{m}\end{align*} in scientific notation).

Sample nanosized objects:

• Virus, DNA strand (diameter), Ribosome, Hemoglobin, Sucrose molecule
• Carbon nanotube (diameter), Buckyballs
• Some enzymes (e.g. ATP synthase), some “molecular motors” (e.g. kinesin)
• Photosynthetic machinery in plants and bacteria,

Sample objects that are smaller:

• Water molecule
• Atoms
• Sub-atomic particles (protons, neutrons, electrons)

Sample objects that are larger than but still not visible to the naked eye:

• Bacteria, Ameoba
• Human egg cell, Human sperm cell
• Red blood cell

2. Name two properties that can differ for nanosized objects and much larger objects of the same substance. For each property, give a specific example. (2 points each, total of 4 points)

Optical properties (such as color and transparency):

• Bulk gold appears yellow in color, nanosized gold appears red in color.
• Regular zinc oxide appear white on the skin, the nano-version appears clear.

Electrical properties (such as conductivity):

• Carbon nanotubes conductivity change with diameter, “twist,” and number of walls.
• Physical properties (such as density and boiling point).
• Nanoparticles have lower melting and boiling points b/c there is a greater percentage of atoms at the surface (require less energy to overcome intermolecular attractions).

Chemical properties (such as reactivities and reaction rates):

• Nanoparticles have a greater percentage of atoms at the surface and thus greater reactivities (students may mention any of the examples of this done in the labs).

3. Describe two reasons why properties of nanosized objects are sometimes different than those of the same substance at the bulk scale. (2 points each, 4 points total)

Dominance of electromagnetic forces:

• Gravitational force is a function of mass and distance and is weak between (low-mass) nanosized particles.
• Electromagnetic force is a function of charge and distance is not affected by mass, so it can be very strong even when we have nanosized particles.

Quantum effects:

• At very small scale, the classical mechanical models that we use to understand matter at the macroscale don’t work.
• The quantum mechanical model that does help us understand matter is based on probability, not certainty and unusual results such as quantum tunneling (when an electron can “pass through” an energy barrier) may occur.

Surface to volume ratio:

• As surface area to volume ratio increases, a greater amount of a substance comes in contact with surrounding material, this increase reaction rates.

Random molecular motion:

• While random molecular motion (molecules moving around in space, rotating around their bonds, and vibrating along their bonds) is present for all particles, at the macroscale this motion is very small compared to the sizes of the objects and thus is not very influential in how object behave.
• At the nanoscale however, these motions can be on the same scale as the size of the particles and thus have an important influence on how particles behave.

4. What do we mean when we talk about “seeing” at the nanoscale? (2 points)

• “Seeing” an object means using a tool that interacts with the object to produce some representation of it (often an image).
• While many common tools use the interaction between visible light and an object to create a representation, at the nanoscale the objects we want to “see” are smaller than the wavelengths of visible light so this approach is not useful.
• To “see” at the nanoscale, we need to use tools that leverage other kinds of interactions with the surface of the object (like electrical and magnetic forces) to create a representation of the object.

5. Choose one technology for seeing at the nanoscale and briefly explain how it works. (3 points)

Atomic Force Microscope (AFM)

• Uses a tiny tip that moves in response to the electromagnetic forces between the atoms of the surface and the tip.
• Either measures the tiny upward and downward movement of the tip necessary to remain in close contact with the surface or makes the tip vibrate to tap the surface and senses when contacts is made.
• In both bases, the signals (forces or contact) change based on the features of the object’s surface (height, angle etc.) and are used to infer a topographical image of the object.

Scanning Tunneling Microscope (STM)

• Uses a fine tip that can conduct electricity; the nano-object to be imaged must also conduct electricity.
• The tip is put very near, but not touching the object surface and the “tunneling” of electrons between the tip and the atoms of the object’s surface being creates a flow of electrons (a current).
• The signals (current) changes based on the features of the object’s surface (height, angle etc.) and are used to infer a topographical image of the object.

6. Describe one application (or potential application) of nanoscience and its possible effects on society. (3 points)

Existing Applications Include:

• Stain Resistant Clothes: Fine-spun fibers (“nanowhiskers”) are embedded into fabrics and act like peach fuzz to create a cushion of air around the fabric so that liquids bead up and roll off. This innovation will leads to less stains, less need for washing clothes (using detergent) and dry cleaning (using chemicals), and even less need to replace (and thus produce clothing). These could all have positive impacts on the environment.
• Nano Solar Cells: Traditional solar cells provide one source of clean energy but they are expensive to produce. A new kind of solar cells use nanoparticles of \begin{align*}TiO_2\end{align*} coated with dye molecules to capture the energy of visible light and convert it into electricity. These solar cells are less expensive to produce and have the potential to be used in a wide range of applications.
• Clear Sunscreen: Traditional inorganic sunscreens (\begin{align*}ZnO\end{align*} and \begin{align*}TiO_2\end{align*}) provide powerful protection from the full range of UV light, but are often not used or under-applied because they appear white on the skin (due to the scattering of visible light). \begin{align*}ZnO\end{align*} and \begin{align*}TiO_2\end{align*} nanoparticles provide the same UV protection as their larger counterparts, but are so small that they don’t scatter visible light and thus appear clear on the skin.
• Building Smaller Devices and Chips: A technique called nanolithography lets us create much smaller devices than current approaches. This technique can be used to further miniaturize the electrical components of microchips. Dip pen nanolithography is a ‘direct write’ technique that uses an AFM to create patterns and to duplicate images. “Ink” is laid down atom by atom on a surface, through a solvent––often water.
• Health Monitoring: Several nano-devices are being developed to keep track of daily changes in patients’ glucose and cholesterol levels, aiding in the monitoring and management of diabetes and high cholesterol for better health. For example, some researchers have created coated nanotubes in a way that will fluoresce in the presence of glucose. Inserted into human tissue, these nanotubes can be excited with a laser pointer and provide real-time monitoring of blood glucose level.

Potential Applications Include:

• Paint That Cleans the Air: A titanic-oxide-based compound in nanosized particles has been claimed to clean the air by decomposing the major ingredients that cause air pollution such as formaldehyde and nitride. This compound could be used in paints, acting as a permanent air purifier and helping to improve the air quality in polluted areas.
• “Paint-On” Solar Cells: Scientists are trying to develop a photovoltaic material using semiconducting nanorods that can be spread like plastic wrap or paint. These nano solar cells could be integrated with other building materials, and offer the promise of cheap production costs that could finally make solar power a widely used electricity alternative.
• Drug Delivery Systems: Nanotubes and buckyballs could serve as drug delivery systems. Because they are inert and small enough to cross many membranes, including the bloodbrain barrier, they could be used to carry reactive drugs to the right part of the body and “deliver” the drug inside the appropriate cell.
• Water Treatment: Advanced nanomembranes could be used for water purification, desalination, and detoxification, nanosensors could detect contaminants and pathogens, and nanoparticles could degrade water pollutants and make salt water and even sewage water easily converted into usable, drinkable water. This could help address water crises across the plant.
• Clean Energy: Hydrogen fuel is currently expensive to make, but with catalysts made from nanoclusters, it may be possible to generate hydrogen from water by photocatalytic reactions. Novel hydrogen storage systems could be based on carbon nanotubes and other lightweight nanomaterials, nanocatalysts could be used for hydrogen generation, and nanotubes could be used for energy transport.
• Detecting Disease with Quantum Dots: Quantum dots are small cadmium-based devices that contain a tiny droplet of free electrons, and emit photons when submitted to ultraviolet (UV) light. Scientists are exploring ways to seal the dots in polymer capsules to protect the body from cadmium exposure; the surface of each capsule can then be designed to attach to different harmful molecules (for example those indicating presence of cancer). As the dots collect in a tumor, they become visible in ultraviolet light under a microscope, allowing doctors to identify and locate cancer earlier.

## Introduction to Nanoscience

### Teacher Lesson Plan

Contents

• Introduction to Nanoscience: Teacher Lesson Plan
• Introduction to Nanoscience: PowerPoint with Teacher Notes
• Introduction to Nanoscience Worksheet: Teacher Key

Orientation

This lesson is a first exposure to nanoscience for students. The goal is to spark student’s interest in nanoscience, introduce them to common terminology, and get them to start thinking about issues of size and scale.

• The Personal Touch reading, worksheet and class discussion focus on applications of nanotechnology (actual and potential) set in the context of a futuristic story. They are designed to spark student’s imaginations and get them to start generating questions about nanoscience.
• The Introduction to Nanoscience reading, PowerPoint slides and worksheet explain key concepts such as why nanoscience is different, why it is important, and how we are able to work at the nanoscale.
• The Scale Diagram shows, for different size scales, the kinds of objects that are found, the tools needed to “see” them, the forces that are dominant, and the models used to explain phenomena. This diagram will be used throughout the Size Matters Unit.

Refer to the “Challenges and Opportunities” chart at the beginning of the unit before starting this lesson. Tell students that although making and using products at the nanoscale is not new, our focus on the nanoscale is new. We can gather data about nanosized materials for the first time because of the availability of new imaging and manipulation tools. You may not know all of the answers to the questions that students may ask. The value in studying nanoscience and nanotechnology is to learn how science understanding evolves and to learn science concepts.

Essential Questions (EQ)

What essential questions will guide this unit and focus teaching and learning?

(Numbers correspond to learning goals overview document)

1. How small is a nanometer, compared with a hair, a blood cell, a virus, or an atom?

2. Why are properties of nanoscale objects sometimes different than those of the same materials at the bulk scale?

4. How do we see and move things that are very small?

5. Why do our scientific models change over time?

6. What are some of the ways that the discovery of a new technology can impact our lives?

Enduring Understandings (EU)

Students will understand:

(Numbers correspond to learning goals overview document)

1. The study of unique phenomena at the nanoscale could change our understanding of matter and lead to new questions and answers in many areas, including health care, the environment, and technology.

4. New tools for seeing and manipulating increase our ability to investigate and innovate.

Key Knowledge and Skills (KKS)

Students will be able to:

(Numbers correspond to learning goals overview document)

1. Describe, using the conventional language of science, the size of a nanometer. Make size comparisons of nanosized objects with other small sized objects.

3. Describe an application (or potential application) of nanoscience and its possible effects on society.

Prerequisite Knowledge and Skills

• Familiarity with atoms, molecules and cells.
• Knowledge of basic units of the metric system and prefixes.
• Ability to manipulate exponential and scientific notation.
• Some knowledge of the light microscope.

Related Standards

• NSES Science and Technology: 12EST2.1, 12EST2.2
• NSES Science as Inquiry: 12ASI2.3
• AAAS Benchmarks: 11D Scale #1, 11D Scale #2
Day Activity Time Materials
Prior to this lesson

Homework: The Personal Touch: Reading & Student Worksheet

Homework: Introduction to Nanoscience: Reading & Student Worksheet

\begin{align*}30\;\mathrm{min}\end{align*}

\begin{align*}40\;\mathrm{min}\end{align*}

The Personal Touch

Introduction to Nanoscience

Day 1 \begin{align*}(50\;\mathrm{min})\end{align*} Use The Personal Touch reading & worksheet as a basis for class discussion. Identify and discuss some student questions from the worksheet. \begin{align*}15\;\mathrm{min}\end{align*}
Show the Introduction to Nanoscience: PowerPoint Slides, using teacher’s notes as talking points. Describe and discuss:
• The term “nanoscience” and the unit “nanometer”
• The tools of nanoscience
• Examples of nanotechnology
\begin{align*}20\;\mathrm{min}\end{align*}

Introduction to Nanoscience: PowerPoint Slides

Computer and projector

Hand out Scale Diagram and explain the important points represented on it. Tell students to keep the handout since it will be used throughout the unit. \begin{align*}5\;\mathrm{min}\end{align*} Photocopies of Scale Diagram
In pairs, have students review answers to Introduction to NanoScience: Student Worksheet \begin{align*}5\;\mathrm{min}\end{align*}
Return to whole class discussion for questions and comments. \begin{align*}5\;\mathrm{min}\end{align*}

Introduction to Nanoscience

What’s happening lately at a very, very small scale

What is Nanoscale Science?

• The study of objects and phenomena at a very small scale, roughly \begin{align*}1\end{align*} to \begin{align*}100\;\mathrm{nanometers (nm)}\end{align*}
• \begin{align*}10\;\mathrm{hydrogen}\end{align*} atoms lined up measure about \begin{align*}1\;\mathrm{nm}\end{align*}
• A grain of sand is \begin{align*}1\;\mathrm{million nm}\end{align*}, or \begin{align*}1\;\mathrm{millimeter}\end{align*}, wide
• An emerging, interdisciplinary science involving
• Physics
• Chemistry
• Biology
• Engineering
• Materials Science
• Computer Science

How Big is a Nanometer?

• Consider a human hand

Are You a Nanobit Curious?

• What’s interesting about the nanoscale?
• Nanosized particles exhibit different properties than larger particles of the same substance
• As we study phenomena at this scale we...
• Develop new theories
• Discover new questions and answers in many areas, including health care, energy, and technology
• Figure out how to make new products and technologies that can improve people’s lives

So How Did We Get Here?

New Tools!

As tools change, what we can see and do changes.

Using Light to See

• The naked eye can see to about \begin{align*}20\;\mathrm{microns}\end{align*}
• A human hair is about \begin{align*}50-100\;\mathrm{microns}\end{align*} thick
• Light microscopes let us see to about \begin{align*} 1\;\mathrm{micron}\end{align*}
• Bounce light off of surfaces to create images

Using Electrons to See

• Scanning electron microscopes (SEMs), invented in the 1930s, let us see objects as small as \begin{align*}10\;\mathrm{nanometers}\end{align*}
• Bounce electrons off of surfaces to create images
• Higher resolution due to small size of electrons

Touching the Surface

• Scanning probe microscopes, developed in the 1980s, give us a new way to “see” at the nanoscale
• We can now see really small things, like atoms, and move them too!

Scanning Probe Microscopes

• Atomic Force Microscope (AFM)
• A tiny tip moves up and down in response to the electromagnetic forces between the atoms of the surface and the tip
• The motion is recorded and used to create an image of the atomic surface
• Scanning Tunneling Microscope (STM)
• A flow of electrical current occurs between the tip and the surface
• The strength of this current is used to create an image of the atomic surface

So What?

Is nanoscience just seeing and moving really small things?

• Yes, but it’s also a whole lot more. Properties of materials change at the nanoscale!

Is Gold Always “Gold”?

• Cutting down a cube of gold
• If you have a cube of pure gold and cut it, what color would the pieces be?
• Now you cut those pieces. What color will each of the pieces be?
• If you keep doing this - cutting each block in half - will the pieces of gold always look “gold”?

Nanogold

• Well... strange things happen at the small scale
• If you keep cutting until the gold pieces are in the nanoscale range, they don’t look gold anymore... They look RED.
• In fact, depending on size, they can turn red, blue, yellow, and other colors
• Why?
• Different thicknesses of materials reflect and absorb light differently

Nanostructures

What kind of nanostructures can we make?

What kind of nanostructures exist in nature?

Carbon Nanotubes

• Using new techniques, we’ve created amazing structures like carbon nanotubes
• \begin{align*}100\;\mathrm{time}\end{align*} stronger than steel and very flexible
• If added to materials like car bumpers, increases strength and flexibility

Carbon Buckyballs (C60)

• Incredible strength due to their bond structure and “soccer ball” shape
• Could be useful “shells” for drug delivery
• Can penetrate cell walls
• Are nonreactive (move safely through blood stream)

Biological Nanomachines in Nature

• Life begins at the nanoscale
• Ion pumps move potassium ions into and sodium ions out of a cell
• Ribosomes translate RNA sequences into proteins
• Viruses infect cells in biological organisms and reproduce in the host cell Influenza virus

Building Nanostructures

How do you build things that are so small?

Fabrication Methods

• Atom-by-atom assembly
• Like bricklaying, move atoms into place one at a time using tools like the AFM and STM
• Chisel away atoms
• Like a sculptor, chisel out material from a surface until the desired structure emerges
• Self assembly
• Set up an environment so atoms assemble automatically. Nature uses self assembly (e.g., cell membranes)

Example: Self Assembly By Crystal Growth

• Grow nanotubes like trees
• Put iron nanopowder crystals on a silicon surface
• Put in a chamber
• Add natural gas with carbon (vapor deposition)
• Carbon reacts with iron and forms a precipitate of carbon that grows up and out
• Because of the large number of structures you can create quickly, self-assembly is the most important fabrication technique

### Teacher Notes

Overview

This series of slides introduces students to what nanoscience is, how big is a nanometer, various types of microscopes used to see small things, some interesting nanostructures, and interesting properties of these structures.

Slide 1: Introduction to Nanoscience

Explain to students that you’re going to explain what nanoscience is and how we see small things, give a few examples of interesting structures and properties of the nanoscale, and describe how scientists build very small structures.

Slide 2: What is Nanoscale Science?

Nanoscale science deals with the study of phenomena at a very small scale \begin{align*}- 10^{-7} \;\mathrm{m}\ (100\;\mathrm{nm})\end{align*} to \begin{align*}10^{-9} \;\mathrm{m}\ (1 \;\mathrm{nm}) -\end{align*} where properties of matter differ significantly from those at larger scales. This very small scale is difficult for people to visualize. There are several sizeand scale-related activities as part of the NanoSense materials that you can incorporate into your curriculum that help students think about the nanoscale.

This slide also highlights that nanoscale science is a multidisciplinary field and draws on areas outside of chemistry, such as biology, physics, engineering and computer science. Because of its multidisciplinary nature, nanoscience may require us to draw on knowledge in potentially unfamiliar academic fields.

Slide 3: How Big is a Nanometer?

This slide gives a “powers of ten” sense of scale. If you are running the slides as a PowerPoint presentation that is projected to the class, you could also pull up one or more powers of ten animations. See http://www.micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10 for a nice example that can give students a better sense of small scale.

As you step through the different levels shown in the slide, you can point out that you can see down to about #3 \begin{align*}(1000\;\mathrm{microns})\end{align*} with the naked eye, and that a typical microscope as used in biology class will get you down to about #5 \begin{align*}(10\;\mathrm{microns})\end{align*}. More advanced microscopes, such as scanning electron microscopes can get you pretty good resolution in the #6 \begin{align*}(1\;\mathrm{micron})\end{align*} range. Newer technologies (within the last \begin{align*}20\;\mathrm{years}\end{align*} or so) allow us to “see” in the #7 \begin{align*}(100\;\mathrm{nanometer})\end{align*} through #9 \begin{align*}(1\;\mathrm{nanometer})\end{align*} ranges. These are the scanning probe and atomic force microscopes.

Slide 4: Are You a Nanobit Curious?

This slide highlights why we should care about nanoscience: It will change our lives and change our understanding of matter. A group of leading scientists gathered by the National Science Foundation in 1999 said: "The effect of nanotechnology on the health, wealth and standard of living for people in this century could be at least as significant as the combined influences of microelectronics, medical imaging, computer-aided engineering and man-made polymers developed in the past century.” (Accessed August, 2005, from http://www.techbizfl.com/news_desc.asp?article_id=1792.)

Slide 5: So How Did We Get Here?

This slide denotes the beginning of a short discussion of the evolution of imaging tools (i.e. microscopes). One of the big ideas in science is that the creation of tools or instruments that improve our ability to collect data is often accompanied by new science understandings. Science is dynamic. Innovation in scientific instruments is followed by a better understanding of science and is associated with creating innovative technological applications.

Slide 6: Using Light to See

You may want to point out that traditional light microscopes are still very useful in many biology-related applications since things like cells and bacteria can readily be seen with this tool. They are also fairly inexpensive and are easy to set up.

Slide 7: Using Electrons to See

Point out that the difference between the standard light microscope and the scanning electron microscope is that electrons, instead of various wavelengths of light, are “bounced” off the surface of the object being viewed, and that electrons allow for a higher resolution because of their small size. You can use the analogy of bouncing bb’s on a surface to find out if it is uneven (bb’s scattering in all different directions) compared to using beach balls to do the same job.

Slide 8: Touching the Surface

Point out how small the tip of the probe is compared to the size of the atoms in the picture. Point out that this is one of the smallest tips you can possibly make, and that it has to be made from atoms. Also point out that the tip interacts with the surface of the material you want to look at, so the smaller the tip, the better the resolution. But because the tip is made from atoms, it can’t be smaller than the atoms you are looking at. Tips are made from a variety of materials, such as silicon, tungsten, and even carbon nanotubes.

Slide 9: Scanning Probe Microscopes

Point out the difference between the AFM and the STM: the AFM relies on movement due to the electromagnetic forces between atoms, and the STM relies on electrical current between the tip and the surface. Mention that the AFM was invented to overcomes the STM’s basic drawback: it can only be used to sense the nature of materials that conduct electricity, since it relies on the creation of a current between the tip and the surface. The AFM relies on actual contact rather than current flow, so it can be used to probe almost any type of material, including polymers, glass, and biological samples.

Point out that the signals (forces or currents) from these instruments are used to infer an image of the atoms. The tip’s fluctuations are recorded and fed into computer models that generate images based on the data. These images give us a rough picture of the atomic landscape.

Slide 10: So What?

The following slides will give examples to help illustrate why we care about seeing and moving things at a very small scale. What makes the science at the nanoscale special is that at such a small scale, different physical laws dominate and properties of materials change.

Slide 11: Is Gold Always Gold?

Help students think about what happens when you keep cutting something down. At what point will you get down to the individual atoms, and at what point does “color” change and go away? Remind them that individual atoms do not have color. The color of a substance is determined by the wavelength of the light that bounces off it, and one atom is too small to reflect light on its own. Only once you have an aggregate (a bunch) of atoms big enough can you begin to discern something approaching “color.” For example, a bunch of salt crystals together look white, but an individual salt crystal is colorless.

Slide 12: Nanogold

Prompt your students to look at their jewelry, etc. and think about color of materials. Use analogies to drive home the concept that different thicknesses of a material can produce different colors. For example, oil on water produces different colors based on how thin the film of oil is. In an oil slick the atoms aren't changing; there are just different thicknesses (numbers of atoms) reflecting different colors. Leaves on a tree look green because the atomic structure on surface of leave reflects back green wavelength and absorbs all others. As leaves die, the atomic structure changes so you get brown reflected back as the chlorophyll breaks down.

For gold, color is based on the crystalline or atomic structure at the nanoscale: light absorbs differently based on the thickness of the crystal. In the Personal Touch story, Sandra's dress changes color because she can change the arrangement of atoms in her dress, which will then reflect different colors.

Slide 13: Nanostructures

The next few slides provide examples of what kind of nanostructures scientists can create and nanostructures that exist in nature.

Slide 14: Carbon Nanotubes

This slide describes a recently-created structure that has some amazing properties. Nanotubes are very light and strong and can be added to various materials to give them added strength without adding much weight. Nanotubes also have interesting conductance (electrical) properties.

Slide 15: Carbon Buckyballs

Buckyballs are another very strong structure based on its interlaced “soccer ball” shape. It has the unique property of being able to carry something inside of it, penetrate a cell wall, and then deliver the package into the cell (not sure how you “open” the buckyball!). It is also non-reactive in general in the body, so your body will not try to attack it and it can travel easy in the bloodstream.

Slide 16: Biological Nanomachines in Nature

There are many natural nanoscale devices that exist in our biological world. Life begins at the nanoscale! For example, inside all cells, molecules and particles of various sizes have to move around. Some molecules can move by diffusion, but ions and other charged particles have to be specifically transported around cells and across membranes. Biology has an enormous number of proteins that self-assemble into nanoscale structures. See the “Introduction to Nanoscience: Student Reading” for more examples.

Slide 17: Building Nanostructures

The next two slides provide examples of how we build things that are so small.

Slide 18: Fabrication Methods

This slide summarizes the three main methods that are used to make nanoscale structures. First, the tips of scanning probe microscopes can form bonds with the atoms of the material they are scanning and move the atoms. Using this method with xenon atoms, IBM created the tiniest logo ever in 1990. Alternately, scientists can chisel out material from the surface until the desired structure emerges. This is the process that the computer industry uses to make integrated circuits. Finally, self assembly is the process by which molecular building blocks “assemble” naturally to form useful products. Molecules try to minimize their energy levels by aligning themselves in particular positions. If bonding to an adjacent molecule allows for a lower energy state, then the bonding will occur. We see this happening in many places in nature. For example, the spherical shape of a bubble or the shape of snowflake are a result of molecules minimizing their energy levels. See the “Introduction to Nanoscience: Student Reading” for more information.

Slide 19: Example: Self Assembly By Crystal Growth

One particular type of self-assembly is crystal growth. This technique is used to “grow” nanotubes. In this approach, “seed” crystals are placed on some surface, some other atoms or molecules are introduced, and these particles mimic the pattern of the small seed crystal. For example, one way to make nanotubes is to create an array of iron nanopowder particles on some material like silicon, put this array in a chamber, and add some natural gas with carbon to the chamber. The carbon reacts with the iron and supersaturates it, forming a precipitate of carbon that then grows up and out. In this manner, you can grow nanotubes like trees!

### Teacher Key

Below is a set of questions to answer during and/or following the introduction to nanoscience slide presentation.

1. What is the range of the “nanoscale”?

Roughly \begin{align*}1\end{align*} to \begin{align*}100\;\mathrm{nanometers\ (nm)}\end{align*} in at least one dimension.

2. What is the smallest size (in meters) that the human eye can see?

The naked eye can see down to about \begin{align*}20\;\mathrm{microns}\end{align*} (micrometers). One micron is \begin{align*}10^{-6}\;\mathrm{meters}\end{align*}, so ten microns is \begin{align*}10^{-5}\;\mathrm{meters}\end{align*}, and \begin{align*}20\;\mathrm{microns}\end{align*} is \begin{align*}2 \times 10^{-5}\;\mathrm{meters}\end{align*}. That’s \begin{align*}20\;\mathrm{millionths}\end{align*} of a meter.

3. How much more “power” can a light microscope add to the unaided eye? In other words, what is the smallest resolution that a light microscope can show?

Light microscopes let us see to about \begin{align*}1\;\mathrm{micron}\end{align*}, or \begin{align*}10^{-6}\;\mathrm{meters}\end{align*}. That’s \begin{align*}20 \;\mathrm{times}\end{align*} smaller than the eye can see on its own.

4. Briefly describe how light microscopes and electron microscopes work.

Light microscopes “bounce” visible light of off surfaces to create images. Electron microscopes “bounce” electrons off of surfaces to create images. (Electron microscopes provide higher resolution because electrons are so small, i.e., smaller than a wavelength of visible light.)

5. Name one of the new microscopes that scientists have used to view objects at the nanoscale and explain how that microscope allows you to view objects.

The scanning tunneling microscope (STM) and the atomic force microscope (AFM) are both new scanning probe microscopes (SPM) that can be used to view objects at the nanoscale.

STM: A flow of electrical current occurs between the tip of the microscope probe and the surface of the object. The variation in strength of this current due to the shape of the surface is used to form an image.

AFM: The tip of the microscope probe moves in response to electromagnetic forces between it and the atoms on the surface of the object. As the tip moves up and down, the movement is used to form an image.

6. Give a short explanation of why the nanoscale is “special.”

Nanosized particles exhibit different properties than larger particles of the same substance. Studying phenomena at this scale can improve and possibly change our understanding of matter and lead to new questions and answers in many areas.

7. Name one example of a nanoscale structure and describe its interesting properties.

Examples given in the slides: (1) Carbon nanotubes are \begin{align*}100 \;\mathrm{time}\end{align*} stronger than steel, yet very flexible. (2) Carbon buckyballs can pass through cell membranes and be used for drug delivery.

## Scale of Objects

Contents

• Scale of Objects: Teacher Lesson Plan
• Number Line/Card Sort Activity: Teacher Instructions & Key
• Cutting it Down Activity: Teacher Instructions & Key
• Scale of Objects Activity: Teacher Key
• Scale of Small Objects Quiz: Teacher Key

### Teacher Lesson Plan

Orientation

This lesson helps students think about the enormous scale differences in our universe. There are three classroom activities that you can choose between and combine.

• The Student Reading on Visualizing the Nanoscale reviews common size units and provides several examples to help students imagine the nanoscale.
• The Number Line/Card Sort Activity has students place objects along a scale and reflect on the size of common objects in relation to each other.
• The Scale of Small Objects Activity/Worksheet has students identify the size scale of objects with less focus on their relation to each other.
• The Cutting It Down Activity has students cut a strip of paper in half as many times as possible and focuses on tools and their precision at different scales.
• The Scale of Small Objects Quiz tests the absolute and relative size of objects.

Essential Questions (EQ)

What essential questions will guide this unit and focus teaching and learning?

(Numbers correspond to learning goals overview document)

1. How small is a nanometer, compared with a hair, a blood cell, a virus, or an atom?

Enduring Understandings (EU)

Students will understand:

(Numbers correspond to learning goals overview document)

2. There are enormous scale differences in our universe, and at different scales, different forces dominate and different models better explain phenomena.

Key Knowledge and Skills (KKS)

Students will be able to:

(Numbers correspond to learning goals overview document)

1. Describe, using the conventional language of science, the size of a nanometer. Make size comparisons of nanosized objects with other small sized objects.

Prerequisite Knowledge and Skills

• Familiarity with atoms, molecules and cells.
• Knowledge of basic units of the metric system and prefixes.
• Ability to manipulate exponential and scientific notation.

Related Standards

• NSES Science as Inquiry: 12ASI2.3
• AAAS Benchmarks: 11D Scale #1
Day Activity Time Materials
Prior to this lesson Homework: Reading & Worksheet: Visualizing the Nanoscale \begin{align*}30 \;\mathrm{min}\end{align*} Photocopies of Visualizing the Nanoscale: Student Reading
Day 1 \begin{align*}(40 \;\mathrm{min})\end{align*} Use Visualizing the Nanoscale: Student Reading as a basis for class discussion and student questions. Use the Scale Diagram: Dominant Objects, Tools, Models, and Forces at Various Different Scales as a reference. \begin{align*}10 \;\mathrm{min}\end{align*} Students will refer to the Scale Diagram handout; photocopy it if not previously handed out.

Number Line/Card Sort Activity

or

Cutting it Down Activity

or

Scale of Objects Activity

\begin{align*}20 \;\mathrm{min}\end{align*}

Photocopies of Number Line/Card Sort Activity: Student Instructions & Worksheet

A set of cards (objects and units) for each small group of students (consider printing cards on card stock for reuse)

Photocopies of Cutting It Down Activity: Student Instructions & Worksheet

Strips of Paper

Scissors

Photocopies of Scale of Objects Activity: Student Instructions & Worksheet

Return to whole class discussion for questions and comments \begin{align*}5 \;\mathrm{min}\end{align*}
Scale of Small Objects: Student Quiz \begin{align*}5 \;\mathrm{min}\end{align*}

Photocopy Scale of Small Objects: Student Quiz

Teacher Key for correcting Student Quiz

### Number Line/Card Sort Activity: Teacher Instructions & Key

Overview

In this activity, your students will explore their perception of the size of different objects. Have your students form into pairs or small groups, and give each group the Number Line/Card Sort Activity: Student Instructions & Worksheet handout and two sets of cards: one with objects on them and one with units on them. Their task is to create a number line and place the cards at the appropriate places on the number line.

You may also want to discuss with your students why we are using powers of \begin{align*}10\end{align*} for the units in this exercise instead of using a “regular” linear scale (e.g., a meter stick). Here are some questions and issues you may want to bring up:

The number line units are powers of \begin{align*}10\end{align*}; that is, they are a base \begin{align*}10\end{align*} logarithmic scale. Why don’t we just use a linear scale, like a meter stick? Using a linear scale, we could easily mark off \begin{align*}1\;\mathrm{meter}, 1\;\mathrm{cm},\end{align*} and \begin{align*}1\;\mathrm{mm}\end{align*}. But it’s hard to mark (or see) smaller than that. Plus, most of the cards (for small objects) would pile up on top of each other!

Instead, we’d like to spread our cards out to clearly see which objects are bigger or smaller than others. We can do this if we use a logarithmic scale. The word logarithm is a synonym for the words “exponent” or “power.” Powers of \begin{align*}10\end{align*} use a base \begin{align*}10\end{align*} logarithm scale. In base \begin{align*}10\end{align*}, \begin{align*}\mathrm{Log}_{10}(10^{-10}) = -10\end{align*}. So, each card unit represents an exponent \begin{align*}(-10, -9, - 8 \ldots -1, 0)\end{align*} of \begin{align*}10\end{align*}. These are integers that are equidistant from each other.

Materials

• Cards for the objects
• Cards for the units, in powers of \begin{align*}10\;\mathrm{meters}\end{align*}

Instructions

On a surface like a lab table, order the cards for powers of \begin{align*}10\end{align*} in a vertical column, with the largest at the top and the smallest at the bottom. Space the cards equidistant from each other, leaving a gap between the cards for \begin{align*}10^{-10}\end{align*} and \begin{align*}10^{-15}\end{align*}. This is your number line.

Next, place each object next to the closest power of \begin{align*}10\end{align*} in the number line that represents the size of that object in meters. Some objects may lie between two powers of \begin{align*}10\end{align*}.

When you are done placing all of the cards, record your results in the table on the next page and answer the questions that follow.

Card choices adapted from Tretter, T. R., Jones, M. G., Andre, T., Negishi, A., & Minogue, J. (2005). Conceptual Boundaries and Distances: Students' and Experts' Concepts of the Scale of Scientific Phenomena. Journal of Research in Science Teaching.

Size (meters) Objects
\begin{align*}10^\circ\end{align*}

\begin{align*}21.\;\mathrm{height}\end{align*} of a typical NBA basketball player

\begin{align*}4.\;\mathrm{height}\end{align*} of a typical 5-year-old child

\begin{align*}10^{-1}\end{align*}

\begin{align*}20.\;\mathrm{length}\end{align*} of a phone book

\begin{align*}16.\;\mathrm{length}\end{align*} of a business envelope

\begin{align*}9.\;\mathrm{width}\end{align*} of an electrical outlet cover

\begin{align*}10^{-2}\end{align*}

\begin{align*}17.\;\mathrm{diameter}\end{align*} of a quarter

\begin{align*}7.\;\mathrm{width}\end{align*} of a typical wedding ring

\begin{align*}14.\;\mathrm{length}\end{align*} of an apple seed

\begin{align*}10^{-3}\end{align*}

\begin{align*}1.\end{align*} thickness of a penny

\begin{align*}23.\end{align*} thickness of a staple

\begin{align*}11.\end{align*} thickness of sewing thread

\begin{align*}10^{-4}\end{align*}

\begin{align*}6.\;\mathrm{length}\end{align*} of a dust mite

\begin{align*}8.\;\mathrm{length}\end{align*} of an amoeba

\begin{align*}18.\;\mathrm{length}\end{align*} of a human muscle cell

\begin{align*}10^{-5}\end{align*} \begin{align*}3.\;\mathrm{diameter}\end{align*} of a red blood cell
\begin{align*}10^{-6}\end{align*} \begin{align*}13.\;\mathrm{width}\end{align*} of a bacterium
\begin{align*}10^{-7}\end{align*}

\begin{align*}24.\end{align*} wavelength of visible light (between \begin{align*}10^{-7}\end{align*} and \begin{align*}10^{-6}\end{align*})

\begin{align*}15.\;\mathrm{diameter}\end{align*} of a virus

\begin{align*}10^{-8}\end{align*}

\begin{align*}10.\;\mathrm{diameter}\end{align*} of a ribosome

\begin{align*}5.\;\mathrm{width}\end{align*} of a proteinase enzyme

\begin{align*}19.\;\mathrm{diameter}\end{align*} of a carbon nanotube

\begin{align*}10^{-9}\end{align*} \begin{align*}12.\;\mathrm{width}\end{align*} of a water molecule
\begin{align*}10^{-10}\end{align*} \begin{align*}22.\;\mathrm{diameter}\end{align*} of a nitrogen atom
\begin{align*}10^{-15}\end{align*} \begin{align*}2.\;\mathrm{nucleus}\end{align*} of an oxygen atom

Questions

1. Which items were the hardest for you to estimate size for? Why?

Students will probably list small objects they know the least about. For example, if they haven’t taken biology, they may list virus, ribosome, etc.

2. Why are we using powers of \begin{align*}10\end{align*} for the number line instead of a regular linear scale (like a meter stick)?

With a powers of \begin{align*}10\end{align*} scale, we can spread the unit markers out evenly so that we can clearly place and see all of the cards. If we used a linear scale, most of the cards would pile up on top of each other. And we can’t easily make marks much smaller than a millimeter anyway, so we couldn’t make or see our scale if it were linear!

### Cutting it Down Activity: Teacher Instructions & Key

Purpose

The purpose of this activity is to help students understand the smallness of the nanoscale, appreciate the impossibility of creating nanoscale materials with macro scale objects, and to understand the invisibility of the nanoscale to the unaided eye. [1]

Materials

For each group of students, provide

• Scissors
• A strip of paper (cut a narrow strip from an \begin{align*}8.5 \times 11\;\mathrm{inch}\end{align*} sheet of paper, approximately \begin{align*}8.5\;\mathrm{inches}\end{align*} long by \begin{align*}1/4\;\mathrm{inch}\end{align*} wide, or \begin{align*}216\;\mathrm{mm}\ \times\ 5\;\mathrm{mm}\end{align*})
• Pen or pencil
• Ruler
• Calculator

Classroom Activity

Show the students the strip of paper and tell them what its dimensions are. Explain to them that the challenge is to cut the piece of paper in half repeatedly in order to make it \begin{align*}10\;\mathrm{nm}\end{align*} long.

Have the students get in pairs and give each pair the ruler, calculator, scissors, pen/pencil (if necessary), strip of paper, and the Cutting It Down Activity: Student Worksheet. Remind them to answer the first two questions on the worksheet before they begin cutting. Tell them they have \begin{align*}10 \;\mathrm{minutes}\end{align*} to complete the activity.

As a variation, you could have students do the exercise more than once with different kinds of scissors or other cutting tools to demonstrate the power and limitations of tools.

Discussion

When the students have finished the activity, discuss the questions on their worksheets. Focus on the following questions first:

• Were their predictions to the first two questions accurate?
• How many times were they able to cut the paper?

After discussing these questions, focus on the remaining questions on their worksheets. As a closing point, emphasize that the demonstration shows how small nano really is and how inadequate macro scale tools (like the scissors), are in dealing with the nanoscale.

• If you have had students use different kinds of scissors or other cutting tools, you can also discuss the relationship between form and size of the tool and its precisions and usefulness at a certain size scale. For example, an \begin{align*}x-\end{align*}acto blade can be used to make much finer cuts than a pair of scissors, although both are too big to be useful at the nanoscale.

Student Instructions

How many times do you think you would need to cut a strip of paper in half in order to make it between zero and 10 nanometers long? In this activity, you’ll cut a strip of paper in half as many times as you can, and think about the process.

BEFORE you begin cutting the strip of paper, answer the following questions (take a guess):

1. How many times do you need to cut the paper in half to obtain a \begin{align*}10\;\mathrm{nanometer}\end{align*} long piece?

Answers will vary, since this is a prediction. Should be a fairly large integer value.

2. How many times do you think you can cut the paper before it becomes impossible to cut?

Answers will vary, since this is a prediction. Should be an integer value that is smaller than the answer to question 1.

Now cut the strip of paper in half as many times as you can. Remember to keep track of how many cuts you make.

AFTER completing the activity, answer the following questions.

3. Were your predictions to the above two questions accurate?

Answers will vary, but should indicate if their predictions matched their results.

4. How many times were you able to cut the paper?

Answers will vary, but should be an integer number, likely in the range of \begin{align*}6-8\end{align*} cuts.

5. How close was your smallest piece to the nanoscale?

Very far. By cutting with a typical pair of scissors, you probably can get down to about the \begin{align*}1\;\mathrm{mm}\end{align*} range, which is \begin{align*}10^{-3}\;\mathrm{meters}\end{align*}. The nanoscale range is \begin{align*}10^{-7}\end{align*} to \begin{align*}10^{-9}\;\mathrm{meters}\end{align*}, or \begin{align*}4\end{align*} to \begin{align*}6\end{align*} powers of ten smaller.

6. Why did you have to stop cutting?

Couldn’t position the paper on the scissors; the scissors were too big relative to the paper to cut any more, etc.

7. Can macroscale objects, like scissors, be used at the nanoscale?

No.

8. Can you think of a way to cut the paper any smaller?

Answers might include using a microscope, smaller scissors, or finer cutting tools.

### Activity: Teacher Key

In this activity, you will explore your perceptions different sizes. For each of the following items, indicate its size by placing an “X” the box that is closest to your guess.

Key:

A. Less than \begin{align*}1\;\mathrm{nanometer}\ (1\;\mathrm{nm})\end{align*} [Less than \begin{align*}10^{-9}\;\mathrm{meter}\end{align*}]

B. Between \begin{align*}1\;\mathrm{nanometer\ (nm)}\end{align*} and \begin{align*}100\;\mathrm{nanometers}\ (100\;\mathrm{nm})\end{align*} [Between \begin{align*}10^{-9}\end{align*} and \begin{align*}10^{-7}\;\mathrm{meters}\end{align*}]

C. Between \begin{align*}100\;\mathrm{nanometers}\ (100\;\mathrm{nm})\end{align*} and \begin{align*}1\;\mathrm{micrometer}\ (1\;\mathrm{\mu m})\end{align*} [Between \begin{align*}10^{-7}\end{align*} and \begin{align*}10^{-6}\;\mathrm{meters}\end{align*}]

D. Between \begin{align*}1\;\mathrm{micrometer}\ (1\;\mathrm{\mu m})\end{align*} and \begin{align*}1\;\mathrm{millimeter}\ (1\;\mathrm{mm})\end{align*} [Between \begin{align*}10^{-6}\end{align*} and \begin{align*}10^{-3}\;\mathrm{meters}\end{align*}]

E. Between \begin{align*}1\;\mathrm{millimeter}\end{align*} \begin{align*}(1\;\mathrm{mm})\end{align*} and \begin{align*}1\;\mathrm{centimeter}\ (1\;\mathrm{cm})\end{align*} [Between \begin{align*}10^{-3}\end{align*} and \begin{align*}10^{-2}\;\mathrm{meters}\end{align*}]

F. Between \begin{align*}1\;\mathrm{centimeter}\ (1\;\mathrm{cm})\end{align*} and \begin{align*}1\;\mathrm{meter}\ (\;\mathrm{m})\end{align*} [Between \begin{align*}10^{-2}\end{align*} and \begin{align*}10^\circ \;\mathrm{meters}\end{align*}]

G. Between \begin{align*}1\;\mathrm{meter}\end{align*} and \begin{align*}10\;\mathrm{meters}\end{align*} [Between \begin{align*}10^\circ\end{align*} and \begin{align*}10^1\;\mathrm{meters}\end{align*}]

H. More than \begin{align*}10\;\mathrm{meters}\end{align*} [More than \begin{align*}10^1\;\mathrm{meters}\end{align*}]

Less than \begin{align*}1\;\mathrm{nm}\end{align*} \begin{align*}1\;\mathrm{nm}\end{align*} to \begin{align*}100\;\mathrm{nm} \end{align*} \begin{align*}100\;\mathrm{nm} \end{align*} to \begin{align*}1\;\mathrm{\mu m}\end{align*} \begin{align*}1\;\mathrm{\mu m}\end{align*} to \begin{align*}1\;\mathrm{mm} \end{align*} \begin{align*}1\;\mathrm{mm}\end{align*} to \begin{align*}1\;\mathrm{cm}\end{align*} \begin{align*}1\;\mathrm{cm}\end{align*} to \begin{align*}1\;\mathrm{m}\end{align*} \begin{align*}1\;\mathrm{m}\end{align*} to \begin{align*}10\;\mathrm{m}\end{align*} More than \begin{align*}10\;\mathrm{m}\end{align*}
Object A B C D E F G H
1. Width of a human hair \begin{align*}x\end{align*}
2. Length of a football field \begin{align*}x\end{align*}
3. Diameter of a virus \begin{align*}x\end{align*}
4. Diameter of a hollow ball made of 60 carbon atoms (a “buckyball”) \begin{align*}x\end{align*}
5. Diameter of a molecule of hemoglobin \begin{align*}x\end{align*}
6. Diameter of a hydrogen atom \begin{align*}x\end{align*}
7. Length of a molecule of sucrose \begin{align*}x\end{align*}
8. Diameter of a human blood cell \begin{align*}x\end{align*}
9. Length of an ant \begin{align*}x\end{align*}
10. Height of an elephant \begin{align*}x\end{align*}
11. Diameter of a ribosome \begin{align*}x\end{align*}
12. Wavelength of visible light \begin{align*}x\end{align*}
13. Height of a typical adult person \begin{align*}x\end{align*}
14. Length of a new pencil \begin{align*}x\end{align*}
15. Length of a school bus \begin{align*}x\end{align*}
16. Diameter of the nucleus of a carbon atom \begin{align*}x\end{align*}
17. Length of a grain of white rice \begin{align*}x\end{align*}
18. Length of a postage stamp \begin{align*}x\end{align*}
19. Length of a typical science textbook \begin{align*}x\end{align*}
20. Length of an adult’s little finger \begin{align*}x\end{align*}

Adapted from Tretter, T. R., Jones, M. G., Andre, T., Negishi, A., & Minogue, J. (2005). Conceptual Boundaries and Distances: Students’ and Experts’ Concepts of the Scale of Scientific Phenomena. Journal of Research in Science Teaching.

### Scale of Small Objects: Teacher Key

1. Indicate the size of each object below by placing an “X” the appropriate box.

Key:

A. Less than \begin{align*}1\;\mathrm{nanometer}\ (1\;\mathrm{nm})\end{align*} [Less than \begin{align*}10^{-9}\;\mathrm{meter}\end{align*}]

B. Between \begin{align*}1\;\mathrm{nanometer}\ (\;\mathrm{nm})\end{align*} and \begin{align*}100\;\mathrm{nanometers}\ (100\;\mathrm{nm})\end{align*} [Between \begin{align*}10^{-9}\end{align*} and \begin{align*}10^{-7}\;\mathrm{meters}\end{align*}]

C. Between \begin{align*}100\;\mathrm{nanometers}\ (100\;\mathrm{nm})\end{align*} and \begin{align*}1 \;\mathrm{micrometer}\ (1\;\mathrm{\mu m})\end{align*} [Between \begin{align*}10^{-7}\end{align*} and \begin{align*}10^{-6}\;\mathrm{meters}\end{align*}]

D. Between \begin{align*}1\;\mathrm{micrometer}\ (1\;\mathrm{\mu m})\end{align*} and \begin{align*}1\;\mathrm{millimeter}\ (1\;\mathrm{mm})\end{align*} [Between \begin{align*}10^{-6}\end{align*} and \begin{align*}10^{-3}\;\mathrm{meters}\end{align*}]

E. Between \begin{align*}1\;\mathrm{millimeter}\ (1\;\mathrm{mm})\end{align*} and \begin{align*}1\;\mathrm{centimeter}\ (1\;\mathrm{cm})\end{align*} [Between \begin{align*}10^{-3}\end{align*} and \begin{align*}10^{-2}\;\mathrm{meters}\end{align*}]

Less than \begin{align*}1\;\mathrm{nm}\end{align*} \begin{align*}1\;\mathrm{nm}\end{align*} to \begin{align*}100\;\mathrm{nm}\end{align*} \begin{align*}100\;\mathrm{nm}\end{align*} to \begin{align*}1\ \mu\mathrm{m}\end{align*} \begin{align*}1 \mu \mathrm{m}\end{align*} to \begin{align*}1\;\mathrm{mm}\end{align*} \begin{align*}1\;\mathrm{mm}\end{align*} to \begin{align*}1\;\mathrm{cm}\end{align*}
Object A B C D E
1. Width of a human hair \begin{align*}x\end{align*}
2. Diameter of a hollow ball made of \begin{align*}60\end{align*} carbon atoms (a “buckyball”) \begin{align*}x\end{align*}
3. Diameter of a hydrogen atom \begin{align*}x\end{align*}
4. Diameter of a human blood cell \begin{align*}x\end{align*}
5. Wavelength of visible light \begin{align*}x\end{align*}

2. Order the following items in order of their size, from smallest to largest.

a. Width of a water molecule

b. Diameter of a gold atom

c. Thickness of a staple

d. Diameter of a virus

e. Length of an amoeba

f. Diameter of a carbon nanotube

Smallest:

___d_____
___a_____
___f_____
___d_____
___e_____

Largest:

___c_____

## Unique Properties at the Nanoscale

### Teacher Lesson Plan

Contents

• Unique Properties at the Nanoscale: Teacher Lesson Plan
• Unique Properties at the Nanoscale: PowerPoint with Teacher Notes
• Unique Properties Lab Activities: Teacher Instructions
• Unique Properties at the Nanoscale: Teacher Reading
• Unique Properties at the Nanoscale Quiz: Teacher Key

Orientation

This lesson is central to understanding the science that occurs at the nanoscale, and contains the most rigorous science content.

• The Unique Properties at the Nanoscale PowerPoint focuses on how and why properties of materials change at the nanoscale.
• The Student Reading on Size-Dependent Properties provides more details on why properties change at the nanoscale. It may be appropriate for students taking college preparatory chemistry.
• The Unique Properties Lab Activities demonstrate specific aspects of size-dependent properties without using nanoparticles. It is appropriate for most students.
• The Unique Properties Quiz tests students understanding of size-dependent properties.

Essential Questions (EQ)

What essential questions will guide this unit and focus teaching and learning?

(Numbers correspond to learning goals overview document)

2. Why are properties of nanoscale objects sometimes different than those of the same materials at the bulk scale?

5. Why do our scientific models change over time?

Enduring Understandings (EU)

Students will understand: (Numbers correspond to learning goals overview document)

2. There are enormous scale differences in our universe, and at different scales, different forces dominate and different models better explain phenomena.

3. Nanosized particles of any given substance exhibit different properties than larger particles of the same substance.

Key Knowledge and Skills (KKS)

Students will be able to: (Numbers correspond to learning goals overview document)

2. Explain why properties of nanoscale objects sometimes differ from those of the same materials at the bulk scale.

Prerequisite Knowledge and Skills

• Familiarity with properties of matter.
• Some knowledge of atomic structure, Bohr’s model of the atoms and the quantum mechanical model of the atom.
• Familiarity with polarity of molecules.

Related Standards

• NSES Science and Technology: 12EST2.1, 12EST2.2
• NSES Science as Inquiry: 12ASI2.3
• AAAS Benchmarks: 11D Scale #1, 11D Scale #2
Day Activity Time Materials
Prior to this lesson Homework: Reading: Size-Dependent Properties \begin{align*}45\;\mathrm{min}\end{align*} Photocopies of Size-Dependent Properties: Student Reading
Day 1 \begin{align*}(50\;\mathrm{min})\end{align*}

Show the PowerPoint slides: Unique Properties at the Nanoscale, using teacher’s notes as talking points. Discuss:

• Normal properties of a substance.
• What properties change from bulk characteristics to nanoscale properties, and how they change\begin{align*}^*\end{align*}
• How the dominance of electromagnetic forces make a difference in properties\begin{align*}^*\end{align*}
• How the quantum mechanical model of the atom, uncertainty of measurement, and tunneling make a difference for nanoscale objects\begin{align*}^*\end{align*}

\begin{align*}^*\end{align*} Note: Not required by NSES Standards

\begin{align*}40\;\mathrm{min}\end{align*}

PowerPoint slides: Unique Properties at the Nanoscale

Computer and Projector

Prepare for the Unique Properties Station Lab

Review student grouping and procedural arrangements

\begin{align*}10\;\mathrm{min}\end{align*} Photocopies of Student Lab Worksheet
Day 2 \begin{align*}(40\;\mathrm{min})\end{align*} Conduct Unique Properties Lab Activity \begin{align*}40 \;\mathrm{min}\end{align*} Post Student Directions at each station and prepare stations per Teacher Lab Instructions
Homework: Complete the Student Lab Worksheet \begin{align*}30\;\mathrm{min}\end{align*}
Day 3 \begin{align*}(45\;\mathrm{min})\end{align*} (optional) Discuss student results from the lab activity, and review concepts of unique properties at the nanoscale \begin{align*}30\;\mathrm{min}\end{align*}
Quiz: Unique Properties at the Nanoscale \begin{align*}15\;\mathrm{min}\end{align*}

Photocopies of Unique Properties at the Nanoscale: Student Quiz

Teacher Key for correcting Student Quiz

Unique Properties at the Nanoscale

The science behind nanotechnology

Are You a Nanobit Curious?

• What’s interesting about the nanoscale?
• Nanosized particles exhibit different properties than larger particles of the same substance
• As we study phenomena at this scale we...
• Develop new theories
• Discover new questions and answers in many areas, including health care, energy, and technology
• Figure out how to make new products and technologies that can improve people’s lives

Size-Dependent Properties

How do properties change at the nanoscale?

Properties of a Material

• A property describes how a material acts under certain conditions
• Types of properties
• Optical (e.g. color, transparency)
• Electrical (e.g. conductivity)
• Physical (e.g. hardness, melting point)
• Chemical (e.g. reactivity, reaction rates)
• Properties are usually measured by looking at large \begin{align*}(\sim 10^{23})\end{align*} aggregations of atoms or molecules

Optical Properties Example: Gold

• Bulk gold appears yellow in color
• Nanosized gold appears red in color
• The particles are so small that electrons are not free to move about as in bulk gold
• Because this movement is restricted, the particles react differently with light

Optical Properties Example: Zinc Oxide (ZnO)

• Large ZnO particles
• Block UV light
• Scatter visible light
• Appear white
• Nanosized ZnO particles
• Block UV light
• So small compared to the wavelength of visible light that they don’t scatter it
• Appear clear

Electrical Properties Example: Conductivity of Nanotubes

• Nanotubes are long, thin cylinders of carbon
• They are 100 times stronger than steel, very flexible, and have unique electrical properties
• Their electrical properties change with diameter, “twist”, and number of walls
• They can be either conducting or semi-conducting in their electrical behavior

Physical Properties Change: Melting Point of a Substance

• Melting Point (Microscopic Definition)
• Temperature at which the atoms, ions, or molecules in a substance have enough energy to overcome the intermolecular forces that hold the them in a “fixed” position in a solid
• Surface atoms require less energy to move because they are in contact with fewer atoms of the substance
Physical Properties Example: Melting Point of a Substance II
\begin{align*}{\color{blue}\mathrm{At\ the\ macroscale}}\end{align*} \begin{align*}{\color{blue}\mathrm{At\ the\ nanoscale}}\end{align*}
The majority of the atoms are...

...almost all on the inside of the object

...split between the inside and the surface of the object

Changing an object's size... ...has a very small effect on the percentage of atoms on the surface ...has a big effect on the percentage of atoms on the surface
The melting point... ...doesn’t depend on size ...is lower for smaller particles

Size-Dependent Properties

Why do properties change?

Scale Changes Everything

• There are enormous scale differences in our universe!
• At different scales
• Different forces dominate
• Different models better explain phenomena
• (See the Scale Diagram handout)

Scale Changes Everything II

• Four important ways in which nanoscale materials may differ from macroscale materials
• Gravitational forces become negligible and electromagnetic forces dominate
• Quantum mechanics is the model used to describe motion and energy instead of the classical mechanics model
• Greater surface area to volume ratios
• Random molecular motion becomes more important

Dominance of Electromagnetic Forces

• Because the mass of nanoscale objects is so small, gravity becomes negligible
• Gravitational force is a function of mass and distance and is weak between (low-mass) nanosized particles
• Electromagnetic force is a function of charge and distance is not affected by mass, so it can be very strong even when we have nanosized particles
• The electromagnetic force between two protons is \begin{align*}10^{36}\;\mathrm{times}\end{align*} stronger than the gravitational force!

Quantum Effects

• Classical mechanical models that we use to understand matter at the macroscale break down for...
• The very small (nanoscale)
• The very fast (near the speed of light)
• Quantum mechanics better describes phenomena that classical physics cannot, like...
• The colors of nanogold
• The probability (instead of certainty) of where an electron will be found

Surface Area to Volume Ratio Increases

• As surface area to volume ratio increases
• A greater amount of a substance comes in contact with surrounding material
• This results in better catalysts, since a greater proportion of the material is exposed for potential reaction

Random Molecular Motion is Significant

• Tiny particles (like dust) move about randomly
• At the macroscale, we barely see movement, or why it moves
• At the nanoscale, the particle is moving wildly, batted about by smaller particles
• Analogy
• Imagine a huge 10-meter balloon being batted about by the crowd in a stadium. From an airplane, you barely see movement or people hitting it; close up you see the balloon moving wildly.

What Does This All Mean?

• The following factors are key for understanding nanoscale-related properties
• Dominance of electromagnetic forces
• Importance of quantum mechanical models
• Higher surface area to volume ratio
• Random (Brownian) motion
• It is important to understand these four factors when researching new materials and properties

### Teacher Notes

Overview

This series of slides introduces and describes some of the differences in properties between nanoscale and macroscale (bulk) materials and the underlying causes of these differences.

Slide 1: Unique Properties at the Nanoscale

Explain that with the new scientific tools that operate on the nanoscale, we are finding out that many familiar materials act differently and have different characteristics and properties when we have very small (nanoscale) quantities of them. This presentation will discuss these size-dependent properties and why they change at the nanoscale.

Slide 2: Are You a Nanobit Curious?

This slide focuses on the differences in properties between nanoscale and macroscale materials. It is important to emphasize that not all nanoscale materials will exhibit different properties from their macroscale counterparts. The differences in properties depend on many things besides size, including arrangement of atoms and/or molecules in the particles, charge, and shape.

This slide also highlights why we should care about nanoscience: It will change our lives and change our understanding of matter. We are continually learning more and more about the properties of nanoscale particles, including how to manipulate them to suit our needs.

Slide 3: Size-Dependent Properties

The next few slides focus on how nanosized materials exhibit some size-dependent effects that are not observed in bulk materials.

Slide 4: Properties of a Material

This slide summarizes the content in the “What Does it Mean to Talk About the Characteristics and Properties of a Substance?” and “How Do We Know the Characteristics and Properties of Substances?” paragraphs in the student reading on sizedependent properties. It is important to talk with your students about how we know about the properties of materials––how are they measured and on what sized particles are the measurements made? In most cases, measurements are made on macroscale particles, so we tend to have good information on bulk properties of materials but not the properties of nanoscale materials (which may be different).

This slide also points out four types of properties that are often affected by size. This is not an exhaustive list but rather a list of important properties that usually come up when talking about nanoscience.

Slide 5: Optical Properties Example: Gold

The gold example is discussed in the reading and is included here to give a simple comparison between the nano and bulk properties of a particular material. This slide aligns with the “What’s Different at the Nanoscale” paragraph in the properties reading. It is important to point out to your students that we can’t say exactly what color a material will always be at a given particle size. This is because there are other factors involved like arrangement of atoms and molecules in the particles and charge(s) present on particles. However, it is possible to control for these various factors to create desired effects, as in this case the creation of “red” gold using \begin{align*}12\;\mathrm{nanometer}-\end{align*}sized particles.

Slide 6: Optical Properties Example: Zinc Oxide (ZnO)

This slide highlights another properties example that is in the reading. Here a comparison is made between large and nanosized zinc oxide particles––particles typically found in sunscreen. This is a good slide to use to discuss the electromagnetic spectrum, where ultraviolet rays are on the spectrum, and why we are so concerned about them. It can also be used to spark discussion about visible light and how it interacts with matter to allow us to see objects as having different colors and opacities. More detail on this topic is provided in the Nanosense Clear Sunscreen unit.

Slide 7: Electrical Properties Example: Conductivity of Nanotubes

This slide highlights another properties example that is not in the reading. Electrical properties of materials are based on the movement of electrons and the spaces, or “holes,” they leave behind. The electronic properties of a nanotube depend on the direction in which the sheet was rolled up. Some nanotubes are metals with high electrical conductivity, while others are semiconductors with relatively large band gaps. Which one it becomes depends on way that it is rolled (also called the "chirality" of the nanotube"). If it's rolled so that its hexagons line up straight along the tube's axis, the nanotube acts as a metal. If it's rolled on the diagonal, so the hexagons spiral along the axis, it acts as a semiconductor. See the “Unique Properties at the Nanoscale: Teacher Reading” for more information.

Slide 8: Physical Properties Change: Melting Point of a Substance

Note that even in a solid, the atoms are not really “fixed” in place but vibrating around a fixed point. In liquids, the atoms also rotate and move past each other in space (translational motion) though they don’t have enough energy to completely overcome the intermolecular forces and move apart as in a gas.

Slide 9: Physical Properties Example: Melting Point of a Substance II

At the nanoscale, a smaller object will have a significantly greater percentage of its atoms on the surface of the object. Since surface atoms need less energy to move (because they are in contact with fewer atoms of the substance), the total energy needed to overcome the intermolecular forces hold them “fixed” is less and thus the melting point is lower.

Slide 10: Size-Dependant Properties

The next few slides focus on why nanosized materials exhibit size-dependent effects that are not observed in bulk materials.

Slide 11: Scale Changes Everything

Ask your students to refer to the Scale Diagram handout. Use the diagram to point out how there are enormous scale differences in the universe (left part of the diagram), and where different forces dominate and different models better explain phenomena (right part of diagram). Scale differences are also explored in more detail in “Visualizing the Nanoscale: Student Reading” from lesson 2.

Slide 12: Scale Changes Everything II

This slide highlights four ways in which nanoscale materials may differ from their macroscale counterparts. It is important to emphasize that just because you have a small group of some type of particle, it does not necessarily mean that a whole new set of properties will arise. Whether or not different observable properties arise depends not only on aggregation, but also on the arrangement of the particles, how they are bonded together, etc. This slide sets up the next four slides, where each of the four points (gravity, quantum mechanics, surface area to volume ratio, random motion) is described in more detail.

Slide 13: Dominance of Electromagnetic Forces

This slide compares the relative strength between the electromagnetic and gravitational forces. The gravitational force between two electrons is feeble compared to the electromagnetic forces. The reason that you feel the force of gravity, even though it is so weak, is that every atom in the Earth is attracting every one of your atoms and there are a lot of atoms in both you and the Earth. The reason you aren't bounced around by electromagnetic forces is that you have almost the same number of positive charges as negative ones, so you are (essentially) electrically neutral. Gravity is only (as far as we know) attractive. Electromagnetic forces (which include electrical and magnetic forces) can be either attractive or repulsive. Attractive and repulsive forces cancel each other out; they neutralize each other. Since gravity has no repulsive force, there’s no weakening by neutralization. So even though gravity is much weaker than electrical force, gravitational forces always add to each other; they never cancel out.

Slide 14: Quantum Effects

This slide highlights why, at the nanoscale, we need to use quantum mechanics to describe behavior rather than classical mechanics. The properties reading describes the differences. You can decide how much discussion to have about classical and quantum mechanics with your students. For the purposes of this introductory unit, it is important to let students know that we use a different set of “rules” to describe particles that fall into the nanoscale and smaller range.

Slide 15: Surface Area to Volume Ratio Increases

This slide highlights the fact that as you decrease particle size, the amount of surface area increases. The three-part graphic on the slide illustrates how, for the same volume, you can increase surface area simply by cutting. Each of the three blocks has the same total volume, but the block that has the most cuts has a far greater amount of surfaces area. This is an important concept since it effects how well a material can interact with other things around it. With your students, you can use following example. Which will cool a glass of water faster: Two ice cubes, or the same two ice cubes (same volume of ice) that have been crushed?

Slide 16: Random Molecular Motion is Significant

This slide highlights the importance of random (“Brownian”) motion at small scales. Tiny particles, such as dust, are in a constant state of motion when seen through microscope because they are being batted about by collisions with small molecules. These small molecules are in constant random motion due to their kinetic energy, and they bounce the larger particle around. At the macroscale, random motion is much smaller than the size of the particle, but at the nanoscale this motion is large when compared to the size of the particle.

A nice animation that illustrates this concept is available at http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/brownian/brownian.html

Slide 17: What Does This All Mean?

This slide summarizes the key ideas in the properties reading: Understanding how electromagnetic forces, quantum models, surface area to volume ratio, and random motion influence properties of nanoscale materials helps us to better understand how to create materials with specific properties.

### Lab Activities: Teacher Instructions

Overview

There are three sets of curricular materials for this lab:

1. Unique Properties Lab Activities: Teacher Instructions. This document, which includes the purpose, safety precautions, and procedures for each lab station, and a complete list of materials for station. Occasionally, a suggestion is given for optional variations on the labs, under the heading “Teacher Notes.”
2. Unique Properties Lab Activities: Student Instructions. The set of directions for students is to be printed and posted at each of the appropriate lab stations. They include a statement of purpose, safety precautions, materials needed and procedures for the student to follow.
3. Unique Properties Lab Activities: Student Worksheet. Each student should be given this worksheet onto which they will record their observations. The worksheet also includes questions about each lab, designed to stimulate the student to think about how the lab demonstrates concepts fundamental to the mechanisms that make nanotechnology unique.

Each of the following labs is designed to demonstrate a specified aspect of nanotechnology without actually using nanoparticles. The lab is to be set up at multiple stations. Each student or group of students will conduct investigations at each station. You may choose to vary the way that students are assigned to lab stations without compromising the learning experience for the students, as long as they have an opportunity to share their thoughts and observations with each other. Note that Lab stations D through H are all on surface area to volume effects.

Post the appropriate Student Instructions at each station for students to follow. There needs to be running tap water and paper towels at each lab station. The instructions for each lab will specify if goggles are needed, as well as any other safety precautions. Each student should have their own lab sheet for recording their data and answering questions.

The lab stations are:

• Serial Dilution Lab
• Ferrofluid Display Cell Lab
• Bubbles Self-Assembly Lab
• Surface Area to Volume Effects... Which Shape Can Dissolve the Fastest?
• More Surface Effects... Faster Explosion?
• More Surface Effects... Is All Water the Same?
• Surface Area to Volume Effects... Burn Baby Burn!
• Surface Area to Volume Effects... Bet I Can Beat’cha!

A complete list of materials can be found on the last page of this set of teacher instructions.

Time Duration

Each lab should take approximately 8 minutes or less. It should take students no more than 50 minutes to complete all of the lab activities. Lab Stations D through G illustrate the concept of surface area to volume ratio effects, so if time is short, you may want to make some of those lab stations optional, use only a subset of these labs, or assign different stations to different groups of students.

Lab Station A

Serial Dilution Lab

Purpose

The purpose of this lab is to investigate the effects of decreasing the concentration of a solution on the two properties of color and odor. Nanosized materials, (from 1 to 100 nm), often appear to have different colors and scents than they do at larger sizes.

Safety Precautions

• Wear goggles while conducting this lab.
• Do not eat or drink anything while in the lab.

Materials

Reagents

A stock solution “assigned” the value of 1.0 Molar. You can use unsweetened, scented Kool-Aid to make the solution. Prepare as directed on the package, and then dilute with twice as much water as the directions indicate. Alternately, you may use \begin{align*}1\end{align*} drop of food coloring per liter of water, and add an ester of your choice to this mixture. You may have to experiment to ensure that with a 5-part serial dilution, the odor and color change enough from one test tube to another for students to notice.

Materials

• A 1.0 M colored stock solution
• Five test tubes that can hold 10 mL each
• One 25 mL graduated cylinder
• A test tube holder
• Grease marker
• Tap water
• One 1.0 mL graduated pipette, plastic or glass
• A sheet of white paper for background, to help students to judge color

Procedures

Concentration

1. Label each of your test tubes from 1 to 5..
2. Use a pipette to place 10.0 mL of 1.0 Molar of colored solution into test tube #1.
3. Remove \begin{align*}1.0\;\mathrm{mL}\end{align*} from test tube #1 and inject this into test tube #2. Then add \begin{align*}9.0\;\mathrm{mL}\end{align*} of water into test tube #2.
4. Remove \begin{align*}1.0\;\mathrm{mL}\end{align*} from test tube #2 and inject this into test tube #3. Then add \begin{align*}9.0\;\mathrm{mL}\end{align*} of water into test tube #3.
5. Continue in this fashion until you have completed test tube #5.
6. Note that each subsequent test tube has the concentration of the previous test tube divided by \begin{align*}10\end{align*}.
7. On your lab sheet, record the concentration of the solution in each test tube.

Color

1. Hold the white paper behind your test tubes to determine the color change.

2. Use test tube #1 as the strongest color.

3. Continue from test tube #2 to #5 using the gauge below.

4. Record on your lab sheet the strength of each test tube according to the scale above. At what strength are you no longer able to detect color? Explain why this has happened.

Odor

1. Waft, with your hand, the air over the top of the test tube towards your nose. Sniff. Record the strength of odor according to the scale below on you lab worksheet.

2. Use test tube #1 as the strongest odor.

3. Continue with test tube #2 to #5 in the same manner.

4. Record on your lab sheet the concentration at which the odor of your solution is no longer detectable. Record other observations and questions as asked on the lab sheet. Explain why you think this happened.

Teacher Notes

If you have a spect-20 spectrophotometer available, you may use this to measure the absorption of each of the five solutions.

Lab Station B

Ferrofluid Display Cell Lab

Purpose

The purpose of this lab is to design a series of activities that investigate and compare the force of magnetism in ferrofluid (small pieces of iron suspended in fluid) and in a solid piece of iron.

Safety Precautions

• Do not shake or open the bottle of ferrofluid!
• Use care when handling glass.

Materials

• One capped bottle of ferrofluid (nanosized iron particles suspended in a solution). A Ferrofluid Preform Display Cell can be obtained for \begin{align*}\30\end{align*} plus tax and shipping from: http://www.teachersource.com/catalog/ (Search for item “FF-200”)
• A plastic \begin{align*}100\;\mathrm{mL}-\end{align*}graduated cylinder
• A large empty test tube and stopper
• A piece of iron (a slug or rod), about \begin{align*}1-\mathrm{inch}\end{align*} in length. This can be purchased from a chemical supply house. You may replace a slug of iron with an iron nail or washer, available from a hardware store. Note: Most nails are steel rather than iron.
• Two circle magnets. These magnets come with the ferrofluid display cell. You may add other magnets to provide variety for students.

Procedures

1. Make observations and record your observations of the ferrofluid and the iron object separately.
2. Predict how the magnet will influence the ferrofluid and the iron object.
3. Use the magnets to observe how the force of magnetism influences the ferrofluid and the iron object.

Teacher Notes

You may also check out other ferrofluid products if you are interested. There is an entire kit designed for a variety of experiments using ferrofluid and an experiment booklet you can purchase separately.

Lab Station C

Bubbles Self-Assembly Lab

Purpose

One of the methods proposed to mass manufacture nanosized objects is to use nature’s own natural tendency to self-assemble objects. Fluid or flexible objects will automatically fill the space of the container, taking the most efficient shape. The purpose of this lab is to demonstrate how bubbles self-assemble.

Safety Precautions

• Do not eat or drink anything in lab.
• Use caution when handling glassware.

Materials

• A bubble solution [Bubble Formula: Dawn Ultra or Joy Ultra/ Water (Distilled Water Works Best)/Glycerine or White Karo Syrup (Optional) 1 Part/10 Parts/.25 Parts]
• Small shallow dish
• Toothpicks
• Paper towels
• Straw (coffee stirrers work best)

Procedures

1. Stir the solution with the straw to create bubbles, as needed.
2. Pour about \begin{align*}10.0\;\mathrm{mL}\end{align*} of bubble solution into the shallow dish.
3. Caution: Be careful not to spill the solution or to drop the dish!
4. Draw what you see in your worksheet. This is your “before” diagram.
5. Take the toothpick and pop one of the bubbles. Notice how the arrangement of bubbles changed. Draw what has happened. This is your “after” diagram. Repeat this procedure several times (you do not need to illustrate after the first “before” and “after” observations).

Lab Stations D through G

Surface Area to Volume Effects

Overview

One of the characteristics of nanosized objects is that the surface area to volume ratio is much greater than bulk sized objects. The purpose of lab investigations D through H is to offer a variety of opportunities for students to compare the effects of varying the surface area to volume ratio on the rate of dissolving (Lab D), the rate of bubble formation (Lab E), the time required to boil the same amount of water (Lab F) and the rate of burning (Lab G).

Lab Station D

Surface Area to Volume Effects... Which Shape Can Dissolve the Fastest?

Purpose

One of the characteristics of nanosized objects is that the surface area to volume ratio is much greater than bulk sized objects. The purpose of this lab investigation is to compare the effects of varying the surface area to the volume ratio for two samples of the same substance and mass, but different particle size, on the rate of dissolving in water.

Safety Precautions

• Do not eat or drink anything in lab.
• Use caution when handling glassware.
• Wear safety goggles.

Materials

• Two sugar cubes per group
• Granulated sugar, about a cup per class
• A digital balance or scale, with readout to \begin{align*}0.1\;\mathrm{gram.}\end{align*} A standard laboratory balance can be used instead.
• Two \begin{align*}250-\mathrm{mL}\end{align*} Erlenmeyer flasks
• A \begin{align*}100-\mathrm{mL}\end{align*} graduated cylinder
• A grease marker
• Tap water, about \begin{align*}50-\mathrm{mL}\end{align*}
• A clock or watch with a second hand

Procedures

1. Using a grease marker, label one Erlenmeyer flask #1 and the other :2. (These may have already been marked. No need to mark twice.)
2. Set the scale to zero, after placing a square of paper on top of the scale (this is called “taring”).
3. Measure and record the mass of two cubes of sugar. Put the sugar cubes into flask #1.
4. Measure and record a mass of granulated sugar equal to the mass of the two sugar cubes.
5. Put the granulated sugar into flask #2.
6. Using your graduated cylinder, add \begin{align*}100.0\;\mathrm{mL}\end{align*} of tap water to each flask.
7. Gently swirl each flask exactly \begin{align*}60\;\mathrm{seconds.}\end{align*}
8. Record the relative amount of sugar that has dissolved in each flask on your lab sheet.
9. Swirl each flask for another \begin{align*}60 \;\mathrm{seconds}\end{align*}.

Teacher Notes

You may vary this lab by:

• Using salt rather than sugar. Salt comes in chunky crystals in rock salt and regular granulated salt.
• Varying the types of sugar to also include superfine and/or powdered sugar.

If you use any additional substances or variations in concentration, you will have to adjust the directions and the materials needed accordingly.

Lab Station E

More Surface Effects... Faster Explosion?

Purpose

The purpose of the following activities is to give you more experience with examining the effects of changing surface area to volume ratios. Faster explosion looks at the effect of different surface area to volume ratios on the speed of reaction.

Safety Precautions

• Do not eat or drink anything in the lab.

Materials

• Two empty film canisters and their lids (clear canisters work better than black)
• One tablet of Alka Seltzer® per group
• One small mortar and pestle
• Clock or watch with a second hand

Procedures

1. Break the Alka Seltzer® tablet in half as exactly as you can.
2. Put one of the halves of the Alka Seltzer® tablet into the mortar and crush it with the pestle until it is finely granulated.
3. Place the uncrushed Alka Seltzer® and the crushed Alka Seltzer® each into a different film canister. Each canister should contain Alka Seltzer® before you proceed to the next step.
4. Simultaneously fill each film canister halfway with tap water. Quickly put their lids on.
5. On your lab sheet, record how much time it takes for each canister to blow its lid off.
6. Rinse the film canisters with water when finished.

Lab Station F

More Surface Effects... Is All Water the Same?

Purpose

The purpose of the following activities is to provide students with more experience at examining the effects of changing surface area to volume ratios. This lab investigates different surface areas for the same volume of water on the speed of boiling.

Safety Precautions

• Wear safety goggles while conducting this investigation.
• Be careful when handling glass.
• Use extra caution when trying to move hot glassware. Either handle with tongs or wait until glassware is fully cooled.
• Be certain to turn off heat source when you have completed this investigation.

Materials

• Three very different size beakers or flasks. The goal is to get as different as possible surface area among the beakers.
• Hot plate(s) with enough surface area to accommodate the three beakers/flasks, or 3 Bunsen burners
• One \begin{align*}100\;\mathrm{mL}\end{align*} graduated cyclinder
• A centimeter ruler long enough to measure the diameter of the widest opening of the set of beakers/flasks
• Tongs designed to use with glassware
• Clock or watch

Procedures

1. Fill in the chart on your lab sheet with the size and type of beaker or flask.
2. Fill each of the beakers with \begin{align*}100.0\;\mathrm{mL}\end{align*} of tap water.
3. Measure the diameter of each of your beakers and record to the nearest mm. For the Erlenmeyer flask, if you are using one, measure the diameter of the water when it is in the flask.
4. Turn on hotplate(s) or Bunsen burners to an equal flame or setting (if using more than one hotplate) at the same time. Record the start time on your lab sheet.
5. Record the time that the water begins to boil in each of the beakers/flasks. Record this time in the appropriate column on your lab sheet in the table provided.
6. Fill out the rest of the lab worksheet for this investigation.

Teacher Notes

Students may think that the temperature at which water boils will vary in each of the containers. To avoid this mistaken assumption, you may want to have the students at this lab station measure the temperature in each of the containers at the beginning of boiling. Students should measure the temperature of the water by putting the temperature in the middle of the mass of water, not on the bottom of the beaker or flask.

Lab Station G

Surface Area to Volume Effects... Burn Baby Burn!

Purpose

These activities are for the purpose of demonstrating the effects of an increased surface area to volume ratio on the rate of combustion (burning).

Safety Precautions

• Do not pick up any hot items with your fingers or with paper towels. Let cool first.
• Wear safety goggles.
• Tie back any long hair.

Materials

• One solid rod of steel, about \begin{align*}2-\mathrm{inches}\end{align*} or a steel nail (any size) or steel washer about \begin{align*}11/2\;\mathrm{inches}\end{align*}. These may be purchased at the hardware store.
• Two sets of tongs
• Two Bunsen burners and starters
• A \begin{align*}2-\mathrm{inch}\end{align*} section of steel wool, fine or very fine grade, per group. This can be purchased in a hardware store or ordered online from http://www.briwaxwoodcare.com/stelwool.htm

Procedures

1. Light the two Bunsen burners to the same level of flame.
2. Pick up the steel rod or nail with the tongs and heat in the hottest part of the flame for \begin{align*}2 \;\mathrm{minutes}\end{align*}, then remove from flame and let cool. Record your observations on your lab sheet.
3. Pick up the section of steel wool with the tongs and place in the hottest part of the flame for \begin{align*}2 \;\mathrm{minutes}\end{align*}, then remove from flame and let cool. Record your observations on your lab sheet.
4. Once the objects are cooled, deposit any waste into the trash.

Lab Station H

Surface Area to Volume Effects... Bet I Can Beat’cha!

Purpose

The purpose of this lab activity is to demonstrate the effect of varying surface area to volume ratios of the same materials on the rate of reaction.

Safety Precautions

• Wear goggles during this lab investigation.
• Don’t eat or drink anything at your lab station.
• Deposit chemical waste according to the instructions of your teacher. Do not flush solution into the drain.
• Use caution when handling glassware.

Reagent

• One teaspoon \begin{align*}CuCl_2 \bullet 2H_2 O\end{align*} crystals, per group

Materials

• One teaspoon
• One glass stirring rod
• Two \begin{align*}100\;\mathrm{mL}\end{align*} beakers
• Two squares, \begin{align*}2\;\mathrm{inches} \times 2\;\mathrm{inches}\end{align*}, of aluminum foil
• A pair of tongs
• Paper towels and a solid waste disposal
• A clock or watch with a second hand display

Procedures

1. Fill each of the \begin{align*}100\;\mathrm{mL}\end{align*} beakers about half full with tap water.
2. Add 1 teaspoon of \begin{align*}CuCl_2 \bullet 2H_2 O\end{align*} crystals to each of the beakers of tap water and mix well with the stirring rod.
3. Form 1 piece of aluminum foil into a loose ball; leave the other piece as is.
4. Put each of the aluminum foil pieces into their own beaker.
5. On your lab sheet, record the time that it takes for each reaction to be complete.
6. Dispose of solution and waste according to your teacher’s instructions.

Teacher Notes

\begin{align*}Cu^{2+}\end{align*} is a heavy metal and must be disposed of properly according to local and state regulations.

Materials List for All Lab Stations

Lab Station A: Serial Dilution Lab

• A stock solution “assigned” the value of \begin{align*}1.0\;\mathrm{Molar.}\end{align*} You can use unsweetened, scented Kool-Aid. Prepare as directed on the package, and then dilute with twice as much water as the directions indicate. Alternately, you may use 1 drop of food coloring per liter of water, and add an ester of your choice to this mixture. You may have to experiment to make certain that with a 5-part serial dilution the odor and color change significantly enough from one test tube to another for students to notice.
• Five test tubes that can hold \begin{align*}10-\mathrm{mL}\end{align*} each
• One \begin{align*}25-\mathrm{mL}\end{align*} graduated cylinder
• A test tube holder
• Grease marker
• Tap water
• One \begin{align*}1.0-\mathrm{mL}\end{align*} graduated pipette, plastic or glass
• A sheet of white paper for background to help students to judge color

Lab Station B: Ferrofluid Display Cell Lab

• A plastic \begin{align*}100\;\mathrm{mL}\end{align*}-graduated cylinder
• A large empty test tube and stopper
• A piece of iron (a slug or rod), about \begin{align*}1-\mathrm{inch}\end{align*} in length. This can be purchased from a chemical supply house. You may replace a slug of iron with an iron nail or washer, available from a hardware store. Note: Most nails are steel rather than iron.
• Two circle magnets. These magnets come with the ferrofluid display tube. You may add other magnets to provide variety for students.
• One capped bottle of ferrofluid (nanosized iron particles suspended in a solution). A Ferrofluid Preform Display Cell can be obtained for \begin{align*}\ 30\end{align*} plus tax and shipping from: http://www.teachersource.com/catalog/ (Search for item “FF-200”)

You can also check out other ferrofluid products if you are interested. There is an entire kit designed for a variety of experiments using ferrofluid and an experiment booklet you can purchase separately.

Lab Station C: Bubbles Self-Assembly Lab

• A bubble solution [Bubble Formula: Dawn Ultra or Joy Ultra/ Water (Distilled Water Works Best)/Glycerine or White Karo Syrup (Optional) 1 Part/10 Parts/.25 Parts]
• Small shallow dish
• Toothpicks
• Paper towels
• Straw (coffee stirrers work best)

Note: Lab stations D through H are all on surface area to volume effects.

Lab Station D: Which Shape Can Dissolve the Fastest?

• Two sugar cubes per group
• Granulated sugar, about a cup per class
• A digital balance or scale, with readout to \begin{align*}0.1\;\mathrm{gram}\end{align*}. A standard laboratory balance can be used instead.
• Two \begin{align*}250-\mathrm{mL}\end{align*} Erlenmeyer flasks
• A \begin{align*}100-\mathrm{mL}\end{align*} graduated cylinder
• A grease marker
• Tap water, about \begin{align*}50-\mathrm{mL}\end{align*}
• A clock or watch with a second hand

Lab Station E: Faster Explosion?

• Two empty film canisters and their lids
• One tablet of Alka Seltzer® per group
• One small mortar and pestle
• Clock or watch with a second hand

Lab Station F: Is All Water the Same?

• Three very different size beakers or flasks. The goal is to get as different as possible surface area among the beakers.
• Hot plate(s) with enough surface area to accommodate the three beakers/flasks, or 3 Bunsen burners
• One \begin{align*}100\;\mathrm{mL}\end{align*} graduated cyclinder
• A centimeter ruler long enough to measure the diameter of the widest opening of the set of beakers/flasks
• Tongs designed to use with glassware
• Clock or watch

Lab Station G: Burn Baby Burn!

• One solid rod of steel, about \begin{align*}2-\mathrm{inches}\end{align*} or a steel nail (any size) or steel washer about \begin{align*}11/2\;\mathrm{inches}\end{align*}. These may be purchased at the hardware store.
• Two sets of tongs
• Two Bunsen burners and starters
• A \begin{align*}2-\mathrm{inch}\end{align*} section of steel wool, fine or very fine grade, per group. This can be purchased in a hardware store or ordered online from http://www.briwaxwoodcare.com/stelwool.htm

Lab Station H: Bet I Can Beat’Cha!

• Copper(II) chloride dihydrate crystals \begin{align*}(CuCl_2 \bullet 2H_2 O)\end{align*}. Order from any chemical supply house.
• A plastic teaspoon that can be used for measuring the crystals
• One glass-stirring rod. [If a stirring rod is unavailable, the teaspoon may be used to stir. Caution: Once the teaspoon has been used to stir the solution, it cannot be used again for measuring out the crystals.
• Two \begin{align*}100-\mathrm{mL}\end{align*} beakers
• Two squares, \begin{align*}2\;\mathrm{inches} \times 2\;\mathrm{inches},\end{align*} of aluminum foil
• A pair of tongs
• Paper towels and a solid waste disposal
• A clock or watch with a second hand display

Optical Properties

The optical properties of a material result from the interaction of light with the composition and atomic structure of the material. Color, luster, and fluorescence are examples of well-known optical properties. At the nanoscale, some interesting optical properties emerge. Gold nanoparticles are one interesting example, and zinc oxide is another. These substances exhibit different properties as bulk samples compared to nanosized samples, as shown in Table 1, below.

Optical properties of gold and zinc oxide for bulk and nano samples
Substance Macro, or Bulk Sample Nanoparticle Sample
Gold “Gold” in color “Red” in color
Zinc Oxide \begin{align*}(ZnO)\end{align*} “White” in color “Clear” in color

What is happening as you go from macro to nano? What underlying principles governing the color changes between a bulk sample or a nano sample for the above two materials?

First, let’s consider zinc oxide. Because zinc oxide absorbs ultraviolet light, it can be used in lotions to protect against sunburn. Traditional zinc oxide sunscreen is white in color––you may have used this yourself or seen it on the noses of life guards and swimmer. "Bulk" \begin{align*}ZnO\end{align*} is white in color (e.g. lifeguard nose), but nano \begin{align*}ZnO\end{align*} is clear. Why is this? The nano \begin{align*}ZnO\end{align*} particles don’t scatter visible light and they also absorb UV rays. Larger particles (greater than \begin{align*}10^{-7}\;\mathrm{meters}\end{align*} in diameter) tend to scatter visible light but still absorb UV rays.

In the case of gold, the explanation is a bit more complicated, although the process of making gold nanoparticles is centuries old. Long ago, artisans that made stained glass experimented with adding a wide variety of metals and metal salts to their molten glass in order to get the glass to take on certain colors. They discovered that if they mixed fine particles of gold in, the result was a beautiful ruby color. Now these artisans did not know (or really care) exactly why this happened, but it does seem curious that gold, a yellow substance, should “stain” glass red. It was not until very recently that the mechanism behind this effect became fully understood.

When light is shone on a piece of metal, the photons kick the electrons in the metal around a bit. In an ordinary chunk of metal, electrons are free to move more or less randomly throughout the metal's crystal structure. However, if you have a very thin film of metal lying upon an insulator (such as glass), the electrons are confined to that thin region. When the light is shone upon them, rather than being free to be bumped around randomly, the electrons will move in a coherent wave.

These coherent waves of electrons are called "surface plasmons." The size of these waves of electrons depends primarily upon the thickness of the film. If an incoming photon has just the right wavelength, its energy will be completely absorbed by the metal, and turned into a surface plasmon. We call this surface plasmon resonance, meaning the incoming photon resonates with the kind of electron waves the film is apt to produce. Photons that do not resonate with the metal film will be reflected back.

The result is that when you shine white light (which consists of photons of many wavelengths) upon such a metal film, the film selectively absorbs photons at a certain small range of wavelengths. What we see reflected back then is the white light with a particular color "subtracted" from it. For example, if you subtract the red photons from white light, the light that is left will look cyan.

The gold nanoparticle story is basically a case of the larger surface area/volume ratio. If the gold has too much interior volume, the effect wouldn't happen; the surface plasmons only occur at interfaces between conductors and nonconductors, and if there's a bunch of "non-interface" (interior) conductors, the effect basically dissipates. So, since the nanoparticles are pretty much all surface you get the Surface Plasmon Resonance (SPR) effect.

While the stained glass makers only had one technique for creating one particular kind of gold nanoparticles, modern scientists and engineers can create an infinite variety of them. Now that the mechanism is understood, researchers have worked to create nanoparticles that are “tuned” to particular frequencies. They can tune the particle by varying its shape, size, and the thickness of the gold film. A recent application of this technology is in cancer treatment. Doctors can embed gold nanoparticles that are tuned to absorb infrared light in cancer cells. Then, the doctor shines infrared light upon the tissue. As the nanoparticles absorb the infrared light, they heat up. Eventually they heat up enough to destroy the cancerous cells.

Electrical Properties

Electrical properties of materials are based on the movement of electrons and the spaces, or “holes,” they leave behind. These properties are based on the chemical and physical structure of the material. It turns out that structures at the nanoscale have been found to have some interesting electrical properties. There is a plethora of research involving electrical conductivity and carbon nanotubes, in particular.

A nanotube can be though of as single or multiple sheets of graphite that have been rolled up into a tube, as shown in Figure 1, below.

A plane of graphite (left) rolled up (middle) gives you a nanotube (right), matching points A with A', B with B' and so forth [1].

The electronic properties of the resulting nanotube depend on the direction in which the sheet was rolled up. Some nanotubes are metals with high electrical conductivity, while others are semiconductors with relatively large band gaps. Which one it becomes depends on way that it is rolled (also called the "chirality" of the nanotube"). If it's rolled so that its hexagons line up straight along the tube's axis, the nanotube acts as a metal. If it's rolled on the diagonal, so the hexagons spiral along the axis, it acts as a semiconductor.

Why is this? As shown above, the wall of a nanotube is similar to graphite in structure. Graphite has one of the four valence electrons delocalized, and therefore can be shared between adjacent carbons. However, it turns out that a single sheet of graphite (also known as graphene) is an electronic hybrid: although not an insulator, it is not a semiconductor or a metal either. Graphene is a "semimetal" or a "zero-gap" semiconductor. When rolled into a carbon nanotube, it becomes either a true metal or a semiconductor, depending on how it is rolled. Shape and geometry make all the difference: diamond, yet another allotrope of carbon that has a 3D tetrahedral structure, is an insulator.

Experiments have been conducted on single walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) to discover whether electric conductance within them is ballistic or diffuse. In a ballistic conductor, all the electrons going into one end come out of the other end without scattering, regardless of how far they have to travel. In a diffuse conductor, some of the electrons are scattered before they get a chance to exit. Experiments suggest that SWCNTs are diffusive, and MWCNTs are ballistic. If adjacent carbon layers in MWCNTs interacted as in graphite, electrons would not be confined to one layer, but research suggests that the current mainly flows through the outermost layer.

One area that is being explored is the possibility of carbon nanotubes being superconductors near room temperature. Superconductors are ballistic conductors that also exhibit a resistance of zero, which means enormous current flow at tiny voltages. At present, we only know of superconductors that work at extremely cold temperatures, below about \begin{align*}130 \;\mathrm{K}\end{align*}(Kelvin; \begin{align*}-143^\circ C\end{align*}). Why is superconductivity near room temperature such a big deal? If a material could carry current with no resistance at room temperature, no energy would be lost as heat. This could lead to faster, lower-power electronics, and the ability to carry electricity long distances with \begin{align*}100\end{align*} per cent efficiency. Although there is no conclusive evidence that nanotubes can be superconductors near room temperature, there are some promising indicators. For example, when the researchers put a magnetic field across a bundle of MWCNT at temperatures up to \begin{align*}400 \;\mathrm{K}\ (127^\circ C)\end{align*}, the bundle generated its own weak, opposing magnetic field. Such a reaction can be a sign of superconductivity. When the MWCNTs cooled off and the magnetic field was turned off, they stayed magnetized. This could be a result of a lingering current within the tubes because there is little resistance to make it fade away––another sign of a superconductor.

Electrical conductivity within carbon nanotubes remains a mystery. There are many theories and models that attempt to predict and describe the electrical conductance of these structures, but they fall short of satisfactory explanations, and in fact, sometimes contradict one another. Research continues in this area.

Carbon nanotubes aren’t the only nanoscale structure to exhibit unique electrical properties. For example, if extra electrons are added to buckyballs, they can turn into superconductors. DNA may be used in the future as electrical conductors. Quantum dots have great potential to behave as very small semiconductors, as the electronic structure can be tunable to produce a predictable band gap. Miniature laboratories on a computer chip could employ nanoelectrodes for testing conductance.

Mechanical Properties

Mechanical properties are related to the physical structure of a material. Strength and flexibility are examples of well-known mechanical properties. At the nanoscale, carbon nanotubes have particularly interesting mechanical properties. We will focus on nanotubes here, to illustrate how a nanoscale material can exhibit different properties than their bulk counterparts or other forms of carbon that you are familiar with, like graphite and diamond.

As mentioned in the section on electrical properties, a nanotube is similar to graphite in structure. A nanotube can be thought of as single or multiple sheets of graphite that have been rolled up into a tube. In a sheet of graphite, each carbon atom is strongly bonded to three other atoms, which makes graphite very strong in certain directions. However, adjacent sheets are only weakly bound by van der Waals forces, so layers of graphite can be slide over one another or be peeled apart, as happens when writing with a pencil. The diagram below shows how in graphite, carbon atoms in adjacent layers do not line up and are only weakly held together.

Layered lattice structure of graphite, with widely separated planes that are only weakly held together by weak van der Waals forces [2].

In contrast, it’s not easy to peel a carbon layer from a multiwall nanotube. Nanotubes are very strong––one of the strongest materials we know of. They’re many times stronger than steel, yet lighter. They are also more resistant to damage; that is, they are highly elastic. Nanotubes can be bent to surprisingly large angles before they start to ripple, buckle, or break. Even severe distortions won’t break them (see below).

A severely distorted nanotube still doesn’t break [3].

Why are nanotubes so strong? We know that each carbon atom within a single sheet of graphite is connected by a strong chemical bond to three neighboring carbon atoms. Why does rolling this strong graphite lattice make an even stronger structure? Because of the resulting geometry: Cylinders are one the strongest known structural shapes because compared to other geometries, stress on the perimeter is more easily distributed throughout the structure. Diamond––a 3D tetrahedral structure where each carbon atom forms \begin{align*}4\end{align*} bonds––is the strongest material known because of its full covalent bonding. But compared to nanotubes, diamonds have less interesting properties (e.g., they are insulators, they are not elastic, they are denser, and they are very expensive). And some researchers suggest that carbon nanotubes with tiny diameters can approach the strength of diamonds!

In diamond, each carbon atom forms bonds, tetrahedrally arranged, to other carbon atoms, resulting in a very strongly bonded 3D structure. Very small diameter carbon nanotubes could be as strong as diamond. [4]

Just how strong are nanotubes relative to other materials? Young's Modulus (Y) is one measure of how stiff, or elastic, a material is. The higher this value is, the less it deforms when a force is applied. Another measure, tensile strength, describes the maximum force that can be applied per unit area before the material snaps or breaks. A third interesting measure of a material is the density, which gives you an idea of how light the material is. Table 2, below, shows the Young’s Modulus, tensile strength, and density of nanotubes compared to other common materials. (GPa stands for gigapascals.) For example, wood is very light (low density) but weak (low Young’s Modulus and low tensile strength), while nanotubes are many times stronger than steel (nanotubes have a higher Young’s Modulus and much higher tensile strength) and yet much lighter (lower density). Nanotubes also have higher tensile strength even than diamond and a similar (slightly lower) elasticity, and yet they are half as dense.

Comparison of mechanical properties of various materials.
Material Young’s Modulus (GPa) Tensile Strength (GPa) Density (g/cm3)
Single wall nanotube \begin{align*}\sim 800\end{align*} \begin{align*}>30\end{align*} \begin{align*}1.8\end{align*}
Multi wall nanotube \begin{align*}\sim 800\end{align*} \begin{align*}>30\end{align*} \begin{align*}2.6\end{align*}
Diamond \begin{align*}1140\end{align*} \begin{align*}>20\end{align*} \begin{align*}3.52\end{align*}
Graphite \begin{align*}8\end{align*} \begin{align*}0.2\end{align*} \begin{align*}2.25\end{align*}
Steel \begin{align*}208\end{align*} \begin{align*}0.4\end{align*} \begin{align*}7.8\end{align*}
Wood \begin{align*}16\end{align*} \begin{align*}0.008\end{align*} \begin{align*}0.6\end{align*}

How do researchers measure the stiffness or elasticity of nanotubes? One way is to arrange nantobues like trees on a surface so that they are fixed at the bottom, and then measure the amplitude of the thermal vibrations of the free ends. Another way is to deposit them on a material that has tiny pores (holes) about \begin{align*}200\;\mathrm{nm}\end{align*} wide. Occasionally a nanotube will span a pore by chance, like a bridge over a valley. They will then apply an AFM tip to the nanotube to see how much load or force it can take before breaking.

A carbon nanotube on a porous ceramic membrane, ready for mechanical measurements by AFM [5].

What are the implications of such strength? Think of what happened when the materials used for tennis rackets and golf clubs changed from wood to steel, then to composites of carbon––light but strong carbon fibers mixed into another material. The result was lighter, more powerful equipment. Carbon fiber is also used in airplanes to make them stronger and lighter. Carbon nanotubes are \begin{align*}10,000 \;\mathrm{times}\end{align*} thinner than commercial carbon fiber, and much stronger. Adding nanotubes to material used for airplanes or cars, for example, would make them even stronger yet lighter, so less fuel would be needed to move them, reducing operating costs. They could also be used to earthquake-proof homes and bridges. The exceptional strength of nanotubes makes them also attractive as tips for scanning probe microscopes. They might even be used to link Earth to geostationary orbiting space platforms in the form of a space elevator.

In summary, the special properties of carbon nanotubes mean that they could be the ultimate high-strength fiber. The impacts of light and strong structural materials would be enormous.

(Accessed August 2005.)

Optical properties

Electrical properties

Mechanical properties

### Quiz: Teacher Key

For questions 1-4, choose which force best matches the statement. (1 point each)

a. gravitational force

b. electromagnetic forces

__a__ 1. Describe(s) the attraction of the masses of two particles to each other.

__b__ 2. Dominate(s) for nanosized objects.

__b__ 3. Do/does not vary with mass.

__a__ 4. Stronger for objects with greater mass.

5. Identify a property that doesn’t have meaning when you only have a few nanosized particles, and explain why. (2 points)

Possible answers include boiling point, melting point, vapor pressure. There aren’t enough particles for the property to emerge.

6. Compare the surface-to-volume ratios of a large piece of gold with a nanosized piece of gold. (1 point)

The surface-to-volume ratio for the nanosized piece of gold would be much higher than that for a large piece.

7. Explain in your own words why surface-to-volume ratios are important in determining the properties of a substance. You may use a drawing or example to help clarify your explanation. (3 points)

When surface-to-volume ratio is low, more particles are in the interior of the substance and subject to similar forces. When it is high, more particles experience forces from the substance as well as from the surrounding material. The effect of this can be seen in a drop of water. The adhesive force of the surface can exceed the attraction of the water molecules to each other and cause the drop to flatten out. Reaction rates also increase as surface-to-volume ration increases, since a greater percentage of the particles are on the surface, which means more particles are immediately available to react. (the collision rate of the reacting molecules increases).

8. Name and explain three properties that are likely to change as when an object is nanosized. You may give examples to help clarify your explanation. (3 points)

Answers may include: optical properties (such as color and transparency), electrical properties (such as conductivity), physical properties (such as density and boiling point) and chemical properties (such as reactivities and reaction rates).

9. Explain the concept of electron tunneling and address why this may be a problem for nanosized objects. (2 points)

Electrons can jump across small gaps. This could cause defects in nanoscale structures.

## Tools of the Nanosciences

### Teacher Lesson Plan

Contents

• Tools of the Nanosciences: Teacher Lesson Plan
• Scanning Probe Microscopy: Teacher Reading
• Scanning Probe Microscopy: PowerPoint with Teacher Notes
• Black Box Activity: Teacher Instructions & Key
• Seeing and Building Small Things Quiz: Teacher Key
• Optional Extensions for Exploring Nanoscale Modeling Tools: Teacher Notes

Orientation

This lesson focuses on two of the most widely used new probe imaging tools: the Atomic Force Microscope (AFM) and the Scanning Probe Microscope (SPM).

• The Scanning Probe Microscopy PowerPoint explains how these two tools work, the difference between them, and what you can see and build with them.
• The Student Reading on Seeing and Building Small Things provides more details on scanning probe tools and describes self-assembly as another way to build things.
• The Black Box Activity gives students the opportunity to use probes to “see” the unknown surface of a mystery box and consider firsthand the challenges of using probes.
• The Seeing and Building Small Things Quiz tests students knowledge of scanning probes and self-assembly.

You may want to extend this lesson beyond one day to incorporate building a model of an AFM. Two different strategies are suggested in the Optional Extensions for Exploring Nanoscale Modeling Tools: Teacher Notes.

Essential Questions (EQ)

What essential questions will guide this unit and focus teaching and learning?

(Numbers correspond to learning goals overview document)

4. How do we see and move things that are very small?

5. Why do our scientific models change over time?

Enduring Understandings (EU)

Students will understand:

(Numbers correspond to learning goals overview document)

4. New tools for seeing and manipulating increase our ability to investigate and innovate.

Key Knowledge and Skills (KKS)

Students will be able to:

(Numbers correspond to learning goals overview document)

5. Explain how an AFM and a STM work, and give an example of their use.

Prerequisite Knowledge and Skills

• Familiarity with atoms and molecules.

Related Standards

• NSES Science and Technology: 12EST2.1, 12EST2.2
• NSES Science as Inquiry: 12ASI2.3
• AAAS Benchmarks: 11D Scale #1, 11D Scale #2
Day Activity Time Materials
Prior to this lesson Homework: Student reading: Seeing and Building Small Things \begin{align*}30 \;\mathrm{min}\end{align*} Photocopies of student reading
Teacher Resource: Scanning Probe Microscopy: Teacher Reading \begin{align*}30 \;\mathrm{min}\end{align*} One copy for the teacher
Day 1 \begin{align*}(50 \;\mathrm{min})\end{align*}

Show the Scanning Probe Microscopy: PowerPoint Slides, using teacher’s notes as talking points.

Highlight the AFM and STM, and the relationship between new tools and the ability to gather new data and to innovate using new technologies.

\begin{align*}20 \;\mathrm{min}\end{align*}

Introduction to Nanoscience: PowerPoint Slides

Computer and projector

Conduct Black Box Activity \begin{align*}20 \;\mathrm{min}\end{align*}

Prepare black boxes according to teacher instructions

Photocopies of the Black Box Activity: Student Instructions and Questions

Discuss Black Box Activity and student reading: Seeing and Building Small Things \begin{align*}10 \;\mathrm{min}\end{align*}
Day 2 \begin{align*}(50 \;\mathrm{min})\end{align*} Optional: Extensions for Exploring Nanoscale Modeling Will vary Teacher notes
Student Quiz: Seeing and Building Small Things \begin{align*}10 \;\mathrm{min}\end{align*} Photocopies of Student Quiz Teacher Key for correcting Student Quiz

### Scanning Probe Microscopy: Teacher Reading

Introduction

In 1981, Gerd Binnig and Heinrich Rohrer, two IBM scientists working in Zurich, Switzerland, invented the first scanning tunneling microscope (STM). They were awarded the Nobel Prize in physics for this work, which gave birth to the development of a new family of microscopes known as scanning probe microscopes (SPM). All SPMs are based on scanning a probe just above a sample surface while monitoring the interaction between the probe and surface. The different types of interactions that are monitored are what characterize the different types of scanning probe microscopes. The STM monitors the electron tunneling current between a probe and a conducting sample surface, while the more recently developed atomic force microscope (AFM) monitors the Van der Waals forces of attraction or repulsion between a probe and a sample surface. The advantage of this new family of scanning probe microscopes is that we are able to image and manipulate matter as small as \begin{align*}0.1\;\mathrm{Angstrom}\ (.01\;\mathrm{nm})\end{align*}. So how do these probe microscopes work to obtain images down to the atomic level?

The Scanning Tunneling Microscope (STM)

The STM is based upon a quantum mechanical phenomenon known as electron tunneling. Tunneling is the movement of an electron through a classically forbidden potential energy state. A common analogy is that of a car of a roller coaster at the bottom of a large hill. Based on classical mechanics, one would predict that the car would not make it over the hill if it did not have enough kinetic energy. However, viewed from a quantum mechanical viewpoint, an electron is no longer just a particle having either enough or not enough energy to make it past a potential energy barrier. Rather, an electron also exhibits wave like properties, and as such, the electron is no longer confined to strict energy boundaries. As a wave, there is a small but finite probability that the electron can be found on the classically forbidden side of the potential energy barrier. When an electron behaves in such a manner, it is said to have tunneled.

Electron tunneling is the core concept behind the STM. In the STM, a probe, commonly referred to as the tip, is brought close to the surface of a sample being examined (see Figure 1). The energy barrier that is classically forbidden is the gap (air, vacuum) between the tip and the sample. When the tip and the sample are brought within a distance of around \begin{align*}1 \;\mathrm{nm}\end{align*} of each other, tunneling occurs from the tip to the sample or vice versa, as long as the sample is an electrical conductor. A current can then be measured as result of electrons tunneling.

Tip and surface and electron tunneling [1]

The magnitude of the tunneling current is very sensitive to the gap distance between the tip and the sample. The tunneling current drops off exponentially with increased gap distance. If the distance is increased by as small as \begin{align*}1\;\mathrm{Angstrom}\end{align*}, the current flow is decreased by an order of magnitude.

Imaging of the surface of a sample based on electron tunneling current can be carried out in one of two ways:

1. Constant height mode: The tunneling current is monitored as the tip is scanned across a sample. The changes in current give rise to an image of the topography of the sample.
2. Constant current mode: The tip is moved up and down as the surface changes in order to keep the actual tip-to-sample height constant. This maintains a constant current, and the movement of the tip is monitored as it is scanned across a sample. The changes in tip height give rise to an image of the topography of the sample. This mode is more commonly used.

STM Tips

Because of the dependence of the tunneling current upon the tip to sample distance is exponential, it is then only the closest atom on the tip of the STM probe that will interact with the sample surface (see Figure 2). Tunneling occurs between the electrons of a single atom on the tip of an STM probe, and one atom at a time on the sample surface.

How are these tips made? It is actually not as difficult as one would think. STM tips can be made by etching a pit into a crystalline surface such as silicon to make a mold. Then a thin layer of the material to be used to make the tip, such as silicon nitride, is placed onto the silicon mold, filling the pit. When the silicon nitride layer is removed from the silicon that contained the etch pit, an STM tip is produced. Tungsten and platinum are also commonly used to make STM tips.

An STM tip

But how do we make sure that the tip is one atom sharp? Actually, is not necessary to worry about placing one atom at the very tip. Looking closer at the tip, you will see that there is invariably a crystalline structure there (see Figure 3). And if you were to look even closer, at the atomic level, you would in fact see a truly atomic tip. Again, because electron-tunneling current changes so dramatically with distance (an increase in distance of one Angstrom causes a decrease in tunneling current by a power of ten), that one atom at the tip will produce a tunneling current. Interference from surrounding atoms is negligible due to their distance from the sample surface.

Zoom in of tip [3]

Moving the STM Tip

In order to get a precise picture of the topography of a sample, the STM tip must scan across the surface in increments as small as Angstroms. It is impossible for human manipulation to move a probe at such a small scale. To solve this problem, piezoelectric materials are used to move the STM tip in increments that the human hand cannot.

Piezoelectric materials are materials that change shape when a voltage is applied. Some examples of piezoelectric materials are ceramics, quartz, human bone, and lead zirconium titanate, which is typically used in STMs. The STM tip is connected to a tube containing piezoelectric material. Voltage can then be applied to the piezoelectric material, causing fine changes in dimension, which causes the tip to move Angstroms at a time.

Putting It All Together

The operation of an STM is based on electron tunneling, which occurs when a tip approaches a conducting surface at a very small distance (1nm). The tip is mounted onto a piezoelectric tube, which allows tiny, controlled movements of the tip by applying a voltage to the tube. As the tip is scanned along a sample in this way, the tip maintains a constant current or a constant tip-to-sample-surface distance. The resulting movement of the tip is recorded and displayed revealing a surface picture at the atomic level (see Figure 4).

Diagram of an STM [4]

Challenges in using an STM

In practice, several challenges arise when using the scanning tunneling microscope. One is vibrational interference. Since the tip of an STM is only a nanometer or so from the surface of a sample, it is easy to crash the tip into the sample. Any minor cause for vibration, such as a sneeze or motion in the room, could result in damaging the tip.

Contamination from particles in the air such as dust can also be problematic. A small dust particle is made up of millions of atoms, and would certainly interfere with the microscope performance. For this reason, STMs are commonly run under vacuum. The chemical reactivity of particles in air with the tip or sample surface is another reason to scan samples under vacuum.

One other drawback of the STM is that it is only useful for producing images of conducting or semiconducting materials because it relies on the tunneling movement of electrons. It is not effective in producing images of nonconducting materials. Another scanning microscope, the atomic force microscope, allows us to see nonconducting materials at the atomic level.

The Atomic Force Microscope (AFM)

The atomic force microscope (AFM) is another type of scanning probe microscope in the same family as STMs. It’s based on the same idea: a probe tip scanning a sample to create an image of a sample’s topography. But rather than monitoring the electron tunneling current between a scanning tip and sample, the AFM monitors the forces of attraction and repulsion between a scanning tip and a sample.

In an AFM, the scanning tip is attached to a spring or cantilever that allows the tip to move as it responds to forces of attraction or repulsion it has for a sample surface. The cantilever is a beam around \begin{align*}0.1\;\mathrm{mm}\end{align*} long and a few microns thick. It is supported on one end and has the scanning tip hanging from it on the other. Parallel to how the STM works, as the AFM tip is scanned over the sample at constant force, the tip attached to a cantilever or spring moves up and down, producing an image of the topography. Piezoelectric materials are again used to control the small distances needed to see a sample at the atomic level.

A laser beam is used to measure the movement of the cantilever (see Figure 5). The laser beam is positioned so that it reflects off the backside of the cantilever, which usually has a gold coating, behaving like a mirror. The reflected beam hits a detector that magnifies and monitors the movement of the cantilever.

Deciding on a tip to use requires careful consideration. Because it is the mechanical movement of the tip itself that ultimately produces the image, the size of the tip used must be chosen carefully. It must be small enough to get into all the “nooks and crannies” of a sample surface. The sharpness of a tip must be appropriately chosen.

Laser used to measure cantilever movement [5]

Interatomic interaction for STM (top) and AFM (bottom); shading shows interaction strength [6]

In addition, unlike the STM where only the one atom sharp tip registers surface topography due to electron tunneling occurring only over short distances, with the AFM, several atoms near the tip will play a role (see Figure 6). Forces of attraction and repulsion occur over longer distances. Several atoms near the tip of an AFM will be attracted or repulsed by several atoms on the sample surface.

The AFM is also more versatile than the STM. It can be adjusted to monitor different forces depending on the type of contact the tip has with a sample as well as the type of tip used to scan a sample. Depending on the force being monitored, different images of a sample surface can then be produced.

For example, an AFM can be in “contact mode,” where the tip is in direct contact with a surface sample. This measures vander Waals forces. A drawback of contact mode is the lateral frictional force that would exist as a tip is “dragged” over a sample. To address this, some samples are scanned using the “tapping mode” which oscillates the cantilever tip, while tapping a sample. The benefit of this mode is that frictional forces are dramatically reduced.

Another mode, called the “lift” mode, allows one to image a surface by monitoring magnetic forces and electrostatic forces. In addition, because the tip is attached to a cantilever or spring, lateral movement and angled deflection can also be measure to produce an image.

How the AFM works [7]

Using STMs and AFMs in Nanoscience

Not only do STMs and AFMs allow us to see images at the nanoscale level, they also enable us to manipulate matter at this level. By applying small voltages to an STM tip, atom-by-atom manipulation is possible. Being able to change the orientations of atoms (or clumps of atoms) as well as deposit or remove atoms (or clumps of atoms) is just the beginning of the development of many future applications.

References

(Accessed August 2005.)

Scanning Probe Microscopy

“Seeing” at the nanoscale

Scanning Probe Microscopes (SPMs)

• Monitor the interactions between a probe and a sample surface
• What we “see” is really an image
• Two types of microscopy we will look at:
• Scanning Tunneling Microscope (STM)
• Atomic Force Microscope (AFM)

Scanning Tunneling Microscopes (STMs)

• Monitors the electron tunneling current between a probe and a sample surface
• What is electron tunneling?
• Classical versus quantum mechanical model
• Occurs over very short distances

STM Tips

• Tunneling current depends on the distance between the STM probe and the sample

STM Tips II

• How do you make an STM tip “one atom” sharp?

Putting It All Together

• The human hand cannot precisely manipulate at the nanoscale level
• Therefore, specialized materials are used to control the movement of the tip

Challenges of the STM

• Works primarily with conducting materials
• Vibrational interference
• Contamination
• Physical (dust and other pollutants in the air)
• Chemical (chemical reactivity)

Atomic Force Microscopes (AFMs)

• Monitors the forces of attraction and repulsion between a probe and a sample surface
• The tip is attached to a cantilever which moves up and down in response to forces of attraction or repulsion with the sample surface
• Movement of the cantilever is detected by a laser and photodetector

AFM Tips

• The size of an AFM tip must be carefully chosen

The AFM

• Specialized materials are again used to manipulate materials at the nanoscale level

So What Do We See?

And What Can We Do?

• Using STMs and AFMs in Nanoscience
• Allows atom by atom (or clumps of atoms by clumps of atoms) manipulation as shown by the images below

### Scanning Probe Microscopy Slides: Teacher Notes

Overview

This series of slides introduces students to two major types of scanning probe microscopy that are used to see and manipulate matter at the nanoscale level. It is recommended that you read the accompanying teacher background reading, as it provides more in-depth explanations of the ideas addressed in the PowerPoint slides.

Slide 1: Scanning Probe Microscopy

Explain to the students that we will cover how scanning probe microscopes can be used to help us “see” at the nanoscale level.

Slide 2: Two Types of Scanning Probe Microscopes (SPMs)

All SPMs monitor some type of interaction between a probe and a sample surface. The type of interaction that is monitored depends on the type of SPM you are using.

• STMs monitor an electrical current between a probe and a sample surface, meaning it is useful for seeing the surface of conducting materials.
• AFMs monitor the force of attraction or interaction between a probe and a sample surface, and can be used to see the surface of all types of materials.

You may also want to discuss that what we are “seeing” is really an image and how this image may be similar or different to what we can see with other tools, such as light microscopes.

Slide 3: Scanning Tunneling Microscopes (STMs)

In the classical view of the electron, an electron is a particle that will be found in locations where it has enough energy to exist.

In the quantum mechanical view of the electron, an electron is a wave that primarily exists in areas of high probability. However, due to its wave nature, there is a finite possibility that the electron may exist in a location beyond high probability energy states, thus allowing for tunneling. Tunneling occurs at very short distances, around \begin{align*}1\;\mathrm{nm.}\end{align*}

You may talk about the two different microscopy modes: constant height vs. constant current. You may also address the fact that the double-headed arrow signifies that electron tunneling can occur tip to probe or probe to tip, depending on how the instrument is biased. But electrons do not tunnel in both directions at the same time.

Slide 4: STM Tips

Only the atom at the very tip of an STM tip will experience electron tunneling with a sample surface, because electron tunneling is exponentially dependent upon distance.

Slide 5: STM Tips II

A series of pictures zooming in on an STM tip shows that a one atom sharp tip will almost inevitably be naturally occurring.

Slide 6: Putting it All together

The animation runs a little slow; you might want to talk over it. The specialized material is referencing piezoelectric materials. You may choose to go into this or skip it depending on your class level.

Slide 7: Challenges of the STM

Vibrational interference might include sneezing or other air movement in the room that could cause crashing of the tip into the sample surface. Running the STM in a vacuum addresses some of the challenges.

Slide 8: Atomic Force Microscopes (AFMs)

You might want to start by defining what a cantilever is. AFMs monitor the forces of attraction between a scanning probe tip and a sample surface. Because movement of the tip occurs at the nanoscale level–which the human eye cannot detect without aid–the movement of a laser beam detects movement in the cantilever.

Slide 9: AFM Tips

Unlike STM tips where the electron tunneling will selectively occur between the closest atom on the tip and a sample surface, the AFM tip measures interactions between several atoms at the tip. For this reason, the size of the tip must be carefully chosen. Smaller and sharper tips yield finer resolution and vice versa. You might want to refer back to the Black Box activity and some of the follow-up questions that were addressed or discussed there.

Slide 10: The AFM

The AFM is a bit more versatile than the STM. Technology has found new ways to monitor different force interaction between a tip and a sample surface, leading to their respective images at the atomic level.

Slide 11: So What Do We See?

These images of nickel and \begin{align*}ZnO\end{align*} are taken from IBM research labs.

Slide 12: And What Can We Do?

In general, manipulation is done by applying voltages and charges to an STM tip.

### Black Box Lab Activity: Teacher Instructions & Key

Purpose

To use different probes to determine the layout of objects on the bottom surface of a closed box, and to consider the limitations and challenges in using probes to “see.” The idea is to get students thinking about how the scanning probe microscopes give us a picture of the surface of atoms, and to consider some of the basic challenges in scanning probe microscopy.

Materials

• One black box
• One pencil and magnet probe
• One cotton swab probe
• One skewer probe

How to Make a Black Box

1. Glue different objects to the bottom of each box. Use a variety of objects in various arrangements to make this as challenging an activity as appropriate. The class as a whole can have the same surface, or each pair can have their own unique surface. Use objects of different compositions and shapes––such as pastas, magnets, macaroni noodles, and Q-tips––and glue them in pattern such as a square, circle, or triangle. Do not use cotton balls, since they come apart after many jabs with probes. Also, use a strong super glue or rubber cement to keep the objects (especially the magnets) in place. When arranging, keep in mind that we want the students to be able to deduce the bottom surface more accurately when using the smaller barbecue skewer probe. An arrangement that would allow this differentiation (such as macaroni noodles \begin{align*}1/4\;\mathrm{cm}\end{align*} apart instead of \begin{align*}2\end{align*} ping pong balls \begin{align*}5\;\mathrm{inches}\end{align*} apart) is favorable.
2. Cut a small (e.g., \begin{align*}1/2\;\mathrm{inch}\end{align*}) hole in the top of the box, through which students will insert the probes. A square box will work best, since it will allow students to reach all parts of the bottom surface from a center top hole. If shoeboxes are used, cut more than one hole in the top so that all areas of the bottom surface can be reached.
3. For the pencil and magnet probe, glue an eraser-size magnet onto the eraser end of the pencil. With this probe, students will find strong pulls and repulsions by the magnets that are at the bottom of your black box.
4. Prepare enough black boxes and probes for each pair to work with their own set.

Student Instructions

1. Obtain from your teacher a box, pencil and magnet probe, a cotton swab probe, and a barbeque skewer probe.

2. Place the pencil and magnet probe into the center hole, and determine as best you can what the surface of the bottom of the box looks like. Draw your best guess below.

A rough sketch of the surface, highlighting any magnets.

3. Replace the pencil and magnet probe with the cotton swab probe, using the swab end as the probe. Is there any additional information you are able to conclude about the surface of the bottom of the box? Draw your best guess below.

A more specific sketch, perhaps identifying some general shapes of the objects.

4. Replace the cotton swab probe with the barbecue skewer probe, using the pointed end of the skewer as the probe. Is there any additional information you are able to conclude about the surface of the bottom of the box? Draw your best guess below.

A more specific drawing, identifying the layout and composition of the surface.

Questions

1. Describe the technique you used to investigate the surface of the bottom of the box.

A systematic survey of the bottom surface, scanning back and forth, row by row.

2. What kinds of information about the bottom surface were you able to deduce?

The layout of the bottom of the box, as well as the composition of the various materials on the bottom surface of the box.

3. How accurate do you think your drawing is?

The basic layout and the general composition of the different objects are pretty accurate. The specific shapes and the texture of the surfaces are some properties that could not accurately be interpreted.

4. What could you do to get a better idea of what the bottom surface looks like, besides opening the box?

Use a finer probe, use your fingers as a probe to increase sensitivity, scan the bottom surfaces in smaller increments.

5. What if a ping-pong ball was attached to the probing end of the skewer? How might this have affected your interpretations?

A ping-pong ball would have revealed general information, such as the general layout. The resolution would have been less specific and less accurate compared with what the barbecue skewer told us.

6. What difficulties did you encounter in using this probing technique to “see” the unknown? Or what challenges could there be in using such a technique?

The tip of the probe could be damaged, or the bottom surface could be damaged during probing. The size of the probe must be appropriately small.

### Seeing and Building Small Things Quiz: Teacher Key

1. Name the scanning probe instrument that uses electrical current to infer an image of atoms. Briefly describe how it works.

Scanning tunneling microscope (STM): As the STM tip is scanned across a surface, the STM measures the flow of electron tunneling current between the tip and the surface. This tunneling current depends strongly on the distance between the probe tip and the sample, and thus is sensitive to peaks and valleys of the surface. The changes in the strength of this current can be used to create an image of the surface.

2. Name the scanning probe instrument that reacts to forces inherent in atoms and molecules to infer an image of atoms. Briefly describe how it works.

Atomic force microscope (AFM): As the AFM tip is scanned across a surface, the AFM measures the tiny up and down movements of the tip that occur due to the electromagnetic forces of attraction and repulsion between the tip and the sample. This movement can be used to create an image of the surface.

3. Scanning probe instruments can also be used to create things atom by atom. Briefly summarize the downside of using such tools to create an aspirin tablet.

Creating an aspirin table one atom at a time would be very expensive and slow; it would take millions of years just to create one tablet because there are a huge number (more than one trillion billion) of aspirin molecules in an aspirin tablet.

4. How does dip pen nanolithography (DPN) work? Using a drawing in your explanation.

DPN writes structures to a surface the same way that we write ink using a pen. A reservoir of atoms or molecules (the “ink”) is stored in the tip of an AFM. The tip is then moved across a surface, leaving the molecules behind on the surface in specific positions. (Drawing should show the transfer of molecules from the AFM tip to the surface.)

5. Name two things in nature that are created by self-assembly processes.

Many answers are possible here; for example, a bubble, snowflake, crystal growth, DNA, cell walls and functions, etc.

6. Circle true or false for each of the following.

E-beam lithography is a type of self assembly. True False

One type of self-assembly is crystal growth. True False

Nanotubes can be grown like trees from seed crystals. True False

The rules governing self-assembly are fully understood. True False

### Optional Extensions for Exploring Nanoscale Modeling Tools: Teacher Notes

Exploring AFM Models

Wooden AFM

Mr. Victor Brandalaise and Dr. Maureen Scharberg at San Jose State University have developed a large-scale wood model of an atomic force microscope (AFM). The cost for the materials for this model is approximately \begin{align*}\ 30\end{align*}. The wood cantilever has a sewing needle tip, and on top of the cantilever near the tip is a mirror. A laser pointer is positioned to beam light from above the cantilever. As the tip skims along a surface, such as copper pellets, a piece of textured plastic, or popcorn kernels, the laser beam reflects the surface onto a piece of paper. From behind the piece of paper, which is attached to a piece of transparent plastic, students can easily trace the amplified surface. For more information, contact Dr. Scharberg at (408) 924-4966 or email scharbrg@pacbell.net

LEGO AFM

As part of their “Exploring the Nanoworld” program, the Materials Research Science and Engineering Center on Nanostructured Materials and Interfaces (MRSEC) at the University of Wisconsin offers materials showing how to assemble a large-scale AFM with LEGO bricks; see http://mrsec.wisc.edu/Edetc/LEGO/PDFfiles/2-1app.PDF.

To learn more about exploring the nanoworld with LEGO bricks, or how to order LEGO kits for this purpose for your classroom, see http://mrsec.wisc.edu/Edetc/LEGO/index.html

How Such Models Could Be Used

Using such models, your students could examine a range of surfaces composed of pure or mixed materials. Students could compare traces from the different instruments and, given unidentified traces made by other students, try to infer the surface type. These activities could lead to discussions of measurement error, identification of impurities in samples, and the advantages and appropriateness of different imaging techniques for different surface types. These activities would provide a revealing view of the instruments and principles behind them.

For assessment, students could be asked to depict the functionality of an AFM using the ChemSense Animator tool available for free download at http://chemsense.org. Using ChemSense, students could draw the components of the AFM and create an animation that predicts what will happen as the cantilever scans across a surface of a sample. In tandem, they could be asked to draw an associated graph that illustrates the changes in force over the surface as the tip moves in their animation. Students would describe the output of the instrument terms of magnetic repulsion or energy distribution.

Wood AFM model

Exploring Self Assembly

(Source: White paper by Bob Tinker, The Concord Consortium)

The Molecular Workbench (MW) software, available at http://molo.concord.org/software for both Macintosh and Windows platforms, can be used to model nano-engineering concepts such as self assembly. Self-assembly is a nano-engineering concept borrowed from biological systems. The underlying mechanisms for self-assembly are the general van der Waals mutual attraction of all atoms, Coulomb forces due to charged regions of molecules, and shape.

Shape and Smart Surfaces

To build in the impact of shape, MW has “Smart Surfaces” that can be drawn by the user. These surfaces are actually chains of MW atoms linked together with elastic bonds and covered by a flexible surface that hides the atoms. Charge can be added to the periphery of a Smart Surface. The result is a good approximation to a large molecule. It can hold its general shape, but it does vibrate, respond to temperature, and have both long-range Coulomb forces as well as short-range van der Waals forces.

Smart surfaces can be made to self-assemble. Above is an example of a particularly interesting kind of self-assembling object based on nine identical sub-units.

To run the “Smart Surfaces” model, launch MW from and then look for “self assembly” under “Recent models and activities.” http://molo.concord.org/software and then look for “self assembly” under “Recent models and activities.”

The importance of shape in docking

The model at the left demonstrates the importance of shape in docking, something similar to self-assembly. This model can be heated to separate the two molecules and then both the ball and triangle bounce around. On cooling, the triangle eventually finds its way back to the complementary surface through a random walk that takes quite a long time. This gives one an appreciation for the time-scale of molecular events of this type.

## Applications of Nanoscience

### Teacher Lesson Plan

Contents

• Applications of Nanoscience: Teacher Lesson Plan
• Applications of Nanoscience: PowerPoint with Teacher Notes
• What’s New Nanocat? Poster Session: Teacher Instructions & Rubric

Orientation

This lesson introduces students to applications of nanoscience, explores how nanoscale science and engineering could improve our lives, and describes some potential risks of nanotechnology.

• The Applications of Nanoscience PowerPoint slides illustrate a variety of current and potential nanotechnology applications.
• The What’s New Nanocat project gives students the opportunity to work in groups to research an application of nanoscience, prepare and present it, and give peer feedback.

Essential Questions (EQ)

What essential questions will guide this unit and focus teaching and learning?

(Numbers correspond to learning goals overview document)

3. Occasionally, there are advances in science and technology that have important and long-lasting effects on science and society. What scientific and engineering principles will be exploited to enable nanotechnology to be the next big thing?

6. What are some of the ways that the discovery of a new technology can potentially impact our lives?

Enduring Understandings (EU)

Students will understand:

(Numbers correspond to learning goals overview document)

1. The study of unique phenomena at the nanoscale could change our understanding of matter and lead to new questions and answers in many areas, including health care, the environment, and technology.

Key Knowledge and Skills (KKS)

Students will be able to:

(Numbers correspond to learning goals overview document)

3. Describe an application (or potential application) of nanoscience and its possible effects on society.

4. Compare a current technology solution with a related nanotechnology-enabled potential solution for the same problem

Prerequisite Knowledge and Skills

• Ability to research topics independently (for optional activity).

Related Standards

• NSES Science and Technology: 12EST2.2, 12EST2.4
• History and Nature of Science. 12GHNS3.3
• NSES Science as Inquiry: 12ASI2.3
Day Activity Time Materials
Day 1 \begin{align*}(35 \;\mathrm{min})\end{align*} Show the PowerPoint slides: Applications of Nanoscience, using teacher’s notes as talking points. Describe and discuss interactively with students the examples shown of possible applications. Try to stimulate student interest! \begin{align*}20 \;\mathrm{min}\end{align*}

PowerPoint slides: Applications of Nanoscience

Computer and projector

What’s New Nanocat? Assign or allow students to choose the nanotechnology topic they want to investigate for the project. Students will work in groups of 3 or 4. \begin{align*}15 \;\mathrm{min}\end{align*}

What’s New Nanocat? Teacher Instructions and Rubric

Prepare a sign-up sheet for each student group to indicate their chosen topic and the names of all students in their group.

Days 2-4 (full class) Students conduct independent investigation and prepare a presentation, in groups, on chosen/assigned topic. 3 days

Computers with internet connection, journal articles, library.

Materials for making a poster presentation using PowerPoint or posters.

Day 5 (full class) Students make their presentations to the class. Class members discuss and ask questions. 1 day

Copies of the What’s New Nanocat? Poster Session: Peer Feedback Form

Scoring rubric will be used to score student presentations.

May require computer and projector for those students wishing to present their topic using PowerPoint.

You may want to display paper posters or share PowerPoint slide presentations.

Applications of Nanoscience

How might nanoscale science and engineering improve our lives?

Potential Impacts of Nanotechnology

• Materials
• Stain-resistant clothes
• Health Care
• Chemical and biological sensors, drugs and delivery devices
• Technology
• Better data storage and computation
• Environment
• Clean energy, clean air

Materials: Stain Resistant Clothes

• Nanofibers create cushion of air around fabric
• \begin{align*}10\;\mathrm{nm}\end{align*} carbon whiskers bond with cotton
• Acts like peach fuzz; many liquids roll off

Materials: Paint That Doesn’t Chip

• Protective nanopaint for cars
• Water and dirt repellent
• Resistant to chipping and scratches
• Brighter colors, enhanced gloss
• In the future, could change color and self-repair?

Environment: Paint That Cleans Air

• Nanopaint on buildings could reduce pollution
• When exposed to ultraviolet light, titanium dioxide \begin{align*}(TiO_2)\end{align*} nanoparticles in paint break down organic and inorganic pollutants that wash off in the rain
• Decompose air pollution particles like formaldehyde

Environment: Nano Solar Cells

• Nano solar cells mixed in plastic could be painted on buses, roofs, clothing
• Solar becomes a cheap energy alternative!

Technology: A DVD That Could Hold a Million Movies

• Current CD and DVD media have storage scale in micrometers
• New nanomedia (made when gold self-assembles into strips on silicon) has a storage scale in nanometers
• That is \begin{align*}1,000 \;\mathrm{times}\end{align*} more storage along each dimension (length, width)......or \begin{align*}1,000,000 \;\mathrm{times}\end{align*} greater storage density in total!

Technology: Building Smaller Devices and Chips

• Nanolithography to create tiny patterns
• Lay down “ink” atom by atom

Health Care: Nerve Tissue Talking to Computers

• Neuro-electronic networks interface nerve cells with semiconductors
• Possible applications in brain research, neurocomputation, prosthetics, biosensors

Health Care: Detecting Diseases Earlier

• Quantum dots glow in UV light
• Injected in mice, collect in tumors
• Could locate as few as \begin{align*}10\end{align*} to \begin{align*}100\end{align*} cancer cells

Health Care: Growing Tissue to Repair Hearts

• Nanofibers help heart muscle grow in the lab
• Filaments ‘instruct’ muscle to grow in orderly way
• Before that, fibers grew in random directions

Health Care: Preventing Viruses from Infecting Us

• Nanocoatings over proteins on viruses
• Could stop viruses from binding to cells
• Never get another cold or flu?

Health Care: Making Repairs to the Body

• Nanorobots are imaginary, but nanosized delivery systems could...
• Break apart kidney stones, clear plaque from blood vessels, ferry drugs to tumor cells

Pause to Consider

\begin{align*}{\color{blue}\mathrm{How\ delicate\ are\ nanoscale-sized\ objects?}}\end{align*}

\begin{align*}{\color{blue}\mathrm{How\ well\ do\ we\ understand\ the\ environmental\ and\ health\ impacts\ of\ nanosized\ clusters\ of\ particles?}}\end{align*}

Nanodevices Are Sensitive!

• Radiation particles can cause fatal defects
• Development requires very clean environments
• Redundant copies compensate for high defect rate

Potential Risks of Nanotechnology

• Health issues
• Nanoparticles could be inhaled, swallowed, absorbed through skin, or deliberately injected
• Could they trigger inflammation and weaken the immune system? Could they interfere with regulatory mechanisms of enzymes and proteins?
• Environmental issues
• Nanoparticles could accumulate in soil, water, plants; traditional filters are too big to catch them
• New risk assessment methods are needed
• National and international agencies are beginning to study the risk; results will lead to new regulations

Summary: Science at the Nanoscale

• An emerging, interdisciplinary science
• Integrates chemistry, physics, biology, materials engineering, earth science, and computer science
• The power to collect data and manipulate particles at such a tiny scale will lead to
• New areas of research and technology design
• Better understanding of matter and interactions
• New ways to tackle important problems in healthcare, energy, the environment, and technology
• A few practical applications now, but most are years or decades away

### Teacher Notes

Overview

This series of slides introduces students to some of the areas thought to have great potential for impact on our lives through nanotechnology innovations. Example applications and references for further information are provided. Don’t feel that you need to show all of these slides. Show the ones that you think will most interest and reach your particular students.

Slide 1: Applications of Nanoscience

Explain to students that you’re going to present several examples of how new innovations in nanotechnology might impact our lives.

Slide 2: Potential Impact of Nanotechnology

Point out that tools for manipulating materials are becoming more sophisticated and improving our understanding of how atoms and molecules can be controlled. This will lead to significant improvements in materials, and, in turn, to new products, applications, and markets that could have revolutionary impact on our lives.

This presentation will focus on innovations related to nano materials, the environment, technology, and healthcare. A few of these products being commercialized now, but most are in research labs or are envisioned for the distant future.

References:

Slide 3: Materials: Stain Resistant Clothes

Manufacturers are embedding fine-spun fibers into fabric to confer stain resistance on khaki pants and other products. These “nanowhiskers” act like peach fuzz and create a cushion of air around the fabric so that liquids bead up and roll off. Each nanowhisker is only ten nanometers long, made of a few atoms of carbon. To attach these whiskers to cotton, the cotton is immersed in a tank of water full of billions of nanowhiskers. Next, as the fabric is heated and water evaporates, the nanowhiskers form a chemical bond with cotton fibers, attaching themselves permanently. The whiskers are so tiny that if the cotton fiber were the size of a tree trunk, the whiskers would look like fuzz on its bark.

Nano-resistant fabric created by NanoTex is already available in clothing available in stores like Eddie Bauer, The Gap, and Old Navy. This innovation will impact not only khaki wearers, but also dry cleaners who will find their business declining, and detergent makers who will find less of their project moving off the shelf.

References:

Slide 4: Materials: Paint That Doesn’t Chip

Nanopaints are ceramic based coatings that make the paint a lot more durable and resistant to rock chips and scratches. In addition to holding up better to weathering, nanopaints have richer and brighter colors than traditional pigments. In the future, nanopaints may also even change color

References:

Slide 5: Environment: Paint That Cleans Air

Chinese scientists have announced that they have invented nanotech-based coating material that acts as a permanent air purifier. If the coating proves to be effective at air cleaning, it will be gradually used on buildings to improve air quality. The core of the material is a titanium-dioxide-based compound developed using advanced nanotechnology. Exposed under sunlight, the substance can automatically decompose ingredients like formaldehyde that cause air pollution.

References:

Slide 6: Environment: Nano Solar Cells

Enough energy from the sun hits the earth every day to completely meet all energy needs on the planet, if only it could be harnessed. Doing so could wean us off of fossil fuels like oil and provide a clean energy alternative. But currently, solar-power technologies cost as much as 10 times the price of fossil fuel generation. Chemists at U.C. Berkeley are developing nanotechnology to produce a photovoltaic material that can be spread like plastic wrap or paint. These nano solar cells could be integrated with other building materials, and offer the promise of cheap production costs that could finally make solar power a widely used electricity alternative.

Current approaches embed nanorods (bar-shaped semiconducting inorganic crystals) in a thin sheet (\begin{align*}200\;\mathrm{nanometers}\end{align*} deep) of electrically conductive polymer. Thin layers of an electrode sandwich these nanorod-polymer composite sheets. When sunlight hits the sheets, they absorb photons, exciting electrons in the polymer and the nanorods, which make up \begin{align*}90\end{align*} percent of the composite. The result is a useful current that is carried away by the electrodes. Eventually, nanorod solar cells could be rolled out, ink-jet printed, or even painted onto surfaces, so that even a billboard on a bus could be a solar collector.

References:

Slide 7: Technology: A DVD That Could Hold a Million Movies

In 1959, Richard Feynman asked if we could ever shrink devices down to the atomic level. He couldn’t find any laws of physics against it. He calculated that we could fit all printed information collected over the past several centuries in a \begin{align*}3-\;\mathrm{dimensional}\end{align*} cube smaller than the head of a pin. How far have we come? A \begin{align*}2-\;\mathrm{dimensional}\end{align*} version of Feynman’s vision is in research labs. The picture on this slide illustrates the potential of nano-devices for data storage. On the left are images of two familiar data storage media: the CD-ROM and the DVD. On the right is a self-assembled memory on a silicon surface, formed by depositing a small amount of gold on it. It looks like CD media, except that the length scale is in nanometers, not micrometers. So the corresponding storage density is a million times higher! The surface automatically formats itself into atomically-perfect stripes (red) with extra atoms on top (white). These atoms are neatly lined up at well-defined sites along the stripes, but occupy only about half of them. It is possible to use the presence of an atom to store a 1, and the absence to store a 0. The ultimate goal would be to build a data storage medium that needs only a single atom per bit. The big question is how to write and read such bits efficiently.

References:

Slide 8: Technology: Building Smaller Devices and Chips

A technique called nanolithography lets us create much smaller devices than current approaches. For example, the Atomic Force Microscope (AFM) nanolithography image of the Mona Lisa was created by a probe oxidation technique. This technique can be used to further miniaturize the electrical components of microchips. Dip pen nanolithography is a ‘direct write’ technique that uses an AFM to create patterns and to duplicate images. “Ink” is laid down atom by atom on a surface, through a solvent––often water.

References:

Slide 9: Health Care: Nerve Tissue Talking to Computers

Researchers are studying the electrical interfacing of semiconductors with living cells-in particular, neurons–to build hybrid neuro-electronic networks. Cellular processes are coupled to microelectronic devices through the direct contact of cell membranes and semiconductor chips. For example, electrical interfacing of individual nerve cells and semiconductor microstructures allow nerve tissue to directly communicate their impulses to computer chips. Pictured is a snail neuron grown on a CMOS chip with \begin{align*}128 \times 128\end{align*} transistors. The electrical activity of the neuron is recorded by the chip, which is fabricated by Infineon Technologies. This research is directed (1) to reveal the structure and dynamics of the cell-semiconductor interface and (2) to build up hybrid neuroelectronic networks. Such research explores the new world at the interface of the electronics in inorganic solids and the ionics in living cells, providing the basis for future applications in medical prosthetics, biosensorics, brain research and neurocomputation.

References:

Slide 10: Health Care: Detecting Diseases Earlier

Quantum dots are small devices that contain a tiny droplet of free electrons, and emit photons when submitted to ultraviolet (UV) light. Quantum dots are considered to have greater flexibility than other fluorescent materials, which makes them suited for use in building nano-scale applications where light is used to process information. Quantum dots can, for example, be made from semiconductor crystals of cadmium selenide encased in a zinc sulfide shell as small as \begin{align*}1\;\mathrm{nanometer}\end{align*} (one-billionth of a meter). In UV light, each dot radiates a brilliant color.

Because exposure to cadmium could be hazardous, quantum dots have not found their way into clinical use. But they have been used as markers to tag particles of interest in the laboratory. Scientists at Georgia Institute of Technology have developed a new design that protects the body from exposure to the cadmium by sealing quantum dots in a polymer capsule. The surface of each capsule can attach to different molecules. In this case, they attached monoclonal antibodies directed against prostate-specific surface antigen, which is found on prostate cancer cells. The researchers injected these quantum dots into live mice that had human prostate cancers. The dots collected in the tumors in numbers large enough to be visible in ultraviolet light under a microscope. Because the dots are so small, they can be used to locate individual molecules, making them extremely sensitive as detectors. Quantum dots could improve tumor imaging sensitivity tenfold with the ability to locate as few as \begin{align*}10\end{align*} to \begin{align*}100\end{align*} cancer cells. Using this technology, we could detect cancer much earlier, which means more successful, easier treatment.

References:

Slide 11: Health Care: Growing Tissue to Repair Hearts

Cardiac muscle tissue can be grown in the lab, but the fibers grow in random directions. Researchers at the University of Washington are investigating what type of spatial cues they might give heart-muscle cells so that they order themselves into something like the original heart-muscle tissue. Working with one type of heart muscle cell, they have been able to build a two-dimensional structure that resembles native tissue. They use nanofibers to “instruct” muscle cells to orient themselves in a certain way. They have even able to build a tissue-like structure in which cells pulse or ‘beat’ similar to a living heart.

This image on this slide shows cardiac tissue grown with the aid of nanofiber filaments. It displays well-organized growth that is potentially usable to replace worn out or damaged heart tissue. The ultimate goal of building new heart-muscle tissue to repair and restore a damaged human heart is a long way off, but there have been big advances in tissue engineering in recent years.

References:

Slide 12: Health Care: Preventing Viruses from Infecting Us

If we could cover the proteins that exist on the influenza virus, we could prevent the virus from recognizing and binding to our body cells. We would never get the flu! A protein recognition system has already been developed. More generally, this work suggests that assembled virus particles can be treated as chemically reactive surfaces that are potentially available to a broad range of organic and inorganic modification.

References

Slide 13: Health Care: Making Repairs to the Body

The image on this slide depicts what one nanoscientist from the Foresight Institute imagines might be possible one day in the far future. It shows how a nanorobot could potentially interact with human cells. When people hear of nanotechnology from science fiction, this is often the form that it takes. But we may not know for decades whether such a probe is even possible. But if they are developed someday, they could be used to maintain and protect the human body against pathogens. For example, they could (1) be used to cure skin diseases (embedded in a cream, they could remove dead skin and excess oils, apply missing oils), (2) be added to mouthwash to destroy bacteria and lift plaque from the teeth to be rinsed away, (3) augment the immune system by finding and disabling unwanted bacteria and viruses, or (4) nibble away at plaque deposits in blood vessels, widening them to prevent heart attacks.

References:

Slide 14: Pause to Consider

The next 2 slides focus on the delicate nature of nanosized objects, the potential risks of nanotechnology to humans and the environment, and the need study the risks and regulate the development of products that contain nanoparticles.

Slide 15: Nanodevices Are Sensitive!

Because of their small size, nanodevices are very sensitive and can easily be damaged by the natural environmental radiation all around us. In the picture for this example, we see a pit caused by an alpha particle hitting the surface of mica. An alpha particle is a highenergy helium nucleus that is the lowest-energy form of nuclear radiation. Alpha particles are also the particles that Rutherford used for the gold foil experiment in which he discovered the arrangement of protons within the atom that is now commonly known as the nucleus. The impact of alpha particles on a solid surface can cause physical damage by causing other atoms in the surface to be moved out of place. These types of defects can be potentially fatal in high-density electronics and nanodevices. To compensate, extremely clean manufacturing environments and very high redundancy—perhaps millions of copies of nanodevices for a given application––are required.

References:

Slide 16: Potential Risks of Nanotechnology

Nanotechnology’s potential is encouraging, but the health and safety risks of nanoparticles have not been fully explored. We must weigh the opportunities and risks of nanotechnology in products and applications to human health and the environment. Substances that are harmless in bulk could assume hazardous characteristics because when particles decrease in size, they become more reactive. A growing number of workers are exposed to nanoparticles in the workplace, and there is a danger that the growth of nanotechnology could outpace the development of appropriate safety precautions. Consumers have little knowledge of nanotechnology, but worries are already beginning to spread. For example, environmental groups have petitioned the Food and Drug Administration to pull sunscreens from the market that have nano-size titanium dioxide and zinc oxide particles. As nanotechnology continues to emerge, regulatory agencies must develop standards and guidelines to reduce the health and safety risks of occupational and environmental nanoparticle exposure.

References:

Slide 17: Summary: Science at the Nanoscale

Nanoscience is an emerging science that will change our understanding of matter and help us solve hard problems in many areas, including energy, health care, the environment, and technology. With the power to collect data and to manipulate particles at such a tiny scale, new areas of research and technology design are emerging. Some applications––like stain resistant pants and nanopaint on cars––are here today, but most applications are years or decades away. But nanoscience gives us the potential to understand and manipulate matter more than ever before.

Nanoscience is truly an interdisciplinary science. Progress in nanoscale science and technology results from research involving various combinations of biology, chemistry, physics, materials engineering, earth science, and computer science. Nanoscience also provides a way to revisit the core concepts from these domains and view them through a different lens. Learning about nanoscience can support understanding of the interconnections between the traditional scientific domains and provide compelling, realworld examples of science in action.

### What's New Nanocat? Poster Session: Teacher Instructions & Rubric

Summary

Students will work in pairs to create a poster that compares a current technology with a related, new nanotechnology application. A list of applications (including references) to choose from will be provided to the students. The list is based on applications that have been mentioned or discussed in class or in associated readings (e.g., nanotubes as stronger tethers, nano solar cells as omnipresent collectors, stain-resistant nanopants).

The student will assume the role of a scientist working on the new nanotechnology application, and explain the proposed usage of the new technology in a poster session. The student will produce a poster showing a current technology and how it is used; a new, related nanotechnology and how it is proposed to be used; how the new nanotechnology works; and how the new nanotechnology will help improve understanding or solve a problem.

The posters will be displayed in class and the students will explain the technology by explaining the poster. This could be done in a science fair type arrangement or in class as a presentation. The presentation must include diagrams along with written descriptions to help someone gain a better understanding of the science. It can also optionally include animations.

Time Frame: \begin{align*}2-3\;\mathrm{hours}\end{align*} to create posters, \begin{align*}1\;\mathrm{hour}\end{align*} for poster session

Criteria for Evaluation

The poster will be graded based on a rubric. The student’s discussion and answers to questions during the poster session will influence the grade. The students must demonstrate understanding of the technology s/he is explaining.

Relevant Learning Goals

• Nanoscience is an emerging science that could vastly change our understanding of matter and lead to new questions and answers in many areas, including health care, the environment, and technology.
• Nanotechnology focuses on manipulating matter at the nanoscale to create structures that have novel properties or functions.

Required Resources

• List of applications from which students can choose their poster topic.
• Access to the Web to research the technologies, find relevant diagrams, etc.
• Optional use of ChemSense to create diagrams or animations to illustrate how the technologies work
• Optional access to PowerPoint or other slide creation tool for creating poster pages
• If posters are to be displayed in the classroom, access to posterboard, paper, and printer, and glue or tape are required.
Rubric for NanoCat Poster Evaluation
Novice (1) Absent, inaccurate, or confused Apprentice (2) Partially developed Skilled (3) Adequately developed Masterful (4) Fully developed
Written explanations Shows little understanding or major misunderstanding of ideas or processes. Concepts, data, and arguments are inadequate. Many grammatical errors. Shows limited understanding or misunderstanding of key ideas. Concepts, data, and arguments are simple or somewhat inadequate. Some grammar errors. Shows a solid understanding of ideas, no misunderstanding of key ideas. Concepts, data, arguments are appropriate. Grammar is mostly correct. Shows clear, complete, and sophisticated understanding of ideas, advanced beyond the grasp usually found at this age. Easy to read, with correct grammar.
Graphic explanations Shows little understanding of processes, or inadequate for addressing the application. Shows limited understanding of ideas. Graphics are crude, simple, or reveal a key misunderstanding. Shows solid understanding. Graphics show no misunderstanding of key ideas, are not overly simple. Shows clear, complete, and sophisticated understanding of ideas and processes.
Accuracy and Research Misunderstanding of nanoscience is evident in inaccurate explanations or science-fiction-like ideas presented as facts. Demonstrates little or no research. Limited understanding is evident by some inaccurate or simple explanations, or futuristic ideas confused with fact. Demonstrates average research. Shows solid understanding with clear explanations with sound scientific basis, no clear inaccuracies. Demonstrates solid research. Shows sophisticated understanding based on current facts and scientific theory, and futuristic ideas presented as such. Demonstrates extensive research.
Attractiveness Distractingly messy or bad design. Somewhat organized, acceptable design, but messy. Solid organization, with good design, layout, and neatness. Sophisticated presentation that is well organized and neat, with good design and layout.
Attribution Diagrams and text do not have any source citations. More than two diagrams and text do not have source citations. All but one or two diagrams and text have source citations. All text and borrowed diagrams have source citations.
Oral Team Presentation Most members did not participate, communication was unclear, hard to hear, little eye contact, answered few questions. Few members participated, communication was somewhat unclear, answered half of audience questions well. Most members participated, communicated clearly, answered most audience questions reasonably well. All team members participated, communicated clearly, kept eye contact, and answered audience questions well.

## One-Day Introduction to Nanoscience

### Teacher Lesson Plan

Contents

• One-Day Introduction to Nanoscience: Teacher Lesson Plan
• One-Day Introduction to Nanoscience: Teacher Demonstration Instructions
• One-Day Introduction to Nanoscience: PowerPoint with Teacher Notes

Remaining materials (the introductory student readings, worksheets, worksheet keys and scale diagram) can be found in Lesson 1: Introduction to Nanoscience.

Orientation

This abridged version of the Size Matters unit provides a one-day overview of nanoscience for teachers with very limited time. The goal of this lesson is to spark student’s interest in nanoscience, introduce them to common terminology, and get them to start thinking about issues of size and scale. It includes a presentation and visual demonstrations, and recommends use of readings, worksheets, and diagrams from Size Matters Lesson 1.

• The What’s the Big Deal about Nanotechnology? PowerPoint introduces size and scale, applications of nanoscience, tools of the nanosciences, and unique properties at the nanoscale.
• The mesogold and/or ferrofluid demonstrations visually illustrate how nanosized particles of a substance exhibit different properties than larger sized particles of the same substance.
• The Introduction to Nanoscience Student Reading and Worksheet (from Lesson 1) explains key concepts such as why nanoscience is different, why it is important, and how we are able to work at the nanoscale.
• The Personal Touch Student Reading and Worksheet (from Lesson 1) focus on applications of nanotechnology (actual and potential) set in the context of a futuristic story. They are designed to spark student’s imaginations and get them to start generating questions about nanoscience.
• The Scale Diagram (from Lesson 1) shows, for different size scales, the kinds of objects that are found, the tools needed to “see” them, the forces that are dominant, and the models used to explain phenomena.

If you extend this lesson beyond one day, consider incorporating the following popular activities from Lessons 2 and 3:

• The Number Line/Card Sort Activity (from Lesson 2) has students place objects along a scale and reflect on the size of common objects in relation to each other.
• The Unique Properties Lab Activities (from Lesson 3) demonstrate specific aspects of size-dependent properties without using nanoparticles.

Refer to the “Challenges and Opportunities” chart at the beginning of the unit before starting this lesson. Tell students that although making and using products at the nanoscale is not new, our focus on the nanoscale is new. We can gather data about nanosized materials for the first time because of the availability of new imaging and manipulation tools. You may not know all of the answers to the questions that students may ask. The value in studying nanoscience and nanotechnology is to learn how science understanding evolves and to learn science concepts.

Essential Questions (EQ)

What essential questions will guide this unit and focus teaching and learning?

(Numbers correspond to learning goals overview document)

1. How small is a nanometer, compared with a hair, a blood cell, a virus, or an atom?

2. Why are properties of nanoscale objects sometimes different than those of the same materials at the bulk scale?

4. How do we see and move things that are very small?

6. What are some of the ways that the discovery of a new technology can impact our lives?

Enduring Understandings (EU)

Students will understand:

(Numbers correspond to learning goals overview document)

1. The study of unique phenomena at the nanoscale could change our understanding of matter and lead to new questions and answers in many areas, including health care, the environment, and technology.
2. There are enormous scale differences in our universe, and at different scales, different forces dominate and different models better explain phenomena.
3. Nanosized particles of any given substance exhibit different properties than larger particles of the same substance.
4. New tools for seeing and manipulating increase our ability to investigate and innovate.

Key Knowledge and Skills (KKS)

Students will be able to:

(Numbers correspond to learning goals overview document)

1. Describe, using the conventional language of science, the size of a nanometer. Make size comparisons of nanosized objects with other small objects.

3. Describe an application (or potential application) of nanoscience and its possible effects on society.

Prerequisite Knowledge and Skills

• Familiarity with atoms, molecules and cells.
• Knowledge of basic units of the metric system and prefixes.

Related Standards

• NSES Science and Technology: 12EST2.1, 12EST2.2
• NSES Science as Inquiry: 12ASI2.3
• AAAS Benchmarks: 11D Scale #2
Day Activity Time Materials
Prior to this lesson Homework: (Optional) Reading & Worksheet: The Personal Touch (from Lesson 1) \begin{align*}30 \;\mathrm{min}\end{align*} Copies of The Personal Touch: Student Reading & Worksheet (from Lesson 1)
Homework: Reading & Worksheet: Introduction to Nanoscience (from Lesson 1) \begin{align*}40 \;\mathrm{min}\end{align*} Copies of Introduction to Nanoscience: Student Reading & Worksheet (from Lesson 1)
Day 1 \begin{align*}(50 \;\mathrm{min})\end{align*} (Optional) Use The Personal Touch story & worksheet as a basis for class discussion. Identify and discuss some student questions from the worksheet. \begin{align*}8 \;\mathrm{min}\end{align*} The Personal Touch: Student Reading & Worksheet (from Lesson 1)
Show and pass around samples of mesogold and/or ferrofluid plus a strong magnet. \begin{align*}2 \;\mathrm{min}\end{align*}

Mesogold

Ferrofluid and a strong magnet

Show the PowerPoint slides: What’s the Big Deal about Nanotechnology? Describe and discuss:
• The term “nanoscience” and the unit “nanometer”
• The tools of nanoscience
• Examples of nanotechnology
\begin{align*}25 \;\mathrm{min}\end{align*}

What’s the Big Deal about Nanotechnology? PowerPoint Slides & Teacher Notes

Computer and projector

Hand out Scale Diagram (from Lesson 1) and explain the important points represented on it. \begin{align*}5 \;\mathrm{min}\end{align*} Copies of Scale Diagram (from Lesson 1)
In pairs, have students review answers to the Introduction to NanoScience: Student Worksheet (from Lesson 1) \begin{align*}5 \;\mathrm{min}\end{align*}
Return to whole class discussion for questions and comments. \begin{align*}5 \;\mathrm{min}\end{align*}

### Teacher Demonstration Instructions

Overview

Nanotechnology creates and uses structures that have novel properties because of their small size. The following two examples visually illustrate how nanosized particles of a given substance exhibit different properties than larger sized particles of the same substance. Paired with appropriate questions, these visual demonstrations can lead to stimulating discussion with your students.

Mesogold

Nanosized particles of gold––sometimes referred to as “mesogold”–– exhibit different properties than bulk gold. For example, mesogold has a different melting point than bulk gold, and the color of mesogold can range from light red to purple depending on the size, shape, and concentration of the gold particles present.

This difference in color has to do with the nature of interactions among the gold atoms and how they react to outside factors (like light)––interactions that average out in the large bulk material but not in the tiny nanosized particles.

Mesogold colloidal gold from Purest Colloids, Inc. [1]

A number of organizations manufacture gold nanoparticles. Mesogold made by Purest Colloids, Inc., contains nanosized particles of gold suspended in water. At \begin{align*}10\end{align*} parts per million (ppm) the liquid appears clear ruby red in color, illustrating how optical properties (color) of mesogold and bulk gold differ.

The gold nanoparticles in Purest Colloid’s mesogold are about \begin{align*}0.65\;\mathrm{nanometers}\end{align*} in diameter, and each particle consists of approximately \begin{align*}9\end{align*} gold atoms. An atom of gold is about \begin{align*}0.25\;\mathrm{nanometers}\end{align*} in diameter, so the gold nanoparticles in Mesogold are only slightly larger than two times the diameter of a single gold atom. These particles stay suspended in deionized water, making it a true colloid. Other companies manufacture slightly larger mesogold particles, typically in the range of \begin{align*}70-90\;\mathrm{nm}\end{align*}.

Gold nanoparticles are being investigated medical research for use in detecting and killing cancer cells and a variety of other applications. They are also advertised as mineral supplements, but without any accompanying scientific support of health benefits.

More information on mesogold is available on the Purest Colloids website [1].

How to Use It as a Demonstration

Show and pass around one or more samples of the mesogold. You may also want to show and pass around a piece of gold (e.g., a ring or gold foil) for comparison.

Point out to your students how nanosized particles of a given substance (mesogold) exhibit different properties (red color) than larger sized particles of the same substance (bulk gold that looks gold in color).

Questions to stimulate classroom discussion:

1. How do you know the bulk gold (e.g., ring or foil) is really made of gold atoms?

Possible responses might include that it looks like gold, or because (in the case of a ring) jewelry is often made out of gold or may even have a stamp on it that “verifies” that it is made of gold.

2. What could you do to determine that it is really made of gold atoms?

You could test its physical properties––such as density, melting point, hardness (through a scratch test)––and compare these with the standard values for gold found in physical data charts.

3. Is it possible that a standard microscope could help determine if it is real gold?

No. Possible responses might include that a standard light microscope can only has resolution down to \begin{align*}10^{-6}\;\mathrm{m}\end{align*}, but we need to see down to the \begin{align*}10^{-9}\;\mathrm{m}\end{align*}.

4. How do you know the mesogold is really made of gold atoms?

You could test its physical properties. Scientists use atomic emission spectrography to identify substances like mesogold by their spectral lines.

5. Would the same criteria you used to determine if the bulk gold is really made of gold also work for determining if the mesogold is really made of gold?

No, the criteria could differ, since nanoparticles exhibit different properties than bulk materials––and if you only have a few nanosized particles, some properties such as melting point and density may not even make sense.

6. What other properties of mesogold might differ from bulk gold?

Melting point and conductivity are examples of properties that might vary.

Mesogold can be ordered from http://www.purestcolloids.com/mesogold_price_list.htm or by calling 609-267-6284 from 9 am to 5 pm Eastern time. Prices range from around \begin{align*}30-\end{align*}\\begin{align*}70\end{align*} per bottle, depending on size \begin{align*}(250\;\mathrm{or}\ 500\;\mathrm{mL})\end{align*} and quantity ordered. One \begin{align*}250\;\mathrm{mL}\end{align*} bottle should be enough for demonstration purposes.

Ferrofluid

Ferrofluids contain nanoparticles of a magnetic solid, usually magnetite \begin{align*}(Fe_3O_4)\end{align*}, in a colloidal suspension. The nanoparticles are about \begin{align*}10\;\mathrm{nm}\end{align*} in diameter. Ferrofluids are interesting because they have the fluid properties of a liquid and the magnetic properties of a solid. For example, a magnet placed just below a dish or cell containing ferrofluid generates an array of spikes in the fluid that correspond to the magnetic lines of force.

Ferrofluid from Educational Innovations, Inc. [2]

When the magnet is removed, the spikes disappear. Ferrofluids were discovered by NASA when it was trying to control liquid in space. They have been used in many applications, including computers disk drives, low friction seals and loudspeakers. Medical researchers are even experimenting with using ferrofluids to deliver drugs to specific locations in the body by applying magnetic fields.

How to Use It as a Demonstration

Show and pass around one or more samples of ferrofluid along with a strong magnet. Let students play with the ferrofluid and magnet and see what they can make it do. You may also want to show and pass around another magnetic material, like a piece of iron, for comparison. Tell your students that since we have been able to make the particles in the ferrofluid so small, we have been able to change the physical state of the material from a solid to a liquid.

Demonstrate that when you bring a magnet close to the liquid, you can see how the particles stream into a star, revealing lines of magnetic force. Point out that this example also illustrates how nanosized particles of a given substance (in this case, a solid called magnetite) exhibit different properties than larger sized particles of the same substance (even though bulk magnetite is a magnetic solid, it does not change visually like the fluid does when you bring a magnet close to it).

Questions to stimulate discussion:

1. What is a liquid?

A liquid is a fluid that flows and takes the shape of its container. Fluids are divided into liquids and gases. In a liquid, the molecules are close together and have more freedom to move around than a solid but not as much as a gas.

2. When you put the magnet near the ferrofluid, it distorts. What causes this distortion?

The distortion is caused by the magnetic field of the magnet. The forces exerted by the magnetic field causes the particles of the ferrofluid (which are themselves like “mini-magnets”) to line up in this pattern. Think about how two magnets have some orientations in relation to each other that they like more than others.

3. What does this distortion represent?

The lines you observe show the direction(s) in which the force field of the magnet acts at each point in space.

4. Why does the solid magnetic material does not distort it’s shape in the same way as the ferrofluid?

The solid material does not distort because its particles are held more tightly (by attractive van der Waals forces, etc.) and thus must respond to the magnetic force as a group, not as individual particles.

5. If the ferrofluid particles feel magnetic forces of attraction towards each other, why does the fluid not condense into a solid?

The nanoparticles are coated with a stabilizing dispersing agent (surfactant) to prevent particle agglomeration even when a strong magnetic field is brought near the ferrofluid. The surfactant must overcome the attractive van der Waals and magnetic forces between the particles to keep them from clumping together.

Sealed display cells of ferrofluid can be ordered from Educational Innovations, Inc., at http://www.teachersource.com (click on “Browse or Search the Catalog”, “Electricity! Magnetism! Engines!” and then “Ferrofluids”) or call 1-888-912-7474. The Ferrofluid Preform Display Cell (item FF-200) is about \begin{align*}25\end{align*} and comes with a pair of circle magnets. A Ferrofluid Experiment Booklet is also available (item FF-150) for about\begin{align*}6\end{align*}.

References

What’s the Big Deal about Nanotechnology?

Science at the nanoscale involves a change of perspective!

What is Nanoscale Science?

• The study of objects and phenomena at a very small scale, roughly \begin{align*}1\end{align*} to \begin{align*}100\;\mathrm{nanometers\ (nm)}\end{align*}
• \begin{align*}10\;\mathrm{hydrogen}\end{align*} atoms lined up measure about \begin{align*}1 \;\mathrm{nm}\end{align*}
• A grain of sand is \begin{align*}1\;\mathrm{million\ nm}\end{align*}, or \begin{align*}1\;\mathrm{millimeter}\end{align*}, wide
• An emerging, interdisciplinary science involving
• Physics
• Chemistry
• Biology
• Engineering
• Materials Science
• Computer Science

How Big is a Nanometer?

• Consider a human hand

Are You a Nanobit Curious?

• What’s interesting about the nanoscale?
• Nanosized particles exhibit different properties than larger particles of the same substance
• As we study phenomena at this scale we...
• Develop new theories
• Discover new questions and answers in many areas, including health care, energy, and technology
• Figure out how to make new products and technologies that can improve people’s lives

Potential Impacts

\begin{align*}{\color{blue}\mathrm{How\ might\ nanoscale\ science\ and\ engineering\ improve\ our\ lives?}}\end{align*}

Innovations In Development or Under Investigation

• Health Care
• Chemical and biological sensors, drugs and delivery devices, prosthetics and biosensors
• Technology
• Better data storage and computation
• Environment
• Clean energy, clean air

Health Care: Nerve Tissue Talking to Computers

• Neuro-electronic networks interface nerve cells with semiconductors
• Possible applications in brain research, neurocomputation, prosthetics, biosensors

Technology: A DVD That Could Hold a Million Movies

• Current CD and DVD media have storage scale in micrometers
• New nanomedia (made when gold self-assembles into strips on silicon) has a storage scale in nanometers
• That is \begin{align*}1,000 \;\mathrm{times}\end{align*} more storage along each dimension (length, width)...... or \begin{align*}1,000,000 \;\mathrm{times}\end{align*} greater storage density in total!

Technology: Building Smaller Devices and Chips

• Nanolithography to create tiny patterns
• Lay down “ink” atom by atom

Environment: Nano Solar Cells

• Nano solar cells mixed in plastic could be painted on buses, roofs, and clothing
• Solar becomes a cheap energy alternative!

So How Did We Get Here?

\begin{align*}{\color{blue}\mathrm{New\ Tools!\ As\ tools\ change,\ what\ we\ can\ see\ and\ do\ changes}}\end{align*}

Using Light to See

• The naked eye can see to about \begin{align*}20\;\mathrm{microns}\end{align*}
• A human hair is about \begin{align*}50-100\;\mathrm{microns}\end{align*} thick
• Light microscopes let us see to about \begin{align*}1\;\mathrm{microns}\end{align*}
• Bounce light off of surfaces to create images

Using Electrons to See

• Scanning electron microscopes (SEMs), invented in the 1930s, let us see objects as small as \begin{align*}10\;\mathrm{nanometers}\end{align*}
• Bounce electrons off of surfaces to create images
• Higher resolution due to small size of electrons

Touching the Surface

• Scanning probe microscopes, developed in the 1980s, give us a new way to “see” at the nanoscale
• We can now image really small things, like atoms, and move them too!

Size-Dependent Properties

\begin{align*}{\color{blue}\mathrm{So\ now\ that\ we\ can\ see''\ what's\ going\ on...}}\end{align*}

\begin{align*}{\color{blue}\mathrm{How \ do \ properties \ change \ at \ the \ nanoscale?}}\end{align*}

Properties of a Material

• A property describes how a material acts under certain conditions
• Types of properties
• Optical (e.g. color, transparency)
• Electrical (e.g. conductivity)
• Physical (e.g. hardness, melting point)
• Chemical (e.g. reactivity, reaction rates)
• Properties are usually measured by looking at large \begin{align*}(\sim 10^{23})\end{align*} aggregations of atoms or molecules

Optical Properties Change: Color of Gold

• Bulk gold appears yellow in color
• Nanosized gold appears red in color
• The particles are so small that electrons are not free to move about as in bulk gold
• Because this movement is restricted, the particles react differently with light

Electrical Properties Change: Conductivity of Nanotubes

• Nanotubes are long, thin cylinders of carbon
• They are \begin{align*}100 \;\mathrm{times}\end{align*} stronger than steel, very flexible, and have unique electrical properties
• Their electrical properties change with diameter, “twist”, and number of walls
• They can be either conducting or semi-conducting in their electrical behavior

Physical Properties Change: Melting Point of a Substance

• Melting Point (Microscopic Definition)
• Temperature at which the atoms, ions, or molecules in a substance have enough energy to overcome the intermolecular forces that hold the them in a “fixed” position in a solid
• Surface atoms require less energy to move because they are in contact with fewer atoms of the substance
Physical Properties Example: Substance’s Melting Point II
\begin{align*}{\color{blue}\mathrm{At\ the\ macroscale}}\end{align*} \begin{align*}{\color{blue}\mathrm{At\ the\ nanoscale}}\end{align*}
The majority of the atoms are...

...almost all on the inside of the object

...split between the inside and the surface of the object

Changing an object’s size... ...has a very small effect on the percentage of atoms on the surface ...has a big effect on the percentage of atoms on the surface
The melting point... ...doesn’t depend on size ... is lower for smaller particles

Size Dependant Properties

\begin{align*}{\color{blue}\mathrm{Why\ do\ properties\ change?}}\end{align*}

Scale Changes Everything

• There are enormous scale differences in our universe!
• At different scales
• Different forces dominate
• Different models better explain phenomena
• (See the Scale Diagram handout)

Scale Changes Everything II

• Four important ways in which nanoscale materials may differ from macroscale materials
• Gravitational forces become negligible and electromagnetic forces dominate
• Quantum mechanics is the model used to describe motion and energy instead of the classical mechanics model
• Greater surface to volume ratios
• Random molecular motion becomes more important

Dominance of Electromagnetic Forces

• Because the mass of nanoscale objects is so small, gravity becomes negligible
• Gravitational force is a function of mass and distance and is weak between (low-mass) nanosized particles
• Electromagnetic force is a function of charge and distance is not affected by mass, so it can be very strong even when we have nanosized particles
• The electromagnetic force between two protons is \begin{align*}10^{36}\;\mathrm{times}\end{align*} stronger than the gravitational force!

Quantum Effects

• Classical mechanical models that we use to understand matter at the macroscale break down for...
• The very small (nanoscale)
• The very fast (near the speed of light)
• Quantum mechanics better describes phenomena that classical physics cannot, like...
• The colors of nanogold
• The probability (instead of certainty) of where an electron will be found

Surface to Volume Ratio Increases

• As surface to volume ratio increases
• A greater amount of a substance comes in contact with surrounding material
• This results in better catalysts, since a greater proportion of the material is exposed for potential reaction

Random Molecular Motion is Significant

• Tiny particles (like dust) move about randomly
• At the macroscale, we barely see movement, or why it moves
• At the nanoscale, the particle is moving wildly, batted about by smaller particles
• Analogy
• Imagine a huge \begin{align*}(10\;\mathrm{meter})\end{align*} balloon being batted about by the crowd in a stadium. From an airplane, you barely see movement or people hitting it; close up you see the balloon moving wildly.

Nanotechnology is a Frontier in Modern-Day Science

\begin{align*}{\color{blue}\mathrm{What\ else\ could\ we\ possibly\ develop?}}\end{align*}

\begin{align*}{\color{blue}\mathrm{What\ other\ things\ are\ nanoengineers,\ researchers\ and\ scientists\ investigating?}}\end{align*}

Detecting Diseases Earlier

• Quantum dots glow in UV light
• Injected in mice, collect in tumors
• Could locate as few as \begin{align*}10\end{align*} to \begin{align*}100\end{align*} cancer cells

Growing Tissue to Repair Hearts

• Growing cardiac muscle tissue is an area of current research
• Grown in the lab now, but the fibers grow in random directions
• With the help of nanofiber filaments, it grows in an orderly way
• Could be used to replace worn out or damaged heart tissue

Preventing Viruses from Infecting Us

• The proteins on viruses bind to our body cells
• Could cover these proteins with nanocoatings
• Stop them from recognizing and binding to our cells
• We would never get the flu!
• A protein recognition system has been developed

Making Repairs to the Body

• Nanorobots are imaginary, but nanosized delivery systems could...
• Break apart kidney stones, clear plaque from blood vessels, ferry drugs to tumor cells

Pause to Consider

\begin{align*}{\color{blue}\mathrm{How\ delicate\ are\ nanoscale-sized\ objects?}}\end{align*}

\begin{align*}{\color{blue}\mathrm{How\ well\ do\ we\ understand\ the\ environmental\ and\ health\ impacts\ of\ nanosized\ clusters\ of\ particles?}}\end{align*}

Nanodevices Are Sensitive!

• Radiation particles can cause fatal defects during manufacturing
• Development requires very clean environments
• Only a few, out of many produced, are perfect

Potential Risks of Nanotechnology

• Health issues
• Nanoparticles could be inhaled, swallowed, absorbed through skin, or deliberately injected
• Could they trigger inflammation and weaken the immune system? Could they interfere with regulatory mechanisms of enzymes and proteins?
• Environmental issues
• Nanoparticles could accumulate in soil, water, plants; traditional filters are too big to catch them
• New risk assessment methods are needed
• National and international agencies are beginning to study the risk; results will lead to new regulations

Summary: Science at the Nanoscale

• An emerging, interdisciplinary science

Nanotechnology: A New Day

• The nanotechnology revolution will lead to...
• New areas of research and technology design
• Better understanding of matter and interactions
• New ways to tackle important problems in healthcare, energy, the environment, and technology

### Teacher Notes

Overview

These slides introduce students to what nanoscience is, and capture in a relatively brief overview what is interesting about science at the nanoscale. We want students to see that science is a dynamic, exciting, and evolving undertaking that impacts the world around us through the technological development that accompanies the progress in scientific understanding and tool development.

In contrast to the other lessons in the Size Matters unit that focus primarily (and more deeply) on one aspect of nanoscience, this one-day overview surveys all of the topics addressed by the other Size Matters lessons. Questions such as “How big is a nanometer” and “What are the various types of microscopes used to see small things” are addressed. Properties of materials that can vary at the nanoscale are identified, and some fundamental differences between the nanoscale and bulk scale are highlighted. Finally, examples of currently existing commercial applications, areas of research, and visions for the future are presented. A final slide summarizes key points about nanoscience as an emerging, interdisciplinary science.

Slide 1: What’s the Big Deal about Nanoscience?

Explain to students that you’re going to explain what nanoscience is and how we see small things, and give a few examples of interesting structures and properties of the nanoscale.

Slide 2: What is Nanoscale Science?

Nanoscale science deals with the study of phenomena at a very small scale––\begin{align*}10^{-7}\;\mathrm{m} (100\;\mathrm{nm})\end{align*} to \begin{align*}10^{-9}\;\mathrm{m}(1\;\mathrm{nm})\end{align*}––where properties of matter differ significantly from those at larger scales. This very small scale is difficult for people to visualize. There are several size- and scale-related activities as part of the NanoSense materials that you can incorporate into your curriculum that help students think about the nanoscale.

This slide also highlights that nanoscale science is a multidisciplinary field and draws on areas outside of chemistry, such as biology, physics, engineering and computer science. Because of its multidisciplinary nature, nanoscience may require us to draw on knowledge in potentially unfamiliar academic fields.

Slide 3: How Big is a Nanometer?

This slide gives a “powers of ten” sense of scale. If you are running the slides as a PowerPoint presentation that is projected to the class, you could also pull up one or more powers of ten animations. See http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10 for a nice example that can give students a better sense of small scale.

As you step through the different levels shown in the slide, you can point out that you can see down to about #3 (\begin{align*}1000\;\mathrm{microns}\end{align*}) with the naked eye, and that a typical microscope as used in biology class will get you down to about #5 (\begin{align*}10\;\mathrm{microns}\end{align*}). More advanced microscopes, such as scanning electron microscopes can get you pretty good resolution in the #6 (\begin{align*}1\;\mathrm{micron}\end{align*}) range. Newer technologies (within the last 20 years or so) allow us to “see” in the #7 (\begin{align*}100\;\mathrm{nanometer}\end{align*}) through #9 (\begin{align*}1\;\mathrm{nanometer}\end{align*}) ranges. These are the scanning probe and atomic force microscopes.

Slide 4: Are you a Nanobit Curious?

This slide highlights why we should care about nanoscience: It will change our lives and change our understanding of matter. A group of leading scientists gathered by the National Science Foundation in 1999 said: "The effect of nanotechnology on the health, wealth and standard of living for people in this century could be at least as significant as the combined influences of microelectronics, medical imaging, computer-aided engineering and manmade polymers developed in the past century.” (Accessed August, 2005, from http://www.techbizfl.com/news_desc.asp?article_id=1792.)

Slide 5: Potential Impacts

The next few slides provide examples of how nanoscale science and engineering might improve our lives.

Slide 6: Innovations In Development or Under Investigation

Point out that tools for manipulating materials are becoming more sophisticated and improving our understanding of how atoms and molecules can be controlled. This will lead to significant improvements in materials, and, in turn, to new products, applications, and markets that could have revolutionary impact on our lives.

This next few slides focus on innovations related to the environment, technology, and healthcare. A few of these products being commercialized now, but most are in research labs or are envisioned for the distant future.

Slide 7: Health Care: Nerve Tissue Talking to Computers

Researchers are studying the electrical interfacing of semiconductors with living cells––in particular, neurons––to build hybrid neuro-electronic networks. Cellular processes are coupled to microelectronic devices through the direct contact of cell membranes and semiconductor chips. For example, electrical interfacing of individual nerve cells and semiconductor microstructures allow nerve tissue to directly communicate their impulses to computer chips. Pictured is a snail neuron grown on a CMOS chip with \begin{align*}128 \times 128\end{align*} transistors. The electrical activity of the neuron is recorded by the chip, which is fabricated by Infineon Technologies. This research is directed (1) to reveal the structure and dynamics of the cell-semiconductor interface and (2) to build up hybrid neuro-electronic networks. Such research explores the new world at the interface of the electronics in inorganic solids and the ionics in living cells, providing the basis for future applications in medical prosthetics, biosensorics, brain research and neurocomputation.

References:

Slide 8: Technology: A DVD That Could Hold a Million Movies

In 1959, Richard Feynman asked if we could ever shrink devices down to the atomic level. He couldn’t find any laws of physics against it. He calculated that we could fit all printed information collected over the past several centuries in a \begin{align*}3-\;\mathrm{dimensional}\end{align*} cube smaller than the head of a pin. How far have we come? A \begin{align*}2-\;\mathrm{dimensional}\end{align*} version of Feynman’s vision is in research labs. The picture on this slide illustrates the potential of nano-devices for data storage. On the left are images of two familiar data storage media: the CD-ROM and the DVD. On the right is a self-assembled memory on a silicon surface, formed by depositing a small amount of gold on it. It looks like CD media, except that the length scale is in nanometers, not micrometers. So the corresponding storage density is a million times higher! The surface automatically formats itself into atomically-perfect stripes (red) with extra atoms on top (white). These atoms are neatly lined up at well-defined sites along the stripes, but occupy only about half of them. It is theoretically possible to use the presence of an atom to store a \begin{align*}1\end{align*}, and the absence to store a \begin{align*}0\end{align*}. The ultimate goal would be to build a data storage medium that needs only a single atom per bit. The big question is how to write and read such bits efficiently.

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Slide 9: Technology: Building Smaller Devices and Chips

A technique called nanolithography lets us create much smaller devices than current approaches. For example, the Atomic Force Microscope (AFM) nanolithography image of the Mona Lisa was created by a probe oxidation technique. This technique can be used to further miniaturize the electrical components of microchips. Dip pen nanolithography is a ‘direct write’ technique that uses an AFM to create patterns and to duplicate images. “Ink” is laid down atom by atom on a surface, through a solvent––often water.

References:

Slide 10: Environment: Nano Solar Cells

Enough energy from the sun hits the earth every day to completely meet all energy needs on the planet, if only it could be harnessed. Doing so could wean us off of fossil fuels like oil and provide a clean energy alternative. But currently, solar-power technologies cost as much as 10 times the price of fossil fuel generation. Chemists at U.C. Berkeley are developing nanotechnology to produce a photovoltaic material that can be spread like plastic wrap or paint. These nano solar cells could be integrated with other building materials, and offer the promise of cheap production costs that could finally make solar power a widely used electricity alternative.

Current approaches embed nanorods (bar-shaped semiconducting inorganic crystals) in a thin sheet (\begin{align*}200\;\mathrm{nanometers}\end{align*} deep) of electrically conductive polymer. Thin layers of an electrode sandwich these nanorod-polymer composite sheets. When sunlight hits the sheets, they absorb photons, exciting electrons in the polymer and the nanorods, which make up \begin{align*}90\end{align*} percent of the composite. The result is a useful current that is carried away by the electrodes. Eventually, nanorod solar cells could be rolled out, ink-jet printed, or even painted onto surfaces, so that even a billboard on a bus could be a solar collector.

References:

Slide 11: So How Did We Get Here?

This slide denotes the beginning of a short discussion of the evolution of imaging tools (i.e. microscopes). One of the big ideas in science is that the creation of tools or instruments that improve our ability to collect data is often accompanied by new science understandings. Science is dynamic. Innovation in scientific instruments is followed by a better understanding of science and is associated with creating innovative technological applications.

Slide 12: Using Light to See

You may want to point out that traditional light microscopes are still very useful in many biology-related applications since things like cells and some of their features can readily be seen with this tool. They are also inexpensive relative to other microscopes and are easy to set up.

Slide 13: Using Electrons to See

Point out that the difference between the standard light microscope and the scanning electron microscope is that electrons, instead of various wavelengths of light, are “bounced” off the surface of the object being viewed, and that electrons allow for a higher resolution because of their small size. You can use the analogy of bouncing bb’s on a surface to find out if it is uneven (bb’s scattering in all different directions) compared to using beach balls to do the same job.

Slide 14: Touching the Surface

Point out how small the tip of the probe is compared to the size of the atoms in the picture. Point out that this is one of the smallest tips you can possibly make, and that it has to be made from atoms. Also point out that the tip interacts with the surface of the material you want to look at, so the smaller the tip, the better the resolution. But because the tip is made from atoms, it can’t be smaller than the atoms you are looking at. Tips are made from a variety of materials, such as silicon, tungsten, and even carbon nanotubes.

The different types of scanning probe microscopes are discussed in Lesson 4: Tools of the Nanosciences. For example, in the STM, a metallic tip interacts with a conducting substrate through a tunneling current (STM). With the AFM, the van der Waals force between the tip and the surface is the interaction that is traced.

Slide 15: Size-Dependent Properties

The next few slides focus on how nanosized materials exhibit some size-dependent effects that are not observed in bulk materials.

Slide 16: Properties of a Material

It is important to talk with your students about how we know about the properties of materials––how are they measured and on what sized particles are the measurements made? In most cases, measurements are made on macroscale particles, so we tend to have good information on bulk properties of materials but not the properties of nanoscale materials (which may be different).

This slide also points out four types of properties that are often affected by size. This is not an exhaustive list but rather a list of important properties that usually come up when talking about nanoscience.

[Note: This slide summarizes the content in the “What Does it Mean to Talk About the Characteristics and Properties of a Substance?” and “How Do We Know the Characteristics and Properties of Substances?” paragraphs in the Size-Dependant Properties student reading.]

Slide 17: Optical Properties Change: Color of Gold

The gold example illustrates a simple comparison between the nano and bulk properties of a particular material. It is important to point out to your students that we can’t say exactly what color a material will always be at a given particle size. This is because there are other factors involved like arrangement of atoms and molecules in the particles and the charge(s) present on particles. However, it is possible to control for these various factors to create desired effects, as in this case the creation of “red” gold using 12 nanometer-sized particles.

[Note: This slide summarizes the content in the “What’s Different at the Nanoscale” paragraph in the Size-Dependant Properties student reading.]

Slide 18: Electrical Properties Example: Conductivity of Nanotubes

Electrical properties of materials are based on the movement of electrons and the positively-charged spaces, or “holes,” they leave behind. The electronic properties of a nanotube depend on the direction in which the sheet was rolled up. Some nanotubes are metals with high electrical conductivity, while others are semiconductors with relatively large band gaps. Which one it becomes depends on way that it is rolled (also called the "chirality" of the nanotube"). If it's rolled so that its hexagons line up straight along the tube's axis, the nanotube acts as a metal. If it's rolled on the diagonal, so the hexagons spiral along the axis, it acts as a semiconductor. See the “Unique Properties at the Nanoscale: Teacher Reading” for more information.

Slide 19: Physical Properties Change: Melting Point of a Substance

Note that even in a solid, the atoms are not really “fixed” in place but are rather vibrating or rotating around a fixed point. In liquids, the atoms also rotate and move past each other in space (translational motion), although they don’t have enough energy to completely overcome the intermolecular forces and move apart as in a gas.

Slide 20: Physical Properties Example: Melting Point of a Substance II

At the nanoscale, a smaller object will have a significantly greater percentage of its atoms on the surface of the object. Since surface atoms need less energy to move (because they are in contact with fewer atoms of the same substance), the total energy needed to overcome the intermolecular forces hold them “fixed” is less and thus the melting point is lower.

Slide 21: Size-Dependant Properties

The next few slides focus on why nanosized materials exhibit size-dependent effects that are not observed in bulk materials.

Slide 22: Scale Changes Everything

Ask your students to refer to the Scale Diagram handout. Use the diagram to point out how there are enormous scale differences in the universe (left part of the diagram), and where different forces dominate and different models better explain phenomena (right part of diagram). Scale differences are also explored in more detail in “Visualizing the Nanoscale: Student Reading” from Lesson 2: Size and Scale.

Slide 23: Scale Changes Everything II

This slide highlights four ways in which nanoscale materials may differ from their macroscale counterparts. It is important to emphasize that just because you have a small group of some type of particle, it does not necessarily mean that a whole new set of properties will arise. Whether or not different observable properties arise depends not only on aggregation, but also on the arrangement of the particles, how they are bonded together, etc. This slide sets up the next four slides, where each of the four points (gravity, quantum mechanics, surface to volume ratio, random motion) is described in more detail.

Slide 24: Dominance of Electromagnetic Forces

This slide compares the relative strength between the electromagnetic and gravitational forces. The gravitational force between two electrons is feeble compared to the electromagnetic forces. The reason that you feel the force of gravity, even though it is so weak, is that every atom in the Earth is attracting every one of your atoms and there are a lot of atoms in both you and the Earth. The reason you aren't bounced around by electromagnetic forces is that you have almost the same number of positive charges as negative ones, so you are (essentially) electrically neutral. Gravity is only (as far as we know) attractive. Electromagnetic forces (which include electrical and magnetic forces) can be either attractive or repulsive. Attractive and repulsive forces cancel each other out; they neutralize each other. Since gravity has no repulsive force, there’s no weakening by neutralization. So even though gravity is much weaker than electrical force, gravitational forces always add to each other; they never cancel out.

Slide 25: Quantum Effects

This slide highlights that, at the nanoscale, we need to use quantum mechanics to describe behavior rather than classical mechanics. The properties reading describe the differences. You can decide how much discussion to have about classical and quantum mechanics with your students. For the purposes of this introductory unit, it is important to let students know that we use a different set of “rules” to describe particles that fall into the nanoscale and smaller range.

Slide 26: Surface to Volume Ratio Increases

This slide highlights the fact that as you decrease particle size, the amount of surface area increases. The three-part graphic on the slide illustrates how, for the same volume, you can increase surface area simply by cutting. Each of the three blocks has the same total volume, but the block that has the most cuts has a far greater amount of surfaces area. This is an important concept since it effects how well a material can interact with other things around it. With your students, you can use following example. Which will cool a glass of water faster: Two ice cubes, or the same two ice cubes (same volume of ice) that have been crushed?

Slide 27: Random Molecular Motion is Significant

This slide highlights the importance of random (“Brownian”) motion at small scales. Tiny particles, such as dust, are in a constant state of motion when seen through microscope because they are being batted about by collisions with small molecules. These small molecules are in constant random motion due to their kinetic energy, and they bounce the larger particle around. At the macroscale, random motion is much smaller than the size of the particle, but at the nanoscale this motion is large when compared to the size of the particle. A nice animation that illustrates this concept is available at http://galileo.phys.virginia.edu/classes/109N/more_stuff/Applets/brownian/brownian.html

Slide 28: Nanotechnology is a Frontier of Modern-Day Science

The next few slides focus on some cutting-edge research and applications that nanoscientists and engineers are working on.

Slide 29: Detecting Diseases Earlier

Quantum dots are small devices that contain a tiny droplet of free electrons, and emit photons when submitted to ultraviolet (UV) light. Quantum dots are considered to have greater flexibility than other fluorescent materials, which makes them suited for use in building nanoscale applications where light is used to process information. Quantum dots can, for example, be made from semiconductor crystals of cadmium selenide encased in a zinc sulfide shell as small as 1 nanometer (one-billionth of a meter). In UV light, each dot radiates a brilliant color.

Because exposure to cadmium could be hazardous, quantum dots have not found their way into clinical use. But they have been used as markers to tag particles of interest in the laboratory. Scientists at Georgia Institute of Technology have developed a new design that protects the body from exposure to the cadmium by sealing quantum dots in a polymer capsule. The surface of each capsule can attach to different molecules. In this case, they attached monoclonal antibodies directed against prostate-specific surface antigen, which is found on prostate cancer cells. The researchers injected these quantum dots into live mice that had human prostate cancers. The dots collected in the tumors in numbers large enough to be visible in ultraviolet light under a microscope. Because the dots are so small, they can be used to locate individual molecules, making them extremely sensitive as detectors. Quantum dots could improve tumor imaging sensitivity tenfold with the ability to locate as few as \begin{align*}10\end{align*} to \begin{align*}100\end{align*} cancer cells. Using this technology, we could detect cancer much earlier, which means more successful, easier treatment.

References:

Slide 30: Growing Tissue to Repair Hearts

Cardiac muscle tissue can be grown in the lab, but the fibers grow in random directions. Researchers at the University of Washington are investigating what type of spatial cues they might give heart-muscle cells so that they order themselves into something like the original heart-muscle tissue. Working with one type of heart muscle cell, they have been able to build a two-dimensional structure that resembles native tissue. They use nanofibers to “instruct” muscle cells to orient themselves in a certain way. They have even able to build a tissue-like structure in which cells pulse or ‘beat’ similar to a living heart.

This image on this slide shows cardiac tissue grown with the aid of nanofiber filaments. It displays well-organized growth that is potentially usable to replace worn out or damaged heart tissue. The ultimate goal of building new heart-muscle tissue to repair and restore a damaged human heart is a long way off, but there have been big advances in tissue engineering in recent years.

References:

Slide 31: Preventing Viruses from Infecting Us

If we could cover the proteins that exist on the influenza virus, we could prevent the virus from recognizing and binding to our body cells. We would never get the flu! A protein recognition system has already been developed. More generally, this work suggests that assembled virus particles can be treated as chemically reactive surfaces that are potentially available to a broad range of organic and inorganic modification.

References

Slide 32: Making Repairs to the Body

The image on this slide depicts what one nanoscientist from the Foresight Institute imagines might be possible one day in the far future. It shows how a nanorobot could potentially interact with human cells. When people hear of nanotechnology from science fiction, this is often the form that it takes. But we do not know if such a probe is possible. Nanobots like this, if even possible, are probably decades away. What are currently being researched, with hopeful outcomes, are nanosized drug delivery systems that could be used to diagnose disease and fight pathogens.

The fantasy nanobot, for example, could (1) be used to cure skin diseases (embedded in a cream, they could remove dead skin and excess oils, apply missing oils), (2) be added to mouthwash to destroy bacteria and lift plaque or tartar from the teeth to be rinsed away, (3) augment the immune system by finding and disabling unwanted bacteria and viruses, or (4) nibble away at plaque deposits in blood vessels, widening them to prevent heart attacks.

References:

Slide 33: Pause to Consider

The next two slides focus on the delicate nature of nanosized objects, the potential risks of nanotechnology to humans and the environment, and the need study the risks and regulate the development of products that contain nanoparticles.

Slide 34: Nanodevices are Sensitive

Because of their small size, nanodevices are very sensitive and can easily be damaged by, for example, the natural environmental radiation all around us. In the picture for this example, we see a pit caused by an alpha particle hitting the surface of mica. An alpha particle is a high-energy helium nucleus that is the lowest-energy form of nuclear radiation. Alpha particles are also the particles that Rutherford used for the gold foil experiment in which he discovered the arrangement of protons within the atom that is now commonly known as the nucleus. The impact of alpha particles on a solid surface can cause physical damage by causing other atoms in the surface to be moved out of place. These types of defects can be potentially fatal in high-density electronics and nanodevices. To compensate, extremely clean manufacturing environments and very high redundancy—perhaps millions of copies of nanodevices for a given application––are required.

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Slide 35: Potential Risks of Nanotechnology

Nanotechnology’s potential is encouraging, but the health and safety risks of nanoparticles have not been fully explored. We must weigh the opportunities and risks of nanotechnology in products and applications to human health and the environment. Substances that are harmless in bulk could assume hazardous characteristics because when particles decrease in size, they become more reactive. A growing number of workers are exposed to nanoparticles in the workplace, and there is a danger that the growth of nanotechnology could outpace the development of appropriate safety precautions. Consumers have little knowledge of nanotechnology, but worries are already beginning to spread. For example, environmental groups have petitioned the Food and Drug Administration to pull sunscreens from the market that have nano-size titanium dioxide and zinc oxide particles. As nanotechnology continues to emerge, regulatory agencies must develop standards and guidelines to reduce the health and safety risks of occupational and environmental nanoparticle exposure.

References:

Slides 36: Summary: Science at the Nanoscale

Nanoscience is truly an interdisciplinary science. Progress in nanoscale science and technology results from research involving various combinations of biology, chemistry, physics, materials engineering, earth science, and computer science. Nanoscience also provides a way to revisit the core concepts from these domains and view them through a different lens. Learning about nanoscience can support understanding of the interconnections between the traditional scientific domains and provide compelling, realworld examples of science in action.

Engineering is a discipline rarely discussed in science. Yet, engineering and design are the disciplines that accompany, and sometimes precede, new findings in science. The focus on nanotechnology highlights the intimate nature of the pairing of science and engineering to produce products for society.

Slides 37: Nanotechnology: A New Day

Nanoscience is an emerging science that will change our understanding of matter and help us solve hard problems in many areas, including energy, health care, the environment, and technology. With the power to collect data and to manipulate particles at such a tiny scale, new areas of research and technology design are emerging. Some applications––like stain resistant pants and nanopaint on cars––are here today, but most applications are years or decades away. But nanoscience gives us the potential to understand and manipulate matter more than ever before.

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