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Study Guide
According to the National Nanotechnology Initiative, nanotechnology is defined as “research to discover new behavior and properties of materials with dimensions at the nanoscale, which ranges roughly from 1 to 100 nanometers (nm)”. The important feature of nanotechnology is the ability to manipulate material at the molecular level to create stronger and better materials.
I) Origin of the Field
Making and studying things on a molecular scale has a long history, but the concept of the field of nanotechnology originated from physicist Richard Feynman’s talk titled “There’s Plenty of Room at the Bottom” in 1959. Feynman described a process in which things are manipulated and controlled at the nanoscale. Feynman also discussed the idea of miniaturization–that man would create powerful nanoscale devices.
See the Entire Talk: This idea was explored in depth in the 1980s by Dr. K. Eric Drexler, who proposed the “grey goo” scenario (See “Challenges”).
II) Why nano?
Materials can behave differently at the nano scale. They may conduct electricity or heat better. They may be stronger. They may have different magnetic properties. They may reflect light better. They also have a larger surface area relative to their volume, which allows for more interactions with the atoms around them. For example, gold conducts heat and electricity well, but does not absorb light well. However, gold nanoparticles are able to absorb laser light, and can turn that into heat. This heat can be used to kill cells, such as cancer cells. Carbon structures at the nanoscale are incredibly strong, and carbon nanoparticles are already being used to build bicycles and car parts.
Figure 1: Buckminsterfullerene, C60. This molecule, Buckminsterfullerene, is the simplest member of the carbon structures called fullerenes. Fullrenes are molecules composed entirely of carbon, and may take on different shapes such as spheres, ellipsoids, tubes, or planes.
III) How are nanomaterials made?
Nanoparticles are produced by living organisms, by fires, volcanic activity and in vehicle exhaust. Some nanomaterials can self–assemble from their components; for example, fragments of carbon can assemble into tubes (carbon nanotubes). Chemical synthesis and self–assembly has also made it possible to make some very simple molecular machines, but these cannot yet perform useful tasks. To make more sophisticated nanomaterials, bottom–up and top–down synthesis approaches have been proposed. Both approaches are in relatively early stages of development.
Bottom-up Approach
This approach begins with small components to build complex materials. Larger structures are built atom by atom or molecule by molecule. The atom to be manipulated can be bound to a molecule that acts as a “tool tip” at the end of a mechanical manipulator. The covalent bonds holding together the atoms in the device being assembled must be stronger than the intermolecular forces holding the atom to the tool tip. The electrical forces that hold materials together make atoms and molecules “sticky” and difficult to manipulate one–by–one.
The bottom–up approach has the advantage of not being wasteful, because it does not involve carving smaller pieces from a big piece of material. However, this technique is very laborious and technically challenging. Therefore, it is not currently suitable for an industrial process.
Top-down Approach
This approach begins with larger materials to build smaller devices by removing pieces from the original material. An example of this approach is the synthesis of a microchip. One starts with a big piece of silicon wafer, and carves out pieces to construct the microchip. To make materials at very small scales, it is not possible to use regular tools to carve or mold the components because such tools are too large, and, at the sub–microscopic scale, their surfaces are too rough. Even photolithography–the process of creating a pattern, such as those in integrated circuits, using light–is not currently precise enough to work at the nanoscale.
IV) Nanoscale Material in Nature
In nature, organisms have been constructing things at the nanoscale for a long time. For examples, geckos have super–fine hairs on their feet, which allow them to stick to walls and glass. Hemoglobin is a nanoscale molecule in our blood that carries oxygen to different parts of the body. Within cells, nutrients are transported by natural nano–scale molecular machines made of protein.
V) Nanoscience Applications:
In the Near Future:
- Cancer: Quantum dots have shown promise at revealing tumors. Quantum dots are nanoparticles that are semiconductors (like silicon wafers), and have properties that are between regular bulk semiconductors and those of individual molecules. When these quantum dots are used in conjunction with magnetic resonance imaging (MRI), they can provide clear images of tumor sites. Groups of atoms–functional groups–may be attached to the quantum dots to help them bind to tumor cells.
- Nanofiltration: Nanofiltration is a way to filter water to produce clean, drinkable water. This is especially important in countries that lack access to clean water. Nanoscale titanium dioxide is also used to kill bacteria, such as E. coli, in drinking water.
Perhaps One Day:
- Medical industry: Patients might be able to drink fluids containing nanorobots designed to attach to cancer cells and viruses. These nanorobots might even be programmed to perform surgeries.
- Environment: Airborne nanorobots could be programmed to fix the ozone hole, and clean up contaminants in the water and air.
VI) Challenges, Risks and ethics
We still do not have a complete understanding of particles at the molecular and atomic scales. Since particles behave differently at the nanoscale, there is a concern that they may be toxic.
Eric Drexler, who introduced the term “nanotechnology”, proposed a “grey goo” scenario which refers to self–replicating nanorobots malfunctioning and replicating out–of–control as they pull carbon from the earth to make more of themselves. Since then, Drexler has changed his view about the “grey goo” scenario. Currently, no nanorobots exist, and self–replicating machines may not even be possible.
Since nanotechnology could be especially useful in the field of medicine, it may allow people to enhance themselves physically. By using nanotechnology, we may be able to make ourselves smarter, stronger, and create other abilities that we currently do not possess. Where do we draw the line for this? Also, if these treatments are expensive, will they further increase the gap between the economically advantaged and the economically disadvantaged?
Nanotechnology and Chemistry
Nanotechnology is an interdisciplinary science that includes biology, medicine, engineering, and physics, and is especially closely tied to the field of chemistry.
Atoms, Molecules, and Elements
Atoms are infinitesimally small building blocks of matter. Molecules are formed from two or more atoms joined together. An element is a substance that cannot be separated into simpler substances by chemical means. There are 118 elements currently known (though element number 117 has yet to be isolated).
Carbon is element number six in the periodic table, and has an atomic mass of 12.022amu. Since carbon is on the right side of the metalloids (elements that have both metal and nonmetal properties – Boron, Silicon, Germanium, Antimony, and Tellurium), it is considered a nonmetal.
Dimensions and Units
In chemistry, many properties of matter are quantitative, and a lot of things can be measured. The International System of Units (SI units) is used for these measurements. SI is the modern metric system of measurement. For example, the SI base unit for length is the meter (m). The prefixes such as giga, mega, kilo, deci, centi, milli, micro, nano, pico, and femto are used to show the different variations of a meter.
Table 1: Table of Greek Prefixes and Their Meaning
| Prefix | Meaning |
| Giga | 109 |
| Mega | 106 |
| Kilo | 103 |
| Deci | 10-1 |
| Centi | 10-2 |
| Milli | 10-3 |
| Micro | 10-6 |
| Nano | 10-9 |
| Pico | 10-12 |
| Femto | 10-15 |
Bonding
Carbon is one of the most abundant elements on earth and is present in all living organisms. As a group 4A element, it is able to form four strong covalent bonds. Another important property of carbon atoms is that they are able to bond to one another, forming long chains and rings. Carbon has four valence electrons, so it is able to bond to four other atoms to form many different types of molecules. For example, in Buckminsterfullerene, C60, the molecule is composed of six– and five–membered carbon rings.
Atomic Structure and VSEPR Theory
In a carbon nanotube, the properties of the tube depend on the arrangement of carbon atoms. With the right arrangement, carbon nanotubes can be made that are stronger than steel. Molecules have a three–dimensional geometric shape. Valence Shell Electron–Pair Repulsion (VSEPR) theory describes the three–dimensional shape the molecules take on. Since electron pairs tend to repel each other, molecules optimize geometric shapes so that the electron pairs are farthest apart.
Quantum Mechanics
Quantum mechanics is the study of systems with atomic scale dimensions. In quantum mechanics, matter and radiation have wave–like and particle–like behavior. Positions of particles are described in terms of probabilities rather than certainties. At large scales and with large numbers of particles, classical physics is a good approximation of quantum mechanics. But at small scales, things can behave in a way that conflicts with our everyday, classical, experience. A person cannot walk through a wall or teleport, but at the nanoscale, electrons can – and it’s called tunneling.
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