Nivaldo J. Tro

http://www.cengage.com/chemistry/tro

Mark Erickson • Hartwick College

Chapter 19Nanotechnology

Plenty of Room at the Bottom:Out of SciFi and into the Lab• Five atoms, end to end, measure

one nanometer (10-9 m).

• Human hair measures 20,000 nm in diameter.

• Can we make a machine so tiny that it could navigate the bloodstream?

• Nature has already done this.

• Some see nanotechnology as bioimitation.

Plenty of Room at the Bottom:Quantum Mechanical Size Effects• Bulk properties of macroscopic

materials are familiar.– Silicon is an insulator.– Copper is an opaque metallic

conductor.– Aluminum is a stable

structural material.– Gold and platinum are metals

used in jewelry.• Nano-sized materials exhibit

different properties.• Quantum mechanical size effects• Surface phenomena

Quantum Mechanical Size Effects• Size effects occur when a material is prepared in dimensions

so small that the electron has a limited amount of space (compared with its size).

• Electrons have higher energies than they would have in the bulk material, resulting in different properties.

• Quantum dots used for– Anticancer treatment– Counterfeit prevention measures– Lighting devices

Surface Properties• A finely divided material places most of the atoms making up

the material on the exposed surface and not in the interior of the material.

• Silicon nanoparticles become conductive (silicon is normally a semiconductor) and emit visible light when energized.

• Copper, which is normally opaque, becomes transparent.

• Aluminum becomes easily combustible.

• gold and platinum change colors and even show catalytic activity.

Concept Check 19.1• How do quantum dots get their color properties?

Concept Check 19.1 Solution• Quantum dots are bits of semiconducting material

similar to the materials used in light-emitting diodes (LEDs).

• These bits are so small that their light-emitting properties can be tuned simply by changing their size.

Scanning Tunneling Microscope• In 1981 Binnig and Rohrer

designed the first scanning tunneling microscope (STM).

• While measuring electrical conductivity over a surface, they noticed “bumps” in their measurements that were interpreted as individual atoms.

Scanning Tunneling Microscope• Modern STMs scan

surfaces of interest with atomically fine metallic tips.

• By using the tip as a tiny magnet, we can not only image atoms, but move them around.

Atomic Visibility• STMs made the atomic world visible for the first time.• Premier tool for scientists developing nanotechnology• Binnig and Rohrer were awarded the 1986 Nobel Prize in

physics for this work.

Atomic Force Microscope• STMs can image only metallic

surfaces.

• Atomic force microscopes (AFM) can image nonmetallic surfaces.

• AFMs track a laser reflected off the back of a cantilever. Tracking the laser movement as the tip is moved back and forth across the surface produces an image.

• Tapping AFMs can image biological samples.

A tapping-mode AFM image of two transcription factor proteins (blue) interacting with DNA chain (red).

Atomic Force Microscope (AFM)

Lambda phage DNA on mica obtained by tapping-mode AFM.

AFM

Buckyballs• Graphite: Carbon atoms in

layered sheets• Diamond: Three-dimensional

honeycomb• Buckyballs: 60 carbon atoms

bonded forming a hollow sphere– Smalley, Curl, and Kroto

awarded the 1996 Nobel Prize in chemistry

– Named for R. Buckminster Fuller, American architect of geodesic designs resembling C60

Nanotubes• 1991 marks the birth of the buckytube

– Shape is tubular instead of spherical

• A few atoms in diameter but theoretically could extent as far as kilometers in length

• Strong as steel– Can be made electrically conducting

Concept Check 19.2• List the three forms of carbon.

Concept Check 19.2 Solution• Carbon has three forms (allotropes):

1) Graphite

2) Diamond

3) Fullerenes (buckyballs and carbon nanotubes)

• All three forms are pure carbon. They differ in how the carbon atoms are bonded to each other.

Carbon Nanotubes

• Image of a nanoradio taken by a transmission electron microscope

• The “tower” is a single carbon nanotube that is– less than one micron long– 10 nanometers wide

• The waves shown here have been added for visual effect only.

Conducting Electricity with Nanotubes

• Tiny electric circuits may allow– Flat-panel displays– Water desalination– Flexible, foldable monitor displays

Moore’s Law• In 1965, Gordon Moore,

cofounder of Intel, introduced a concept now called Moore’s Law.

• The law states that the number of transistors that can be placed on an integrated circuit increases every 24 months.

• Trends have matched Moore’s Law predictions for many years.

Nanomedicine• Doctors can encase foreign

cells in materials designed so that the body will not reject them because antibodies and not pass through the membrane nanometer sized pores.– Pancreatic animal cells can

be introduced into a human diabetic patient.

– Nanovesicles that deliver oxygen to tissues, acting like red blood cells.

Artificial Cells and Nanorobots• Can we construct nanomachines that mimic living cells?

• Can we construct nanorobots that can work within biological systems?

• Current work involves targeted drug delivery.– Protection of healthy cells from chemo drugs– Concentrated delivery of toxins to cancerous tissue

Products of Current Nanotechnology

• Textiles– Clothing is quietly being transformed by nanotechnology.– Modifying textile fibers on the nanoscale can lead to products with

improved performance, including materials that shed spills and stains as well as socks that kill the bacteria that cause foot odor.

• Bandages– By incorporating nanoparticles of bacteria-killing silver, these

bandages claim faster wound healing.

• Cosmetics– More than 30 different cosmetic products incorporate nanoingredients. – These nanomaterials—including buckyballs, nano silica, nano zinc

oxide, and other nanoencapsulated material—are key ingredients in anti-aging formulations and sunscreens.

Products of Current Nanotechnology• Glare-resistant, fog-reducing coatings for eyeglasses

– Contain nanoparticles that diffuse glare and repel the polar attraction of water molecules

• Light-emitting diodes– Found on almost all electronic devices and in every color, LEDs

are an example of nanotechnology that uses quantum effects to tune the color of the light emitted from infrared to ultraviolet.

• Self-cleaning windows– Have a coating of nano titanium dioxide– The coating becomes activated when exposed to sunlight and

catalytically burns off the oils and grime on the surface.

• Blu-ray DVDs– Recording “bits” on Blu-ray discs are less than 150 nanometers

long, allowing more than 50 Gb of data to be stored on a 12 cm disc!

Nanoproblems• Can nanotechnology visionaries go too far?

– A society where all problems—everything from aging to food supply—are solved by arrays of nanorobots rearranging atoms.

• How will the ethics of such power be handled?– Advances due to nanotechnology will undoubtedly

be expensive. Will its benefits be available to all or just to the rich?

Concept Check 19.3• List some barriers to developing nanotechnology.

Concept Check 19.3 Solution• Nanomachines must be built differently than full-sized

machines because they are so small.

• At the molecular level, everything has attractions to everything else—how should machines be engineered to function in spite of those attractions?

• Furthermore, in spite of recent advances, no one has constructed a fully functional nanomachine in the laboratory, so caution is in order.

• Ethics of nanotechnology: handling the new capabilities and expense of nanotechnology.

Chapter SummaryMolecular Concept

• Atomic scale microscopes

• Buckyballs

• Nanotubes

Societal Impact

• Making machines smaller carries with it the potential to put machines into places we could not before.

• Chief among these are storage devices that can put more information into a smaller amount of space, and medical devices that allow, for example, the introduction of foreign cells into the human body, the construction of artificial cells, and the construction of nanorobots that may one day be able to navigate within the human body.