Introduction to Nanotechnology

Nanotechnology –The Next Big Thing Really very Small

In 1959, physicist and Nobel Prize winner Richard Feynman gave a lecture to the American Physical Society called "There's Plenty of Room at the Bottom". The focus of his speech was about the field of miniaturization and how he believed man would create increasingly smaller, powerful devices. These little nanothings will revolutionize our industries and our lives.

Many things that will become practical with the power of nanotechnology
  • PC's will be billions of times faster than today.
  • Safe and affordable space travel.
  • Virtual end to illness, aging, death.
  • No more pollution with automatic cleanup of existing pollution.
  • End of famine and starvation.
  • Reintroduction of many extinct plants and animals.
  • Terraforming Earth and the Solar System.
An example: A Super Nanomaterial - Carbon Nanotubes (CNTs)
  • CNTs are 100 times stronger and 1/6th the weight of steel.
  • Chemically inert, not attacked by strong acids or alkali.
  • Collectively, nanotubes can exhibit extremely high surface area.
  • High tensile strength (60GPa) and Young’s modulus (1TPa).
  • Have unique electrical properties. Very high current densities (10 7 - 10 9 A/cm 2 ) and electrical conductivity (10 -6 ohm m typically).
  • High thermal conductivity (1750-5800 W/mK).
  • High aspect ratio structures with diameters in nanometers, lengths in microns.
NANOTECHNOLOGY – A BRIEF OVERVIEW:

At the nanoscale, at least one dimension of the particle should be in the nano range i.e. 1-100 nm or about 10 to 106 atoms or molecules per particle where size-dependant quantum effects come to bear. Nanosized particles exhibit unique properties than larger particles of the same substance. They often require very different production approaches. There are two processes to create nanomaterials, classified as ‘top-down’ and ‘bottom-up’. It will let us make most products lighter, stronger, smarter, cheaper, cleaner and more precise.

The bulk properties of materials often change dramatically with nano ingredients. At nanoscale the properties of the materials depend upon the shape and size of the nanoparticles of that material. Everything in this universe is made of atoms and if we can manipulate the atom, then that changes the rules of the game for almost every product.

  • If we rearrange the atoms in coal, we get diamonds.
  • If we rearrange the atoms in sand (and add a pinch of impurities) we get computer chips.
  • If we rearrange the atoms in dirt, water and air we get grass.
  • If we rearrange the atoms in grass, we get cheeseburger.
Interesting behavior of some materials after rearrangement of atoms at nano level
  • Opaque substances become Transparent (Copper).
  • Inert materials become Catalysts (Platinum).
  • Stable materials turn Combustible (Aluminium).
  • Solids turn into Liquids at room temperature (Gold).
  • Insulators become Conductors (Silicon).
  • At normal scale, Gold is chemically inert but at nanolevel it becomes Catalyst.
  • Bulk gold appears yellow in color but nanosized gold appears red in color. In fact, depending on size, they can turn red, blue, yellow, and other colors.
  • Nano Silver kills over 650 different bacterial species in minutes.
  • Large ZnO particles can scatter visible light and appear white while nanosized ZnO particles don’t scatter and are colourless.
  • The majority of the atoms are almost all on the inside of the object at macroscale but split between the inside and the surface of the object at nanoscale.
  • Changing an object’s size has a very small effect on the percentage of atoms on the surface at macroscale but has a big effect on the percentage of atoms on the surface at nanoscale.
  • The melting point doesn’t depend on size at macroscale but is lower for smaller particles at nanoscale.
SCALE CHANGES EVERYTHING – MYSTERY OF NANOTECHNOLOGY
Four important ways in which nanoscale materials may differ from macroscale materials

1. Electromagnetic Forces dominate and Gravitational Forces become negligible as the mass of nanoscale objects is so small.

2. Quantum Effects begin to dominate the behavior of matter at the nanoscale affecting the optical, electrical and magnetic behavior of materials. Materials can be produced that are nanoscale in one dimension (for example, very thin surface coatings), in two dimensions (for example, nanowires and nanotubes) or in all three dimensions (for example, nanoparticles).

3. Surface area to volume ratio increases which change or enhance properties such as reactivity, strength and electrical characteristics. When surface area increases, a greater amount of a substance comes in contact with surrounding material resulting better catalysts since a greater proportion of the material is exposed for potential reaction.

4. Random molecular motion becomes prominent. At the macro scale, we barely see movement, or why it moves. At the nanoscale, the particle is moving wildly, batted about by smaller particles. Similarity: 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.

WIDE APPLICATION AREAS – THROWING LIGHT ON SOME OF THEM
  • Energy
  • Cosmetics
  • Nanodevices
  • Nano Fabrics
  • Optical Engineering
  • Nanobio-technology
  • Medicine & Drugs
  • Bio Engineering
  • Defence & Security
How might Nanoscale science and technology improve our lives?
Energy

The most advanced nanotechnology applications related to energy are:

Reduction of energy consumption

A reduction of energy consumption can be reached by better insulation systems, by the use of more efficient lighting or combustion systems, and by use of lighter and stronger materials in the transportation sector. Currently used light bulbs only convert approximately 5 % of the electrical energy into light.

Increasing the efficiency of energy production

Commercially available solar cells have much lower efficiencies (15-20%). Nanotechnology could help to increase the efficiency of light conversion by using nanostructures with a continuum of bandgaps.

The use of more environmental friendly energy systems

Probably the most prominent nanostructured material in fuel cells is the catalyst consisting of carbon supported noble metal particles with diameters of 1-5 nm. Suitable materials for hydrogen storage contain a large number of small nanosized pores.

Enhanced renewable energy sources - Recycling of batteries

The use of batteries with higher energy content or the use of rechargeable batteries or supercapacitors with higher rate of recharging using nanomaterials could be helpful for the battery disposal problem.

Manufacturing improvements by reducing materials and process rates.
Environmental / Green Chemistry
Filtration

Nanofiltration is mainly used for waste-water treatment, air purification and energy storage and the removal of ions or the separation of different fluids. Using nanoscale particles increases the efficiency to absorb the contaminants and is comparatively inexpensive compared to traditional precipitation and filtration methods.

Destructive Adsorbents

Nanoparticulate metal oxides exhibit high intrinsic surface reactivities, high surface areas and strongly chemisorb acidic gases & polar organics.

Solar Cells

Semiconductor nanoparticles, with size-tunable bandgaps, hold the potential for more efficient solar cells for both photoviltaics (electricity production) and water splitting (hydrogen production).

Remediation

Photoexcitation of fine particles of semiconductor leads to electron-hole pairs that are useful for both oxidation and reduction of pollutants, for use in decontaminating water.

Nanopaint on buildings could reduce pollution

When exposed to ultraviolet light, titanium dioxide (TiO2) nanoparticles in paint break down organic and inorganic pollutants that wash off in the rain.

Catalysis

Platinum nanoparticles are now being considered in the next generation of automotive catalytic converters because the very high surface area of nanoparticles could reduce the amount of platinum required.

Consumer goods

Nanotechnology is already impacting the field of consumer goods, providing products with novel functions ranging from easy-to-clean to scratch-resistant.

Foods

Nanotechnology can be applied in the production, processing, safety and packaging of food.

  • Clay nanocomposites are being used to provide an impermeable barrier to gasses such as oxygen or carbon dioxide in lightweight bottles, cartons and packaging films.
  • Storage bins are being produced with silver nanoparticles embedded in the plastic. The silver nanoparticles kill bacteria from any material that was previously stored thus minimizing health risks from harmful bacteria.
  • Nanoparticles are being developed that will deliver vitamins or other nutrients in food and beverages without affecting the taste or appearance.
  • Silicate nanoparticles provide a barrier to gasses (for example oxygen), or moisture in a plastic film used for packaging. This could reduce the possibly of food spoiling or drying out.
  • Zinc oxide nanoparticles can be incorporated into plastic packaging to block UV rays and provide anti bacterial protection, while improving the strength and stability of the plastic film.
  • Nanosensors are being developed that can detect bacteria and other contaminates, such as salmonella, at a packaging plant.
Textiles

The use of engineered nanofibers already made clothes water and stain-repellent or wrinkle-free. Textiles with a nanotechnological finish can be washed less frequently and at lower temperatures. Nanotechnology has been used to integrate tiny carbon particle membrane and guarantee full-surface protection from electrostatic charges for the wearer.

Cosmetics

One field of application is in sunscreens. The traditional chemical UV protection approach suffers from its poor long-term stability. A sunscreen based on mineral nanoparticles such as TiO2 offer several advantages.

OTHER APPLICATIONS
Refineries

Using nanotech applications, refineries producing materials such as steel and aluminium will be able to remove any impurities in the materials.

Protective nanopaints for cars
  • Water and dirt repellent
  • Resistant to chipping and scratches
  • Brighter colors, enhanced gloss
  • In the future, could change color and self-repair?
A DVD that could hold a million movies

Current CD and DVD media have storage scale in micrometers. A new nanomedia (Prepared when gold self-assembles into strips on silicon) has a storage scale in nanometers. That is 1,000 times more storage along each dimension (length, width) or 1,000,000 times greater storage density in total.

References:

1. http://www.nanosense.org/activities/sizematters/index.php. 2. http://en.wikipedia.org/wiki/List_of_nanotechnology_applications. 3. http://www.azonano.com/Details.asp?ArticleID=1073. 4. http://www.nanotech-now.com/introduction.htm. 5. Book – Nanoscale Materials in Chemistry by K. J. Klabunde.