The prefix nano in the word nanotechnology means a billionth (1 x ). Nanotechnology deals with various structures of matter having dimensions of the order of a billionth of a meter. Introduction Nanotechnology Region

While the word nanotechnology is relatively new, the existence of functional devices and structures of nanometer dimensions is not new, and in fact such structures have existed on Earth as long as life itself. Lycurgus Cup

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Nanotechnology in Nature

History of Nanotechnology Richard Feynman was awarded the Nobel Prize in physics in 1965 for his contributions to quantum electrodynamics, a subject far removed from nanotechnology. In 1960 he presented a visionary and prophetic lecture at a meeting of the American Physical Society, entitled “There is Plenty of Room at the Bottom” where he speculated on the possibility and potential of nanosized materials.

He envisioned etching lines a few atoms wide with beams of electrons, effectively predicting the existence of electron-beam lithography, which is used today to make silicon chips. He envisioned building circuits on the scale of nanometers that can be used as elements in more powerful computers. He recognized the existence of nanostructures in biological systems. Many of Feynman’s speculations have become reality. However, his thinking did not resonate with scientists at the time.

Quantum Size Effect Quantum size effect where the electronic properties of solids are altered with great reductions in particle size. This effect does not come into play by going from macro to micro dimensions. However, quantum effects become dominant when the nanometer size range is reached.

Electronic Structure Bulk Metal Large Metal Cluster 100 atom Small Metal Cluster 3 atom Transition from Bulk to Nanoparticle Conduction band Valance band

Different Types of Nanostructured Materials

Nanoparticles:  Metal nanoparticles  Gold nanoparticle  Silver nanoparticles  Metal oxide nanoparticles  Fe2O3 nanoparticles  TiO2 nanoparticles  SiO2 nanoparticles

Nanorods:  Metal nanorods  Gold nanorode  Silver nanorode  Platinum nanorods  Metal oxide nanorods  Fe2O3 nanorode  TiO2 nanorode

Nanoneedles:  Metal nanoneedles  Gold nanoneedle  Copper nanoneedle  Silver nanoneedle

Nanoflowers:  Metal nanoflowers  Gold nanoflower  Silver nanoflower  Metal oxide nanoflowers  SiO2 nanoflower  MoS2 nanoflower

Nanowires:  Metal nanowires  Copper nanowire  Silver nanowire  Metal oxide nanowires  SiO2 nanowire

Nanotubes:  Metal nanotubes  Platinum nanotube  Silver nanotube  Carbon nanotubes  Single walled  Multi walled

The Nanostructured Materilas Properties

1.Electrical Properties Armchair Zigzag Chiral

2. Optical Properties

3. Chemical Properties  Size Effect  Shape Effect

4. Mechanical Properties The larger the value of Young’s modulus, the less flexible the material Carbon nanotubes have Young’s moduli ranging from 1.28 to 1.8TPa Whilw, Young’s modulus of steel is 0.21TPa. This would imply that carbon nanotubes are very stiff and hard to bend. However, this is not quite true because they are so thin. The deflection D of a cylindrical hollow beam of length L with a force F on the end and the inner and outer radii of r i, r 0 has been shown to be D=FL 3 /3EI where I is the area moment of inertia given by  (r i 4 – r 0 4 /4). Since the wall thickness of carbon nanotubes is about 0.34nm, r i 4 – r 0 4 is very small, somewhat compensating for the large value of E. Most materials fracture on bending because of the presence of defects such as dislocations or grain boundaries. Because carbon nanotubes have so few defects in the structure of their walls, this does not occur.

5. Thermal Properties

One of the most interesting observed properties of nanoparticles is that clusters made up of nonmagnetic atoms can have a net magnetic moment. For example, clusters of rhenium show a pronounced increase in their magnetic moment when they contain less than 20 atoms. Figure below is a plot of the magnetic moment versus the size of the rhenium cluster. The magnetic moment is large when n is less than Magnetic Properties

Different Methods for Nanostructured Materials Synthesis

Two General Routs for Nanomaterials Synthesis

The Comparison During Time

Top – Down Methods 1. Lithography through Etching Process

2. Lithography through UV Radiation

2. Ball Milling and Mechanical Alloying

2. Lithography through UV Radiation Electrospinning involves the application of a high voltage electric field to a polymer solution or melt, so that mutual charge repulsion on the surface of the liquid overcomes the surface tension and causes a thin liquid jet to be ejected. As the jet travels towards a collector (at a different electric potential), electrostatic repulsion from charges on the surface causes the jet diameter to narrow.

Bottom – Up Methods 1. Micelles and Microemulsions

3. Precipitation and Reduction FeCl2 & FeCl3 were precipitaed by adding NH4OH solution to produce Fe3O4 nanoparticles HAuCl4 was reduced to Au nanoparticle by adding NaBH4 solution

2. Sol gel and Aerogel

4. Electrodeposition and Electroless Deposition

Stabilization of nanoparticles were synthesized through solution methods Capping and functionalization

5. Sputtering

6. Chemical Vapor Deposition (CVD)

6. Molecular Beam Epitaxy (MBE) & Chemical Beam Epitaxy (CBE)

Common Methods for Characterization of Nanomaterials

1. Microscopic Methods  Scanning Electron Microscopy  Scanning Tunneling Microscopy

 Atomic Force Microscopy  Transmision Electron Microscopy

2. Surface Analysis  X-Ray Photoelectron Spectroscopy  Auger Spectroscopy

3. Structural Analysis  X-Ray Diffraction Analysis FT-IR Spectroscopy  NMR Spectroscopy

4. Elemental Analysis  Inductively Coupled Plasma  Atomic Absorption Spectroscopy

4. Physical Properties Analysis  UV-Vis Spectrophotometry  Dynamic Light Scattering

Fields of Studies and Applications 1.Nanocatalysts 2.Nanocomposites 3.Nanoadsorbant 4.Nanosensors 5.Nanobiotechnology 6.Nanomedicine 7.Nanocomputation 8.Nanomagnetization 9.Nanofiltartion 10. Nanofluids 11. Nanoelectronic Devices 12. Solar Cells 13. Feul Cells

Some Useful References for Nanotechnology Research Journals: 1.Nanoletter 2.ACSnano 3.Nanotoday 4.J. nanoparticle research 5.Nature nanotechnology Links:

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