The prefix nano in the word nanotechnology means a billionth (1 x 10-9).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

Church Windows

Photography

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, effectivelypredicting the existence of electron-beam lithography, which is used today to makesilicon chips.

He envisioned building circuits on the scale of nanometers that can be used as elements inmore 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 EffectQuantum 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 nanoparticlesGold nanoparticleSilver nanoparticles

Metal oxide nanoparticlesFe2O3 nanoparticlesTiO2 nanoparticlesSiO2 nanoparticles

Nanorods:

Metal nanorodsGold nanorodeSilver nanorodePlatinum nanorods

Metal oxide nanorodsFe2O3 nanorodeTiO2 nanorode

Nanoneedles:

Metal nanoneedlesGold nanoneedleCopper nanoneedleSilver nanoneedle

Nanoflowers:

Metal nanoflowersGold nanoflowerSilver nanoflower

Metal oxide nanoflowersSiO2 nanoflowerMoS2 nanoflower

Nanowires:

Metal nanowiresCopper nanowireSilver nanowire

Metal oxide nanowiresSiO2 nanowire

Nanotubes:

Metal nanotubesPlatinum nanotubeSilver nanotube

Carbon nanotubesSingle walled Multi walled

The Nanostructured Materilas

Properties

1. Electrical Properties

Armchair

Zigzag

Chiral

2. Optical Properties

3. Chemical Properties

Size EffectShape Effect

4. Mechanical PropertiesThe larger the value of Young’s modulus, the less flexible the materialCarbon 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 ri , r0 has been shown to be

D=FL3/3EI

where I is the area moment of inertia given by P (ri4– r0

4 /4). Since the wall thickness of carbon nanotubes is about 0.34nm, ri

4– r04 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 15.

5. 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 Methods1. 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 MicroscopyTransmision Electron Microscopy

2. Surface Analysis

X-Ray Photoelectron Spectroscopy Auger Spectroscopy

3. Structural AnalysisX-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:

1. www.nano.ir

2. www.nanosociety-ir.com

3. www.nanohub.org

4. www.nanochemistry.it

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