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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