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CHAPTERNANO TECHNOL0GY
2.1 Introduction
Nanoscience the study and nanotechnology is the
is
exploitation of the strange propertiesof
materiaIs Smaller than 100nm, to create new useful obiects,
Nanometre isa unit, which amounts
to one billionth of a meter (Inm = 10
m). Materials in the nano-range
exhibit some remarkable
properties like hardness and conductivity.For
example opaque substance becomes transparent
Copper); insulatorsbecome (Eg
semiconductors (Eg-Silicon).These índuced
properties are due to the
variation in the surface potential
induced during the transition from microscopic range to
nanometer range. As the particle size decreases.the
surface contaíns more and more atoms and
Surface atoms dominate the the
properties of the whole materíal. A
comparison of s1Ze of the
nanoparticle with other some
smallparticles is given below.
atom Carbon
red blood Sand
0.1 nm nanotube Transistor particles
5-10 nm 35 nm cell 1 mm
10 um
Micro molecules Macro Micro Macro
Molecules Particle Particle
10! 10 10'
Quantum dot
10 10 10 10° 10'nm
1 nm 10nm
DNA protein
150 um
human hair diameter
Fig. 2.1. Acomparison of nanoparticles with other some small particles
The importance of nanotechnology
was first pointed out by the Nobel
Fevnman in
1959 through his lecture
nanotechnology reached its great
" There is a Plenty of Rooms
Bottom". The term at the
laureate. Richard
public awareness in
1986 with the publication of
creation: The coming era of nanotechnolo3 "Engines of
by Eric Dexler. Now this
interdisciplinary one, which involves emerging field is an
Physics and
Chemistry (for the
characterization of Nanomaterials), preparation and
Biology (for medical
engineering also. applications) and other branches of
The study of fundamental relationship between physical property and
comes under the category of Nanoscience. phenomena
The historyof Nanotechnology
started from early years of
metallic nanoparticles Roman and Chinese. They used
give colours to ceramic and
to
stainless steel materials.
field of Nanotechnology was accelerated with the
The research in the
discoverv of Scanning
(STM)in 1981 and Atomic Force Microscope
(AFM)in 1987. Now we areTunneling
in the third
Microscope
FNanotechnology, which focuses on the generation
heterogeneous combination of various nanostructures.
, Nano Technology 27
2.2 Tools and Techniques
Nanomaterials are present in the universe in different forms,But in laboratory nanomaterials
are produced through either of the following methods;
1. Sol-gel synthesis
2. Inert gas condensation
3. Mechnical alloying or high energy ball
milling
4. Plasma synthesis
5. Electrodepostion.
Atomic force microscope (AFM)and Scanning TunnelingMicroscope (STM) are the two
devices used for theanalysis of nanostructures. In an AFM, aprobe supported with a spring is used
forscanning purpose. The probe scans line by line where the topography is derived from the
bending and deflections of the cantilever. In STM,a probe slides alongthe surface, just as a finger
moves along a thin metallic shcet. A voltage is applied between the tip of the probe and the
surface. As the electricity begins to flow, the STM can determine the minute variations in distance,
travelled by the electrons. In this way STM maps the surface of a sample.
2.3 Production of Nanomaterials
(Top-Down and Bottom- Up methods)
Many technologies have been explored so far to fabricate nanostructures and nanomaterials.
technologies can be grouped into several ways; one way is to group them
These different
Bulk
Powder
Nanoparticle
Cluster
O000 Atom
synthesis.
and bottom-up
showing the top-down
A schematic diagram
2.2
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