This document discusses nanotechnology and nanophysics. It defines nanoscience as the study of structures between 1-100 nm, known as nanostructures. There are two main techniques for synthesizing nanomaterials: bottom-up and top-down. Bottom-up techniques build materials atom by atom through methods like molecular self-assembly and positional assembly. Nanophysics studies how materials behave differently at the nanoscale due to changes in internal structure and properties governed by quantum mechanics rather than classical physics. Nanotechnology involves manipulating individual atoms and molecules to produce new materials with novel properties.

1. NANOTECHNOLOGY-NANOPHYSICS
1.INTRODUCTION:
Nano, Greek for 'dwarf', means one billionth. The
measurement at this level is in nanometer (abbreviated
"nm") — billionth of a meter. To get a sense of nanoscale,
a human hair measures roughly 75,000 nm, a bacterial
cell measures a few hundred nanometres. On the other
side, ten hydrogen atoms lined up end-to-end make up 1
nm. The smallest thing which can be seen with naked
human eye is of the order of 10,000 nm. 'Nanoscience' is
the study of the fundamental principles of molecules and
structures with at least one dimension is in the size range
of 1nm to 100 nm. These structures are known as
'nanostructures'. The research and application of the
nanostructures into nanoscale devices is called
'nanotechnology'.
1.1NANOPARTICLES:
An atom or small molecule in the form of vapour is
smaller than a nanometer in size. But as they are in
gaseous form and their molecules are not in arranged
manner, hence do not fall in category of nanoscience. The
nanostructures are the smallest solid thing that is
possible to make. At nanoscale, most of the physical

2. properties like conductivity, hardness or melting point
are totally different than when they are in gaseous or
crystal form. At nanoscale these properties depend on
not only on the material but also the size of the
nanostructure.
At such a size, the classical Newtonian mechanics or
thermodynamics is not able to explain the observed
properties. So one has to apply quantum mechanics to
explain the properties of nanoscale materials. The basic
nanoscience is not new, the chemist have been doing
nanoscience for hundreds of years. The stained glass
windows in medieval charges contain different size gold
nano particles. The different size gold particles created
different colours as orange, purple, red or greenish in the
glass. The new about current nanoscience is aggressive
focus on developing applied technology and the right
tools for doing it. Here, we will be studying different
properties, methods of synthesis and applications of
nanotechnology.
Nanophysics it is amazing what one can do by just
putting atoms where you want them. -Richard Smalley
(Nobel laureate and co discoverer of the bucky ball)
'Nano' the Greek word means "dwarf" i.e. very small.
1 nm =10-9
m - only three to five atoms wide. The

3. fundamental of nanophysics lies in the fact that when size
of material is reduced to nanoscale, it shows dramatic
change in properties. It is because, there is total change
in internal structure of material at nanoscale. e.g. there
are two familiar, forms of carbon as diamond and
graphite. But at nanoscale, it gives new structure - carbon
nanotube - which is one hundred times stronger than
steel. The isolated atom has discrete energy levels while
bulk material forms energy bands. Nanomaterials
represent intermediate state. At nanoscale, electronic
energy levels change and it is governed by quantum
mechanics. All the materials are made up of atoms and
their properties depend on atomic arrangement. The
atomic arrangement in the material can be controlled
with the help of nanotechnology. Nanotechnology is the
art and science of manipulating and rearranging
individual atoms and molecules to produce new
material with entirely new structure and exploit the
novel properties for applications in different devices
and systems. Thus nanotechnology refers to
manipulation of matter on atomic and molecular scale.
Nanotechnology is abroad multidisciplinary field
encompassing all branches of science, engineering and

4. technology as well as medical, economics, social sciences
and many other disciplines.

5. 1.2 .Production techniques : Basically there are two main
techniques used in synthesis of nanomaterials as shown
in fig 6.1.
1.2.1 Bottom up technique: In bottom up approach,
materials are built up atom by atom. The atoms and
molecules arrange themselves into definite pattern.
Components are made of single molecule, which are held
together by covalent force. There are different
approaches.
(a) Molecular self assembly :
Molecular self assembly is the assembly of molecules
without guidance or management from an outside
source. In self assembly, components are in state of

6. random motion and find the position with suitable
mutual orientation. Different such arrangements are
possible and most stable arrangement is preferred.
Biological molecules have ability to self assemble to form
unique structures like cells, organs. The information
required to build up a living cell or organ is stored in the
DNA and transferred to proteins by the process called
transcription and translation.
Learning this technique of self assembling from
nature one of the primary aspects of nanotechnology.
Biomimetics refers to use of biological systems as models
for designing systems and devices. Thus biomimetics is
imitating nature and it has applications in robotics,
artificial intelligence, medical industry etc. Artificial
synthesis of vitamins and antibiotics is a example of
biomimetics. Applications of self assembly-
1. In diagnostic tools.
2. To produce computer chip with smaller
component :size and better computing power.
3.In sensors to detect chemical and biological
molecules.
(b) Positional assembly :
In positional assembly, components are not in state of
random motion and do not take random position, but

7. they are kept at or near a fixed position by some
restoring force. When the two components are
deliberately moved into close proximity and linked
together, the components are assembled. Simple
example of positional assembly is enzymes which bind
two substrate molecules. The two bound molecules are
positioned with respect to each other. To assemble
molecular components into some large parts, takes long
amp and lot of robotic arms are needed; this is known
as massive parallelism. In future this molecular
manufacturing system is expected to use some form of
convergent assembly. It is based on the idea that smaller
parts can be assembled into larger parts, larger parts
can be assembled into still larger parts and so on.
Different methods used for the synthesis of
nanomaterials using bottom up strategy are electro
deposition, sol gel method, colloidal method, solution
phase reduction etc.