Nanomaterials in Nanotechnology

1. NANOMATERIALS AND
NANOTEHNOLOGY

2. INTRODUCTION OF NANOMATERIALS
• Term Nano originated from the Greek Nanos-
‘dwarf’.
• It is one-billionth of a meter.
• A nanoparticle is a small particle that ranges
between 1 to 100 nanometres in size.
• Nanoparticles can exhibit significantly
different physical and chemical properties to
their larger material counterparts.

3. • Richard P. Feynman (Nobel Laureate in Physics,
1965) is often credited for introducing the concept of
nanotechnology.
• American Physical Society at California Institute of
Technology on 26 December 1959, he delivered a
famous lecture entitled “There’s Plenty of Room at
the Bottom”.
• suggested that it would be possible to arrange the
atoms the way we want.
• Physicist should be able to synthesize any chemical
substance by putting the atoms down where the
chemist says.
• The term nanotechnology was also popularized by the
invention of scanning tunneling microscope and
fullerene.

4. Nano science and Nano chemistry
• Nanoscience is the branch of science concerned
with the development and production and uses
of materials whose basic components are of
Nano scale size, i.e. 1 -100 nm in size.
• Nanochemistry is a branch of Nanoscience, deals
with the synthesis and chemical applications of
nanomaterial.
• Nanochemistry is the combination of chemistry
and nanoscience.

5. Nanotechnology
• Nanotechnology
Nanotechnology is the creation of functional
materials, devices, and systems through control
of matter on the nanometre (1 to 100 nm)
length scale and the exploitation of novel
properties and phenomena developed at that
scale.

9. SIZE OF NANOPARTICLES

18. NATURAL NANOSTRUCTURED
FEATURES

23. Surface Area to Volume ratio (aspect ratio)
• When the given volume is divided into smaller pieces
the surface area increases
• So the particle size decreases a greater proportion of
atoms are found at the surface compared to those
inside
• It makes materials more chemically reactive

24. Size dependent properties
nanomaterial
• Bulk material -constant physical properties
regardless of its size,
• Nano-scale materials-size-dependent properties
• Bulk materials- larger than one micrometre (or
micron), the percentage of atoms at the surface is
insignificant in relation to the number of atoms in
the bulk of the material
• Interesting and unexpected properties of
nanoparticles largely due to the large surface area
of the material

25. Optical properties and their size-
dependence
• Nanoparticles are small enough to confine
their electrons and produce quantum effects
• Eg: Gold nanoparticles appear deep red to
black in solution
• change in optical properties due to two
factors
• i)Quantum confinement of electrons within
nanoparticles
• Ii) surface plasmon resonance

26. Quantum size effects
• Size is small-quantum effects play, which limit the
energies at which electrons and holes can exist in
the particles.
• Similar to a particle in a box, the energy
separation between adjacent levels increasing
with decreasing dimensions.
• The quantum size effect observed in
semiconductor nanoparticles
• Band gap increases with decreasing size,
resulting the inter band transition shifting to
higher frequencies

27. Surface plasmon resonance
• Nanoscale metals tuned to obtain spectrum of
colours
• For an example, gold, a shiny, bright yellow colour
metal in the bulk scale, give out brilliant red or
violet colours in an aqueous solution when the
gold particles in the nanoscale
• Origin of colour of metallic nanoparticles is
explained with an approach called localized
surface plasmon resonance

28. Electrical properties and their size-
dependence
• In a metallic nanomaterial, the electronic movement is
restricted to the inside of the nanoparticles and most of
the electrons are tightly localised
• Electrical properties of nanomaterials tunable due to their
size dependence
• For metallic conductors like copper, electrical conductivity
generally gets reduced to a very low critical value as their
size is reduced
• Nano dimension is reached, the same metal may become a
semiconductor or even an insulator
• carbon nanotubes (CNT) can conduct electricity extremely
well, but conductivity varies sensitively with the diameter
and helicity of the CNT lattices.

29. Catalytic properties and their size-
dependence
• Nanomaterials possess tremendous catalytic properties
• Particles - nanoscale -have many atoms on their surface,
which are very weakly bonded to the lattice atoms of
the lattice
• Have very high surface energy and are highly active, and
surface atoms are in a state of physical instability and
are chemically active, perform many chemical reactions
• catalytic properties in nanomaterials due to their very
high surface-to volume ratio
• The higher this ratio, the higher the catalytic properties
in nanomaterials due to the increase in surface energy

37. METHOD OF SYNTHESIS

38. Methods of synthesis of nanomaterials:
Nanostructure materials -great attention because their physical,
chemical, electronic and magnetic properties dramatic change from
higher dimensional counterparts and depend on their shape and size
• Many techniques have been developed to synthesize and fabricate
nanostructure materials with controlled shape, size, dimensionality and
structure.
• The properties in tern depend on the atomic structure, composition,
microstructure, defects and interfaces which are controlled by
thermodynamics and kinetics of the synthesis.

41. (a) Top-down approach:
 Breaking down of the bulk material
 Top-down synthesis techniques are extension of those
that have been used for producing micron sized particles
 Top-down approaches are inherently simpler and depend
either on removal or division of bulk material or on
miniaturization of bulk fabrication processes to produce
the desired structure with appropriate properties
 The biggest problem with the top-down approach is the
imperfection of surface structure
 For example, nanowires made by lithography are not
smooth and may contain a lot of impurities and structural
defects on its surface.
 Examples of such techniques are
 high-energy wet ball milling, electron beam lithography,
atomic force manipulation, gas-phase condensation,
aerosol spray, etc.

42. (b) Bottom-up approach
✓ Alternative approach, which has the potential of
creating less waste and hence the more economical,
is the ‘bottom- up’
✓ Bottom-up approach refers to the build up of a
material from the bottom: atom-by-atom,
molecule-by-molecule, or cluster-by cluster.
✓ Organometallic chemical route, revere-micelle
route, sol-gel synthesis, colloidal precipitation,
hydrothermal synthesis, template assisted sol-gel,
electrode position etc., are some of the well- known
bottom–up techniques reported for the preparation
of luminescent nanoparticles.