This document discusses nanoscience and nanotechnology. It begins by defining nanoscience as the study of structures between 1-100nm, where properties change significantly from their bulk counterparts due to high surface area to volume ratios and quantum effects. It then provides examples of how these factors enhance mechanical, electrical, optical and other properties. Applications discussed include microelectronics, energy efficiency, medicine, and textiles. In the concluding questions, it asks about the significance of nanoscale, medical applications of nanomaterials, classifications of nanomaterials, and properties such as mechanical, electrical and optical.

1. NANOSCIENCE AND
NANOTECHNOLOGY
Presented by
Suja Devi V
AssistantProfessor
Dept.of Applied Science,
SCT college

2. Nanoscience and Nanotechnology
The origin of nanotechnology is from the lectures
delivered by Richard Feynmann which is entitled as
“There is plenty of room at the bottom”.
The word “nano” is derived from a Greek word meaning
dwarf and 1nm=10-9 m.
Nanoscience is the study of fundamental principles of
molecules and structures with atleast one dimension
roughly between 1nm and 100nm.
Application of nanoscience to productive
scale/manufacturing scale is nanotechnology.

3. *Two main factors that causes significant
change in the properties of nanomaterials from
their bulk counterpart
• Increased surface area to volume ratio
and
• Quantum effects
• These factors can enhance properties
such as strength, reactivity, electrical
optical,mechanical etc..

4. Increase in surface to volume ratio for
nanomaterials
• To understand this we consider a spherical material of
radius r,
• Surface area of sphere/Volume of sphere
=4ᴫr2/(4/3 ᴫr3 ) =3/r.
As the size of sphere decreases, the above ratio increases.
The reactivity of materials depends on molecules on the
surface and nanomaterials have large surface area with
large no: of particles and hence their surface energy will
be more which results in enhanced reactivity and
thermodynamical properties.

5. Quantum confinement
• The quantum effects dominate the behaviour of
matter at nanoscale affecting optical, electrical
and magnetic properties.
• According to band theory,solid materials have
energy bands and isolated atoms possess
discrete energy levels.For nanomaterials,if the
dimensions of potential wells or boxes are of the
order of the deBroglie wavelength of
electrons,then the energy levels of electron
change and the electron will remain confined to
a small region of the material.This is called
quantum confinement.

6. Properties of nanomaterials
• Nano materials shows specific properties different from their
bulk counterpart due to large surface area to volume ratio, large
surface energy ,spatial confinement and reduced imperfections.
Mechanical properties.
• The mechanicalstrength of nanostructures is enhanced due to less
surface defects.
• Due to large surface to volume ratio nanomaterials have lower
melting point and reduced lattice constant
• In nanoscale level -hardness and toughness of metals and alloys
are increased.
• The transition from bulk to nanophase reduces elastic strength
and increases plastic behaviour
• Some brittle materials becomes ductile by reducing their grain
size.

7. Optical properties
• Optical properties are due to increase in energy level
spacing and surface plasmon resonance
• Different sized nanoparticles scatter different
wavelengths of light incident on it ( they have different
absorption spectra)and hence they appear with different
colours.For eg:nano gold appears in purple,red,green
etc. depending on their grain size.
• The bulk copper is opaque whereas in nanoscale it is
transparent.
• In nanoparticles of semiconductor elements such as
Ge,Si etc.. – a shift in optical absorption spectra is
seen.

8. Electrical properties
• The electrical conductivity and energy bandwidth of
some materials change when they pass from bulk to
nanophase.Eg: bulk silicon is a semiconductor whereas
in nanophase it is conductor.
• Electrical conductivity of nanomaterials depends on
increased perfection, reduced impurity and
dislocations.
• In metals Conductivity decreases with reduced size as
their energy bands become narrower and hence the
ionisation potential energy increases.
• Also conductivity may be enhanced due to better
ordering in microstructure and decreased due to
increased surface scattering.

9. Applications
• In microelectronics- the reduction in size of electronic
components leads to faster switching times.
• The magnetic strength of material is directly proportional to
the surface to volume ratio.The nanocrystalline high power
rare earth magnet finds applications in submarines,electric
motors,MRI instruments and in ultrasensitive analytical
instruments.
• In computers- Quantum computers use fast quantum
algorithms and have quantum bit memory space(qubit),so it
involves in several computations at the same time.
• Energy efficiency-Nanostructures with a continuum of energy
band gaps have an increased solar energy conversion efficiency
as compared to ordinary semiconductor solar cells.

10. Other applications
• Medical field--Nano materials are used for the
development of diagnostic devices,drug delivery
systems etc.
• Magnetic nanoparticles are used to label
molecules,structures or micro organism of an antibody.
• Iron nanoparticles are used in cancer treatment.
• Nanotechnology is used to reproduce or repair damaged
tissues.
• The genetic sequence of a sample can bedetected by
tagging gold nanoparticles with small segment of DNA.
• In textile industry- clothes made of nanofibres are water
and stain resistant and wrinkle free.

11. Answer the following questions .
1.Explain the significance of nanoscale?
Key:Explain the factors responsible for
change in properties at nanorange.
2.Give some medical applications applications
of nanomaterials
3.List the classifications of nanomaterials.
4.Describe the mechanical,electrical and
optical properties of nanomaterials.(essay
qn.part)
Refer Text also.

12. ThankYou