Deals with basic concepts of Nanomaterial, Synthesis, Fullerenes, Carbon nano tubes, nano wires and rods. Dendrimers

1. NANOMATERIALS
Dr. S. Sreenivasa
Associate Professor and Chairman
DOS and R in Organic Chemistry
Tumkur University, Tumakuru

2. Size Dependent Properties of Nanomaterials
Why materials in the nano range alone are having so
much importance?
• Nanomaterials exhibit distinctively different physical
properties.
• In nanoscale range a material will show different
properties when the size is slightly varied.
• Transition from atoms or molecules to bulk form takes
place in nano scale range.
• Nanomaterials are governed by quantum mechanics rather
than Newtonian physics

3. (A) Surface Area
An interesting comparison…
Surface area of a cube with side length 1m = 6m2
This cube may be cut into 1027 cubes (each with a volume of
1nm3), then the collective surface area = 6000 km2.
Properties influenced by surface area
Catalytic Activity
 Gas Adsorption
 Chemical Reactivity

4. (B) Electrical Properties
• Electronic bands in bulk materials are continuous whereas it is
discrete in nanomaterials
• The separation between different electronic states varies with the
size of nanomaterial
Therefore a conductor in bulk may become semiconductor or

5. (C) Optical Properties
Nanomaterials exhibit unique colours
Electronic transition among the discrete
electronic states
 Scattering of light
Surface Plasmon Resonance (SPR)
o When light falls on a metal surface plasmons start
oscillating in a synchronised manner – SPR
o Resonating electrons have much higher cross sectional
area than the nanoparticle.
o Resonating electrons capture radiation of different
wavelength depending on oscillation frequency.

6. Synthesis
Top-down
Sputtering, pulsed laser deposition, laser ablation, high
energy ball milling, electric arc method, nanolithography,
ion-beam implantation
Expensive catalyst, surface defects, contamination
Bottom-up
 Sol-gel, precipitation, gas condensation, CVD,
hydrothermal & thermolytic process
Simple and cost effective, control over chemical
composition, less defects and high purity

7. Precipitation Method
Precipitation from solution
Steps: i) Nucleation ii) Growth of Particles
 Precursors – metal salts eg. Zinc Acetate
 To the precursor solution acid or base is added to obtain
desired pH.
 A precipitating agent (eg. TAA)is added
 It also causes supersaturation of the solution due to the
added ions.
 Nucleus formation commences at this stage.
 Nucleus further grows into particles and gets precipitated
 The precipitate is filtered, washed with water, air dried and
finally calcined to remove counter anions.

8. Advantages
• Particle size, crystallinity and morphology can be
controlled by varying concentration, temperature,
pH and rate of addition of reagents and mixing
processes.
• If the solution attains supersaturation slowly then
larger particles are formed.
• Simple and rapid preparation.

9. Fullerene
Third allotropic form of carbon
Consists of hexagonal and alternate pentagonal rings
Fullerene with 60 C atoms – with 12 pentagons and 20
hexagons is called Buckminster fullerene.
First Isolated from soot of chimneys.

10. 100 nm
Characteristcs
 Requires high energy to break (10000C).
 Insoluble in water soluble in toluene and CS2.
 It is not toxic but its derivatives are toxic.
Applications
• Powerful antioxidants
• Used as FED’s replacement for LCD and plasma
• Blended with polymers can be used in photovoltaics.
• Used as catalyst, in water purification and in fuel cells

11. Carbon Nanotubes
• They are called bucky tubes
• Posses high strength
• Types SWCNT’s and MWCNT’s

12. Characteristcs
Tensile strength of CNT is greater than carbon
steel.
In hardness scale it is harder than diamond
and boron nitride.
CNT s are having high thermal conductivity
along the material compared to copper.
Shows high thermal insulation along the axis.

13. Nano wires and Nano rods
Figure: Silver nanowires Figure: ZnO nanorods

14. • Depending upon the size and diameter they are
nano wires (dia-1nm) and nanorods (dimension
100-nm)
Applications
 In electronics and optics.
Used as rectifiers, diodes, transistors and LED’s
Nanorods are used in display technology (change in
reflectivity with change in orientation.
Nanorods are selectively absorbed by cancer cells
and heated in IR
They used in energy harvesting

15. • Depending upon the size and diameter they are
nano wires (dia-1nm) and nanorods (dimension
100-nm)
Applications
 In electronics and optics.
Used as rectifiers, diodes, transistors and LED’s
Nanorods are used in display technology (change in
reflectivity with change in orientation.
Nanorods are selectively absorbed by cancer cells
and heated in IR
They used in energy harvesting

16. Dendrimers

17. • Dendrimer in greek means tree like structure.
• Molecules forming tightly packed ball like structure
resulting in low viscosity.
• Because of presence of large surface groups they
act as catalysts.
• Because of presence of cavity used in selective
reaction as sieves (Host – guest)
Applications
 Invitro diagnosis of cardiac problems
Contrasting agents in MRI
Target delivery drugs
Used as proton sensors