Ekeeda Provides Online Engineering Subjects Video Lectures and Tutorials of Mumbai University (MU) Courses. Visit us: https://ekeeda.com/streamdetails/University/Mumbai-University

1. CHAPTER – 6 Nanomaterials
 Explain the structure, properties and uses of fullerene.
The fullerenes can be considered, after graphite and diamond, to be the third well-defined
allotrope of carbon. Fullerenes were first isolated in 1990, in considerable quantity.
The molecule was named after R. Buckminster Fuller, the inventor of geodesic domes, which '
conform to the same underlying structural formula. A hollow, pure carbon molecule in which the atoms lie
at the vertices of a polyhedron with 12 pentagonal faces and any number of hexagonal faces.
(When graphite was vaporised with a short-pulse, high-power laser) it turned into Fullerence - C60•
But this was not a practical method for making large quantities.
Each carbon is bound to three other carbons in a pseudo-spherical arrangement consisting of
alternating pentagonal and hexagonal rings, in the manner of a soccer ball. Hence its nickname, buckyball.
Every carbon is equivalent. NMR spectrum of C60 reveals a single line.
Buchminster fullerene is a beautiful thing it was found as a byproduct of soot formation.
Scrape the inside of the chimney and you will get few buckyballs on the finger.
Properties and applications
Fullerences are spheroidal organic molecules. Following are the physical and chemical properties of
fullerences,
1. Fullerene and its derivatives show superconductivity and ferro-magnetism.
2. The fullerenes are used in synthetic, pharmaceutical, and industrial applications, as
inhibitor of the HIV protease, to make new drugs or proteins.
3. fullerene are used in cosmetics preparation applicable in halting the process of aging.
4. The other type of fullerene C80 can act as a very good MRI contrast agent.
5. They can be useful in light emitting diodes (LED), molecular electronics and computing, as lubricants,
rocket fuel etc.
6. Fullerene C50, shows odd magnetic and electronic properties due to its shape being intermediate between a
sphere and a disk.
 What are (i) SWCNT and (ii) MWCNT ? describe the production of SWCNT by LASER method.
(6 marks)
In 1996 CNTs were first synthesized using a dual-pulsed laser and achieved yields of >70 wt%
purity. In this method the samples were prepared by laser vaporization of graphite rods with a 1 : 1 catalyst
mixture of Cobalt and Nickel at 1200°C in flowing argon, followed by heat treatment in a vacuum at
1OOO°C to get the Coo and other fullerenes.
The use of two successive laser pulses minimizes the amount of carbon deposited as soot. The
second laser pulse breaks up the larger particles ablated by the first one, and feeds them into the growing
nanotube structure. The material produced by this method appears as a mat of ''ropes", 10-20nm in
diameter and up to 100pm or more in length.
Each rope is found to consist primarily of a bundle of single walled nanotubes, aligned along ~
common axis. By varying the temperature, the catalyst
composition, and other process I,parameters, the average nanotube
diameter and size distribution can be varied. Arc-discharge and
laser vaporization are currently the principal methods for obtaining
small quantities of high quality CNTs.

2.  Write short note on, any two the following :
(i) Nanocones (ii) Haeckelites
(i) Nanocones
Carbon nanocones, were discovered in 1994 which are the most simple example of the
nanostructured carbon. They are made, of the hexagonal plane with a different number of pentagonai
defects, more precisely, from one to five.
Each cut, or the pentagonal disclination, has the angle 2 /6. The fivefold (or positive
disclination) could be stable, but the most stable configuration for more than one defect is the
configuration, where they are separated by hexagons.
The nanocones are produced by
1. Carbon condensation on a graphite substrate
2. Pyrolysis of heavy oil.
3. Laser ablation of graphite targets.
In laser ablation, graphite surface is heated with intensive short laser pulse. The graphite
evaporates some number of atoms from the graphene sheet, and other atoms rearrange into the conical
surface as shown above. The growth of nanocones is yet under study.
(ii) Haeckelites
The presence of defects such as pentagons and heptagons in fullerenes modifies the electronic
properties.

3. A new hypothetical type of grapheme sheet, which admits pentagons, heptagons and hexagons, has been
proposed, noting that the number of heptagons should be the same in order to compensate for the negative curvature
of the heptagons and the positive curvature of the pentagons
These arrangements are now called 'Haeckelites' in honour of Ernst Haeckel, a German zoologist
who produced a beautiful drawing of radiolaria (micro-skeleta of zoo-plankton), in which heptagonal,
hexagonal and pentagonal rings were observed.
Properties
They show metallic behaviour. Thus, it is possible to roll up Haeckelite sheets to form nanotubes,
which will be conductors, independent of the diameter and chirality. Another property of Haeckelite tubes
retain stiffness of classical CNTs, composed of only hexagons; (the Young's modulus of Haeekelite tubes
is around 1.0 TPa.) In addition, Haeckelites also exhibit local rugosity due to the local curvature
introduced by the presence of heptagons and pentagons.

4.  What are carbon-nanotubes? Explain different types of carbon-nanotubes. (2 marks)
Carbon particles as graphene sheets are made into tubular forms called as Carbon nanotubes.
They have diameters of few nanometers and their lengths are up to several micrometers. They were
discovered in 1991 by liJima. Carbon nanotubes have very important future applications.
Structural features
Each nanotube is made up of a hexagonal network of covalently bonded carbon atoms. Carbon nanotubes
are of two types:
(i) single-walled
(ii) multi-walled.
A single-walled carbon nanotube (SWNT) consists of a single graphene cylinder whereas a
multi-walled carbon nanotube (MWNT) consists of several graphene cylinders which are arranged in
concentric form. Due to such structures, these CNTS show electronic, mechanical, optical and chemical
characteristics, thermal conductivity, density, and lattice structure. which make them highly useful for
many application. The intrinsic properties of CNTS depend on the diameter
 Explain the use of nano materials in the field of any two of the following :
(i) Medicine
(ii) Electronics
(iii) catalysis (6 marks)
(i) Medicine
Nanomaterials are of the size 1 x 10-9
m. Hence they are comparable or even smaller than a
single cell 10 - 100 f.lm and virus 20 - 450 nm, protein 5 - 50 nm. Thus the materials can freely move
through tissues, they can also bind to a biological system. Endothelian layers of fast growing tumour
tissues are porous thus these nanoparticles can pass through them bringing out a specialised effect as a
medicine. Drug delivery is done through self assemblies like phospholipids or through block polymers.
The drugs molecules can be interrelated in lipohilic wall which acts like a cell membrane.
Liposome protects the drug from being assimilated during digestion or metabolised in certain
environments. Hydrophobic character of the liposome dissolves drug and allows it to pass through blood,
brain unaffected. When it arrives at a specific targetted site the drug is released due to temperature or PH
at the site inflamed of the organ or the concentration at the site lyposomes have PH 4 - 5 and tumour
tissues also have PH 4 - 5. Thus lyposomes open up at PH 4 - 5 allowing the drug to be released.
Magnetic components like magnetite or are coated with and then with
biocompatible polymer. This polymer has attachment point for the attachment with toxic drugs or anti
bodies. A magnet is placed outside the body near the target site to capture the magnetic particles, flowing
in a circulatory system.
Similarly the action of cytostatic anticancer drugs is localised there by reducing side effects on
the patients body especially arthritis, dextrane coated with iron oxides are used and are extracted via
liver treatment.
(ii) Electronics
To increase the speed at which electric charges work, the distance between them needs to be
decreased. Thus number of transistors per unit area increases every year. But there is a limit for this
growth. A time at which the space to store one bit becomes about 4 nm, the things happen at quantum
level heat will be developed, neighbourings bits would interact.
At present atomic scale memory is possible. A bit is encoded by the pres/abs of -Si atom inside
5 x 4 = 20 atoms. Thus 19 atoms prevent or absorb the heat energy. Thus storage capacity of hard disks is increased.
Thin films of organic materials emitting light (OLED) are known. Thin film transistors TFT and thin film organic
photovoltaic cells are known.
The deposition at a reasonable cost is possible because of organo inorganic metallic
compounds which are normally the self assembeled, nanomaterials. They can form thin films by simple
techniques the spray, spin cooling vapour deposition, inkjet printing etc.
(a) Displays

5. 1. The huge market for large area, high brightness, flat-panel displays, as used in television screens and
computer monitors, is driving the development of some nanomaterials.
2. Nanocrystalline zinc selenide, zinc sulphide, cadmium sulphide and lead telluride synthesized by sol-gel
techniques (a process for making ceramic and glass materials, involving the transition from a liquid 'sol' phase
to a solid 'gel' phase) are candidates for the next generation of light-emitting phosphors. CNTs are being
investigated for low voltage field-emission displays; their strength, sharpness, conductivity and inertness
make them potentially very efficient and long-lasting emitters.
(iii) Catalysis
In general, nanoparticles have a high surface area, and hence provide higher catalytic activity.
Nanotechnologies are enabling changes in the degree of control in the production of nanoparticles, and
the support structure on which they reside.
It is possible to synthesise metal nanoparticles in solution in the presence of a surfactant to
form highly ordered monodisperse films of the catalyst nanoparticles on a surface. This allows more
uniformity in the size and chemical structure of the catalyst, which in turn leads to greater catalytic
activity and the production of fewer byproducts. It may also be possible to engineer specific or
selective activity. These more active and durable catalysts could find early application in cleaning up
waste streams.
This will be particularly beneficial if it reduces the demand for platinum-group metals, whose
use in standard catalytic units is starting to emerge as a problem, given the limited availability of these
metals.