For UG students Engineering, Science (Physics, Chemistry), Biotechnology, Nanochemistry, Nanotechnology

1. Basic Chemistry
of
Nanomaterials
Prof. Harish Chopra,
Department of Chemistry,
SLIET, Longowal (Pb) INDIA

2. Introduction
Nanoscale materials are defined as a set of
substances where at least one dimension is
less than approximately 100 nanometers.
A nanometer is one millionth of a
millimeter - approximately 100,000 times
smaller than the diameter of a human
hair. Nanomaterials are of great
significance because they show distinctive
optical, magnetic, electrical, and other
properties. These unique properties have
the potential for great impacts in
electronics, medicine, and other fields.
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3. The two main reasons for unique properties of
nanomaterials are:
❏ Increased relative surface area:
Nanomaterials have a much greater
surface area to volume ratio than their
conventional materials, which can lead to
greater chemical reactivity and affect
their strength
❏ New quantum effects: The quantum
effects lead to novel
optical,
electrical
magnetic behaviours 3

4. History
4
❏ 1857 Michael Faraday synthesized the
colloidal gold particles.
❏ 1940’s, precipitated and fumed silica nanoparticles
manufactured in USA and Germany used as ultrafine
carbon black for rubber reinforcements. Nanoscale
amorphous silica particles were used in many everyday
consumer products, ranging from non dairy coffee creamer
to automobile tires, optical fibers and catalyst supports.
❏ 1960-70’s development of magnetic recording tapes
from metallic nanopowders was reported.
❏ 1976 showed nanocrystals produced by the now popular
inert-gas evaporation technique.
❏ Recently, it has been found that the Maya blue paint is
a nanostructured hybrid material.

5. Classification
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Nanomaterials are classified as:
❏ Zero dimensional (atomic clusters, filaments and cluster
assemblies),
❏ One dimensional (multilayers),
❏ Two dimensional (ultrafine-grained overlayers or buried layers),
❏ Three dimensional nanostructures (nanophase
materials consisting of equiaxed nanometer sized grains)

6. Types
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7. Synthesis
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The synthesis of nanomaterials can be
achieved in either the ‘bottom up’ or
the ‘top down’ approaches, i.e. either to
assemble atoms together or to disassemble
(break, or dissociate) bulk solids into
finer pieces constituted of only a few
atoms.
The nanostructures can be created based
on methods of self-organization and
self-assembly (bio-mimetic processes).
Using these methods, synthesized
materials can be arranged into useful
shapes so that finally the material can be
applied to a certain application.

8. Mechanical Grinding
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Mechanical abrasion is a ‘top down’ method for the synthesis of
nanomaterials, where the material is synthesized by the structural
breakdown of coarser-grained structures.
The advantages of this method are:
1. It is very simple method to make nanocrystalline materials because
the equipment required is relatively inexpensive and essentially all
classes of materials can be synthesized by this method.
2. Scaling up to large quantities of material for various applications is
very easy.
The disadvantages of this method are:
1. Greater possibility of contamination from milling media and/or
atmosphere,
2. To consolidate the powder product without coarsening the
nanocrystalline microstructure

9. Mechanism of Mechanical Grinding
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Mechanical milling is normally done using high energy shaker,
planetary ball, or tumbler mills. The energy transferred to the powder
from refractory or steel balls depends on the rotational (vibrational)
speed, size and number of the balls, ratio of the ball to powder mass, the
time of milling and the milling atmosphere. Nanoparticles are produced
by the shear action during abrasion milling or grinding.

10. Wet Chemical Synthesis
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The wet chemical synthesis of nanomaterials can be classified into two
broad groups:
1. The top down method: In this method, the single crystals are
etched in an aqueous solution for producing nanomaterials, E. g.,
synthesis of porous silicon by electrochemical etching.
2. The bottom up method: This approach consists of sol-gel
method, precipitation etc. where materials containing the desired
precursors are mixed in a controlled fashion to form a colloidal
solution.
.

11. Nanoparticle Synthesis
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12. Sol-gel Synthesis
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The sol-gel process, involves the development of inorganic networks by the
formation of a colloidal suspension (sol) which undergoes gelation to form a
network in a continuous liquid phase (gel). The substrates for synthesizing
these colloids consist generally of a metal or metalloid element surrounded
by various reactive ligands.
Sol-gel synthesis of TiO2

13. Properties of Nanomaterials
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The properties of nanomaterials are significantly
different from those of atoms and bulks materials
whereas the most microstructured materials
have similar properties to the corresponding
bulk materials. This is primarily due to the
nanometer size of the materials which
render them the following characteristics which
do not exist in the corresponding bulk
materials:
❏ Large fraction of surface atoms
❏ High surface energy
❏ Spatial confinement
❏ Reduced imperfections

14. Applications of Nanomaterials
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Nanomaterials are having wide range of
applications because of their superior chemical,
physical, and mechanical properties. Some of the
important applications are:
❏ Fuel Cells
❏ Catalysis
❏ Phosphors for High-Definition TV
❏ Next-Gen Computer Chips
❏ Elimination of Pollutants
❏ Sunscreen lotion
❏ Sensors

15. Applications of Nanomaterials
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Cancer Therapy
Drug Transporters
Therapeutics
Drug Delivery
Gene Therapy
vaccinesImmunoassay
Fungicides
Cosmetics
Protein
microassay
Live imaging
Bio- imaging
Biosensors
Tissue Regeneration

16. Carbon Nanomaterials
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The continuously increasing commercial use of engineered carbon-based
nanomaterials includes technical, medical, environmental and
agricultural applications. During the relatively short time since the
discovery of fullerenes in 1985, carbon nanotubes in 1991, and graphene in
2004, the unique properties of carbon-based nanomaterials have attracted
great interest, which has promoted the development of methods for large-
scale industrial production.

17. Graphite
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Graphite is one of the oldest and most widely used natural materials. More
traditionally known as the main ingredient of pencil lead, from which the name
“graphite” originated, it is now more widely used in several large-scale
industrial applications, such as carbon raising in steelmaking, battery
electrodes, and industrial-grade lubricants. The graphite has unique
combination of physical properties due to its macromolecular structure, which
consists of stacked layers of hexagonal arrays of sp2 carbon.

18. Fullerenes
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Fullerenes are an allotropic modification of carbon, often
termed as a molecular form of carbon, or carbon
molecules. Fullerenes were discovered in 1985 by
H.W. Kroto, R.F. Curl and R.E. Smalley, who were
later awarded with the nobel prize for chemistry in 1996.
The fullerene family includes a number of atomic Cn
clusters (n > 20), composed of carbon atoms on a
spherical surface. In fullerenes, carbon atoms are usually
present in the sp2-hybrid form and linked together by
covalent bonds. Fullerene C60 is the most common
fullerene. The spherical molecule is highly symmetric and
consists of 60 carbon atoms, located at the vertices of
twenty hexagons and twelve pentagons. The diameter of
fullerene C60 is 0.7 nm.

19. Carbon Nanotubes
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Carbon nanotubes (CNTs) are one of the carbon allotropes with
exceptional properties suitable for technical applications. These
were discovered in 1991 by the Japanese researcher S. Iijima.
Carbon nanotubes are characterized by cylindrical structures with
a diameter of several nanometers, consisting of rolled graphene
sheets. Carbon nanotubes may vary in length, diameter, chirality
(symmetry of the rolled graphite sheet) and the number of layers.
Based on structure, CNTs may be classified into two main groups:
Single-walled nanotubes (SWCNTs)
Multi-walled nanotubes (MWCNTs).

20. Graphene
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Graphene is a 2D allotropic form of carbon, formed by single layers of carbon
atoms. In graphene, carbon atoms exhibit sp2-hybridization connected by
σ- and π-bonds in a two-dimensional hexagonal crystal lattice with a
distance of 0.142 nm between neighboring atoms of carbon hexagons. The
first graphene samples were described in 2004 by A. Geim (Dutch-British
physicist) and K. Novoselov (Russian-British physicist), awarded with a Nobel
prize in 2010. Graphene has many unique physical properties, such as
extremely high mechanical rigidity and a high thermal stability.

21. Carbon Nanowires
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A nanowire is a nanostructure, with the diameter of
the order of a nanometre (10−9 meters). It can also be
defined as the ratio of the length to width being
greater than 1000. Alternatively, nanowires can be
defined as structures that have a thickness or
diameter constrained to tens of nanometers or less
and an unconstrained length. Many different types of
nanowires exist, including superconducting,
metallic, semiconducting (silicon nanowires) and
insulating (SiO2, TiO2). Molecular nanowires are
composed of repeating molecular units either organic
(e.g. DNA) or inorganic (e.g. Mo6S9−xIx).
Applications in Electronic devices, Nanowire lasers,
Sensing of proteins and chemicals using
semiconductor nanowires

22. Carbon Nanocones
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Carbon nanocones are conical structures which are made predominantly
from carbon and which have at least one dimension of the order one
micrometer or smaller. Nanocones have height and base diameter of the same
order of magnitude; this distinguishes them from tipped nanowires which are
much longer than their diameter. Nanocones occur on the surface of natural
graphite. The opening angle (apex) of the nanocones is not arbitrary, but has
preferred values of approximately 20°, 40°, and 60°.
Uses: These are used to cap ultrafine gold needles, which are widely used
in scanning probe microscopy owing to their high chemical stability and
electrical conductivity.

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References
The some contents are taken from:
Chemistry For Engineers
By
Harish Chopra
Anupama Parmar
[In addition, Internet sources have also been used]

24. Thank You !
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