3. Introduction to Nanomaterials
The word ‘nano’ originates from the Greek word which means ‘dwarf’.
One nanometer (nm) is equal to 10-9meter. Bulk materials can be
defined as the material made out large number atoms or ions that give
rise to the dimensions of micro range or more. Many water molecules
can easily occupy a sphere of 1 nm in diameter.
4. Synthesis of Nanomaterials
There are two approaches to the synthesis of nanomaterials and the
fabrication of nanostructures
Top-down approach:-
involves the breaking down of the bulk material into nano sized structures
or particles. These techniques are an extension of those that have been
used for producing micron- sized particles. An example of such a
technique is high-energy wet ball milling.
Bottom-up:-
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. Many of these
techniques are still under development or are just beginning to be used
for commercial production of nano powders.
5. Characteristics of Nano particles that nanoparticle should posses by any
fabrication technique:
Getting merely a small size is not the only requirement. It should have:-
Identical size of all particles (also called mono sized or with uniform size distribution).
Identical shape or morphology.
Identical chemical composition and crystal structure that are desired among different particles and
within individual particles, such as core and composition must be the same.
Individually dispersed or mono dispersed i.e., no agglomeration.
6. Introduction to ZnO
ZnO is technological and functional material that has a direct band
gap (3.3 eV at room temperature), large bond strength, large exciton
binding energy (Eb=60 meV) and high melting temperature (2248 K) .
ZnO is transparent and can be made highly conductive by doping in
the presence of visible light. It is a unique material that exhibits
semiconducting and piezoelectric properties. nanocombs, nanowires,
nanorods, nanoflowers, and nanobelts have been synthesized under
specific growth condition. Nanostructured ZnO particles have been
used for high energy conversion efficiencies in various applications. It
was observed that the photo physical and photo chemical properties
can be affected by the particle size, shape, morphology of ZnO
nanoparticles.
7. What’s the need ?????
The environmental pollution has received much attention globally due to
the increasing emission of endocrine disruptor chemicals (EDC’s) from
various industries. They are recognized as major contributors to the
environmental pollution, because of their direct (carcinogenic or
mutagen) and indirect effects (ozone and smog precursors) on the
environment and health. EDC’s include a wide range of compounds such
as aromatic and aliphatic hydrocarbons, alcohols, etc., and their
degradation/decomposition is a difficult task. Photocatalytic
degradation of EDC’s using metal oxide nanoparticles has attracted
much attention recently, due to the cost effectiveness and efficiency. It is
being used for solving the problem of environmental pollution. Generally,
oxides are being used as photocatalysts. The search for new
photocatalysts has led to the study of metal oxides doped with transition
metals.
8. Metal oxide nanoparticles, owing to their high surface area, large
pore size, high thermal stability, etc. can be used as effective
photocatalysts in the oxidation of endocrine disruptors (EDC's). Nano
metal oxides like TiO2, ZnO etc are commonly used as the
photocatalysts for the degradation of EDC's. From literature, it is
found that the photocatalytic oxidation of EDC's using zinc oxide has
been proved to be more versatile than the commonly used titanium
dioxide because it has similar band gap energy (3.2 eV) with relatively
large quantum efficiency. ZnO senses the presence of the pollutants
in addition to destroying the organic molecules. This type of
multifunctionality is highly desirable for environmental applications.
9. Aim and Scope of the work
The present work is much focused on preparation of pure and 1.5
weight percentage of M-doped nano ZnO for the photocatalytic
degradation of EDC's. In this project, synthesis and characterizations
of 1.5 wt % M-doped ZnO catalysts and the photocatalytic
degradation of bisphenol, resorcinol, 4-chloro phenol, nonyl phenol
and 2,4,6-trichloro phenol by using them are carried out. The main
objectives of this project are as follows.
1. To prepare pure and 1.5 wt % M-doped (Ce, Mg, Ba) nano ZnO
2. To study the physical and structural properties of the pure and 1.5
wt % M-doped (Ce, Mg, Ba) nano ZnO catalysts by spectroscopic
tools like
X-ray diffraction
DRS
10. 3. To study the morphological features using
HR-SEM
EDX
4. To carry out photocatalytic degradation of resorcinol at different
Time
Catalyst loading
5. To measure the EDC's degradation efficiency using UV-Visible
spectroscopy
11. Materials Required
Zinc acetate dihydrate (Zn(Ac)2.2H2O)
Metal nitrates (Ce, Mg, Ba)
NaHCO3 (250 ml of 0.1 mol/L) and
Triton-X 100.
12. Application
Some of the applications of zinc oxide nanoparticles are given below.
• Zinc oxide is used in the manufacture of rubber and cigarettes (used as a
filter).
• Popularly known calamine lotion is made out of zinc oxide powder. It is also
used in a host of other creams and ointments that are used to treat skin
diseases.
• As an additive in the manufacture of concrete.
• Ceramic industry has a number of uses for zinc oxide powder.
• It is also used as an additive in food products such as breakfast cereals.
• Various paints use zinc oxide as a coating agent.
