Page 242 - Polymer-based Nanocomposites for Energy and Environmental Applications

214 Polymer-based Nanocomposites for Energy and Environmental Applications

TEM analysis revealed that the PPy/α-Fe 2 O 3 and PPy/α-Fe 2 O 3 hybrid composite is in
nanometer range [32]. By impedance spectroscopy study, the presence and absence of
air with NO 2 gas can be found out. When we carried out the same for PPy and its
hybrid nanocomposites within the frequency range 20 Hz to 10 MHz, similar results
were concluded. From the results of impedance spectroscopy, we can conclude that
the potential barrier at grain boundaries of the film supports the impedance. Interac-
tion of oxidizing NO 2 gas molecules with PPy having embedded α-Fe 2 O 3
nanoparticles captures electrons from the composite matrix; hence, PPy/α-Fe 2 O 3
grains were removed that lead to changes in resistivity of the film.

7.5.5 PMMA based nanocomposites
When laponite is grafted with PMMA, i.e., poly(methyl methacrylate) in the presence
of a suitable grafting agent, there is in situ synthesis of layered silicate nanocomposites
by suspension polymerization. Preparation of a scaffold for glucose sensing was
carried out using model enzymes like GOx. Silver electrode was used for monitoring
oxygen consumption in the presence of glucose, and the electrochemical responses
were studied at 0.7 V. When glucose oxidase was fabricated on to the suitable surface
in the presence of ideal cross-linker like glutaraldehyde, then, it acts as more precise
three-dimensional enzymatic structure that acts as improved biosensor. Clay
nanocomposites are used for the electrochemical detection or electrochemical sensor
for glucose. The reason is there is a presence of aromatic units in conjugated polymer
that in turn act as electron carrier for transfer of charge [18]. Electrochemical
polymerization and deposition of film can be carried out by cyclic voltammetry in
(5:95) dichloromethane/acetonitrile solution containing 0.1 M tetrabutylammonium
tetrafluorophosphate (TBAPF 6 ) as the supporting electrolyte.

7.5.6 Natural oil based polymer based sensor

4-Methylphenol, benzene, methylbenzene, and 1, 2-dimethylbenzene organic
compounds that are VOCs, these organic compounds can be detected by using quartz
crystal microbalance (QCM) sensors. The QCM sensor made up of polymerized
linseed oil and used as ideal sensor for this purpose explained in the literature [33].
Nowadays, the sensing film, coating of polymer solution of linseed oil solution, is
used as an adsorbent on QCM sensor for the detection of VOCs, which was prepared
by dip dry method. The prepared film is heated to form a stable cross-linked film in
the presence of organic peroxide like benzoyl peroxide under the influence of inert
atmosphere of argon. We can skip the dependence of inorganic catalyst and air during
polymerization by using benzoyl peroxide as initiator.
From another literature [34], it is explained that the polymer film prepared from the
monomer units like styrene, divinyl benzene, and linseed oil with high sensing ability
by copolymerization process, these are more selective for sensor applications. This
polymer film has high sensing ability in QCM and is used for the detection of volatile
aromatic hydrocarbons such as benzene, toluene, o-xylene, and ethylbenzene vapors.
The schematic mechanism of the sensor was represented in Fig. 7.6. Polymer formed