Page 234 - Polymer-based Nanocomposites for Energy and Environmental Applications

206 Polymer-based Nanocomposites for Energy and Environmental Applications

sensitive to nutrients, toxins, and hormones and to metabolic indicators like glucose,
oxygen level, and osmotic pressure. (b) Chemical sensor—it is a self-contained
analytic device that can provide information about its environment like states of
matter like solid, liquid, or gas phase and about its concentration, reactivity, etc.
Sensors are frequently used in day-to-day life such as touch-sensitive lamp, escalator,
or fingerprint sensor button, which are the classes of tactile sensor. With advancement
of technology sensors like thermoregulators and microcontroller platform that are
used for the measurement of pressure and temperature flow, analog sensors such as
potentiometers and force-sensing resistors are used in robotics, aerospace, vehicles,
and medical sectors using MEMS technology.

7.1.3 Polymer nanocomposites (PNCs) as ideal sensor
When polymer or copolymer is used as matrix and the nanoparticles or nanofillers get
dispersed in the matrix of the polymer, it will form the polymer nanocomposites
(PNCs). The PNCs are of different forms, may be in the form of platelets, fibers,
spheroids, or layer-like, and one of its dimension is in nanometer range, that is, below
100 nm. These PNCs are categorized into multiple-phase system such as blends,
composites, and foams. In all the MPS, one of the dimensions of the matrices is
in nanoscale regime, and most importantly, when the particle size diminished to
nanoscale, there is increase in aspect ratio and decrease in size, and there is greater
interaction among the particles. As a result, properties like tensile strength, heat
resistance, sensitivity, and electrochemical behavior increase tremendously. The
sensitivity of polymer composites can be improved by incorporating materials like
GOx, carbon nanotubes (CNTs), and metal nanoparticles with high electric conduc-
tivity, high effective surface area, and fast electron transfer rate. The nanocomposites
such as A-CNTs fabricated on the polymeric substrate like polydimethylsiloxane
(PDMS) can beusedashighlyflexiblepressure sensor. Poly(methyl methacrylate)
(PMMA)-clay nanocomposite (PCN) like PCN/glucose oxidase (GOx) and poly
(4-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-7-(2,3-dihydrothieno[3, b][1, 4] dioxin-
7-yl)-2-benzyl-1H-benzo[d]imidazole) (poly(BIPE))/GOx is used as glucose sensor; a
potentially modified electrode form of nanocomposite polypyrrole (PPy)/single-walled
CNTs (SWNTs)-horseradish peroxidase (HRP) is used as biosensor and hydrogen pero-
xidesensor.CarbonblackCB/polymercompositeiswidelyusedasgasandorganicvapor
sensor [9–11]. Nowadays, CNTs and graphene-based polymer composites are used as
chemicalsensoroforganicvaporssuchasacetone,methanol,andpropanolandgassensor
like H 2 ,NO 2 ,NH 3 ,andO 2 due to their very high electric conductivity and sensitivity to
charge transfer and chemical doping [12–15]. Hence, PNCs for improved sensor devices
are a matter of concern for the current topic.

7.2 Methods of synthesis of nanocomposites

Nanocomposites are prepared by several methods, out of which the following
three methods of preparation are important. These methods are (1) in situ reaction,
(2) solution casting method, and (3) melt-mixing technique.