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In this paper, we report the fabrication of poly(methyl methacrylate) (PMMA) nanofibers by electrospinning technique and used as substrate for coating pure polyaniline (PANI) and PANI/multiwalled carbon nanotubes (MWCNT) separately during chemical oxidative polymerization. The morphology and structure of PANI and PANI/MWCNT nanofibers were investigated by SEM, UV-VIS, FTIR and XRD. SEM shows that the fibrous structure of PMMA with an average fiber diameter 272 nm. UV-Vis, FTIR and XRD analyses confirmed the formation of PANI and its interaction with MWCNT. Electrical responses of the synthesized samples towards LPG were measured at room temperature for various ppm, which fulfill all the characteristics like sensitivity, response, recovery of the sensors. Sensitivity study shows that materials under investigation are found to be highly sensitive for LPG near to room temperature. PANI/MWCNT nanofibers showed rapid and reversible resistance change upon exposure to LPG as compared to that of PANI nanofibers, which may be due to MWCNT wrapped by conducting PANI results in the formation of a charge transfer complex which increases the protonation of the polyaniline and the transition in the electrical resistance was attributed to a change in the localization length of the composite nanofibers.

In this paper we report the highly sensitive at low temperature and low concentration of liquefied petroleum gas (LPG) sensor based on D-Camphor-10-Sulphonic acid (CSA) doped Polyaniline/Polyethylene Oxide (PANI/PEO) and PANI/ZnO/PEO nanofibers fabricated by electrospinning technique. Nano-sized particles of zinc oxide (ZnO) were synthesized using sol-gel method. The emeraldine base form of polyaniline (PANI) and PANI/ZnO synthesized by chemical oxidative polymerization were treated with CSA for better solubility and conductivity and then blended with PEO solution to get nanofibers using electrospinning. The morphology and structure of electrospun nanofibers of CSA doped PANI/PEO and PANI/ZnO/PEO were investigated by SEM, UV-VIS, FTIR and XRD. The change in electrical resistance of CSA doped PANI/PEO and PANI/ZnO/PEO for 1000 ppm of LPG was measured. Both the samples showed a rapid and reversible resistance change upon exposure to LPG gas at 1000 ppm concentration. Maximum sensitivity was achieved at 36 °C for PANI/ZnO/PEO indicating suitability of nanofibrous PANI/ZnO/PEO towards LPG sensing as compared to pure ZnO and PANI.

Zinc oxide (ZnO) nanoparticles were synthesized by simple route of sol-gel method and nanofibers of polyaniline (PANI) and PANI/ZnO nanocomposites prepared using the electrospinning technique. Electrospun nanofibers of PANI and PANI/ZnO nanocomposites were collected on aluminum substrate for characterization and on Cu-interdigited electrodes to prepare chemiresistor sensor. Electrospun nanofibers of PANI and PANI/ZnO nanocomposites have been characterized by UV-Visible (UV-Vis), Fourier transform infrared (FTIR), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). UV-Visible spectra of nanofibers of PANI/ZnO nanocomposites show hypsochromic shift as that of PANI and some interaction due to ZnO in PANI matrix. The observed changes in the FTIR spectra of the fibers of PANI/ZnO nanocomposites are assosciated with the formation of H-bonding between ZnO and the N-H group present in the PANI chains. X-ray diffraction patterns exhibits hexagonal wurtzite structure of ZnO and broad amorphous peaks of PANI. Heterogeneous structures with fibrous characteristics of diameter less than 300nm of PANI/ZnO nanocomposites are identified in the SEM images. The electrical properties were characterized by I-V characteristic measurements. The changes in resistance of the chemiresistor sensor were utilized for detection of HCl and NH3 chemical vapour at room temperature. The resistance of the sensors was found to be decreased when they were exposed to HCl vapours whereas the resistance of the sensors was found to be increased when they were exposed to NH3 vapours. It was observed that PANI/ZnO nanocomposite sensor shows a high response and sensitivity with good repeatability as compared to that of pure PANI. Sensitivity result shows that PANI/ZnO nanocomposite is highly sensitive to chemical vapours even at room temperature and at very low concentration. Copyright © 2014 VBRI press.

Due to numerous potential applications of conducting polymers, these materials are now world wide studied since the discovery of first conducting polymer (polyacetylene) in 1977. Particularly for sensing concerned, conducting polymers are very sensitive to environmental conditions. The developments in nanostructure conducting polymers and conducting polymer nanocomposites have large impact on sensor research. Due to large surface-area-to-volume ratio of nanostructure conducting polymers, they show superior performance compared to conducting polymers in bulk form. However, the sensitivity and selectivity of nanostructure conducting polymer-based sensors still leave room for improvement. The conducting polymer nanocomposites have gained tremendous recognition in the field of sensors to improve the sensitivity and selectivity due to synergistic effect of size reduction for nanofiller and high electrical conductivity of conducting polymer in nanocomposites. Therefore, the sensitivity and selectivity of conducting polymer nanocomposites-based sensors have been enhanced compared to that of the classical materials-based sensors. This chapter provides the current research activities of the sensors/biosensors based on conducting polymer nanocomposites. The synthesis of nanostructure conducting polymers and conducting polymer nanocomposites, their application in sensors/biosensors are reviewed and discussed in this chapter.

Tin oxide (SnO2) nanoparticles have been synthesized by simple route of sol-gel method. Polyaniline-tin oxide (PANI/SnO2) nanocomposite (sample A) was prepared by an in-situ polymerization of aniline in the presence of as-synthesized SnO2 nanoparticles. Similarly, tin oxide-intercalated polyaniline nanocomposite (sample B) was prepared using tin chloride (SnCl4.5H2O) as precursor during polymerization of aniline. Morphology and structure of both the nanocomposites have been studied using XRD pattern, FTIR spectra and SEM images which reveals that SnO2 was uniformly mixed within the PANI matrix. In this paper we report the comparison of polyaniline-tin oxide (PANI/SnO2) nanocomposites sample A and B for the response to ammonia. A laboratory set up for sensing ammonia has been built up using four probe resistivity unit and the response of the prepared PANI/SnO2 nanocomposites to ammonia vapour for different concentration (5, 10, and 15%) was tested. PANI/SnO2 nanocomposites were found to be good materials for NH3 detection even at room temperature as compared to that of pure SnO2. By comparing the response of sample A and B to the ammonia vapour, the sample A was found to be more sensitive than sample B due to highly porosity and surface activity of sample A. The results were reproducible and checked by repeating observations. Synthesis route for the preparation of PANI/SnO2 nanocomposites is an important factor while selecting the materials for ammonia sensing. Copyright © 2012 VBRI Press.