Effect of mechanical mixing method of preparation of polyaniline-transition metal oxide composites on DC conductivity and humidity sensing response

Abstract

In the present work, optimized polyaniline-titanium dioxide (PANI-TiO2) and polyaniline-yttrium oxide (PANI-Y2O3) composites were prepared by mechanical mixing of chemically synthesized PANI with TiO2 and Y2O3 transition metal oxides respectively. The Fourier transform infrared spectroscopy (FTIR) analysis confirmed relative decrease in depth of delocalization band of PANI in the composites as compared to that in PANI. The X-ray diffraction (XRD) studies confirmed decrease in degree of crystallinity and increase in inter-chain separation of PANI in the composites as compared to those of PANI. The scanning electron microscopy (SEM) images confirmed relatively more agglomerated and porous granular morphology of the composites as compared to that of PANI. Decrease in DC conductivity of the composites as compared to that of PANI confirmed experimentally and then supported theoretically by one dimensional variable ranging hopping (VRH) model. The PANI-TiO2 and PANI-Y2O3 composites, when studied for their humidity sensing performance, recorded remarkable maximum sensing response of 94 and 96% respectively at 97% RH as compared to 40% of PANI. The response and the recovery time of PANI-TiO2 composite were 95 and 122 s respectively and those of PANI-Y2O3 composite were 50 and 80 s respectively. Humidity sensing stability of the composites tested for a period of 1 month and confirmed.