Doping Induced Modifications in Physicochemical and Optoelectronic Properties of Polyaniline Thin Films
Author : Karan R Rathod, Munjaji E Dudhamal, Jayesh R Pawar, Nikhilesh S Bajaj, Vijendra A Chaudhary and Rajesh A Joshi
Abstract :
The present article deals with study of transition element doping effect on physicochemical and optoelectronic properties of Polyaniline thin films synthesized by using solution polymerization method at room temperature over the glass substrates. These as deposited and doped thin films have been comparatively analysed for structural, compositional, morphological, optical absorbance properties with the intension to study its effect over the NH3 gas sensing behaviour. From the Fourier transform infra-red spectrum of as deposited and doped thin films shows shift in peaks corresponding to 1632 cm⁻¹ and 1354 cm⁻¹ attributed to C=C stretching vibrations of benzenoid and quinoid rings, while peaks 1193cm⁻¹ and 833cm⁻¹ are associated with the protonation and doping. Raman spectrum for as deposited and doped thin films exhibits sharpening of the characteristic peaks 1599 cm⁻¹ for C-C stretching in benzenoid, 1509 cm⁻¹ for C=C stretching in quinonoid while 1374 cm⁻¹ for C∼N+ vibrations of delocalized polaronic structures and C=N stretching vibrations in quinonoid units. Morphological images observed from the scanning electron microscopy (SEM) shows granular distribution of particles over the substrate surface for as deposited thin films which gets improved and or reduction in size for doping some elements. Optical absorbance spectra revealed improvement in absorbance coefficient upon doping, peak at 625nm corresponds for exciton induced charge transitions. The NH3 gas sensing characteristics when studied revealed almost similar response and recovery time for doped and as deposited thin films while increment in gas sensitivity is observed upon doping, for Au doped thin films have represented higher sensitivity.
Keywords :
Thin Film, Polyaniline, Benzenoid and Quinoid, Sensor, Polaron, Doping.
