Rahul Patil

Piezoresistivity of conducting polyaniline/BaTiO 3 composites

Conducting polyaniline / barium titanate (PANI / BaTiO 3 ) composites exhibiting piezoresistivity properties have been synthesized by the in situ deposition technique by placing a fine grade powder of BaTiO 3 in the polymerization reaction mixture. The polyaniline was formed preferentially on the ceramic particles giving a much higher yield for PANI than in absence of the BaTiO 3 These composites exhibited piezoresistivity with the piezosensitivity being maximum at a certain composition. The current‐voltage characteristics clearly revealed a nonlinear space charge controlled charge transport process. A large hysteresis in these characteristics was also observed which was dependent on the BaTiO3 content in a composite. The various results have been explained on the basis of the charge transport mechanism in the heterogeneous conducting material having insulating domains dispersed in it.

Deposition and characterization of CdS nanoparticle/polyaniline composite films

In the present work we explore the possibility to deposit CdS/polyaniline composite films through an electrochemical route. The films were generated electrochemically on fluorine-doped tin oxide coated glass substrates from the electrolyte containing mixture of CdS particle solution and aniline monomer solution in an acidic medium. The average particle size in the electrolyte was around 30 A and no considerable increase in the particle size was observed after the film formation. The presence of CdS clusters was confirmed from optical absorption spectra, photoluminescence spectra, XRD and TEM.

Effect of monomer concentration and substrate resistance on redox behaviour of polyaniline films

Abstract The effect of monomer concentration and substrate resistance on the redox properties of polyaniline is investigated using cyclic voltammetry, The mechanism of polymerization is found to be affected drastically by the concentration of monomer while the influence of substrate resistance seems to become a predominant factor only at higher concentration. Both these parameters in combination are found to be responsible for the flattening of cyclic voltammograms due to a significant contribution of the uncompensated ohmic resistance. The extent of reversibility is observed to be a strong function of scan rate and the optimum oxidation-reduction transformation occur at a scan rate of 100 mV s − at moderate monomer concentrations. Additionally, from the optical spectra it is observed that 0.2 M monomer concentration is seen to be appropriate for obtaining selectively the conducting phase of the polymer.

Optical and morphological investigations of electrochemically deposited poly (N-methyl aniline) films

Poly (N-methyl aniline) films have been deposited electrochemically on polyaniline coated electrodes for the first time. The influence of monomer concentration on the optical and morphological properties of the films was investigated. The optical spectra of the films reveal selective deposition of the conducting emeraldine salt phase of the polymer at lower monomer concentration while formation of mixed phases is observed at higher monomer concentration. However, the conducting phase obtained at the lower concentration of 0.2 M exhibits poor morphology in contrast to the uniform morphology observed at a higher concentration of 0.8 M. Further, a transition from fibrillar to granular nature is noted with increasing monomer concentration in the electrolyte solution.

Unusual electrochemical response of oligoalkylthiophene films : Involvement of bipolarons

Cyclic voltammograms of π-conjugated oligoalkylthiophene (13T) films are found to show two oxidation peaks during the 1st potential cycling up to 0.8 V. In the subsequent cycles, however, the 2nd oxidation peak disappears completely and the 1st peak shifts by ca. 0.1 V to the cathodic direction. This finding along with spectroscopic measurements of 13T film before and after electrochemical stimulus suggests first that two different phases to be oxidized at separate potentials coexist in a pristine 13T film and second that one phase can be switched to the other by being oxidized to generate bipolarons.

Electric conduction mechanism in conjugated polymers studied using flicker noise spectroscopy

Spectroscopy of Stochastic Signals (3S) has been used to study conduction behavior in electrochemically deposited conductive polymers (CP) using as example polyaniline and poly(3-methyl thiophene). Within the 3S approach, the conduction process is considered as a stochastic process in heterogeneous disordered system rather than as some classical conduction mechanisms like Schottky or Poole-Frenkel emission. We have been able to distinguish several modes of the conduction process in conducting polymers using the 3S methodology. Particularly, we have established that the transport of charge carriers in highly doped CPs is much less correlated than in non-doped ones, that is, at low doping levels elementary processes involved in the conduction are more correlated than in highly doped polymer. By increasing applied electric field we also achieve lower correlation in a sequence of elementary events contributing to the conductivity of CP. Apparently, the change in the correlation length corresponds to changing mechanism of the electrical conduction. The lower correlation in highly doped sample can be attributed to various factors including change in CP conformation, enhancement in inter-chain charge transfer and generation of polaron lattice. The obtained results show the high informative potential of the 3S method in studying conduction mechanism in conducting polymers.