Electrochemistry of polyaniline Langmuir–Blodgett films (original) (raw)
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Journal of Materials …, 2006
Electropolymerisation of polyaniline (PANI) has been investigated using cyclic voltammetry in aqueous bath. The effect of dopant on the structure, morphology & optical properties of electrodeposited PANI has also been studied using x-ray diffraction (XRD), atomic force microscopy (AFM), optical absorbance & luminescence spectroscopy. It is shown that the presence of a neutral salt (KI) in the deposition matrix imparts enhanced crystallinity to PANI films.
Modification And Designing Of Electrodeposited Polyaniline Films For Potential Applications
AIP Conference Proceedings, 2011
The electrodeposited polypyrrole (PPY) film over ITO coated glass substrate has been prepared and its current voltage response using Schottky emission theory has been analyzed. The electrodeposition of PPY has ben carried out by electrochemical polymerization of 0.2 M pyrrole monomer and cycling the potential between-0.2V to 0.8 V at a scan rate of 20mV/s using KCl as supporting electrolyte. The formation of polymer has been confirmed by X-ray diffraction and FTIR measurements whereas the surface morphology has been observed using scanning electron microscope. The band gap of PPY film has been calculated using UV visible spectroscopy and found to be 2.4 eV. In addition, the current-voltage response of deposited film was also recorded to evaluate its electronic attributes such as barrier height (Ø B) and constant factor (ȕ). The results revealed the Ø B and ȕ values of 0.314 eV and 1.72×10-4 , respectively. These films may have potential applications in electronic and optoelectronic sensing devices.
Influence of charged tail groups of self-assembled monolayers on electrodeposition of polyaniline
Electrochimica Acta, 2004
Self-assembled monolayers (SAMs) of thiols with three different tail groups, −COOH, −SO 3 Na, and −NH 2 , were used to modify the Au substrates for electrodepositing polyaniline (PANI). Electrochemical quartz crystal microbalance (EQCM) results indicated a slower rate of deposition of PANI on a SAM surface consisting of positively charged amine groups compared to polymerization on bare gold and on a SAM of carboxyl acid groups. The properties of the SAM layers are dependent on the pH value of the solutions, and are effective only at very low pH values (pH < 2). A layer of the positively charged amino groups in acidic solution acted as a barrier for electron transfer in electro-oxidation of aniline monomer. The positively charged SAM of amine groups also increased repulsion between the coupled aniline species and the electrode surface and in this way hindered electrodeposition. Modification of the surface with pre-patterned SAMs have been demonstrated to be a convenient and practical way to fabricate selectively deposited thin films of polyaniline.
Comparison of Chemically and Electrochemically Prepared Polyaniline. Films. 1. Electrical Properties
Chemistry of Materials, 1995
Relaxation phenomena in thin polyaniline films synthesized chemically and electrochemically are investigated by UV-vis and IR spectroscopy. It is shown that the relaxation process carried out from the electrochemically oxidized or electrochemically reduced states of the polyaniline always proceeds toward the emeraldine state. The relaxation process in acid is governed by disproportionation and formation of semiquinone radicals. The changes in the population density of the polaronic states within the polaronic band allows determination of the change in the oxidation state and consequently the change in the position of the Fermi energy level. The formation of polaronic states is ascertained by diffusion of ions from or into t h e polyaniline matrix in solution and
Quartz crystal microbalance characterization of electrochemical doping of polyaniline films
Synthetic Metals, 1993
The electrochemical ionic exchange of polyaniline film-coated electrodes was studied in detail by electrogravimetry using an electrochemical quartz crystal microbalance. The influence of film thickness, electrolyte composition and potential sweep rate is discussed. The data obtained from these measurements establish the dependence of ion population inside the film on the degree of oxidation from -0.25 to 0.5 V (versus SCE). Analysis is made by calculating the relative contribution of anions and cations to the polymer electroneutrality from the electrochemical quartz crystal microbalance and electric charge data.
Journal of Electroanalytical Chemistry, 2004
The electropolymerization and doping/dedoping properties of polyaniline ultrathin films on Au electrode surfaces were investigated by a combination of in situ electrochemical techniques, i.e., electrochemical surface plasmon spectroscopy (ESPR) and the electrochemical quartz crystal microbalance (EQCM). In the ESPR measurements, we employed two wavelengths, i.e., 632.8 and 1152 nm in order to distinguish independently the electrochromic behavior. In addition, we used spectroelectrochemical transmittance measurements in order to probe further the optical properties of the polymer films as a function of the applied potential. The real and imaginary parts of the dielectric constant of the polyaniline thin film at several doping levels was determined quantitatively by taking into consideration the thickness values obtained from the EQCM measurement. The combination of these two techniques provides a powerful method for probing the electrical, optical, and dielectric properties of conjugated ultrathin polymer films.
A comparative voltabsorptometric study of polyaniline films prepared by different methods
A comparative cyclic voltabsorptometric study was carried out for polyaniline (PAn) films prepared by electro-chemical polymerization and vacuum thermal evaporation. The absorption values were measured at different characteristic wavelengths (895, 755, 665, 435, and 325 nm) corresponding to the individual absorption bands separated by us earlier from the spectra using the Alentsev-Fock method. Differential voltabsorptometric curves (dA/dt vs. potential (DCVA)) measured in aqueous HCl were compared with ordinary cyclic voltammetry (CVA). The experiments for different sweep rates were also compared. It was found that the DCVA peak at 895 nm corresponds perfectly to the CVA peak both in the electrosynthesized and the vacuum deposited PAn. The DCVA peak at 435 nm (cation-radicals) precedes the CVA peak (similar to the maximum of the EPR signal), while that at 755 nm (polarons or cation-radical dimers) lags behind the CVA peak. For the vacuum deposited films an intense intermediate DCVA and current peaks (at about 0.6 V vs. Ag/AgCl) are observed. The results are discussed in terms of the heterogeneous structure of PAn; particularly, its specific features in the films prepared using different methods.
Controlled Electrochemical Polymerization Strategies for Electroactive Polyaniline Thin Films
Macromolecular Symposia, 2016
Polyaniline (PANI) thin films were successfully deposited using controlled electrodeposition (ED) technique from a mixed solution of 0.1M aniline and 0.5M H 2 SO 4 on ITO coated substrate. The effect of different deposition cycles 10, 25, 50, 75, 100 on thickness, optical and morphological properties of electrodeposited PANI thin films was studied. The formation mechanism of highly conducting form of polyaniline i.e. Emeraldine salt is explained. The support of Fourier transform-infra red (FT-IR) and Raman spectroscopy was given to confirm Emeraldine salt of PANI. Further DC electrical conductivity of PANI has been measured in temperature range from 300 to 500 K using two point probe method. The optical and morphological properties of PANI give its application towards flexible electrochromic glasses.
Electrodeposition of polyaniline nanostructures: A lamellar structure
Synthetic Metals, 2009
The growth process of polyaniline (PANI) nanofibers during the electrochemical polymerization was investigated in detail. The nano-fibrillar morphology appears to be intrinsic to PANI, and the unique character is attributable to a combined effect of electrophilic substitution reaction mainly taking place at the para-position of aniline or its oligomers and aniline oligomers with one-dimensional (1D) structure. Interestingly, the PANI film
Effect of temperature on the electrochemical synthesis and properties of polyaniline films
Journal of Non-Crystalline Solids, 2010
The effect of temperature on the electrochemical oxidative polymerization of aniline and on the electrochemical properties of the resulting polyaniline (PANI) film was studied. The electrochemical deposition of PANI has been carried out on platinum at different temperatures. Three different films (PANI-25, PANI-40 and PANI-60) have been prepared at 25, 40 and 60°C by electrochemical polymerization and characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Increasing the synthesis temperature leads to an increase of the polyaniline films thickness from 0.4 to 0.9 lm and, respectively, 1.1 lm, associated with an increase of the films capacitances from 3 Â 10 À2 F cm À2 to 7 Â 10 À2 F cm À2 and 10 Â 10 À2 F cm À2 . The impedance measurements showed that only PANI-25 and PANI-40 exist in the conductive state over a large potential window, while PANI-60 has an intermediate behavior at low and high electrode potentials.