A. Q. Contractor

Studies on electropolymerization of aniline in the presence of sodium dodecyl sulfate and its application in sensing urea

Abstract In this paper, we report a detailed investigation of the effect of varying concentrations of sodium dodecyl sulfate (SDS) on the rate of polymerization of aniline. Quantitative analysis of the data is done in order to propose a probable mechanism for the growth of polyaniline (PANI) in presence of SDS (SDS–PANI). The SDS–PANI films were characterized by cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM), in situ conductance, in situ UV–vis spectroscopy and scanning electron microscopy (SEM) and were contrasted with polyaniline prepared under identical conditions in the absence of SDS. The polymerization rate was found to decrease initially with increase in concentration of SDS; it passes through a minimum at 1.5 mM and then increases rapidly on further increasing the SDS concentration. EQCM studies showed that the polymerizing species is a charge transfer complex formed between SDS and aniline. Leaching out of SDS was observed during redox cycling of the SDS–PANI films, which results in the formation of a porous polymer film allowing more inclusion of ions. This was further confirmed by observing a higher transport rate of urea across SDS–PANI coated membrane. These porous polyaniline films were then used as transducer for sensing urea.

Synthesis and characterization of functionalized 3,4-propylenedioxythiophene and its derivatives

A functionalized monomer based on 3,4-propylenedioxythiophene, namely ProDOT-OH, was synthesized easily in a single step from commercially available starting materials and was successfully polymerized electrochemically resulting in the formation of an electroactive conjugated film on the working electrode. The presence of the free hydroxyl group makes ProDOT-OH as the material of choice due to ease of derivatization. This has been shown successfully for pre-polymerization functionalization wherein various derivatives were synthesized starting from ProDOT-OH. All the monomers were characterized by 1H, 13C NMR, GC-MS and elemental analysis. The polymers were characterized by cyclic voltammetry, spectroelectrochemistry and in situ conductance measurements.

Novel label-free DNA sensors based on poly(3,4-ethylenedioxythiophene)

We report on the design and development of a novel label-free DNA sensor based on conducting poly(3,4-ethylenedioxythiophene) for the direct detection and quantification of target ssDNA.

Preparation and characterization of mixed LB films of polyaniline and cadmium arachidate

Abstract Langmuir isotherms of mixed monolayers of polyaniline and cadmium arachidate have been studied, and mixed monolayers have been transferred uniformly onto substrates as Langmuir-Blodgett (LB) multilayers. The LB films were characterized by XRD, UV-Vis and FTIR spectroscopy, dc conductivity and cyclic voltammetric measurements. The FTIR results suggest that the films contain arachidate salt, and the XRD results indicate the presence of a layered structure in the mixed LB films.

Conductimetric immunosensor based on poly(3,4-ethylenedioxythiophene).

A conductimetric reagentless immunosensor using the biospecific binding pair of goat antirabbit IgG and rabbit IgG has been designed and fabricated using poly (3,4-ethylenedioxythiophene) as the immobilization matrix-cumtransducer.

In situ measurement of pH in the interior of conducting polymer microtubules

Abstract Visible spectral absorption studies of an indicator trapped in the microenvironment of polypyrrole (PPY) and polyaniline (PANI) films were used to investigate the change in pH accompanying changes in oxidation state of the polymer. An indicator, bromophenol blue was incorporated in the conducting polymer film during the electropolymerization process. In situ UV–vis spectra of these films were recorded in aqueous solution of KCl. The results obtained show that with increasing potential of the film, the pH of the microenvironment decreases both for PPY and PANI. The change in pH is greater in the potential range where the change in electronic conductivity is also greater.

Study of mixed system in monolayers and multilayers transferred by Langmuir–Blodgett technique

Abstract Mixtures in different molar proportions of azo acid, (6Az10COOH, 6A10 ) and arachidic acid (AA) when spread on an aqueous subphase containing CdCl 2 , were found to form inhomogeneous monolayers on the water surface. This inhomogeneity in the monolayers at the air–water interface as well as in the transferred films was studied by using π – A isotherms, XRD and UV–visible spectroscopy. π – A isotherm studies of the monolayers and XRD, UV–visible spectroscopy of Langmuir–Blodgett (LB) multilayers essentially indicated that there was microphase separation. Domains of azo acid and arachidic acid were found. H-aggregate formation of azo acid was observed in pure azo acid as well as in the azo acid composite films. Composite LB films consist of three different phases of molecular organizates and one of these involves molecular arrangement where domains of azo acid and arachidic acid straddle each other. Studies showed that strong molecular interaction in the successive layers in the mixed system led to this characteristic molecular packing in the system. The mean molecular area, Δ G ex π and collapse pressure also showed that the acids were immiscible, thus indirectly suggesting the presence of domains in the system.

Electrochemical synthesis of fully sulfonated n-dopable polyaniline: poly (metanillic acid)

Electrochemical homopolymerization of metanillic acid has been achieved for the first time using a 4:1 acetonitrile-water mixture to get 100% sulfonated polyaniline which is soluble in both organic and aqueous solvents, electrically conducting, and is n-dopable.