Evaluation of amperometric glucose biosensors based on glucose oxidase encapsulated within enzymatically synthesized polyaniline and polypyrrole

In this article potential and suitability of enzymatically synthesized conducting polymers polyaniline (PANI) and polypyrrole (PPY) for fabrication of enzymatic amperometric glucose biosensors were evaluated. The polymerisation of these polymers was induced by catalytic activity of glucose oxidase (GOx) from Penicillium vitale cross-linked by glutaraldehyde (GA) on the graphite rod electrode (GOx-electrode) surface. The main precursors for initiation of polymerisation reactions were hydrogen peroxide as an initiator of polymerisation reaction and β-d-gluconic acid as a medium, which reduced the pH towards acidic one is the most suitable for the formation of PANI and PPY. During the polymerisation reactions the immobilized GOx was self-encapsulated within formed PANI or PPY layers in order to form GOx/PANI- and GOx/PPY-modified electrodes (GOx/PANI-electrode and GOx/PPY-electrode, respectively). Kinetic properties of GOx, which is acting as a biocatalyst in GOx/PANI- and GOx/PPY-electrodes, were studied and results were compared with GOx-electrode. The results show that in both GOx/PANI- and GOx/PPY-electrodes self-encapsulated GOx exhibited different parameters of catalysed reaction kinetics due to increasing diffusion limitations if compared with that of the GOx-electrode and it allowed the detection of glucose in a wider concentration interval. Moreover, both GOx/PANI- and GOx/PPY-electrodes exhibited good operational stability and reproducibility of analytical signal. The electrochemical characteristics of formed PANI and PPY in the GOx/PANI- and GOx/PPY-electrodes were also determined. In addition, the influence of temperature, pH and common interfering compounds on the steady-state current response of modified electrodes were investigated and discussed.     

Branched and curved nanotubular polyaniline synthesized by emulsion polymerization in presence of zinc salts of n-dodecylbenzenesulfonic acid

The presence of zinc salts of DBSA (n-dodecylbenzenesulfonic acid), designated as Zn(DBSA)₂, induced some branches and curvature of the resultant polyaniline nanotubes. These branched or curved nanotubes can be clearly seen from their SEM and TEM micrographs taken for various polyaniline nanotubes prepared in the presence of Zn(DBSA)₂. For branched or curved polyaniline nanotubes, the conjugation chain length can be monitored by the position of their λ_maxs in the UV-Vis-NIR spectra.     

Tailoring of chiroptical properties of substituted polyanilines by controlling steric hindrance

Optically active polyorthoanisidine, polyorthotoluidine, polyorthoethylaniline and polyorthochloroaniline were synthesized with chemical polymerization of corresponding monomers in aqueous medium by using d- or l-camphorsulfonic acid (d- or l-CSA) as chiral dopant, ammonium persulfate as oxidant, and diaminodiphenylamine as initiator. By circular dichroism spectroscopic measurements, it was found that PANI exhibited generally a reversed chirality in comparison with the used chiral dopant, but the substituted PANIs had the same one as the chiral dopant. This revealed that the substituent at ortho position caused helical inversion of conformation in comparison with the parent PANI. Such effect was further confirmed by the influence of the copolymerization of aniline and its derivatives on the chirality of the copolymers. The effect of the substituent on the chirality of the copolymers was increased with the increase of the steric hindrance of the ortho substituent. A mechanism was proposed to explain the effects of steric hindrance on the chirality of PANIs. The clarified relationship between the steric hindrance and the chirality of the polymer can enable us to tailor the chiroptical properties of functional polymer materials for future application.     

锂二次电池阴极材料—聚苯胺

本文介绍了作为锂二次电池阴极材料的聚苯胺的合成方法、结构,导电性和氧化还原可逆性。     

Synthesis and characterization of Ag/polyaniline core-shell nanocomposites based on silver nanoparticles colloid

Ag/polyaniline core-shell nanocomposites were successfully synthesized via in situ chemical oxidation polymerization of aniline based on mercaptocarboxylic acid capped Ag nanoparticles colloid. The morphology and structure of the products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and UV-Vis spectra. A possible formation mechanism of the Ag/polyaniline core-shell nanocomposites was also proposed.     

Stable Langmuir-Blodgett film deposition of polyaniline and arachidic acid

An experimental study was carried out to examine the stable Langmuir-Blodgett (LB) film deposition of mixtures of polyaniline (PA) and arachidic acid (AA) at different concentration ratios, with the aim of developing a systematic methodology for the production of quality PA/AA film at the highest deposition speed. The quality of LB film was examined before, during and after the film deposition process. Images of the PA/AA composite materials at air-liquid interface, based on the Brewster angle microscopy, revealed that a 50/50 concentration ratio of PA/AA composite layer produced the best LB film structure. The feasibility of LB film deposition was determined from dynamic contact angles which were measured by a flow visualization technique. The quality of the deposited film was judged by the transfer ratio and the atomic force microscopy images. The effect of pH was also examined, and it was found that the LB film deposition for the PA/AA system could only be carried out in a narrow range of pH. It was found that the deposited LB film of the PA/AA system had a high transfer ratio and improved surface roughness at the deposition speed 30 mm/min. This deposition speed is much higher than those previously reported.     

Determination of the dopant weight fraction in polyaniline films using a quartz-crystal microbalance

The electrical conductivity of polyaniline depends on factors such as degree of oxidation, type of protonation, and dopant weight fraction. The last of these factors is connected with the loss of mass during the deprotonation of polyaniline, and can thus conveniently be determined in situ by the use of a quartz microbalance. This is illustrated in the present paper which concerns the determination of the weight fraction of acid in thin polyaniline films prepared by the chemical oxidation of aniline in the aqueous solutions of sulfuric and phosphoric acids. It is illustrated that the deprotonation-reprotonation processes are fast, complete, and reversible. Polyaniline has sulfate counter-ions in 0.1 M sulfuric acid while, in 0.5-1 M sulfuric acid, hydrogen sulfate counter-ions are present. The quartz microbalance involving polyaniline films can be used in the sensing of the acidity.     

Some Observations on the Dielectric and Conductivity Behavior of Nanocomposites of Polyaniline with Fe3O4 and CuFe2O4

Nanocomposites of polyaniline with iron oxide (PANI-Fe₃O₄) and copper ferrite (PANI-CuFe₂O₄) were prepared and characterized by FTIR, HRTEM, XRD and FESEM. HRTEM images reveals that the main size distributions are located in the range between 25–34 and 22–28 nm in case of PANI-CuFe₂O₄ and PANI-Fe₃O₄ nanocomposites, respectively. The dielectric constant value for PANI-Fe₃O₄ nanocomposites reaches a maximum value as high as ～7000 (10² Hz), while the same for PANI-CuFe₂O₄ composite attains a maximum value of ～2600 at 10² Hz. A quantitative estimation of the contribution of the grain boundary and resistance parameters has been attempted in terms of Maxwell-Wagner two-layered model.     

Improving the electrochemical properties of polyaniline by co-doping with titanium ions and protonic acid

Polyaniline co-doped with titanium ions and protonic acid was synthesized in aqueous H₂SO₄ solution containing Ti(SO₄)₂ (pH 2), and was characterized via Fourier-transform infrared spectra, UV–vis spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and cyclic voltammetry. Its conductivity was 2.8 S cm⁻¹ at room temperature (25 °C), which is the same order of magnitude as polyaniline doped with protonic acid (5 S cm⁻¹). Compared with polyaniline doped with protonic acid, it showed a better redox reversibility and cycling stability in aqueous pH 4.0 media, even in an acetate electrolyte (pH 4.0). It could be a promising material for several applications due the increase of the operating pH window of polyaniline in an aqueous environment.