Doping Of Polypyrrole Research Articles

Photocatalytic Degradation of Tetracycline Hydrochloride by Zinc oxide/Polypyrrole/Carbon nanotubes

AbstractIn this study, the intermediates of the photocatalytic degradation of tetracycline hydrochloride (TC‐HCl) were analyzed by high performance liquid chromatography‐mass spectrometry. The doping of polypyrrole (PPy) and carbon nanotubes (CNTs) increased the reaction rate of TC‐HCl degradation by ZnO. The prepared ZnO has a large specific surface area, which can improve the adsorption performance. The introduction of PPy and CNTs can promote electron transfer and reduce the recombination of photogenerated electron hole pairs in the composite material ZnO/PPy/CNTs(ZPC), and the photocatalytic performance of the composite sample is improved. In addition, the new visible light catalyst has strong degradation effect on TC‐HCl. Using tetracycline hydrochloride as a pollutant, the photocatalytic degradation performance of each sample was analyzed. After 240 min of photoreaction, the Degradation rate of TC‐HCl (DTC‐HCl) by ZnO was 24.1 %, while that by ZPC was 91.5 %. Meanwhile, the intermediates of photocatalytic degradation of TC‐HCl were analyzed by high performance liquid chromatography‐mass spectrometry. The peak intensity of TC‐HCl from adsorption equilibrium to the end of the photocatalytic reaction occurred at a retention time of about 10.05 min and decreased with the increase of the reaction time. This indicates that TC‐HCl is broken down into small molecules during the reaction. Through the analysis of intermediates and active species, the degradation pathway of tetracycline hydrochloride was deduced.

Immobilization of phosphotungstate through doping in polypyrrole for supercapacitors.

Immobilization of phosphotungstate is achieved through doping in polypyrrole via the electrochemical deposition of polypyrrole (PPy) in the presence of the phosphotungstate anions (PW12) on carbon nanotube film. Electrochemical stability in neutral solution is realized for PW12 in the prepared ECNT-PPy/5PW12, owing to the proton sponge provided by PPy. ECNT-PPy/5PW12 shows a high areal capacitance of 1300.0 mF cm-2 in LiCl solution at 1 mA cm-2. ECNT-PPy/5PW12 also displays high rate capability and good cyclic stability due to the interaction of incorporated PW12 and the polymer matrix. ECNT-PPy/5PW12 can retain 78.6% and 92.0% of its capacitance with 40-fold current increase and after 10 000 galvanostatic charge/discharge cycles, respectively. An asymmetric supercapacitor with the ECNT-PPy/5PW12 anode and CNT-MnO2 cathode demonstrates high volumetric energy density (4.71 mW h cm-3 at 13.85 mW cm-3) and long cycle life (90.0% capacitance retention after 10 000 charge/discharge cycles).

Chemically designed Pt/PPy nano-composite for effective LPG gas sensor

Simultaneous in situ reduction of hexachloroplatinic acid by the amine group in the pyrrole monomer and oxidation of pyrrole to form polypyrrole (PPy) was examined. The reactions were performed at various temperatures to understand the degree of reduction of platinum precursor as well as doping of polypyrrole with Pt(II) chloro-complex. Spectroscopic images revealed different morphologies for the Pt/PPy nano-composite prepared at various temperatures. The as-prepared Pt/PPy nano-composite samples were tested for their ability to sense liquefied petroleum gas (LPG) which resulted in excellent sensing at relatively low temperature. The porous nature and ohmic contact between the PPy and platinum nanoparticles makes the as-prepared Pt/PPy nano-composite highly useful for sensors as well as electronic applications.

Synthesis and Characterization of LiFePO<sub>4</sub> / PPy Composite Powders

A series of lithium iron phosphate /polypyrrole (LiFePO4/PPy) composite powders were synthesized by chemical oxidation method with different doping agent and oxidation agent. The composite powders were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectrum (FTIR), and X-ray diffraction (XRD). The results showed that the composite powders composed of PPy and LiFePO4. And the doping of polypyrrole in LiFePO4 could weaken the XRD intensity of LiFePO4 , but could not destroy its crystallization. With the increase of pyrrole in LiFePO4/ PPy composite powders, the polypyrrole on the surface of LiFePO4 increased and dispersed more homogeneously. Thermogravimetric analysis (TGA) data indicated the heat-stability of LiFePO4/PPy was very good that the composite powders would not oxidate till 300°C in the air flow.

Characterizing the Dopant Behavior of Functionalized Carbon Nanotubes in Conducting Polymers

ABSTRACTThe electrochemical polymerization of conducting polymers, such as polypyrrole, generally requires the incorporation of an anionic dopant to balance the positive charge on the oxidized conducting polymer chains. The susceptibility of multiwalled carbon nanotube (MWNT) surfaces to functionalization makes them exciting candidates for a new class of dopant for conducting polymers. In this work, the doping of polypyrrole with functionalized MWNTs is investigated using a combination of electrochemical impedance spectroscopy, scanning electron microscopy, and quartz crystal microbalance work. The findings described here are particularly relevant in light of recent reports indicating that carbon nanotube-conducting polymer composites hold great promise for use in electrochemical capacitors, also known as supercapacitors [1,2].

In situ optical spectroscopy of electrochemical doping of polypyrrole

The doping of polypyrrole with LiClO 4 has been studied by optical spectroscopy and cyclic voltammetry. Pure and highly conjugated samples are characterized by the lack of absorptions below 2.5 eV in the reduced state, by a low π−π ∗ transition energy (2.88 eV in this work), and by the occurrence of well-defined peaks in cyclic voltammograms. Bipolarons seem to be the dominating species. The conflicting data in the literature concerning the polaron/bipolaron ratio is explained by its being strongly dependent on sample history and method of preparation. Polarons are regarded as playing a role mainly in systems of lower conjugation length.

Competitive doping in polypyrrole

The electrooxidation of pyrrole in electrolytes containing both perchlorate and tetrasulphonato copper (II) phthalocyanine anions produced polypyrrole films from aqueous methanol that were TSCuPc-rich. Potentiostatic and galvanostatic methods gave similar results. However, a similar procedure in acetonitrile produced films that were perchlorate-rich. Electrical conductivity of the films mirrored composition, agreeing with the trend that perchlorate-rich films have higher conductivities than phthalocyanine-rich ones.

Competitive doping in polypyrrole

Polypyrrole samples were prepared by electrooxidation of pyrrole in electrolyte solutions containing two anionic species, and the resulting free-standing films were examined for composition by EDAX and Microanalysis and for conductivity by 4-point method as a function of anion ratio, solvent and preparation procedure.

Physicochemical characterization of mixed conducting composites obtained by electropolymerization of pyrrole into perfluorinated ionomer gels

Polypyrrole/Nafion® composites have been synthesized by the electropolymerization of pyrrole into a stiff gel of a perfluorinated ionomer (Nafion®). These composites have high electronic conductivities (150 S cm −1). In addition, we give evidence of free sulfonic groups not associated with the oxidized polypyrrole. These composites will therefore retain the ability to exchange the cations of the free sulfonic groups not engaged in the doping of polypyrrole. The composition and characteristics of the final composites have been investigated as a function of the initial concentration of pyrrole in the Nafion® gel and of the electrosynthesis charge.

Simultaneous alternating current impedance/electron spin resonance study of electrochemical doping in polypyrrole

The electrochemical doping of polypyrrole has been studied using simultaneous a.c. impedance and in-situ electrochemical e.s.r. measurements. A quantitative estimate of the polypyrrole conductivity as a function of doping level has been obtained and the corresponding change in the polaron concentration measured by in-situ electrochemical e.s.r. It was found that at low doping levels there was a good correlation between these two properties. It is suggested that the polaron may be responsible for the conduction process under such conditions. At higher doping levels conduction would appear to involve the bipolaron.

The use of short chain oligomers as a model for soluble polypyrrole

To investigate the properties of stereoregular polypyrrole in solution short chain oligomers of the polymer were made electrochemically, in conditions resembling the electrochemical polymerisation reaction. The short chain oligomers were produced by incorporating a terminating group in the reaction mixture. The oligomers were made using a variety of counterions. The films were characterised using UV/Vis spectra. The magnetic properties of the polymer in solution were investigated. The work questions some of the theories concerning the nature of doping in polypyrrole.