Polyaniline film formation in hexadecyl trimethyl ammonium bromide admicelles on hydrous zirconia surface

Formation of a thin polyaniline film on hydrous zirconia (ZrO2) surface was carried out using adsorbed surfactant bilayers on ZrO2 as reaction sites. Aniline was adsolubilized in hexadecyltrimethylammonium bromide (HDTAB) admicelles formed on the surface of ZrO2 by adsorption. Subsequent polymerization of the adsolubilized aniline monomer showed effective conversion of aniline to polyaniline. The formation of the polyaniline coated ZrO2 has been confirmed by UV-visible spectroscopy, FT-IR spectroscopy, and conductivity measurements. Various parameters involved during the adsorption process were studied. Selection of pH 9.0 as the pH of all experimental feed solutions was governed by the knowledge of point of zero charge (PZC) of ZrO2. Effect of aniline concentration on HDTAB adsorption was studied and it was observed that increase in aniline concentration decreased the amount of HDTAB adsorbed on ZrO2. Addition of salt (0.05 M NaCl) in the feed solution increased HDTAB adsorption and drastically reduced the effect of aniline concentration on HDTAB adsorption.     

Study of the interaction of molybdenum(VI) ions with γ-alumina by pulse technique

The mechanism of interaction between molybdenum(VI) as aqueous solutions of ammonium paramolybdate and γ-alumina, has been studied in transient conditions by pulse technique, using combined differential refractive index and u.v. absorption detectors. In acidic environment, molybdenum(VI) species are irreversibly adsorbed through an anionic exchange mechanism with liberation of ammonium salts. In a neutral environment, molybdenum(VI) species are only partially irreversibly adsorbed onto γ-alumina through a protonic transfer mechanism with liberation of basic species. The depletion of H₃O⁺ due to adsorption of molybdenum(VI) from neutral solution, provides an explanation of the observed mutual enhancement of cobalt(II) and molybdenum(VI) adsorption on alumina. The general result presented in this paper can be summarized by stating that the amount of irreversibly adsorbed molybdenum(VI) is related to the amount of available basic sites present onto alumina.     

Template synthesis of polyaniline and poly(2-methoxyaniline) nanotubes: comparison of the formation mechanisms

The process of polyaniline (PANI), poly(2-methoxyaniline) (POMA) nanotubes formation was investigated. Polyaniline and poly(2-methoxyaniline) nanotubes were prepared by chemical in situ deposition within the pores of polycarbonate membranes. It was found that the formation of polyaniline and poly(2-methoxyaniline) proceeds by two substantially different mechanisms. In the case of PANI, the polymer is first formed in the polymerization solution (the solution containing the monomer and oxidant, where the polycarbonate substrate is placed), and then it precipitates on/into the membrane. In the case of POMA, the oxidized 2-methoxyaniline molecules are first adsorbed on polycarbonate surface, and then, as a consequence of their accumulation, they recombine to form the polymer.     

Fabrication and characterization of core/shell structured TiO2/polyaniline nanocomposite

A novel core/shell structured TiO(2)/polyaniline nanocomposite was fabricated by grafting aniline on aminobenzoate monolayer that is chemically adsorbed on the TiO(2) nanocrystal surface. The formation and nanostructure of the nanocomposite were investigated by FT-IR and UV-Vis spectra, TEM, FE-SEM, and TG-DTA analysis. Adsorption of aminobenzoate on the TiO(2) surface is an effective method to obtain the uniform nanocomposite. The thickness of polyaniline layer coating on the TiO(2) nanocrystal surface can be controlled in a range of 2-5 nm by this method. A photoelectrochemical study was carried out on the TiO(2)/polyaniline nanocomposite, and found that polyaniline in the nanocomposite acted as a visible-light sensitizer in a photoelectrochemical reaction. The sensitization effect increased with increasing binding strength between polyaniline and TiO(2). A dye-sensitized solar cell with a short circuit current density of 0.19 mA/cm(2) and an open circuit voltage of 0.35 V was fabricated by using the TiO(2)/polyaniline nanocomposite film as a sensitized electrode.     

Crosslinked polyaniline nanorods coupled with molybdenum disulfide on functionalized carbon cloth for excellent electrochemical performance

Journal of Solid State Electrochemistry - In this work, the binary nanocomposite of crosslinked polyaniline nanorods (CPANINRs) and molybdenum disulfide (MoS2) is first synthesized by in situ...     

Polyaniline pH Electrodes

Polyaniline-coated Pt, Pd, and graphite electrodes have been studied. Their potential relationship to pH follows the same principle as the pH glass electrode. They are solid state involving no redox reactions. The potential is derived from the surface charge density caused by protonation or deprotonation. They act as capacitors. The nonprotonated form of polyaniline was used for pH 6.8 to 1.2 and the protonated form of polyaniline was used for pH 6.8 to 13.0. Three regions of curves (acid, neutral, and alkaline) were obtained. The polyaniline-coated graphite electrode is recommended. It offers the advantage of sturdiness and may be used in microscale in HF solution, at high pressure. At pH 2.2, approximately 4,200 H⁺ions were adsorbed by polyaniline per nm². An insignificant number of H⁺ions were adsorbed by polyaniline at pH 6.2; this is close to its isoelectric point.     

Potentiometric monitoring DNA hybridization with polyaniline/Nylon-6 working electrode

Electrically conducting polymers are useful in various applications such as transistors and sensors. A potentiometric pH meter has been developed using polyaniline based working electrode and with improved selectivity using ionophores, the polyaniline based potentiometer has been applied to monitor various ions mainly in environmental applications. The polyaniline working electrode can be used to monitor not only the binding of a biological ionic macromolecules on polyaniline surface but also the binding of the adsorbed macromolecule with another macromolecule. We present first how the working electrode was prepared by polymerization of aniline in Nylon-6 matrix to provide the mechanical strength and then how single strand oligonucleotide probe binds with polyaniline surface. We then present how an electrode modification with mercaptoethanol results in a surface protected against non-specific binding and then finally we present the results of monitoring the complimentary strand binding leading to the formation of the double strand DNA. The text was submitted by the authors in English.     

Adsorbed surfactants as templates for the synthesis of morphologically controlled polyaniline and polypyrrole nanostructures on flat surfaces: from spheres to wires to flat films

Nanostructures of polyaniline (PAni) and polypyrrole (PPy) with controlled morphologies have been synthesized on atomically flat surfaces using adsorbed surfactant molecules as templates. Atomic force microscopy (AFM) has been used to investigate polymer film formation on highly oriented pyrolytic graphite (HOPG) and chemically modified HOPG. Morphological control over the resulting polymer film is possible by the addition of coadsorbing molecules, manipulation of the length of the surfactant hydrophobe, or by changing the surface chemistry of the adsorbing substrate. Phase transitions between spheres, cylinders/wires, and featureless films have been observed which exactly parallel transitions between spheres, cylinders, and flat layers in the adsorbed surfactant. Parallel arrays of PAni nanowires can be synthesized with alignment evident over large areas in a simple self-assembly technique in which fabrication and arrangement take place simultaneously. Such a technique in which one can engineer sub-100-nm-ordered nanoscale pi-conjugated polymer structures of a desired shape by a simple self-assembly process presents potential as templates, sensors, and microelectronic devices.     

Effects of solvent and electrolyte on the electrochromic behavior and degradation of chemically prepared polyaniline-poly(vinyl alcohol) composite films

Effects of solvent and electrolyte on the electrochromic behavior and degradation of polyaniline in nonaqueous aprotic media, as well as its electrochemical redox and degradation mechanisms, were investigated with chemically prepared polyaniline-poly (vinyl alcohol) composite films and polyaniline homogeneous films. Visible and FT-IR absorption spectra of the polyaniline films, oxidized electrochemically at various polarization potentials, showed that the mechanisms in aprotic media involved two successive oxidation processes. In contrast to aqueous systems, the higher oxidation process involved further anion insertion without deprotonation, and the degradation was due to partial formation of the electrochemically inactive quinonediimine structure at excessive polarization potentials. From investigations of solvent and electrolyte effects, it is suggested that the electrochromic behavior and degradation of polyaniline are influenced by the electron-donating and accepting ability of solvents, acceptor strength of electrolyte cations, and the nucleophilic character of electrolyte anions. It was also suggested that some anions like as well as protons, are constrained in the PVA matrix by specific electrostatic interactions and steric effects to improve the stability of polyaniline in the highly oxidized state. © 1994 John Wiley & Sons, Inc.     

Controlled electrophoretic patterning of polyaniline from a colloidal suspension

We present a method for controlled deposition of polyaniline from colloidal suspensions. Stable suspensions of polyaniline colloids (approximately 115 nm in diameter) were formed by dispersing polyaniline/formic acid solution into acetonitrile. It was demonstrated that the positively charged polyaniline colloids can be electrophoretically deposited onto various substrate materials such as platinum and ITO, forming continuous ultrathin films. We examined the film morphology, as well as the effects of process parameters, such as deposition time, colloid concentration, and applied voltage, on the deposition efficiency. Furthermore, the efficacy of the technique was illustrated by electrophoretically patterning polyaniline thin films onto selected individual micrometer-scale sensing elements within a microfabricated sensor array, and by further demonstrating its sensitivity to gaseous analytes including water and methanol.     

Electrocatalytic chirality on magneto-electropolymerized polyaniline electrodes

Chiral polyaniline electrodes were prepared by the magneto-electropolymerization (MEP) method. Cyclic voltammograms (CVs) of l-ascorbic acid (L-AA), d-isoascorbic acid (D-AA), and l-3-(3,4-dihydroxyphenyl)alanine were measured on the MEP polyaniline electrodes and their electrode reactions were electrocatalytic. The CV peak currents varied depending on the chirality of the polyaniline and the optically active species, while the peak potentials were independent of the chirality. The CVs of L-AA and D-AA were also measured on a Pt electrode in a (−)-camphor-10-sulfonic acid supporting electrolyte solution, and the chiral behavior was observed in the peak potentials. It is considered that the electrocatalytic process is responsible for the chiral electrochemical behavior on the polyaniline electrodes. Contribution to special issue on “Magnetic field effects in Electrochemistry”.     

聚苯胺在聚酰亚胺膜基体表面的原位沉积成膜机理

采用分散聚合方法,在聚酰亚胺(PI)膜基体表面原位成膜,制备聚苯胺-聚酰亚胺-聚苯胺(PANI-PI-PANI)导电复合膜.通过反应历程跟踪、扫描电镜(SEM)及静滴接触角-界面张力测量仪研究了PANI在PI基体表面原位成膜的过程及其驱动力.结果表明,PANI在PI基体表面的成膜过程有3个阶段:含苯胺的结构单元(包括An盐酸盐、An阳离子自由基及低聚物)在PI表面吸附成核阶段、膜快速增长阶段和增长完成阶段;PANI膜由PANI小颗粒逐渐堆积而成,直至覆盖整个PI膜表面;PANI成膜的主要驱动力来自亲水-疏水相互作用.     

Development of MoSe2/PANI composite nanofibers as an alternative to Pt counter electrode to boost the photoconversion efficiency of dye sensitized solar cell

Journal of Solid State Electrochemistry - In this work, a simple hydrothermally prepared molybdenum diselenide (MoSe2) was mixed with polyaniline (PANI) nanofibers at 1:1 Wt% in deionized water by...     

Emulsion Polymerization Pathway for Preparation of Polyaniline‐Sulfate Salt,using Non Ionic Surfactant

In this work, aniline was polymerized directly to the polyaniline‐sulfate salt without using a protonic acid. The polyaniline‐sulfate salt was prepared by emulsion polymerization, using a non ionic surfactant such as poly(ethylene glycol)–block poly(propylene glycol)‐block poly(ethylene glycol). In the aniline oxidation process, to give the polyaniline salt by ammonium persulfate, the sulfate ion is generated from ammonium persulfate and doped on to the polyaniline. Ammonium persulfate acts both as an oxidizing agent, as well as the protonating agent in the aniline polymerization process, to give the polyaniline salt. This result indicates that the effect of sulfate ion, generated by ammonium persulfate during oxidation of aniline to the polyaniline salt, may be taken into consideration in the polymerization process of aniline.     

Speciation of molybdenum in river water by size fractionation and catalytic determination.

A speciation scheme of trace molybdenum was proposed for river water based on size fractionation by filtration and ultrafiltration and the catalytic spectrophotometric determination of the reactive molybdenum concentration (CR). The total concentration (CT) of molybdenum was determined by the same method after acid decomposition to obtain the concentration (CT - CR) of unreactive molybdenum. Most molybdenum in natural river-water samples was found to be reactive species. A large part of the molybdenum was found in the fraction of molecular weight (MW) < 10(3), and was estimated to be MoO4(2-) from the chemical equilibria of molybdate ions. The residual part of molybdenum was found in the colloidal and particle fractions (MW > or = 10(4)), and was characterized as reactive molybdenum adsorbed or complexed on humic iron aggregates. The coexistence of silicate contributed to a decrease of the particle size of humic iron aggregates associated with molybdenum. The above-mentioned speciation results were confirmed by an analysis of artificial samples. The changes in the fractionation results by acidification (0.1 M HCl) were also used to characterize molybdenum in natural water.     

Chemical lithography by Ag-nanoparticle-mediated photoreduction of aromatic nitro monolayers on Au

Patterned, amine-terminated monolayers can be fabricated from 4-nitrobenzenethiol (4-NBT) monolayers simply by irradiating under ambient conditions with visible laser after spreading Ag nanoparticles onto selected regions of the 4-NBT monolayers on Au. Au nanoparticles were adsorbed selectively onto the amine groups produced by photoreaction, and polyaniline was found to grow exclusively at the amine groups when electrochemical polymerization was conducted using the patterned substrate as the working electrode. These observations clearly support our previous contention that Ag nanoparticles can act as moderate photoelectron emitters.     

Electrochemical Behavior of Methanol Influenced by Polyaniline Incorporated with Ferrocenesulfonic-carboxylic Acid

After the synthesis of polyaniline in the presence of ferrocenesulfoniccarboxylic acid, its influence on the electrochemical reaction of methanol was studied. The result indicates that the ferrocenyl in ferrocenesulfoniccarbexylic acid plays an important role in the electrocatalytic oxidation of methanol. CH3OH is adsorbed on PANI-Fc before its electrocatalytic oxidation. When the concentration of methanol is 2 mol/L, it begins to be oxidized. The effect of scan rate on the electrochemical reaction of methanol was also studied and 5 mV/s was favourable. It is another method to insert a metal catalyst in polyaniline without its electrodeposition.     

Anion-exchange separation and spectrophotometric determination of molybdenum and tungsten in silicate rocks

A combined ion-exchange spectrophotometric method has been developed for the determination of molybdenum and tungsten in silicate rocks. After the decomposition of samples with a mixture of sulphuric, nitric and hydrofluoric acids, traces of molybdenum and tungsten are separated from other elements by anion-exchange in acid sulphate media containing hydrogen peroxide. The adsorbed molybdenum and tungsten can easily be stripped from the column by elution with sodium hydroxide-sodium chloride solution. The adsorption and desorption steps provide selective concentration of molybdenum and tungsten, allowing the simultaneous spectrophotometric determination of the two metals with dithiol. Results on the quantitative determination of molybdenum and tungsten in the U.S. Geological Survey standard samples are included.     

Atomic-absorption determination of vanadium and molybdenum in tap water and mineral waters after anion-exchange separation.

A method is described for the determination of vanadium and molybdenum in samples of tap and bottled mineral water. After acidification with citric acid the water sample is heated to about 80°C to remove CO₂; sodium citrate and ascorbic acid are added and the resulting solution of pH 3 is passed through a column of the strongly basic anion-exchange resin Dowex 1-X8 (citrate form) on which both vanadium and molybdenum are adsorbed as anionic citrate complexes. Vanadium is eluted with 6 M hydrochloric acid; molybdenum is recovered with 2 M perchloric acid-1 M hydrochloric acid. Vanadium and molybdenum are determined in the eluates by atomic-absorption spectrometry. The samples analysed contained 0.1–0.9 μg l^?1 vanadium and 0.2–13 μg l^?1 molybdenum.     

XPS study of molybdenum sulfide catalyst exposed to CO and H2

Amorphous MoS(3) (air-dried precipitate), crystalline MoS(2) (made in the laboratory under nitrogenous atmosphere), and commercial molybdenum disulfide catalysts have been investigated by X-ray photoelectron spectroscopy (XPS). The chemical species present on the surface and the S/Mo atomic ratios of laboratory catalysts were compared to those present on a commercial molybdenum disulfide catalyst before and after treatment with CO and H(2). Pretreatment of MoS(2) with CO followed by H(2) showed that CO was adsorbed on the surface with no change in the chemical oxidation state of Mo and S. However, the results indicated that CO was not adsorbed when the sequence of gas exposures was reversed.