Direct deposition of gold nanoparticles onto polymer beads and glucose oxidation with H2O2

Gold nanoparticles (Au NPs) were deposited directly from aqueous solution of diethylenediaminegold(III) complex onto polymer beads commercially available, such as poly(methyl methacrylate) (PMMA), polystyrene (PS), and polyaniline (PANI) without surface modification. The dropwise addition of NaBH4 to reduce Au(III) was found to be very effective to obtain small Au0 NPs with a narrow size distribution except for PANI. The catalytic performance of Au NPs deposited on polymer beads for H2O2 decomposition and glucose oxidation with H2O2 were more significantly affected by the kinds of polymer supports than by the size of Au NPs. The equimolar oxidation of glucose with H2O2 could be operated by controlling the decomposition rate of H2O2 over Au/PMMA.     

Reversible encapsulation of nanometer-size polyaniline and polyaniline-Au-nanoparticle composite in starch

In this paper we report a new method of solubilization of polyaniline and polyaniline-Au-nanoparticle composite by encapsulating nanometer-size particles in starch. The solubilization was carried out in the presence of ultrasonic waves. We also report that the encapsulation was completely reversible and the dissolved polyaniline as well as the composite could be recovered by replacement with molecular iodine. In addition, the polymer particles could also replace molecular iodine from starch-iodine complex. UV-Visible and Fourier transform infrared (FTIR) spectroscopic measurements established the reversible nature of encapsulation. Transmission electron microscopic measurements showed that the sizes of the particles encapsulated in starch were on the order of 10-20 nm for both polyaniline and Au-nanoparticle-polyaniline composite particles. X-ray diffraction evidenced the presence ofAu-nanoparticles in the starch-polyaniline-Au-nanoparticle composite. Finally, we also mention here that the dissolved polyaniline could also be recovered as a precipitate by enzyme (diastage) hydrolysis of the polyaniline encapsulating starch.     

Preparation of Polyaniline Modified Electrode for the Electroanalysis of Heme Proteins

ABSTRACT

Polyaniline, which was electroactive in pH5.5 NaAc-HAc buffers, was used to investigate the electrochemistry of some heme proteins. The polyaniline was electropolymerized and deposited on a macro- and a micro- platinum electrode successfully. The optimum preparation method and conditions were that the polymer film was polymerized by a galvanostatic method with 35 μA/cm² current density in a 2.0 mol/L HCl solution containing 1.0 mol/L monomer under nitrogen atmosphere. The deposit amount was about 7.0 mC/cm² for the macro- and 8.5 mC/cm² for the micro- electrode. Experimental results revealed that the commonly used heme proteins, myoglobin and hemoglobin, could exhibit useful current responses at the polymer coated electrode. Since polyaniline modified electrode have a lot of virtues such as stability, good longevity, reversibility, conductivity etc., they may be useful for protein studies in the future. Another application of the polymer is, therefore, reported in this paper.     

Doping of polyaniline with polymeric dopants in solid state,gel state and solutions

Polystyrene with different degrees of sulfonation was empolyed as a polymeric dopant for polyaniline. The purpose of using a polymeric dopant is to avoid the migration of a small molecule dopant to increase stability of the doped complex. We applied the polymeric dopant to polyaniline in three different ways: in solid state, in solution and in gel state. In solid state, the conducting form was achieved only through a novel thermal doping method with the increase in temperature and pressure. In solution, the doping process was shown to be dependent on the nature of the solution and also on the molecular weight of the polymer. In the gel form of polyaniline, a polymeric dopant with a surprising low degree of sulfonation was found to be successful in the doping process.     

Dilute anionic surfactant solution route to polyaniline rectangular sub-microtubes as a novel nanostructure

A facile and low-cost approach has been developed for tailoring polyaniline rectangular sub-microtubes as a novel nanostructure of a conducting polymer in dilute sodium dodecyl sulfate (SDS) solution by the oxidation polymerization of aniline at room temperature. It was found that the size and uniformity of polyaniline rectangular sub-microtubes could be appropriately adjusted by tuning the concentration of aniline and the molar ratio of oxidant to aniline, respectively. The morphological evolution of rectangular sub-microtubes under different reaction times has been followed, and a possible formation mechanism has also been discussed in this report. The directing role of other anionic surfactants with -SO3(-) as the hydrophilic group for constructing polyaniline rectangular sub-microtubes has been investigated in detail.     

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.     

A Conductimetric System Based on Polyaniline for Determination of Ammonia in Fertilizers

Abstract

A simple conductimetric system to determine ammonia concentration using a sensor based on a conductor polymer was developed. The sensitive element to ammonia is a thin polyaniline film deposited by chemical synthesis in an acrylic substrate prepared before hand with two graphite electrodes. The conductance of the polyaniline film decreases when exposed to the ammonia gas and this variation can be related to the ammonia concentration. To determine ammonia in fertilizer samples a system consisting of a measurement cell, a conductivity meter and a strip chart recorder was used. The results were compared with those obtained by three different laboratories employing a Kjeldahl method and are in good agreement. The detection range of the system was 0.6 to 3.7 μg.mL^?1 with a response time of 4 minutes. The relative standard deviation of the proposed method was about 5%.     

Synthesis and characterization of polyaniline/silicon dioxide composites and preparation of conductive films

The focus of this study was to synthesize the inherently conductive polymer polyaniline using an optimized process to prepare polyaniline/silicon dioxide (PANI/SiO₂) composites by in situ polymerization and ex situ solution mixing. PANI and PANI/SiO₂ composite films were prepared by drop‐by‐drop and spin coating methods. The electrical conductivities of HCl doped PANI film and PANI/SiO₂ composite films were measured according to the standard four‐point‐probe technique. The composite films exhibited an increase in electrical conductivity over neat PANI. PANI and PANI/SiO₂ composites were also investigated by spectroscopic methods including UV‐Vis, FT‐IR, and Photoluminescence. UV‐Vis and FT‐IR studies showed that SiO₂ particles affect the quinoid units along the polymer backbone and indicate strong interactions between the SiO₂ particles and the quinoidal sites of PANI (doping effect). The photoluminescence properties of PANI and PANI/SiO₂ composites were studied and the PANI/SiO₂ composites showed increased intensity as compared to neat PANI. The increase of conductivity of PANI/SiO₂ composite may be partially due to the doping or impurity effect of SiO₂ where the silicon dioxides compete with chloride ions. The morphology of particles and films were examined by a scanning electron microscope (SEM). SEM measurements indicated that the SiO₂ were well dispersed and isolated in composite films. Copyright © 2009 John Wiley & Sons, Ltd.     

Electrochemical deposition of nanostructured polyaniline on an insulating substrate

In order to obtain practicable nano-conducting polymer resistive sensors, we investigated the electrochemical deposition of polyaniline (PANI) on the insulating gap area of an interdigitated electrode with a gap width as great as 100 μm. We revealed that the nucleation and growth of PANI on the insulating substrate were influenced by the surface character of the substrate such as hydrophilicity and roughness. By controlling the polymerization conditions, homogeneous PANI films with various nanostructures could be obtained across the insulating gap to form resistive junctions. Among them, a loose 2D nanowire network structure showed the best sensing performance upon exposure to ammonia gas with a low concentration.     

Biochemical synthesis of water soluble polyanilines: Poly(p-aminobenzoic acid)

This report describes the synthesis of a water soluble polyaniline through a biochemical synthetic route. The oxidative free radical coupling mechanism for the synthesis of poly(p-aminobenzoic acid) is catalyzed by horseradish peroxidase in the presence of hydrogen peroxide. The resulting polymer is electrochemically active and undergoes reversible redox reactions. The polymer as synthesized is self doped and undergoes undoping in alkaline or ammonia solutions.     

Synthesis, property characterization and photocatalytic activity of the novel composite polymer polyaniline/Bi2SnTiO7

A novel polyaniline/Bi(2)SnTiO(7 )composite polymer was synthesized by chemical oxidation in-situ polymerization method and sol-gel method for the first time. The structural properties of novel polyaniline/Bi(2)SnTiO(7) have been characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray spectrometry. The lattice parameter of Bi(2)SnTiO(7) was found to be a = 10.52582(8) ?. The photocatalytic degradation of methylene blue was realized under visible light irradiation with the novel polyaniline/Bi(2)SnTiO(7) as catalyst. The results showed that novel polyaniline/Bi(2)SnTiO(7 )possessed higher catalytic activity compared with Bi(2)InTaO(7) or pure TiO(2) or N-doped TiO(2) for photocatalytic degradation of methylene blue under visible light irradiation. The photocatalytic degradation of methylene blue with the novel polyaniline/Bi(2)SnTiO(7) or N-doped TiO(2) as catalyst followed first-order reaction kinetics, and the first-order rate constant was 0.01504 or 0.00333 min(-1). After visible light irradiation for 220 minutes with novel polyaniline/Bi(2)SnTiO(7 )as catalyst, complete removal and mineralization of methylene blue was observed. The reduction of the total organic carbon, the formation of inorganic products, SO(4)2- and NO(3-), and the evolution of CO(2) revealed the continuous mineralization of methylene blue during the photocatalytic process. The possible photocatalytic degradation pathway of methylene blue was obtained under visible light irradiation.     

以DNA为模板构造苯胺-DNA复合物纳米线和聚苯胺纳米导线

在溶液中, 以DNA为模板构造出了线性的苯胺-DNA复合物纳米线. 用压缩气流将得到的复合物纳米线拉直并固定到云母基底上. 用原子力显微镜(AFM)可观察到形貌规整的苯胺-DNA复合物纳米线. 苯胺单体在溶液中能从各个方向上组装到DNA分子上, 从而使DNA模板分子的表面包裹了一层苯胺. 以苯胺-DNA复合物纳米线为前驱体通过进一步化学氧化聚合得到了以DNA为模板的聚苯胺纳米导线.     

水基导电聚苯胺及其复合材料

由于对离子诱导掺杂技术的发展,聚苯胺在有机溶剂中的加工问题已经得到解决,但日益增长的环保要求使得聚苯胺的水系加工倍受关注.本文通过分析聚苯胺水系加工的研究进展,认为从水溶性导电聚苯胺向水分散性导电聚苯胺转变是未来水基导电聚苯胺的主要发展趋势,水基导电聚苯胺复合材料是解决聚苯胺实际应用问题的主要形式.     

Investigation of the origin of the glucose response in a glucose oxidase|polyaniline system

The origin of the signal seen in response to glucose in a polyaniline|glucose oxidase system is explored by immittance spectroscopy, by comparing data from an equivalent circuit model and the parameters obtained from a solution of the faradaic branch of the frequency dispersion for a coupled chemical—electrochemical reaction mechanism. It was shown that an RC subcircuit in the equivalent circuit model was sensitive to peroxide concentration, and the interaction of peroxide with polyaniline at potentials where it either oxidised or reduced the polyaniline was discussed. This information was used to compare the data obtained in a bulk and entrapped glucose oxidaselglucose system, and it was seen that the origin of the response could not be fully attributed to peroxide interaction in the latter case. Under anaerobic conditions with entrapped enzyme, it was proposed that a complex between the gluconolactone product of the enzyme reaction and the polymer leads to a more conducting polymer, with inherent charge compensation, and this results in the observed enhanced current signal.     

Dual potentiometric and UV/Vis spectrophotometric disposable sensors with dispersion cast polyaniline

Simple conducting polymer–polyaniline-based sensors/biosensors, working either in potentiometric or UV/Vis spectrophotometric mode, are proposed. Disposable sensors were produced by coating polyaniline layers, cast from aqueous dispersion of the polymer nanoparticles, on a transparent plastic polyacetate foil. In the potentiometric mode, polyaniline layers are sensitive to a number of metal cations, while in UV/Vis mode, changes of absorbance were recorded only in case of a chemical reaction of cations with the polymer. Pronounced sensitivity of tested sensors to ammonia was used for potentiometric/spectrophotometric biosensing purposes studied on a model example of urease-based sensors of urea. The highest sensitivity and reproducibility of such sensors were observed in urea concentration ranging from 1 to 10 mM.     

Direct measurement of ammonia in simulated human breath using an inkjet-printed polyaniline nanoparticle sensor

A sensor fabricated from the inkjet-printed deposition of polyaniline nanoparticles onto a screen-printed silver interdigitated electrode was developed for the detection of ammonia in simulated human breath samples. Impedance analysis showed that exposure to ammonia gas could be measured at 962 Hz at which changes in resistance dominate due to the deprotonation of the polymer film. Sensors required minimal calibration and demonstrated excellent intra-electrode baseline drift (≤1.67%). Gases typically present in breath did not interfere with the sensor. Temperature and humidity were shown to have characteristic impedimetric and temporal effects on the sensor that could be distinguished from the response to ammonia. While impedance responses to ammonia could be detected from a single simulated breath, quantification was improved after the cumulative measurement of multiple breaths. The measurement of ammonia after 16 simulated breaths was linear in the range of 40–2175 ppbv (27–1514 μg m⁻³) (r² = 0.9963) with a theoretical limit of detection of 6.2 ppbv (4.1 μg m⁻³) (SN⁻¹ = 3).     

Polyaniline coated micro-capillaries for continuous flow analysis of aqueous solutions

The inner walls of fused silica micro-capillaries were successfully coated with polyaniline nanofibres using the “grafting” approach. The optical response of polyaniline coatings was evaluated during the subsequent redoping–dedoping processes with hydrochloric acid and ammonia solutions, respectively, that were passed inside the micro-capillary in continuous flow. The optical absorbance of the polyaniline coatings was measured and analysed in the wavelength interval of [300–850 nm] to determine its optical sensitivity to different concentrations of ammonia. It was found that the optical properties of polyaniline coatings change in response to ammonia solutions in a wide concentration range from 0.2 ppm to 2000 ppm. The polyaniline coatings employed as a sensing material for the optical detection of aqueous ammonia have a fast response time and a fast regeneration time of less than 5 s at room temperature. The coating was fully characterised by scanning electron microscopy, Raman spectroscopy, absorbance measurements and kinetic studies. The response of the coatings showed very good reproducibility, demonstrating that this platform can be used for the development of micro-capillary integrated sensors based on the inherited sensing properties of polyaniline.     

Polyaniline nanoscaffolds for colorimetric sensing of biomolecules via electron transfer process

Biologically important analytes such as cysteine and vitamin-C were detected by electron transfer (ET) via naked eye colorimetric sensing using a tailor-made water-soluble self-doped polyaniline (PSPANa) as a substrate. Monomer (N-3-sulfopropylaniline) was synthesized via ring-opening of propane sultone with excess aniline and polymerized in water using ammonium persulfate to obtain green water-soluble polymer. Vitamin-C (ascorbic acid) and cysteine showed unexpected sharp and instantaneous color change from blue to colorless sensing action. The stoichiometry of the analyte to polymer was determined as 3:2 and 4:1 with association (or binding) constants of K = 2.1 × 10(3) and 1.5 × 10(3) M(-1) for vitamin-C and cysteine, respectively. Efficient electron transfer from vitamin-C (also cysteine) to the quinoid unit of the polyaniline base occurred in solution; as a result, the color of the solution changed from deep blue to colorless. Cyclic voltammetry analysis of PSPANa showed the disappearance of the cathodic peak at -0.21 V upon the addition of analytes (vitamin-C and cysteine) and confirms the electron transfer from the analyte to the polymer backbone. Dynamic light scattering (DLS) and zeta potential techniques were utilized to trace the molecular interactions in the electron transfer process. DLS histograms of the polymer samples confirmed the existence of nanoaggregates of 8-10 nm in diameter. The polymers possessed typical amphiphilic structure to produce micellar aggregates which facilitate the efficient electron transfer occurred between the analyte and polyaniline backbone.     

Molecular properties of sulfonated polyaniline

The molecular characteristics of internally doped sulfonated polyaniline with a sulfonation degree of ∼1 are studied by the methods of viscometry and dynamic light scattering. In diluted aqueous-saline solutions, the molecules of sulfonated polyaniline are individual entities; they do not form intermolecular associates and do not dissociate into separate components. An increase in the concentration of NaCl in solution from 0 to 1 mol/l brings about a sharp gain in the intrinsic viscosity of the polymer and in the hydrodynamic radius of molecules. This effect results from the decomposition of zwitterion pairs responsible for the compact conformation of polymer molecules in water. The equilibrium rigidity of sulfonated polyaniline molecules is calculated from the hydrodynamic characteristics determined in a 1 M NaCl solution, where the electrostatic interaction may be considered to be suppressed. A length of the Kuhn segment of 1.46 nm is higher by a factor of 1.5 than the corresponding length for the initial polyaniline.     

共聚物酸掺杂接枝聚苯胺的研究

采用核壳乳液聚合方法合成了以甲基丙酸甲酯、甲基丙烯酸和丙烯酸丁酯三元共聚物酸为核,聚苯胺为壳的导电高分子复合物。复合物的电导率随着聚苯胺含量的增加而升高。用粒径分析仪、ＴＥＭ、ＦＴ－ＩＲ和ＤＳＣ对复合材料进行了表征。结果表明形成了核壳结构,由于共聚物酸起到了掺杂剂的作用,使制得的复合物能在环己酮、四氢呋喃等普通有机溶剂中有好的溶解性。