Copolypeptide-doped polyaniline nanofibers for electrochemical detection of ultratrace trinitrotoluene

This paper demonstrates a new electrochemical method for the detection of ultratrace amount of 2,4,6-trinitrotoluene (TNT) with synthetic copolypeptide-doped polyaniline nanofibers. The copolypeptide, comprising of glutamic acid (Glu) and lysine (Lys) units, is in situ doped into polyaniline through the protonation of the imine nitrogen atoms of polyaniline by the free carboxylic groups of Glu segments, resulting in the formation of polyaniline nanofibers of emeraldine salt. The free amino groups of Lys segments at the surface of nanofibers provide the receptor sites of TNT through the formation of charge-transfer complex between the electron-rich amino groups and the electron-deficient aromatic rings. Adsorptive stripping voltammetry results demonstrate that the poly(Glu-Lys)-doped nanofibers confined onto glassy carbon electrodes exhibit a remarkable enriching effect and thus sensitive electrochemical response to TNT with a linear dynamic range of 0.5-10 μM and a detection limit down to 100 nM. Moreover, other kinds of nitro compounds show different redox behaviors from TNT at the doped nanofibers, and thus do not interfere with the electrochemical detection of TNT. This study essentially offers a new and simple method for electrochemical detection of ultratrace TNT.     

Polyaniline composites: improving the electrochemical properties by template synthesis

We have been exploring the idea of using the heterogeneous porosity of inorganic (sol-gel silica) and organic (poly(vinylidene fluoride)) films as a template for the preparation of polyaniline composites. The large size pore distribution (~2.5–800 nm) in both template matrices results in a part of the polyaniline growing more ordered than in films synthesized without spatial restriction. Small-angle X-ray scattering and scanning electron microscopy experiments were done to determine the extreme values of the pore diameters. Using other experimental techniques, including cyclic voltammetry, UV-Vis-NIR spectroscopy, electrochemical impedance and chronopotentiometry, we concluded that the electrochemical properties of polyaniline, such as oxidation and reduction charges, diffusion coefficient and charge-discharge capacity, are improved in these composites. Electronic Publication     

Polyaniline and polypyrrole: A comparative study of the preparation

Aniline and pyrrole have been oxidized with ammonium peroxydisulfate in aqueous solutions, in the presence of equimolar quantities of hydrochloric acid. The oxidation of pyrrole was faster; the induction period typical of aniline oxidation was absent in the case of pyrrole. As the proportion of oxidant-to-monomer molar concentration increased up to 1.5, the yield increased in both cases. Similarities between the two oxidations are illustrated and discussed. The oxidant-to-monomer molar ratio 1.25 is proposed to be the optimum stoichiometry, in the accordance with the data published in the literature. The conductivities of the polymers prepared were only slightly dependent on the oxidant-to-monomer ratio in the range 0.3-1.5, and were of the order of 10⁰ S cm⁻¹ for polyaniline and ∼10⁻²-10⁻¹ S cm⁻¹ for polypyrrole. Outside this interval, the conductivity of both polymers was reduced. Polyaniline having conductivity ∼10 S cm⁻¹ was produced in solutions of phosphoric acid of various concentrations. On the contrary, the conductivity of polypyrrole was reduced as the concentration of phosphoric acid became higher. The type of protonation is discussed with the help of FTIR spectra by analyzing the ammonium salts obtained after deprotonation. Sulfate or hydrogen sulfate anions produced from peroxydisulfate always constitute a part of the counter-ions.     

不同磺酸掺杂聚苯胺的制备及在超级电容器中的应用

以MnO₂为氧化剂,采用乳液聚合法,用三种不同的磺酸型表面活性剂制备掺杂聚苯胺(PANI)。通过扫描电子显微镜(SEM)、傅里叶变换红外(FTIR)光谱以及X射线衍射(XRD)等手段对其结构及形貌进行表征;用所得的掺杂聚苯胺制作电极,组装成对称扣式超级电容器,用循环伏安法(CV)、电化学阻抗(EIS)和恒电流充放电技术进行电化学性能研究。结果表明,磺酸表面活性剂的引入有利于PANI纳米纤维的形成和分散,掺杂Nafion的PANI纤维直径在30-40 nm之间,纤维交织成多孔的疏松结构;当放电电流为0.1 A·g^-1时,以PANI-Nafion、PANI-SDS(十二烷基磺酸钠)、PANI-SDBS(十二烷基苯磺酸钠)为电极材料的超级电容器比容量分别为385.3、359.7、401.6 F·g^-1,均高于未掺杂PANI的比容量(235.8 F·g^-1);其中, PANINafion的循环稳定性最好, 1000次循环后其比容量保持率高达70.7%。     

Polyaniline nanofibers by surfactant‐assisted dilute polymerization for supercapacitor applications

Polyaniline nanofibers doped with citric acid was prepared by a novel surfactant‐assisted dilute polymerization technique. It was possible to synthesize polyaniline nanofibers without using any organic solvent by easier pathway. Polyaniline salt was characterized by conductivity, FTIR, and X‐ray diffraction studies. The specific capacitance behavior of the polyaniline nanofibers was characterized using cyclic voltammetry which exhibits highest specific capacitance of 298 F g^?1. The morphology of the obtained nanofibers was characterized by SEM studies. So, these kinds of specific properties of polyaniline nanofibers could be beneficial to the development of energy storage devices. Copyright © 2008 John Wiley & Sons, Ltd.     

Polyaniline coated conducting fabrics. Chemical and electrochemical characterization

Polyaniline coated conducting fabrics have been obtained by chemical oxidation of aniline by potassium peroxydisulfate on polyester fabrics. Two different acids have been employed to carry out the synthesis (HCl and H₂SO₄), obtaining the best results of conductivity with the latter one. The conducting fabrics have been characterized chemically by means of Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR), energy dispersive X-Ray (EDX) and X-ray photoelectron spectroscopy (XPS). The morphology of the coatings has been observed by means of scanning electron microscopy (SEM). The conducting properties of the fabrics have been measured by means of electrochemical impedance spectroscopy (EIS). The electrochemical characterization has been carried out by means of cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM). The conducting fabrics have also shown electrochromic properties, changing its color from green yellowish at −1 V to dark green at +2 V. The durability of the coating has been evaluated by means of washing and rubbing fastness tests.     

碳纳米管/聚苯胺/石墨烯复合纳米碳纸及其电化学电容行为

通过真空抽滤的方法制备碳纳米管纸,并对其进行循环伏安电化学氧化处理.以该电化学氧化处理的碳纳米管(CV-CNT)纸为基体,采用电化学聚合沉积聚苯胺(PANI),随后吸附石墨烯(GR),制备具有三明治夹心结构的碳纳米管/聚苯胺/石墨烯(CV-CNT/PANI/GR)复合纳米碳纸.该结构外层为GR,内层由PANI包裹的CNT形成网络骨架,充分发挥三者各自优势构建柔性电极材料.用场发射扫描电镜(FE-SEM)、透射电子显微镜(TEM)、拉曼光谱对其形貌与结构进行表征,并测试其电化学性能.研究发现:PANI呈纳米晶须状,并均匀包裹在CV-CNT表面;该复合碳纸具有良好的电容特性、大电流充放电特性以及良好的循环稳定性能.电流密度为0.5A·g-1时,比电容可达415F·g-1;20A·g-1时仍能保持106F·g-1的比电容.由于GR的保护作用,1000次循环之后较CV-CNT/PANI保持更高的有效比电容.该CV-CNT/PANI/GR复合碳纸展现出在高性能超级电容器柔性电极材料的潜在应用价值.     

超微电极上聚苯胺的电化学性质研究

本文探讨了盐酸介质中，聚苯胺在超微电极上的伏安性质，峰电流（ｉｐ）ａ与聚合电量、扫描速率等关系，在Ｑｐ较小时，具有薄膜电极特性，Ｑｐ很大时峰电流受扩散控制。     

Fabrication of Polyaniline/Silver Nanocomposite Under Gamma-ray Irradiation

Polyaniline (PANI)/silver composite was one-step synthesized under γ-ray irradiation. The structure of the composite was characterized by Fourier transform infrared spectroscopy, UV-Visible, and X-ray diffraction, which indicated that PANI and face-centered-cubic silver were synthesized under γ-ray irradiation. The reaction mechanism were discussed, which revealed that the PANI was formed by the reaction of aniline cation radicals formed by the reaction of aniline cation and ·OH, and Ag was formed by the reaction of Ag⁺ and e^-_aq. The morphology of the composite consisted of PANI nanofibers and Ag nanoparticles, and the mechanism of the morphology formation was discussed, which revealed that the rapid mixing like polymerization process might play an important role. It was revealed that the transport behavior of the composite well fitted with the variable-range-hopping model in 80-300 K and deviated from the model below 80 K.     

阳离子表面活性剂作用下制备一维纳米结构聚苯胺

在十六烷基三甲基溴化铵(CTAB)存在下, 以盐酸为质子酸, 过硫酸铵为氧化剂, 制备了平均直径为115 nm、具有分叉结构的聚苯胺纳米纤维和平均直径为75 nm的卷曲聚苯胺纳米线, 两者的结构产率高达90%和100%, 电导率分别为1.6×10-2和9.3×10-2 S/cm. 研究发现, 聚苯胺的一维纳米结构受盐酸浓度和苯胺与CTAB摩尔比的协同影响. 用TEM, SEM和FTIR对产物的形貌和化学结构进行了表征. 利用pH监测反应并结合SEM结果研究了聚苯胺纳米线的形成过程, 结果表明, CTAB阳离子与过硫酸根形成的絮状物的诱导作用是聚苯胺纳米纤维和纳米线形成的关键因素.     

原位聚合法制备聚酰胺/聚苯胺复合导电纤维

研究了原位聚合法制备聚酰胺/聚苯胺导电纤维,并对制备的复合纤维进行红外及光学显微镜测试,结果表明聚苯胺与纤维成功复合。对制备的复合纤维进行电导率测试,采用控制单一变量法探讨了苯胺单体在不同的条件下聚合对纤维电导率的影响,并讨论了反应温度对聚合过程和电导率的影响,得出最佳的工艺条件为:纤维经30%的甲酸溶液预处理20min,苯胺单体浓度为0.8M,氧化剂过硫酸铵浓度为1M,掺杂酸为盐酸,浓度为0.8M,冰水浴条件,反应时间为4h,得到的聚酰胺/聚苯胺导电纤维的电导率为3.7S/m。     

乳液法制备掺杂聚苯胺的微观结构研究

在众多的导电聚合物中,聚苯胺(PAn)被认为是最具应用前景的导电聚合物^[1].本征态PAn的电导率约10^-13S/cm数量级,呈电绝缘性.当用质子酸对PAn掺杂后,电导率达到5～10S/cm,可实现从绝缘体到导体的转变.     

Electrodeposition and Characterization of Polyaniline Film

Polyaniline film was prepared by electrochemical method in an acidic solution of aniline. The micromorphology of the polyaniline film was transformed to three-dimensional network structure instead of little particles while the deposition time was extended. The peak wavelength of the photoluminescence spectrum was 491 nm. The luminous intensity increased with the extension of deposition time, and so did the electrochemical activity.     

聚苯胺阳极的性能研究

用磺基水杨酸和硫酸为掺杂剂,过硫酸铵为氧化剂,合成了一种高电导率聚苯胺粉末,并压制成聚苯胺阳极。采用FTIR和DSC/TGA对聚苯胺的结构和热稳定性进行分析,同时也采用加速电解寿命测试和电化学阻抗技术,研究了聚苯胺阳极的电化学性能和该电极在硫酸中的使用寿命。结果表明,在电解过程中槽电压从不稳定-稳定-快速增大的变化过程,电化学行为变化也比较明显。把该电极用于处理含酚废水和铅电极进行对比表明,节电率达34%,转化率达96.8%,是一种优良的电化学催化剂。     

Chemically Modified Ordered Mesoporous Carbon/Polyaniline Composites for Electrochemical Capacitors

Chemically modified ordered mesoporous carbon CMK-3 materials were prepared by means of an easy wet-oxidative method in 2 mol/L nitric acid aqueous solution. A large amount of oxygen-containing functional groups were introduced onto the CMK-3 surface. Modified CMK-3(m-CMK-3) and aniline monomer were polymerized via an in situ chemical oxidative polymerization method. Morphological characterizations of m-CMK-3/PANI (polyaniline) composites were carried out via field emission scanning electron microscopy(SEM)...     

Asymmetrical flow field-flow fractionation analysis of water suspensions of polymer nanofibers synthesized via RAFT-mediated emulsion polymerization

The aim of this work is to present a method based on asymmetric flow-field-flow-fractionation coupled on-line to a static light scattering (AF4-UV-SLS) detector to characterize self-assembled nanofibers (NFs). The method developed herein allows the determination of both the length distribution of the NFs as well as the distribution in terms of aggregation number per unit length (A_gg). Given the remaining synthetic challenges of better controlling the structural homogeneity and particle dimensions, the NF length and aggregation number per unit length are becoming essential for the improvement and control of their chemical processes and a better understanding of their properties. The results obtained with this AF4-UV-SLS method indicate that a well-resolved NF length distribution characterization and A_gg determination were attained. These results provide critical information concerning the physical properties of the investigated NFs and open the door to the characterization of new self-assembled polymers with various asymmetrical architectures.     

Synthesis,Structural Characterization,and Electrochemical Properties of Isotruxene–Polyaniline Hybrid Systems

The synthesis, structural characterization, and electrochemical properties of a series of isotruxene–polyaniline (PANI ) hybrid systems (SITPs , SITAs , and CITs ) are reported. The syntheses were performed by in situ chemical oxidative polymerization of aniline in the presence of isotruxene additives ITP and/or ITA at specific aniline‐to‐additive molar ratios. The polymers SITPs and SITAs display granular morphology, but for the polymers CITs a spherical morphology with a diameter of 300–500 nm is found. These hybrid systems display electrochemical capacitive performance superior to those of the parent PANI prepared under the same condition (e.g., 385–463 vs. 181 F/g at 3 mA /cm² current density during charge–discharge test). Molecular (star‐shaped or hyperbranched vs. linear topology) and supramolecular (isotruxene–PANI π–π and cation–π interactions) models in accounting for the observed morphology and electrochemical properties are provided.     

A study on the influence of anionic surfactants on electrochemical degradation of polyaniline

The influence of anionic surfactants on the electrochemical degradation of polyaniline (PANI), deposited by electro-polymerization onto platinum electrodes, was investigated in an aqueous medium by means of cyclic voltammetry. The degradation rate was found to be greatly dependent on the pH of the solution. The electrochemical degradation of PANI/dodecylsulfate and PANI/dodecylbenzenesulfonate films was compared with that of a PANI/hydrochloride film. The degradation rate in the two former cases decreased by some 50% compared to the PANI/hydrochloride film in aqueous solution at pH = 2. The results were confirmed with theoretical calculations performed on the evaluation of head group charge of surfactants, the distance of anions from PANI positive sites and the shielding of anions on PANI positive sites.     

Polyaniline Nanotubes Prepared by One-Step Synergistic Polymerization of Aniline and Acrylic Acid

The electrochemical property of electrode materials greatly depends on their morphologies. This report introduces a novel and facile synthesis method for polyaniline (PANI) nanotubes from one-step synergistic polymerization of aniline and acrylic acid in an aqueous solution induced by the addition of ammonium persulfate (APS). The molar ratio of aniline to AA (\begin{document}$X_{\rm{ani/AA}}$\end{document}) is found to have great influence on the morphology of the produced PANI. Hollow PANI nanotubes with an average inner diameter of 80 nm and outer diameter of 180 nm can be mainly produced when \begin{document}$X_{\rm{ani/AA}}$\end{document} is not higher than 1. The electrochemical properties of the prepared PANI nanotubes have been investigated using a three-electrode system. The specific capacitance of PANI nanotubes can reach 436 F/g at a current density of 0.5 A/g in 1 mol/L H\begin{document}$_2$\end{document}SO\begin{document}$_4$\end{document} solution. Furthermore, the specific capacitance of the PANI nanotube maintains 89.2% after 500 charging/discharging cycles at a current density of 0.5 A/g, indicating a good cycling stability.