Enzymatically synthesized polyaniline film deposition studied by simultaneous open circuit potential and electrochemical quartz crystal microbalance measurements

The chemical and enzymatic deposition of polyaniline (PANI) films by in situ polymerization was studied and the resulting films were characterized. The film formation and polymerization processes were simultaneously monitored by the evolution of the open circuit potential and quartz-crystal microbalance measurements. Different substrates, such as Indium-Tin oxide electrodes and gold-coated quartz-crystal electrodes were used as substrates for PANI deposition. Electroactive PANI films were successfully deposited by in situ enzymatic polymerization at low oxidation potential. The electrogravimetric response of the enzymatically deposited PANI film was studied by cyclic voltammetry in monomer-free acidic medium. The morphology of the films was observed by scanning electron microscopy, revealing a granular structure in enzymatically deposited PANI. The PANI films were also characterized by thermogravimetric analysis, electrochemical impedance spectroscopy, and X-ray photoelectron and Fourier-transformed infrared spectroscopy. The simultaneous use of quartz crystal microbalance and open circuit potential is presented as a very useful technique to monitor enzymatic reactions involving oxidoreductases.     

铂粒子修饰单壁碳纳米管/聚苯胺复合膜对甲醛的电催化氧化

在溶有单壁碳纳米管(SWNTs)的苯胺溶液中, 通过电化学共聚合法成功制备了单壁碳纳米管(SWNT)/聚苯胺(PANI)复合膜. 用电沉积法将铂沉积到SWNT/PANI复合膜上. 样品的成分和形貌分别用XRD和SEM表征. 四探针和电化学交流阻抗的研究表明被PANI包裹的SWNTs整齐地排列在复合膜中, 从而提高了复合膜的电导率, 促进了电荷转移. 循环伏安(CV)说明Pt修饰的SWNT/PANI复合膜对于甲醛氧化具有良好的电催化活性及稳定性. 研究结果表明SWNT/PANI复合膜是一种非常好的催化剂载体, 有着广泛的应用前景.     

Polyaniline-coated carbon particles and their electrode behavior in organic carbonate electrolyte

In an attempt to increase the interface stability of carbon used in Li-ion batteries, a thin conducting polyaniline (PANI) film was fabricated on the surface of carbon by in situ chemical polymerization. The chemical and electrochemical properties of the composite material were characterized using X-ray diffraction, Raman spectroscopy, scanning electron microscope, cyclic voltammetry, and electrochemical impedance spectroscopy. It was confirmed that the PANI film has an obvious effect on the morphology and the electrochemical performance of carbon. The results could be attributed to the electronic and electrochemical activity of the conducting PANI films.     

Nanoscale measurements of conducting domains and current-voltage characteristics of chemically deposited polyaniline films

Spatial variations in electric conductivity and evolutions of band structures of polyaniline (PANI) films have been studied by use of a so-called current-sensing atomic force microscope (CS-AFM) or atomic force microscope current image tunneling spectroscopy (AFM-CITS). PANI films were deposited chemically onto indium-tin oxide- (ITO-) glass substrates, and their thickness and doping levels were controlled by polymerization and acid-doping conditions. The conducting uniformity of the PANI films depends on their doping level and thickness. Conducting domains were observed in fully doped PANI film, even when the bias voltage was reduced to as small as 30 mV. High current flowing regions gradually disappeared when conducting PANI films were partially dedoped. The point-contact current-voltage (I-V) characteristics of conducting tip-polymer/ITO systems were investigated on PANI films with different thickness and degree of doping. Various types of I-V curves representing metallic, semiconducting, and insulating states were obtained depending on the aggregation of polymer chains and doping level of the polymer film. The band gap energies (estimated from the I-V or dI/dV-V curves) of emeraldine base (EB) (undoped polyaniline) films are all higher than 3.8 eV, and a wide distribution of the band gap energies (0-1.1 eV and 0.75-1.8 eV for fully and partially doped PANI thin films, respectively) was found in a single polymer film.     

The effect of the polyaniline morphology on the performance of polyaniline supercapacitors

The polyaniline (PANI) prepared by the pulse galvanostatic method (PGM) or the galvanostatic method on a stainless steel substrate from an aqueous solution of 0.5 mol/l H₂SO₄ with 0.2 mol/l aniline has been studied as an electroactive material in supercapacitors. The electrochemical performance of the PANI supercapacitor is characterized by cyclic voltammetry, a galvanostatic charge–discharge test and electrochemical impedance spectroscopy in NaClO₄ and HClO₄ mixed electrolyte. The results show that PANI films with different morphology and hence different capacitance are synthesized by controlling the synthesis methods and conditions. Owing to the double-layer capacitance and pseudocapacitance increase with increasing real surface area of PANI, the capacitive performances of PANI were enhanced with increasing real surface area of PANI. The highest capacitance is obtained for the PANI film with nanofibrous morphology. From charge–discharge studies of a nanofibrous PANI capacitor, a specific capacitance of 609 F/g and a specific energy density of 26.8 Wh/kg have been obtained at a discharge current density of 1.5 mA/cm². The PANI capacitor also shows little degradation of capacitance after 1,000 cycles. The effects of discharge current density and deposited charge of PANI on capacitance are investigated. The results indicate that the nanofibrous PANI prepared by the PGM is promising for supercapacitors.     

聚合时间对染料敏化太阳能电池中聚苯胺对电极结构和性能的影响

采用恒电压方法, 以掺杂氟的SnO₂ (FTO)导电玻璃为基底, 采用不同的聚合时间制备SO₄^2?掺杂的聚苯胺对电极(PANI CEs). 利用扫描电子显微镜(SEM)、紫外-可见(UV-Vis)吸收光谱、循环伏安法(CV)和电化学阻抗谱(EIS)等技术详细研究了聚合时间对PANI CEs的表面形貌、结构(如掺杂度、共轭性、氧化态等)和对I^?/I^3?的催化活性的影响. SEM结果表明PANI在FTO上的生长分两个阶段. 适当增加聚合时间可以增加PANI CEs的比表面积, 为催化I^?/I^3?反应提供更多的活性位点, 同时聚苯胺链的共轭性、半氧化态聚苯胺(EB)结构的含量和对阴离子SO₄^2?的掺杂度会随着增加, 进而PANI 的导电率也逐渐增大. 然而, 聚合时间过长会引起薄膜厚度的增加和氧化结构的过多, 使PANI CEs的导电率降低, 电子在PANI 薄膜中的传输阻抗增加, 进而影响其对I^?/I^3?的催化性能. 聚合时间为300 s 时制备出的PANI 薄膜作为染料敏化太阳能电池(DSSCs)对电极和以D149 为染料时, 获得的最高电池光电转换效率为5.30%, 可达到基于Pt 对电极电池效率的88%. 因此, 通过电化学方法制备的PANI CEs有望代替贵金属Pt CEs用于DSSCs中.     

Electrocatalytic oxidation of methanol on Ni modified polyaniline electrode in alkaline medium

Electrolytically deposited Ni on polyaniline film covered carbon paste electrode (Ni/PANI/CPE) was used as anode for the electrooxidation of methanol in alkaline medium. The electrochemical behavior and electrocatalytic activity of the electrode were studied using cyclic voltammetry, impedance spectroscopy, chronomethods, and polarization studies. The morphology and composition of the modified film were obtained using scanning electron microscope and energy dispersive X-ray analysis techniques. The electrooxidation of methanol in NaOH was found to be more efficient on Ni/PANI/CPE than on bare Ni, electrodeposited Ni on Pt, Ni on glassy carbon, and Ni on CPE substrates. Partial chemical displacement of dispersed Ni on PANI with Pt or Pd further improved its performance towards methanol oxidation.     

Electrochemical template synthesis of adherent polyaniline thin films with tubular structure

The synthesis of nano and microstructured thin polyaniline (PANI) films by a simple and very efficient template-assisted method is presented. This work shows the synthesis and characterization of acoustically rigid thin films structured at nanotubular shape by using methyl orange (MO) as a template-assisted system. The amount of the tubes can be easily controlled by the charge passed. The morphology for different films growth was characterized by field emission scanning electron microscopy (FESEM), Atomic force microscopy (AFM), and quartz crystal microbalance with dissipation mode (QCM-D). Raman spectroscopy results show important changes in the conformational PANI chain of the tubular material compare with a non-tubular one that provokes the increase of bipolarons population. This should be responsible by some changes in the electrochemical behavior of tubular film compared with the granular material, due to the higher conductivity when the emeraldine form starts to be formed.     

Development of an optical ammonia sensor based on polyaniline/epoxy resin (SU-8) composite

Polyaniline (PANI)/glycidyl ether of bisphenol A (SU-8) composite film is elaborated in order to detect ammonia gas. These composite films are characterized by ultraviolet-visible (UV-vis) spectroscopy, Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The sensitivity to ammonia is measured by optical absorption changes. The ammonia sensing properties of PANI/SU-8 composite films are studied, and then are compared to pure PANI films elaborated by chemical way. Experimental results show that the PANI/SU-8 optical sensor has simultaneously a rapid response to ammonia gas and regenerates easily, that is advantageous compared to pure PANI films.     

Effect of anti-parallel and twisted alignment techniques on various propertiesof polymer stabilised liquid crystal (PSLC) films

Thin composite films consisting of liquid crystal (LC) domains surrounded by polymer networks, termed as polymer stabilised liquid crystals (PSLCs), were prepared by photo-polymerisation of a pre-polymer dissolved in LC. Four composite films were prepared with different rubbing directions and with and without electric field during photo-polymerisation. Morphological characterisation carried our using a polarising optical microscope (POM) and a scanning electron microscope (SEM) reveal significant changes in LC domain morphology and associated polymer networks with the application of electric field during the fabrication of the films. The electro-optic (EO) properties of PSLC films placed between two crossed polarisers were studied using a He–Ne laser under an action of externally applied electric field. It was found that the PSLC film with twisted alignment and polymerised in the presence of electric field showed better EO properties than other films. Transmittance obtained by EO studies was verified with absorbance studies using a Ultraviolet-Visible spectrophotometer. The dielectric behaviour of PSLC films in the frequency range 20–20 MHz was investigated using a precision impedance analyser. The obtained data were modelled using Debye and Cole–Cole methods to calculate relaxation time and distribution parameter. The relaxation time calculated through the Cole–Cole model is in agreement with response time.     

Polyaniline film deposition from the oxidative polymerization of aniline using K2Cr2O7

The deposition of the polyaniline (PANI) films was monitored using the quartz crystal microbalance (QCM) technique. The films were grown from an aqueous dilute hydrochloric acid solution by the chemical oxidation of aniline using potassium dichromate (KDC). The effect of the initial molar ratio of the KDC/aniline on the yield and the growth rate of the PANI films were studied. There is no optimum initial molar ratio of KDC/aniline of PANI film deposition. Also there was a small depletion period and no degradation to the deposited PANI films. The order of the polymerization kinetics was studied with respect to KDC. The UV-visible spectra of the PANI films grown onto a glass support immersed into the bulk solution were measured. The absorption of the PANI film with the time of polymerization was compared to the growth of the PANI film thickness with time determined from the QCM technique. The characteristics of the PANI film deposition were compared to the corresponding ones that were observed during the oxidative polymerization of aniline with ammonium persulphate (APS).     

Pt微粒修饰纳米纤维聚苯胺电极对甲醇氧化电催化

以脉冲电流法制备的纳米纤维状聚苯胺(PANI)为Pt催化剂载体，用它制备了甲醇阳极氧化的催化电极Pt/（nano-fibular PANI）.研究结果表明, Pt/（nano-fibular PANI）电极对甲醇氧化具有很好的电催化活性,并有协同催化作用.在相同的Pt载量条件下， Pt/（nano-fibular PANI）电极比Pt微粒修饰的颗粒状聚苯胺电极Pt/(granular PANI)具有更好的电催化活性.此外， Pt的电沉积修饰方法同样影响Pt/（nano-fibular PANI）电极对甲醇氧化的催化活性.脉冲电流法沉积Pt形成的复合电极较循环伏安法电沉积得到的Pt复合电极具有更优异的催化活性.     

Electrochemical polymerization of polyaniline doped with Zn2+ as the electrode material for electrochemical supercapacitors

Polyaniline doped with Zn²⁺ (PANI/Zn²⁺) films was synthesized by cyclic voltammetric method on stainless steel mesh substrates in 0.2 mol L^?1 aniline and 0.5 mol L^?1 sulfuric acid electrolyte with various concentrations of zinc sulfate (ZnSO₄·7H₂O). The structure and morphology of PANI and PANI/Zn²⁺ films were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques, respectively. The electrochemical properties of PANI and PANI/Zn²⁺ films were investigated by cyclic voltammetry, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy in 0.5 mol L^?1 H₂SO₄ electrolyte in a three-electrode system. The results show that the surface morphology of PANI/Zn²⁺ is more rough than that of pure PANI. The specific capacitance of the PANI/Zn²⁺ film displays a larger specific capacitance of 738 F g^?1, lower resistance, and better stability as compared with the pure PANI film. Thus, good capacitive performance demonstrates its potential superiority for supercapacitors.     

Impedance measurements at thin polyaniline films – the influence of film morphology

AC impedance measurements of thin 100-nm polyaniline films electrosynthesized in various acidic electrolyte solutions known to support different film morphologies are reported. By carefully defining experimental parameters obtained data could be satisfactorily explained invoking a simple equivalent circuit assuming a double layer capacity assigned to the polymer/solution interface, a pseudocapacity related to the internal _redox capacity of the film, a film and a solution resistance and could be related to film morphologies. The data can be related to structural/morphological features of PANI films in close agreement with generally accepted changes of PANI films as a function of the degree of oxidation and type of anion present during electropolymerization.     

The Electrochemical Properties of Nanocomposite Films Obtained by Chemical In Situ Polymerization of Aniline and Carbon Nanostructures

Interactions between the π bonds in the aromatic rings of polyaniline (PANI) with carbon nanostructures (CNs) facilitate charge transfer between the two components. Different types of phenyleneamine‐terminated CNs, including carbon nano‐onions (CNOs) and single‐walled and multi‐walled carbon nanotubes (SWNTs and MWNTs, respectively), were prepared as templates, and the CN/PANI nanocomposites were easily prepared with uniform core–shell structures. By varying the ratio of the aniline monomers relative to the CNs in the in situ chemical polymerization process, the thickness of the PANI layers was effectively controlled. The morphological and electrical properties of the nanocomposite were determined and compared. The thickness and structure of the PANI films on the CNs were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and infrared spectroscopy. TEM and SEM revealed that the composite films consisted of nanoporous networks of CNs coated with polymeric aniline. The electrochemical properties of the composites were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. These studies showed that the CN/PANI composite films had lower resistance than pure polymeric films of PANI, and the presence of CNs much improved the mechanical stability. The specific electrochemical capacitance of the CNO/PANI composite films was significantly larger than for pure PANI.     

LY12铝合金表面电化学沉积制备DTMS硅烷膜及其耐蚀性研究

采用电化学技术在LY12铝合金表面沉积制备了十二烷基三甲氧基硅烷(DTMS)膜. 反射吸收红外光谱表明, DTMS硅烷试剂与铝合金基体表面发生了化学键合作用, 生成—SiOAl键实现成膜. 通过对膜覆盖电极在质量分数为3.5%的NaCl溶液中的电化学阻抗谱(EIS)测试结果表明, 与开路电位下相比, 采用阴极电位沉积方法得到硅烷膜的耐蚀性能有明显提高, 且存在一个最佳“临界电位”, 在此电位下沉积得到的硅烷膜具有最高的耐蚀性. 扫描电镜观察结果表明, 在“临界电位”下制备得到的硅烷膜的结构最致密. 给出了硅烷膜覆盖电极的阻抗模型及相关参数的拟合结果.     

A comparative study of the polyaniline thin films produced by the cluster beam deposition and laser ablation methods

Polyaniline (PANI) thin films have been prepared by applying the novel neutral and ionized cluster beam deposition (NCBD and ICBD) methods and the pulsed laser deposition (PLD) technique to the PANI samples of half-oxidized emeraldine base (EB-PANI) and protoemeraldine base forms in a high-vacuum condition. Characterization of the oxidation states and structural changes of pristine and doped thin films has been performed by Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and x-ray photoelectron spectroscopy. Spectroscopic measurements demonstrate that the dominant structure of NCBD and ICBD thin films corresponds to the reduced leucoemeraldine base state, whereas the chemical composition of PLD thin films depends critically on the laser fluence and the molecular weight of PANI target. The congruent deposition is only obtained for the PLD films deposited by the laser-induced decomposition of the low-molecular-weight targets in the low to intermediate fluence regime (below 100 mJ/cm2 with a pulse duration of 7 ns). The surface morphology examined by atomic force microscopy measurements shows that the cluster and laser beams are effective in producing smooth, uniform polymeric thin films. After I2 and HCl doping, the electrical conductivities of the NCBD, ICBD, and particularly PLD thin films are increased significantly. The higher conductivity of PLD films is ascribed to higher amounts of quinoid di-imine doping sites in the EB-PANI state, and the overall structure-conductivity characteristics are consistent with the spectroscopic observations.     

纳米纤维聚苯胺膜在不锈钢电极表面的生长过程

研究了脉冲电流法(PGM)聚合苯胺时, 纳米纤维聚苯胺(PANI)膜在不锈钢(SS)电极表面的生长过程. 用计时电位法和扫描电子显微镜(SEM)表征了聚苯胺生长过程的电化学特征和微观形貌; 并通过循环伏安(CV)法研究了苯胺的聚合速率. 结果表明, 聚苯胺的生长经历了两个阶段, 首先是在裸不锈钢电极表面上形成颗粒状聚苯胺, 此时聚合电位约为1.10 V, 经历了30 s后, 电极表面被一层颗粒状聚苯胺膜所覆盖; 在此基础上, 聚苯胺以纳米纤维状结构继续生长, 当颗粒状聚苯胺被纳米纤维状聚苯胺膜完全覆盖时, 聚合电位降至0.75 V左右并保持稳定.     

Peculiarities of Electrochemical Bismuth Film Formation in the Presence of Bromide and Heavy Metal Ions

Bi films were deposited on glassy carbon electrode from solutions with and without KBr. The morphology of both types of the films was characterized by scanning electron microscopy (SEM), and their electrochemical behavior was studied by square wave (SWV) and cyclic voltammetry (CV). Bi films were also co‐deposited with common analyte‐heavy‐metals in the presence of KBr and these films also were characterized by SEM, SWV and CV in order to understand the formation of the mixed metal films. All films studied had a different morphology. Bromide addition made the Bi films more compact and uniform, whereas Pb catalyzed Bi film deposition.     

Structure–electrical property study of anisotropic polyaniline films

The relationships of the structure and electrical properties of anisotropic HCl‐doped polyaniline (PANI) films cast from N,N′‐dimethylpropylene urea (DMPU) solutions and stretched to different draw ratios were studied. The anisotropic structure of the stretched PANI films was examined by X‐ray diffraction, near‐infrared wave‐guide coupling, and polarized infrared measurements. The PANI emeraldine base (EB) films cast from DMPU solutions had a single‐phase noncrystalline structure, and stretching of the films did not cause crystallization to occur. The transition moment angles of two weakly absorbing infrared bands were determined, and the Hermans' orientation functions for the PANI EB films were calculated. The PANI films were then doped with HCl, and the electrical properties were determined by impedance spectroscopy. With a specially designed test fixture, the in‐plane and through‐plane impedance was obtained. The conductivity along the stretch direction increased with orientation. The in‐plane conductivity was significantly higher than the through‐plane conductivity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 823–841, 2003