钒酸基/聚苯胺修饰薄膜的制备及湿敏性能研究

采用交替沉积法制备了钒酸基/聚苯胺薄膜,讨论酸种类和不同层数对薄膜湿敏性能的影响,实验结果表明:钒钛酸/聚苯胺复合膜的湿敏性能优于钒酸/聚苯胺薄膜,双层钒钛酸/聚苯胺薄膜的湿敏性能均优单层,该湿敏薄膜的湿滞为5%RH,灵敏度变化了三个数量级,响应时间为8s,恢复时间为13s,线性度和稳定性均较理想。     

载铂聚苯胺/聚砜复合膜修饰电极对甲醇的电催化氧化行为研究

采用循环伏安法制备聚苯胺(PAN)/聚砜(PSF)复合膜修饰电极,在其上电沉积铂粒子,制得载铂聚苯胺/聚砜复合膜修饰电极,用循环伏安法和交流阻抗法研究它对甲醇的电催化氧化行为。复合膜的化学组分用FTIR进行表征,复合膜内层载铂后的表面形态用SEM进行表征。结果表明,复合膜的内层(与工作电极接触的一面)是聚苯胺,外层(与溶液接触的一面)是聚砜,铂粒子在复合膜内层的多孔聚苯胺上均匀沉积,从而使载铂聚苯胺/聚砜复合膜修饰电极对甲醇有好的电催化氧化性能。     

多壁碳纳米管/磷钼酸修饰电极对抗坏血酸的电催化作用

制备了GC/MWNTs/PMo12O340-修饰电极,研究了其在硫酸溶液中的电化学行为,采用循环伏安法研究了修饰电极对抗坏血酸的电催化特性。结果表明,该修饰电极在硫酸溶液中的电化学行为是表面控制过程。抗坏血酸的浓度在3×10-3～1×10-2mol/L范围内,催化电流与抗坏血酸的浓度呈现良好的线性关系,该修饰电极具有较好的稳定性。     

普鲁士蓝修饰玻碳电极测定2,6-二甲基苯酚

利用电化学方法在玻碳电极表面聚合一层普鲁士蓝,制备普鲁士蓝修饰玻碳电极,运用循环伏安法研究了2,6-二甲基苯酚在该修饰电极上的电化学行为。结果表明,该修饰电极对2,6-二甲基苯酚显示出较好的电化学响应和电催化活性,在pH为4.0的HAc-NaAc缓冲溶液中,2,6-二甲基苯酚浓度与其峰电流在2.0×10-5~1.0×10-2 mol/L范围内呈现良好的线性关系。     

负载硅钨杂多酸纳米银修饰电极的电化学性质研究

以硅钨杂多酸作为光催化还原剂制备了纳米银(SiW12-NS)。用PVP作偶联剂,将SiW12-NS修饰到玻碳电极表面,用循环伏安法(CV)研究其电化学行为。结果表明,修饰电极具有良好的电化学响应和电极稳定性,对BrO3-,NO2-具有良好的电催化还原性能。     

石墨烯/聚苯胺修饰阳极对微生物燃料电池性能的影响

纳米材料修饰阳极可显著提高微生物燃料电池（MFC）性能,本研究主要探索了石墨烯、聚苯胺和石墨烯/聚苯胺复合修饰电极对MFC产电性能的影响。使用电化学方法电镀石墨烯于碳布表面,进一步通过原位聚合法制备聚苯胺来修饰碳布电极。将修饰电极装载入双室型MFC中,测量其产电性能,并对电极进行表征,测量电化学性能。通过扫描电镜观察到, 碳布能够被修饰上石墨烯和聚苯胺,并且聚苯胺附着于碳纤维或石墨烯薄层表面,形成棒状的纳米结构。产电性能方面,装载石墨烯/聚苯胺修饰电极的MFC最大输出电压最高,达到了（291±22）mV,比装载空白碳布电极的对照组MFC提高了175%以上。石墨烯/聚苯胺电极组MFC的最大输出功率密度同样最高,达到了（653 ± 25）mW·m^-2,为空白碳布对照组的10.5倍。实验结果表明：石墨烯/聚苯胺复合修饰电极可有效利用石墨烯导电性好和聚苯胺生物相容性高的优点,显著提高MFC的产电性能。     

石墨烯/聚苯胺修饰阳极对微生物燃料电池性能的影响

纳米材料修饰阳极可显著提高微生物燃料电池(MFC)性能,本研究主要探索了石墨烯、聚苯胺和石墨烯/聚苯胺复合修饰电极对MFC产电性能的影响。使用电化学方法电镀石墨烯于碳布表面,进一步通过原位聚合法制备聚苯胺来修饰碳布电极。将修饰电极装载入双室型MFC中,测量其产电性能,并对电极进行表征,测量电化学性能。通过扫描电镜观察到,碳布能够被修饰上石墨烯和聚苯胺,并且聚苯胺附着于碳纤维或石墨烯薄层表面,形成棒状的纳米结构。产电性能方面,装载石墨烯/聚苯胺修饰电极的MFC最大输出电压最高,达到了(291±22) mV,比装载空白碳布电极的对照组MFC提高了175%以上。石墨烯/聚苯胺电极组MFC的最大输出功率密度同样最高,达到了(653±25) mW·m~(-2),为空白碳布对照组的10.5倍。实验结果表明:石墨烯/聚苯胺复合修饰电极可有效利用石墨烯导电性好和聚苯胺生物相容性高的优点,显著提高MFC的产电性能。     

乙二醇的电化学分析方法研究

本文制备了介孔碳/纳米铂复合材料修饰玻碳电极,并采用循环伏安法研究了乙二醇在该电极上的电化学行为,与乙二醇在裸玻碳电极上的电化学行为进行相应的对比,发现乙二醇在修饰电极上的氧化峰电流较大,且氧化峰电势电位较低,表明乙二醇在该修饰的电极上具有良好的电催化氧化效应。乙二醇在浓度范围为1.0×10~(-5)~1.0×10~(-3)mol/L之间与峰电流ip呈良好的线性关系,据此建立了乙二醇的电化学分析方法,可用于实际样品中乙二醇的测定。     

聚亚甲基蓝/纳米二氧化硅修饰电极的制备及其对NADH的电催化氧化

通过电化学方法制备了聚亚甲基蓝/纳米二氧化硅复合膜修饰电极(PMB-nano-SiO2/GCE),采用扫描电子显微镜(SEM)和交流阻抗法(EIS)对复合膜界面进行了表征,并研究了烟酰胺腺嘌呤二核苷酸(NADH)在修饰电极表面的电化学行为。结果表明,在pH 7.0的磷酸盐缓冲溶液中,NADH氧化峰电位降低和峰电流明显增加,表明该修饰电极对NADH具有良好的电催化氧化性能。NADH浓度在1.0～100.0μmol/L浓度范围内与峰电流呈良好的线性关系,相关系数为0.997。     

钯复合材料电极催化甲醇氧化机理

在NaY/Teflon修饰玻碳电极上电化学辅助沉积钯微粒,制备钯复合材料电极,研究催化反应机理。采用循环伏安法(CV)、计时电流法和扫描电镜进行表征,结果表明,钯复合材料电极对甲醇的催化是单电子过程,改变甲醇氧化途径,降低活化能。该电极具有优越的放电特性,提高甲醇和电极利用率,对甲醇氧化具有良好的电催化活性。     

Poly(glutamic acid) nanofibre modified glassy carbon electrode: Characterization by atomic force microscopy, voltammetry and electrochemical impedance

Glassy carbon electrodes (GCE) were modified with poly(glutamic acid) acid films prepared using three different procedures: glutamic acid monomer electropolymerization (MONO), evaporation of poly(glutamic acid) (PAG) and evaporation of a mixture of poly(glutamic acid)/glutaraldehyde (PAG/GLU). All three films showed good adherence to the electrode surface. The performance of the modified GCE was investigated by cyclic voltammetry and differential pulse voltammetry, and the films were characterized by atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS). The three poly(glutamic acid) modified GCEs were tested using the electrochemical oxidation of ascorbic acid and a decrease of the overpotential and the improvement of the oxidation peak current was observed. The PAG modified electrode surfaces gave the best results. AFM morphological images showed a polymeric network film formed by well-defined nanofibres that may undergo extensive swelling in solution, allowing an easier electron transfer and higher oxidation peaks.     

Characterization of the barrier layer of nanoporous alumina films prepared using two different contact configurations

We investigated the structure of the barrier layers of nanoporous alumina formed by anodization of aluminum films laid over platinum electrodes by cyclic voltammetry technique and scanning electron microscopy. Two methods of anodization were employed in this study—the conventional sub-surface anodization method and a novel pipette anodization method. Measurements of the electron transfer rate constant values at these alumina-modified electrodes demonstrated very different alumina microstructures at the barrier layer region for these two types of alumina-modified electrodes. The sub-surface anodized electrode consists of a barrier layer, which forms a kinetic barrier for the electrochemical reaction of a redox probe at the underlying platinum electrode. In contrast, the quasi-reversible electrochemical behaviour of a redox probe at the pipette-anodized electrodes closely resembles the reaction observed at a bare platinum electrode. Scanning electron microscopy revealed pore structures along the underside surface of the alumina overlayer of a pipette-anodized electrode. These results indicate alumina modified eletrodes fabricated using the pipette anodization method comprise channels which penetrate the barrier layer, giving rise to ‘barrier layer-free’ alumina films.     

Simple design of cast myoglobin/polyethyleneimine modified electrodes

Negatively charged myoglobin (at pH values above its isoelectric point) was immobilized with the positively charged polyion polyethyleneimine (PEI) on pyrolytic graphite electrodes. A modified form of the common layer-by-layer technique was proposed, which consisted in forming non-ordered cast polyion films. The modified Mb electrodes obtained by both techniques were compared by cyclic voltammetry. The cast polyion technique gave less reproducible results but enable the immobilization of higher percentages of the total quantity of protein required to prepare the electrodes. The electrochemical properties of the negatively charged myoglobin were determined, and its capability to catalyze the electrochemical reduction of oxygen and the dechlorination of trichloroacetic acid was demonstrated. The mechanisms are discussed, and the modified pathway that has been proposed to take into account the influence of pH in the Mb-catalyzed reduction of oxygen was confirmed here.     

Interaction between myoglobin and hyaluronic acid in layer-by-layer structures—An electrochemical study

The layer-by-layer (LBL) self-assembled film construction of the biocompatible polymer hyaluronic acid (HA) and single heme redox protein, myoglobin (Mb) is described. The films were built upon gold electrode substrates, both gold quartz crystal electrodes and bulk gold (Au(bulk)) electrodes, and formation of the LBL films was gravimetrically monitored by an electrochemical quartz crystal microbalance. The electrochemical properties of the hyaluronic acid/myoglobin films ({HA/Mb}_n) were investigated after each deposition step using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV response presented an oxidation peak at +0.3 V vs. SCE, not characteristic of the redox protein myoglobin, and, the peak current decreased slightly with each additional bilayer. CV at Au(bulk) electrodes in pH 5.0 acetate buffer solution, containing Mb, presented the same oxidation peak as observed at {HA/Mb}_n modified electrodes, confirming the presence of the same electroactive species. The Mb oxidation peak current depends linearly on scan rate, characteristic of adsorbed thin-layer electrochemical systems, attributed to free adsorbed heme. Impedance spectra, recorded after deposition of each bilayer, were in agreement with the cyclic voltammetry observations.     

Electrochemical behaviour of metal hexacyanoferrate converted to metal hydroxide films immobilized on indium tin oxide electrodes—Catalytic ability towards alcohol oxidation in alkaline medium

In this work, we demonstrate a simple method to modify indium tin oxide (ITO) electrodes in order to perform electro-catalytic oxidation of alcohols in alkaline medium. Metal hexacyanoferrate (MHCF) films such as nickel hexacyanoferrate (NiHCF) and copper hexacyanoferrate (CuHCF) were successfully immobilized on ITO electrodes using an electrochemical method. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the structural and morphological aspects of MHCF films. Cyclic voltammetry (CV) was used to study the redox properties and to determine the surface coverage of these films on ITO electrodes. Electrochemical potential cycling was carried out in alkaline medium in order to alter the chemical structure of these films and convert to their corresponding metal hydroxide films. SEM and XPS were performed to analyze the structure and morphology of metal hydroxide modified electrodes. Electro-catalytic oxidation ability of these films towards methanol and ethanol in alkaline medium was investigated using CV. From these studies we found that metal hydroxide modified electrodes show a better catalytic performance and good stability for methanol oxidation along with the alleviation of CO poisoning effect. We have obtained an anodic oxidation current density of ∼82 mA cm⁻² for methanol oxidation, which is at least 10 fold higher than that of any metal hydroxide modified electrodes reported till date. The onset potential for methanol oxidation is lowered by ∼200 mV compared to other chemically modified electrodes reported. A plausible mechanism was proposed for the alcohol oxidation based on the redox properties of these modified electrodes. The methodology adapted in this work does not contain costlier noble metals like platinum and ruthenium and is economically viable.     

Protoporphyrin-modified gold surfaces for the selective monitoring of catecholamines

Protoporphyrin IX (PPIX) was immobilized on Au surfaces for the electrochemical oxidation of dopamine (DA) and epinephrine (EP). Two procedures for the immobilization were employed. One class of modified electrodes was prepared by immobilizing the PPIX into polypyrrole (PPy) films synthesized by anodic electropolymerization. The other procedure involved the immobilization of PPIX on an electrode modified by a 11-mercaptoundecanoic acid (MUA) self-assembled monolayer (SAM). The modified surfaces were characterized by cyclic voltammetry (CV).The efficiency of these modified surfaces for the electrochemical oxidation of DA and EP was investigated and compared. The peak potential for the oxidation of each analyte at the different electrode surfaces was determined by square-wave voltammetry (SWV).The dependence of the sensitivity of the electrodes for the detection of the catecholamines on the applied potential was also measured. The SAM-based electrodes showed better selectivity for detecting DA in the potential range between 0.2 and 0.4 V versus Pt (QRE). However, higher sensitivity and linearity were observed for the film-based electrodes.     

Copper/polypyrrole multilayer coating for 7075 aluminum alloy protection

The corrosion behavior of 7075 aluminum (Al), copper modified Al (Al/Cu), polypyrrole modified Al (Al/PPy) and copper (under layer)/polypyrrole (top layer) modified Al (Al/Cu/PPy) samples were investigated in 3.5% NaCl solution. The copper plating on aluminum was carried out from acidic copper sulphate solution by electroless method. Polypyrrole (PPy) was electrochemically synthesized on Al and Al/Cu electrodes from 0.1 M pyrrole containing 0.4 M oxalic acid solution using cyclic voltammetry technique. The films synthesized were characterized by Fourier transform infrared spectroscopy (FT-IR). The thermal stability of PPy films was investigated by thermogravimetric analysis (TGA). The surface morphologies were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The corrosion behavior of samples was investigated by electrochemical impedance spectroscopy (EIS) and anodic polarization curves. The data obtained showed that the synthesis of PPy on top of the Cu layer significantly enhances the corrosion resistance of Al by exhibiting a barrier effect against the attack of corrosive environment.     

Electrochemical immobilization of ascorbate oxidase in poly(3,4‐ethylenedioxythiophene)/multiwalled carbon nanotubes composite films

Immobilization of ascorbate oxidase (AO) in poly(3,4‐ethylenedioxythiophene) (PEDOT)/multiwalled carbon nanotubes (MWCNTs) composite films was achieved by one‐step electrochemical polymerization. The PEDOT/MWCNTs/AO modified electrode was fabricated by the entrapment of enzyme in conducting matrices during electrochemical polymerization. The PEDOT/MWCNTs modified electrodes were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The experimental results showed that the composite films exhibited better mechanical integrity, electrochemical activity, higher electronic and ionic conductivity, and larger redox capacitance compared with pure PEDOT films, which would be beneficial to the fabrication of PEDOT/MWCNTs/AO electrochemical biosensors. The scanning electron microscopy studies revealed that MWCNTs served as backbone for 3,4‐ethylenedioxythiophene (EDOT) electropolymerization. Furthermore, the resulting enzyme electrode could be used to determine L ‐ascorbic acid successfully, which demonstrated the good bioelectrochemical catalytic activity of the immobilized AO. The results indicated that the PEDOT/MWCNTs composite are a good candidate material for the immobilization of AO in the fabrication of enzyme‐based biosensor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electrochemical properties of benzylmercapto and dodecylmercapto tetra substituted nickel phthalocyanine complexes: Electrocatalytic oxidation of nitrite

Nickel tetrakis(benzylmercapto)phthalocyanine (NiTBMPc) and nickel tetrakis(dodecylmercapto)phthalocyanine (NiTDMPc) complexes were synthesized and their spectral and electrochemical properties reported. The CV showed four or five redox processes for NiTBMPc and NiTDMPc, respectively. For the first time, spectroelectrochemistry gave evidence for the formation of Ni^II/Ni^I process in a NiPc complex. The rest of the processes were ring based. The NiTBMPc complex was successfully deposited on both gold and glassy carbon electrodes by electropolymerisation while NiTDMPc complex was deposited on gold electrode only. The films were electro-transformed in aqueous 0.1 M NaOH solution to the O–Ni–O oxo bridged form. The modified electrodes were characterized using electrochemical impedance spectroscopy and the results showed typical behavior for modified electrodes. Electrodes with poly-Ni(OH)Pcs films exhibited higher charge transfer resistance values, R_p than their corresponding poly-NiPcs films counterparts. All the modified electrodes showed improved catalytic activities than the unmodified electrodes towards nitrite ions electrooxidation. Better catalytic activities were observed for the modified electrodes when they were transformed to O–Ni–O oxo bridge form. All the modified electrodes exhibited high resistance to electrode surface passivation.