Fluorinated functionalized EDOT-based conducting films

Three ethylenedioxithiophene (EDOT) derivatives bearing either perfluoro- or ether perfluoro-alkyl chains were synthesized with the objective to prepare films with dry and chemically immobilized lubrication properties. The corresponding fluorinated PEDOT films were deposited on platinum surface by electropolymerization. Cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) analyses (both quartz resonant frequency and resonant admittance) of the growing steps are described. The electroactive behavior of the films versus their doping level was followed by electrochemical impedance spectroscopy (EIS) through equivalent circuit fitting procedure and compared to their CV responses. Hysteresis in fit parameters corresponding to capacity and film resistance between the forward and the backward scans are observed and discussed. Control of the chemical structures and charge effects on PEDOT chains are followed by an XPS analysis. From these analyses, it appears that the fluorinated side-arm does not alter both the growing and the electrical properties of the films in respect to the pristine PEDOT taken as reference.     

Electrochemical formation of Ir oxide/polyaniline composite films

The primary goal of this work has been to electrochemically form and then characterize a composite polyaniline (PANI)/hydrous Ir oxide (IrOx) film. Efforts to electrochemically form IrOx and PANI simultaneously in acidic aniline-containing solutions failed, likely as aniline adsorption on Ir prevents IrOx formation. Successful composite films were therefore made by first forming an anodic IrOx film on bulk Ir and then depositing PANI into its pores. Based on the characteristics of the PANI redox peaks, it is seen that all of the PANI film that is electrochemically active is in direct electrical contact with the Ir surface at the base of the IrOx film pores. This is consistent with the cross-sectional SEM and EDX analyses, showing the formation of films of uniform thickness and composition. Thin films of Ir nanoparticles, subsequently converted to IrOx, were also used as a template for PANI formation within the porous structure. These hybrid films exhibit an enhanced internal porosity, ease of multiple coating formation (up to 20 μm in thickness), high charge densities, unusual electrochromic behavior, and very rapid charge transfer kinetics. The formation of composite IrOx/PANI films also resulted in a widening (by 0.3-0.4 V) of the potential window over which a pseudocapacitive and electrochromic response is seen.     

Electrosynthesized molecularly imprinted polypyrrole films for enantioselective recognition of l-aspartic acid

The electrosynthesis, overoxidation and characterization of l-aspartic acid (l-Asp) imprinted polypyrrole (PPy) films have been performed by using electrochemical quartz crystal microbalance (EQCM). Following the determination of the optimal electrosynthesis parameters for the formation of a smooth and uniform PPy/l-Asp films, the overoxidized polypyrrole (oPPy) matrix templated with either l- or d-aspartic acid (l-, d-Asp) was evaluated as a potential enantioselective recognition element. Under potentiodynamic conditions and in strongly acidic media a significantly higher sensitivity of the l-Asp acid imprinted overoxidized polypyrrole film (oPPy/l-Asp) for l-Asp than d-Asp was observed. The results suggest the feasibility of preparing molecularly imprinted films by electropolymerization for the enantioselective recognition of amino acids and the suitability of EQCM for both monitoring the selective recognition as well as to electrochemically modulate the binding process.     

Investigations of ultrathin polypyrrole films: Formation and effects of doping/dedoping processes on its optical properties by electrochemical surface plasmon resonance (ESPR)

In the present work an investigation of the effects of the electropolymerization mode on the optical properties associated to the doping/dedoping processes of nanometric films of polypyrrole (PPy) is reported, monitoring in situ and in real time using simultaneously surface plasmon resonance and electrochemical techniques (ESPR). The electropolymerization of pyrrole was performed by potentiostatic, potentiodynamic and galvanostatic methods and the use of the ESPR technique showed that the electropolymerization mode is essential to the stability of polymer and the reversibility of its optical properties during the doping and dedoping processes. Thus, the optical properties of oxidized and reduced film were obtained by nonlinear least square fitting using Fresnel equations for a four-layer system. Then, the values of the real and imaginary parts of the complex dielectric constant for PPy fims were correlated with the polymer doping level. Finally, quartz crystal microbalance measurements were also applied to obtain correlation between doping/dedoping processes and the changes in the real and imaginary parts of the dielectric constant of the polypyrrole film, showing that the doping and dedoping processes in the polypyrrole film can act directly on its optical properties while the ESPR technique can give the same information indirectly.     

四氨基镍酞菁在金电极上成膜过程的研究

采用循环伏安法（CV）和石英晶体微天平技术（QCM）对四氨基镍酞菁（NiTAPc）在金电极上的聚合成膜过程进行了研究,讨论了扫描速率、溶剂、支持电解质及单体浓度对其成膜过程的影响,考察了该聚合膜在无单体电解质溶液中的氧化还原行为及稳定性。借助电化学石英晶体微天平(QCM)重点讨论了过程溶液中离子在膜中传输的机理。     

The effect of anion identity on the viscoelastic properties of polyaniline films during electrochemical film deposition and redox cycling

Acoustic admittance measurements at thickness shear mode resonators were used to determine shear moduli for polyaniline films during their potentiodynamic electrodeposition and subsequent redox cycling in aqueous background electrolyte. Data were acquired for films doped with perchlorate, sulphate or chloride anion. For all media, film shear moduli increased progressively with film thickness, from values consistent with a diffuse fluid-like layer to values typical of a viscoelastic material. At any given thickness, both the storage and loss moduli were largest in perchlorate medium; values in chloride and sulphate media were similar to each other, but smaller than in perchlorate. These measures of polymer dynamics are consistent with a previous classification of polyaniline film behaviour, in which perchlorate-doped films are viewed as compact while chloride- and sulphate-doped films are viewed as more open. In monomer-free background electrolyte solution, both film shear modulus components for all anions increased modestly upon film oxidation. Despite some hysteresis on the timescale of slow scan voltammetry, these variations were chemically reversible. Based on measurements involving deposition from chloride medium and transfer to sulphate medium, film shear moduli respond promptly to changes in dopant identity; this is consistent with rapid redox-driven exchange of anions with the bathing electrolyte.     

On the p-doping of PEDOT layers in various ionic liquids studied by EQCM and acoustic impedance

Poly(3,4-ethylenedioxythiophene) (PEDOT) films have been polymerized in several ionic liquids on the polycrystalline gold electrode of an electrochemical quartz crystal microbalance (EQCM) at 25 °C and 85 °C. Under cyclic potential variation, the EQCM resonance frequency decreased in the anodic potential region, indicating that the p-doping process is accompanied by the incorporation of anions. Elastic shear moduli G′, G″ - calculated from acoustic impedance measurements - were about 10⁷ Pa, values that are 2 orders of magnitude higher than for PEDOT polymerized in acetonitrile solutions. This difference is explained by the stiffening of the film by incorporated charged species because of the absence of a neutral molecular solvent plasticizing the film.     

Solvent effects on electrochemical behavior of poly(ferrocenylsilane) films

The electrochemical behaviors of poly(ferrocenylsilane) (PFS) films in organic solutions were investigated by means of cyclic voltammetry (CV) and electrochemical quartz crystals microbalance (EQCM). The influences of solvent on the electrochemical behavior of the films were discussed. In “good” solvents, the supporting electrolytes dissociated completely, the films were solvent-swollen moderately which provided a favorable condition for the electrolyte ions penetrating through, and the CV behavior of the films exhibited reversible or nearly reversible features. With increasing the carbon chain length of solvent molecule, however, the polarity of solvent reduced, which conduced to decrease the dissociation of electrolyte and the swelling of the polymer film. The efficiency of electrochemical reaction in the film was depressed, and the CV behavior of the film exhibited low reversibility. The solvent effects on the oxidation process of films exhibited more noticeable than the reduction process. The results supported the viewpoint that penetration of the electrolyte anions played an important role on the charge balance and transfer in the films during the CV process. The different electrochemical behaviors of the two PFS films in various organic solutions indicated that molecular structure of polymer had important influence on the electrochemical properties of the PFS.     

Bio- and bioelectro-catalytic properties of polyaniline/poly(acrylic acid) composite films bearing covalently-immobilized acid phosphatase

Conducting films composed of polyaniline (PANI) and poly(acrylic acid) (PAA) were prepared by electrochemical polymerization of aniline in the presence of various concentrations of PAA. The content of PAA moiety on the surface of the composite films (PANI/PAA films) was estimated by determination of carboxyl groups and found to be controlled by the concentration of PAA in polymerization solution. Acid phosphatase (ACP) was immobilized covalently on the PANI/PAA films by the condensation reaction with the carboxyl groups on the films. It was confirmed that the enzyme activity of the ACP-immobilized PANI/PAA film increased with increasing content of PAA moiety on the surface of the film, accompanying an increase in the amount of the immobilized ACP. The activity of the covalently immobilized ACP was significantly higher than that of the ACP adsorbed on the PANI/PAA film. By use of the ACP-immobilized PANI/PAA film as an enzyme electrode, bioelectrocatalytic oxidation of L-ascorbic acid 2-phosphate (ASA2P) was examined. The enzyme electrode gave the current due to the oxidation of ASA2P in proportion to the content of PAA moiety on the surface of the PANI/PAA film used, which was relevant to the activity of the covalently immobilized ACP.     

Determination of the potential range responsible for the replacement of surface film on LiMn2O4

This study determined the potential range where the dissolution of a surface film on a thin film LiMn₂O₄ electrode, which forms during electrode synthesis, and the formation of a new surface film during cycling at room temperature using an in situ bending beam method (BBM) and an in situ electrochemical quartz crystal microbalance (EQCM) technique with cyclic voltammetry and a galvanostatic charge/discharge cycle. The electrolytes used were LiClO₄/EC-DEC, LiClO₄/PC and LiPF₆/EC-DMC. The deflectogram and massogram showed large peaks during the anodic scan only in the first cycle. These phenomena, were observed regardless of the electrolytes and scan rate used. The tensile strain and the mass reduction in the early stage of the strain peak and the mass peak are related to the dissolution of the initial surface film. In addition, the compressive strain and the mass increase are related to the formation of a new surface film during cycling. The potential ranges where the formation of the new surface film begins ranged from 4.03 to 4.1 V, which appears to terminate at the end of the first anodic scan, and was also observed during the galvanostatic charge/discharge cycle in the same potential range.     

The role of ion and solvent transport during the redox process of conducting polymers

The understanding of the redox behavior of conducting polymers is essential for a successful application of these so-called synthetic metals as functional coatings. The redox process involves the exchange of ions and solvent molecules. This so called doping/dedoping process involves changes of the mechanical and the electronic structure of the polymer. This paper discusses investigations at poly(3,4-ethylenedioxythiophene (PEDOT) and poly(pyrrole) (Ppy) by the electrochemical quartz crystal microbalance (EQCM) technique and electrochemical impedance spectroscopy (EIS). In the case of PEDOT a determination of the anion and the solvent fluxes was possible, and it was found that most anions replace solvent molecules upon their incorporation. The doping/dedoping mechanism of Ppy is more complicated. Here, the first redox cycles are characterized by a complex interplay of cation, anion and solvent fluxes with irreversible changes of the polymer structure. However, in combination with EIS new insights of the ion and solvent exchange and its influence on the electronic properties can be achieved.     

壳聚糖基聚电解质复合膜的制备及性能

为了克服壳聚糖薄膜力学强度差和在体液内降解太快的缺陷, 首先用"一步法"合成了—COOH含量及疏水性可控的苹果酸与乳酸共聚物(PML), 再将共聚物与壳聚糖(CS)复合, 通过溶液浇铸-挥发的方法制备改性复合薄膜。通过红外(FT-IR)、热重分析(TGA)、力学性能测试、降解实验及体外细胞毒性实验等方法对复合膜进行分析, 研究L-苹果酸(MA)与D,L-乳酸(LA)的投料比(n_MA:n_LA)对复合膜性能的影响。结果显示:当n_MA:n_LA为1:1.5时, 该共聚物与CS的复合膜拉伸强度达到54.8MPa, 断裂伸长率为10.7%, 质量损失50%所需时间为28天, 细胞相对增殖率为98.7%。研究表明:通过共聚物与壳聚糖之间的聚电解质相互作用, 有效形成了结构均匀、性能改善的薄膜, 复合膜的柔韧性提高, 降解时间适当延长, 性能可由共聚物的投料比来调节。复合膜无细胞毒性, 生物相容性好, 作为手术后防组织粘连材料具有光明的应用前景。     

磷钨酸/二氧化硅/磺化聚醚醚酮复合膜的制备、表征与性能

以二氧化硅和磷钨酸改性磺化聚醚醚酮制得一种新型磺化聚醚醚酮复合膜。复合膜中杂多酸仍然保持着Keggin型PW12O430-阴离子的特征结构,二氧化硅和磷钨酸以无定形状态均匀分散于复合膜中。磷钨酸/二氧化硅/磺化聚醚醚酮复合膜的阻醇性能优于Nafion115;质子导电性能随着温度的提高有所增加。复合膜在磷钨酸中具有良好的稳定性。     

The influence of lead upd on the oxidation of glucose at platinum electrodes an electrochemical quartz crystal microbalance study

The oxidation of glucose at Pt electrodes with upd deposits of Pb in acid media has been investigated using the electrochemical quartz crystal microbalance (EQCM). Glucose alone has a small effect on the mass response but changes in upd Pb coverage have a large effect. This allows changes in upd Pb coverage to be followed easily despite the fact that the associated current is largely obscured in the cyclic voltammogram. Cyclic voltammetry at low glucose concentrations shows a multiple peak structure in the double layer region of potential at low upd coverages that is charged to the more familiar single peak as upd coverage increases. Mass responses also reveal some blockage of Pb upd by glucose or species derived from it during cyclic voltammetry. Data from mass transients show that the deliberate formation of poisons prior to addition of Pb²⁺ ions to the electrolyte results in a substantial suppression of upd coverage especially between −0.1 and 0.1 V (sce). Finally, mass transients accompanying injections of Pb²⁺ in the presence of glucose in the electrolyte reveal the suppression of adsorption of Pb²⁺ cations on an oxidised Pt surface by species derived from glucose.     

EQCM study of the ECL quenching of the tris(2,2′-bipyridyl)ruthenium(II)/tris-n-propylamine system at a Au electrode in the presence of chloride ions

Significant effect of chloride ions on the electrogenerated chemiluminescence (ECL) behavior of the ruthenium(II)tris(2,2′-bipyridine) (Ru(bpy)₃²⁺)/tri-n-propylamine (TPrA) system at a Au electrode was reported. At low concentrations (e.g., [Cl⁻] < 5 mM), the ECL was enhanced; at relatively high concentrations, however, the ECL intensity decreased with the increase of the [Cl⁻]. At [Cl⁻] = 90 mM, ∼50% and 100% ECL inhibition was observed for the first and the second ECL wave, respectively. The electrogenerated gold-chloride complexes (AuCl₂⁻ and AuCl₄⁻) which were verified using an electrochemical quartz-crystal microbalance (EQCM) method were found to be responsible for the ECL inhibition. This study suggests that care must be taken when a Au working electrode is used for ECL studies in chloride-containing buffer solutions (widely used in DNA probes) and/or with the commonly used chloride-containing reference electrodes since in these cases the ECL behavior may significantly disagree with that obtained using other electrodes and reaction media.     

Electrochemical reduction of 2,4-dinitrophenol on nanocomposite electrodes modified with mesoporous silica and poly(vitamin B1) films

Electrochemical reduction of 2,4-dinitrophenol was investigated on a glassy carbon electrode modified with a nanocomposite Santa Barbara Amorphous silica (SBA-15) film and poly(vitamin B₁) film. For sensitive and selective detections, vanadium pentoxide and cerium oxide nanoparticles were incorporated into the matrix of SBA-15. 2,4-Dinitrophenol was reduced on the modified electrode at −0.39 and −0.25 V, corresponding to the reduction of 4-dinitrophenol and 2-dinitrophenol, respectively. Both cathodic peak currents were controlled by the diffusion of 2,4-dinitrophenol. The amplitude of the peak currents was proportional to the 2,4-dinitrophenol concentration in the range of 3.0–30 μM. The modified electrode demonstrated a long lifetime for the detection of 2,4-dinitrophenol. The detection limit of 2,4-dinitrophenol was 0.5 μM. Moreover, the modified electrode was used successfully to detect 2,4-dinitrophenol in lake water.     

EQCM研究邻氨基苯甲酸/苯胺的共聚膜的溶胀/溶解行为

本文采用电化学石英微天平（EQCM）研究了现场监测了摩尔比不同的邻氨基苯甲酸／苯胺混合溶液的共聚膜在不同pH值B—R缓冲溶液中的不同性质和过程。发现溶液中邻氨基苯甲酸的含量和溶液的PH值对苯胺／邻氨基苯甲酸的共聚膜的溶胀／溶解行为均具有很大的影响。     

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。     

Adsorption of bovine serum albumin and fibrinogen on hydrophilicity-controllable surfaces of polypyrrole doped with dodecyl benzene sulfonate—A combined piezoelectric quartz crystal impedance and electrochemical impedance study

Combined measurements of piezoelectric quartz crystal impedance (PQCI) and electrochemical impedance (EI) were utilized to monitor in situ adsorption of two proteins (bovine serum albumin and fibrinogen) onto the hydrophilicity-controllable surfaces of polypyrrole (PPY) doped with dodecyl benzene sulfonate (DBS). Three of these polymer films, PPY/DBS-I, PPY/DBS-II and PPY/DBS-III, were obtained by galvanostatic electropolymerization of pyrrole in aqueous solutions containing 0.6, 1.2 and 2.0 mmol L⁻¹ sodium dodecyl benzene sulfonate (SDBS), respectively. The PPY/DBS-II obtained from electropolymerization of pyrrole in the presence of 1.2 mmol L⁻¹ SDBS (the critical micelle concentration of SDBS in aqueous solution, CMC) exhibited the greatest hydrophobicity, as suggested by contact angle measurement. And the saturation-adsorption amounts for both proteins were found to be greatest on the surface. The kinetics and adsorption mechanisms of both proteins adsorbed on these three surfaces were discussed. Langmuir and Freundlich models were used for explaining the adsorption behavior of proteins, giving that Langmuir model is better for bovine serum albumin (BSA) and both model are not so available for fibrinogen.     

化学镀Ni-P/Co-Ni-P(La)复合阴极的性能研究

化学镀Ni-P/Co-Ni-P阴极具有很好的电催化性能和抗蚀性能,但在长期电位稳定性方面和抗反电流能力方面不能令人满意。在外层引入稀土元素La后,由于稀土元素特殊的外层电子结构,促进了它的抗氧化性能。化学镀Ni-P/Co-Ni-P(La)复合阴极,分别经120℃或350℃热处理,相对于同样条件下的化学镀Ni-P/Co-Ni-P阴极,长期电解的稳定电位下降60mV和10mV,在抗反电流实验中平台电位也下降了80mV和35mV,表现出良好的电位稳定性和抗反电流能力。