具有伸展链构象聚苯胺/蒙脱土混杂纳米复合物的合成与表征

报道了具有聚苯胺伸展链构象的聚苯胺／ 粘土（ Ｐ Ａｎ／ Ｍ Ｍ Ｔ） 混杂纳米复合物的合成与表征．用插层聚合的方法将聚苯胺分子链嵌入层状蒙脱土的片层之中,从而得到一种高电导率的聚苯胺／ 层状硅酸盐混杂纳米复合物．通过 Ｘ 射线衍射（ Ｘ Ｒ Ｄ） ,付立叶红外（ Ｆ Ｔ Ｉ Ｒ） ,四探针电导率测量以及定性和定量的电子光谱分析等手段对产物进行了表征,结果表明,９０ ％ 以上的聚苯胺的分子链被插入蒙脱土的片层中间．由于聚苯胺分子链在受限的纳米空间生成,聚苯胺以伸展的单分子链构象存在．该构象在苯胺的通常聚合中不可能生成．通过对聚合过程进行吸收光谱监测,发现该聚合是扩散控制过程．     

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.     

层层自组装原位聚合聚苯胺复合膜成膜机理研究

从苯胺单体出发, 通过原位聚合、现场掺杂以及基于静电力的层层自组装制备了聚苯胺复合膜. 通过苯胺活性溶液的温度及颜色变化跟踪聚合反应进程, 同时考察不同聚合反应阶段所得聚苯胺复合膜的紫外-可见吸收, 并进一步探讨聚苯胺复合膜的成膜机理. 研究表明, 成膜机制是由聚合反应初始阶段的苯胺阳离子或苯胺阳离子自由基通过静电作用快速吸附到负电性的基片表面, 形成均匀的聚合中心, 链增长生成聚苯胺; 该聚苯胺在酸性条件下经现场掺杂显电正性, 可吸附电负性的聚苯乙烯磺酸钠(PSS), 以此循环层层组装得到多层聚苯胺复合膜.     

基于邻苯二胺电聚合膜的抗体固定化方法研究

Si等 [1] 在压电石英晶体金电极表面先电聚合了一层聚苯胺膜 (PAn) ,再于 PAn膜上电聚合一层聚间苯二胺膜 (Pm PD) ,形成一双层膜 (Pm PD和 PAn) ,而后通过戊二醛共价键合固定化方法 ,实现对生物蛋白质分子的固定和对生物细胞的测定 .但在上述方法中 ,传感器难以再生且蛋白质分子的固定量较少 .参照文献 [2 ],本文提出了一种在电聚合邻苯二胺薄膜上进行可逆的抗体固定化的新方法 .通过控制溶液的 p H值 ,在带正电的电聚合邻苯二胺膜表面先自组装一层聚阴离子聚苯磺酸根 (PSS)层 ,使传感器得到一个带负电的载体表面 ,再通过静电吸附 ,…     

聚合介质酸度对聚苯胺的结构和性能的影响

不论电化学还是化学聚合,酸度对聚苯胺(PAn)的合成都有很大影响,说明只有在酸性条件下才能合成电活性的聚苯胺,鉴于聚合介质的酸度对聚苯胺的影响尚无详细的报道,本文研究了聚合介质酸度对聚苯胺的结构和性能的影响.     

循环伏安法的电扫描方式对苯胺聚合产物形貌影响的观察

在含有0.2 mol.L-1苯胺的0.5 mol.L-1H2SO4溶液中,以扫描速度50 mV.s-1,扫描电位为-0.1~0.9 V,采用循环伏安法(CV),在金属Ti基体上,通过控制扫描方式分别得到了颗粒状、纤维状及管-片状的苯胺聚合产物,分析了形成不同形貌聚苯胺的原因,并通过扫描电子显微镜(SEM)、循环伏安法和电化学阻抗谱(EIS)对不同形貌聚苯胺的结构和性能进行了表征.结果表明,不同形貌聚苯胺的形成是由于聚苯胺的成核及生长模式不同,而无论何种形貌的聚苯胺膜都具有很大的比表面积和良好的导电性能,其中,管-片状聚苯胺的膜层阻抗最小,导电性能最好.     

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。     

恒电位条件下制备聚苯胺PAn及其电化学行为

恒电位条件下在玻碳电极上用电化学聚合法制备了聚苯胺膜，研究了聚合条件如聚合电位，聚合介质，苯胺浓度等对聚苯胺膜化学性质的影响，从而确定了制备聚苯胺的最佳聚合方法和条件，并讨论了在不同支持电解质溶液中和不同ＰＨ值条件下ＰＡｎ膜的循环伏安行为，认为５５０ｍＶ出现的氧化还原峰与阴离子的掺杂有关。     

聚苯胺修饰电极制备过程中几个问题的探讨

报道聚苯胺修饰电极制备中尚须引起人们重视的几个问题。主要包括：循环伏安法扫描电位上限对聚合的影响，恒电位法最佳的聚合电位，以及仅具２００ｍＶ和９００ｍＶ两峰聚苯胺膜的制备，聚合电量对不同制备方法影响的差异性等等。并对制备聚苯胺修饰电极的几种方法进行了比较，从而指出了最佳的聚合方法和条件。     

聚苯胺对钯催化甲酸电氧化反应的促进作用

钯基纳米材料是甲酸电氧化反应的优良催化剂.本工作制备了两个系列钯基催化剂,并考察了聚苯胺对钯上甲酸电氧化反应的助催化作用.一种是以聚苯胺为基底,在其表面电沉积钯纳米粒子,制得nPANI/Pd催化剂(n表示聚合苯胺的循环数);另一种是直接在商业Pd/C催化剂表面电聚合苯胺,制得Pd/C/nPANI催化剂.结果显示,聚苯胺单独存在时对甲酸电氧化反应没有催化活性,但其可对钯上甲酸电氧化反应呈现明显的促进作用,且促进作用与聚苯胺的厚度(聚合循环数)密切相关.在两个系列催化剂中,15PANI/Pd和Pd/C/20PANI显示出最高的催化性能.15PANI/Pd中钯的质量比催化活性是纯钯催化剂的7.5倍; Pd/C/20PANI中钯的质量比催化活性和本征催化活性分别是商业Pd/C催化剂的2.3和3.3倍.钯催化性能的提升与聚苯胺和钯纳米粒子间的电子效应有关.     

Effects of lateral diffusion on morphology and dynamics of a microscopic lattice-gas model of pulsed electrodeposition

The influence of nearest-neighbor diffusion on the decay of a metastable low-coverage phase (monolayer adsorption) in a square lattice-gas model of electrochemical metal deposition is investigated by kinetic Monte Carlo simulations. The phase-transformation dynamics are compared to the well-established Kolmogorov-Johnson-Mehl-Avrami theory. The phase transformation is accelerated by diffusion, but remains in accord with the theory for continuous nucleation up to moderate diffusion rates. At very high diffusion rates the phase-transformation kinetic shows a crossover to instantaneous nucleation. Then, the probability of medium-sized clusters is reduced in favor of large clusters. Upon reversal of the supersaturation, the adsorbate desorbs, but large clusters still tend to grow during the initial stages of desorption. Calculation of the free energy of subcritical clusters by enumeration of lattice animals yields a quasiequilibrium distribution which is in reasonable agreement with the simulation results. This is an improvement relative to classical droplet theory, which fails to describe the distributions, since the macroscopic surface tension is a bad approximation for small clusters.     

The Role of PANI/Nafion on the Performance of ORR in Gas Diffusion Electrodes of PEM Fuel Cell

In this work, gas diffusion electrodes were fabricated from Nafion and polyaniline (PANI) nanofibers. The goal of this work was to find the optimal combination of Nafion and polyaniline in gas diffusion electrodes. The electrodes were evaluated for oxygen reduction reaction effectiveness, and their electrochemical properties were investigated by using electrochemical techniques, and PEM single cell. The results revealed that electrodes containing both Nafion and polyaniline worked more efficiently than electrodes containing either Nafion or polyaniline only. The optimum combination is noted as 0.6 mg/cm² PANI and 0.4 mg/cm² Nafion.     

Spectroelectrochemical processes in polyaniline films prepared by different methods

Basic in situ spectroelectrochemical methods of the studying of the polyaniline electrosynthesis processes and doping-dedoping of the polyaniline films prepared by different procedures are overviewed. The advantages of the combining of different spectroelectrochemical methods in a single experiment are discussed and the extra information on the processes of electrosynthesis and electrochemical doping-dedoping of polyaniline prepared by the combinations of methods is analyzed. Components of the polyaniline electronic absorption spectra are analyzed and spectroelectrochemical properties of polyaniline films prepared by vacuum evaporation are studied by a complex of methods; the results of the studies are presented.     

Electrochemical Behavior of Methanol Influenced by Polyaniline Incorporated with Ferrocenesulfonic-carboxylic Acid

After the synthesis of polyaniline in the presence of ferrocenesulfoniccarboxylic acid, its influence on the electrochemical reaction of methanol was studied. The result indicates that the ferrocenyl in ferrocenesulfoniccarbexylic acid plays an important role in the electrocatalytic oxidation of methanol. CH3OH is adsorbed on PANI-Fc before its electrocatalytic oxidation. When the concentration of methanol is 2 mol/L, it begins to be oxidized. The effect of scan rate on the electrochemical reaction of methanol was also studied and 5 mV/s was favourable. It is another method to insert a metal catalyst in polyaniline without its electrodeposition.     

Preparation of oriented titanium phosphate and tin phosphate/polyaniline hybrid films by electrochemical deposition

The preparation of hybrid films of metal (Ti and Sn) phosphate nanosheets and polyaniline by simultaneous electrophoretic and electrolytic deposition was performed in an acetonitrile solvent. Emeraldine polyaniline was intercalated between the phosphate nanosheets with a monolayer arrangement. The obtained hybrid films were several tens of micrometers in thickness. The ratio of incorporated polyaniline to metal phosphate in the hybrid films reaches to around 0.45 and 0.30 at suitable concentrations of tetrabutylammonium hydroxide (TBAOH). These amounts correspond with occupancy of polyaniline in the interlayer gallery of several tens percent. Fractions of voids in a horizontal direction were around 22 and 1% in titanium phosphate/polyaniline and tin phosphate/polyaniline hybrid films, respectively. Thus, anodic electrodeposition makes it possible to form thick films of intercalation compounds of alpha-titanium and tin phosphates with polyaniline. These hybrid films were examined for redox activity. The cyclic voltammetry results of these films confirmed that the hybrid films have redox activity by polyaniline. For these voltammograms, the maximum current was observed in the tin phosphate/polyaniline hybrid deposited for 15 min. The redox activity of these hybrids possibly depends on the mesoscopic texture of the film, especially on the amount of voids in a horizontal direction.     

Pb deposition on I-coated Au(111). UHV-EC and EC-STM studies

This article concerns the growth of an atomic layer of Pb on the Au(111)( radical3 x radical3)R30 degrees -I structure. The importance of this study lies in the use of Pb underpotential deposition (UPD) as a sacrificial layer in surface-limited redox replacement (SLRR). SLRR reactions are being applied in the formation of metal nanofilms via electrochemical atomic layer deposition (ALD). Pb UPD is a surface-limited reaction, and if it is placed in a solution of ions of a more noble metal, redox replacement can occur, but limited by the amount of Pb present. Pb UPD is a candidate for use as a sacrificial layer for replacement by any more noble element. It has been used by this group for both Cu and Pt nanofilm formation using electrochemical ALD. The I atom layer was intended to facilitate electrochemical annealing during nanofilm growth. Two distinctly different Pb atomic layer structures are reported, studied using in situ scanning tunneling microscopy (STM) with an electrochemical flow cell and ultrahigh vacuum surface analysis combined directly with electrochemical reactions (UHV-EC). Starting with the initial Au(111)( radical3 x radical3)R30 degrees -I, 1/3 monolayer of I on the Au(111) surface, Pb deposition began at approximately 0.1 V. The first Pb UPD structure was observed just below -0.2 V and displayed a (2 x radical3)-rect unit cell, for a structure composed of 1/4 monolayer each of Pb and I. The I atoms fit in Pb 4-fold sites, on the Au(111) surface. The structure was present in domains rotated by 120 degrees. Deposition to -0.4 V resulted in complete loss of the I atoms and formation of a Pb monolayer on the Au(111), which produced a Moiré pattern, due to the Pb and Au lattice mismatch. These structures represent two well-defined starting points for the growth of nanofilms of other more noble elements. It is apparent from these studies that the adsorption of I- on Pb is weak, and it will rinse away. If Pb is used as a sacrificial metal in an electrochemical ALD cycle and adsorbed I atoms are employed for electrochemical annealing, I atoms will need to be applied each cycle.     

In situ electrochemical SERS studies on electrodeposition of aniline on 4-ATP/Au surface

The electrochemical polymerization of 0.01 M aniline in 1 M H₂SO₄ aqueous solution on roughened Au surface modified with a self-assembled monolayer (SAM) of 4-aminothiophenol (4-ATP) has been investigated by in situ electrochemical surface-enhanced Raman scattering spectroscopy (SERS). The repeat units and possible structures of the electrodeposited polyaniline (PANI) film were proposed; i.e., aniline monomer is coupled in head-to-tail predominately at the C₄ of aniline and amine of 4-ATP, and the thin PANI film is orientated vertically to substrate surface. Simultaneous Raman spectra during potential scanning indicate clearly that the ultrathin PANI film (in initial growth of the film) consists of semiquinone radical cation (IP⁺), para-disubstituted benzene (IP and IP⁺) and quinine diimine (NP) while it is oxidized, and without quinine diimine and semiquinone radical cation while reduced. Meanwhile, the results confirm that 4-ATP monolayer shows a strong promotion on the electrodeposition of aniline monomer, and a possible polymerization mechanism was proposed.     

The role of the organic layer functionalization in the formation of silicon/organic layer/metal junctions with coinage metals

The design of silicon/alkyl layer/metal junctions for the formation of optimal top metal contacts requires knowledge of the mechanistic and energetic aspects of the interactions of metal atoms with the modified surface. This involves (a) the interaction of the metal with the terminal groups of the organic layer, (b) the diffusion of metal atoms through the organic layer and (c) the reactions of metal atoms with the silicon surface atoms. The diffusion through the monolayer and the metal catalyzed breakage of Si-C bonds must be avoided to obtain high quality junctions. In this work, we performed a comprehensive density functional theory investigation to identify the reaction pathways of all these processes. In the absence of a reactive terminal group, gold atoms may penetrate through a compact alkyl monolayer on Si(111) with no energy barrier. However, the presence of thiol terminal groups introduces a high energy barrier which blocks the diffusion of metals into the monolayer. The diffusion barriers increase in the order Ag < Au < Cu and correlate with the stability of metal-thiolate complexes whereas the barriers for the formation of metal silicides increase in the order Cu < Au < Ag in correlation with the increasing metallic radii. The reactivity of gold clusters with functionalized Si(111) surfaces was also investigated. Metal silicide formation can only be avoided by a compact monolayer terminated by a reactive functional group. The mechanistic and energetic picture obtained in this work contributes to understanding of the factors that influence the quality of top metal contacts during the formation of silicon/organic layer/metal junctions.     

Electrocrystallization of rhodium clusters on thiolate-covered polycrystalline gold

This study reports on the electrochemical deposition of rhodium metal clusters on a polycrystalline gold electrode, modified with a monolayer of dodecanethiol through self-assembly from solution. The deposition process was investigated using cyclic voltammetry, chronoamperometry, and electrochemical quartz crystal microbalance. It is shown that the presence of the thiol monolayer drastically alters the nucleation and growth mechanism compared with the mechanism on the bare gold electrode. The small uncovered gold domains, located at the imperfections in the thiolate monolayer which are induced by the gold nanoroughness, act as nucleation sites for small rhodium clusters. At longer times, these clusters can outgrow the organic monolayer. The resulting surface morphology was characterized by scanning electron microscopy. Rhodium electrocrystallization on the bare gold substrate resulted in an ensemble of a very large amount of very small clusters that are difficult to distinguish from the gold roughness. In contrast, in the presence of a self-assembled monolayer (SAM) of dodecanethiol covalently attached to the gold electrode, the resulting deposit consisted of an ensemble of hemispherical particles. The size distribution of the rhodium particles obtained by using double step chronoamperometry was compared to the ones obtained with cyclic voltammetry and "classical" chronoamperometry. It is shown by X-ray photoelectron spectroscopy that the SAM is still present after rhodium deposition on the thiolate-covered gold substrate. Because the rhodium clusters are directly attached to the gold substrate and can thus easily be electrified, the resulting interface could be used as a composite electrode consisting of a random array of gold supported rhodium nano/microparticles separated from each other by an organic phase. On the other hand, it is shown that the SAM is easily removed by electrochemical oxidation without dissolving the rhodium clusters and, thus, leaving a different array of rhodium clusters on the gold surface compared with the topography obtained in the absence of the SAM. From this point of view, substrate modification with such "removable" organic monolayers was found to be an interesting tool to tune the nano- or microtopography of electrochemically deposited rhodium.