碱性介质中甘氨酸在Pt电极上解离吸附和氧化反应的原位红外反射光谱研究

运用原位红外反射光谱研究了碱性介质中甘氨酸在Pt电极上的解离吸附和氧化反应行为,并利用纳米Pt膜电极的异常红外效应鉴定反应过程中生成的表面吸附物种.结果表明:甘氨酸在Pt电极上极易发生解离,生成强吸附于电极表面上的氰基负离子,该吸附物种在低于0V电位下能稳定存在,并抑制甘氨酸的进一步反应.当电位高于0.2V时,氰基负离子被氧化为氰酸根离子进入溶液,使甘氨酸发生氧化反应,生成氰酸盐和碳酸盐等产物.     

碱性介质中L-赖氨酸在纳米金膜电极上的吸附和氧化过程

采用原位红外反射光谱(in situ FTIRS)和循环伏安法(CV)研究了碱性介质中L-赖氨酸在纳米金膜电极(nm-Au/GC)上的解离吸附和氧化过程. 研究结果表明, 在碱性溶液中以阴离子形式存在的赖氨酸[-OOC—CH—NH2—(CH2)4—NH2]在低电位区间(-0.95~-0.80 V, vs. SCE)发生部分解离, 生成AuCN-物种(约2110 cm-1), 同时赖氨酸阴离子的羧基侧还可通过两个氧原子与金电极表面相互作用. 随着电位的升高, 吸附态CN-氧化产生NCO-, OCN-和AuCN, 其对应的红外吸收峰分别位于2254, 2168和2226 cm-1附近.     

碱性介质中甘氨酸在Pt电极上解离吸附和氧化反应的原 …

运用原位红外反射光谱研究了碱性介质中甘氨酸在Ｐｔ电极上的解离吸附和氧化反应行为,并利用纳米Ｐｔ膜极的异常红外效应鉴定反应过程中生成的表现吸附物种。结果表明,甘氨酸在Ｐｔ电极上极易发生解离,生成强吸附于电极表面上的氰基负离子。     

纳米金膜电极上CN~-吸附的电化学和原位红外反射光谱研究

应用循环伏安(CV)和原位红外反射光谱(in situFTIRS)研究碱性介质中氰(CN-)在纳米金膜电极(nm-Au/GC)上的吸附行为.结果显示,当研究电极电位低于0.0 V时,CN-可稳定吸附在nm-Au/GC电极表面,高于0.0 V,则发生氧化脱附.发现nm-Au/GC表面具有异常红外效应(AIREs),即吸附态CN-谱峰呈现出与本体Au电极不同的方向倒反、红外吸收增强(39.2倍)以及半峰宽增加的异常光谱特征.本研究将纳米薄膜材料的这一AIREs从过渡金属拓展到币族金属,进一步证明AIREs是迄今研究的金属及合金纳米材料的普遍特性.     

核-壳结构Au-Pt纳米粒子的光谱表征和电催化性能

用化学还原法合成了核-壳结构Au-Pt纳米粒子.紫外可见光谱(UV-Vis)、电化学循环伏安(CV)和透射电子显微镜(TEM)表征结果指出，所合成的核-壳结构Au-Pt纳米粒子为球形，平均直径为27 nm.以CO为分子探针，结合透射红外光谱研究，发现CO以孪生吸附态形式(COT)吸附在Au-Pt纳米粒子上，在2110 cm－1和2063 cm－1附近分别给出对称和反对称红外吸收峰. CV研究结果指出Au-Pt/GC电极对CO的氧化有较高的催化活性，起始氧化电位较本体Pt电极提前了0.45 V，峰电位提前了0.11 V.     

二十四面体Pt纳米晶电极上甲酸解离吸附反应动力学研究

研究了甲酸在二十四面体Pt纳米晶（THHPtNCs）电极表面解离吸附反应过程.电化学原位红外反射光谱结果显示,甲酸在低电位（-0.20V（SCE））即可在THHPtNCs电极上氧化到CO2,同时发生分子内化学键断裂生成吸附态CO物种.运用程序电位阶跃暂态方法定量研究甲酸解离吸附反应动力学,测得5×10^-3mol·L^-1 HCOOH＋0.1mol·L^-1 H2SO4溶液中甲酸在THHPtNCs电极上解离吸附的最大平均速率υamax为13.19×10^-10mol·cm^-2·s^-1,是商品Pt/C催化剂电极上υamax的1.5倍.研究结果揭示了THHPtNCs的反应活性显著高于Pt/C催化剂.     

酸性和碱性介质中甘氨解离吸附和氧化的EQCM研究

用电化学石英晶体微天平（EQCM）研究酸性和碱性介质中甘氨酸在Pt电极上的吸附和氧化过程，结果表明，甘氨酸的解离吸附和氧化行为与溶液的酸碱性密切相关，酸性溶液中甘氨酸吸附软弱，碱性溶液中则产生强吸附物，且当电位低于0V（vs.SCE)时可吸附于Pt电极表面，此外，碱性溶液中甘氨酸还表现出较高的电氧化活性，通过EQCM定量检测上述过程中Pt电极电极表面的质量变化，测定了不同电位区间（氢区、双电层区和氧区）每传递一个电子所对应的电极表面吸附物的平均摩尔质量。     

酸性和碱性介质中甘氨酸解离吸附和氧化的EQCM研究

用电化学石英晶体微天平(EQCM)研究酸性和碱性介质中甘氨酸在Pt电极上的吸附和氧化过程.结果表明,甘氨酸的解离吸附和氧化行为与溶液的酸碱性密切相关.酸性溶液中甘氨酸吸附较弱,碱性溶液中则产生强吸附物,且当电位低于0V(vs.SCE)时可吸附于Pt电极表面.此外,碱性溶液中甘氨酸还表现出较高的电氧化活性.通过EQCM定量检测上述过程中Pt电极表面的质量变化,测定了不同电位区间(氢区、双电层区和氧区)每传递一个电子所对应的电极表面吸附物种的平均摩尔质量.     

Au@SiO2膜/Ti电极吸附吡啶的表面增强拉曼光谱研究

基于壳层隔绝纳米粒子增强拉曼光谱技术,合成了Au@SiO₂纳米粒子,并对其进行了相关表征. 结果表明,包裹的二氧化硅层连续、致密,Au@SiO₂膜/Ti电极上可获得金属钛电极上吸附吡啶分子的高质量表面增强拉曼光谱（SERS）信号. 通过Pt、Ni电极的测试,证实该信号源于吸附在基底表面的吡啶分子. 此外,Au@SiO₂膜/Ti电极上吸附吡啶分子的现场SERS光谱研究表明,在-0.1 V ~ -0.6 V电位区间,吡啶分子平躺吸附,从-0.6 V起吸附的吡啶分子由平躺逐转变为垂直,而当电位为-1.2 V时,电极表面析氢,吡啶脱附.     

Pt电极表面共吸附层NO和CO氧化还原的CV及原位FTIR研究

应用电化学循环伏安方法（CV）和原位傅里叶变换红外反射光谱（in situ FTIRS）研究了酸性溶液中Pt多晶电极表面NO和CO的共吸附行为及吸附态CO对吸附物种NO氧化还原反应的影响．研究结果表明,0．20V（VS．SCE）时,CO和NO能同时稳定吸附在Pt电极表面,CO以线性吸附态（CO L）存在,NO以桥式吸附态（NOB）和线性吸附态（NO L）共存．CO L 的共存使得NO的还原电流峰电位负移约0．024V,并且促使不易被氧化的NO B在0．93V处被氧化．原位FTIRS研究进一步表明,NO可以置换预吸附在电极表面的CO,NO和CO在Pt多晶电极表面的吸附是一个竞争吸附的过程．在0．45V-1．2V电位区间,NO和CO都能转化为环境友好产物,分别为NO3-和CO2．且Pt电极表面共吸附物种CO的量直接影响NO B的氧化产物NO3-的生成量．     

Sb在Au电极上不可逆吸附的电化学过程

用电化学循环伏安法和电化学石英晶体微天平(EQCM)技术研究了Sb在Au电极上不可逆吸附的电化学过程. 研究结果表明, 在-0.25 V到0.18 V(vs SCE)范围内, Sb可在Au电极上稳定吸附, 并且在0.15 V附近出现特征氧化还原峰. 根据EQCM实验数据, 在电位0.18 V时, Sb在Au电极上的氧化产物是Sb2O3; 同时Sb的吸附阻止了电解液中阴离子和水在Au电极上的吸附. 当电极电位超过0.20 V时, Sb2O3会被进一步氧化成Sb5+化合物, 同时逐渐从Au电极表面脱附.     

异烟酸在碱性溶液中金电极上的现场表面增强振动光谱研究

应用表面增强红外吸收光谱法、循环伏安法和微分电容法研究了0.1 mol•L^－1 KClO₄和0.1 mol•L^－1 KCl碱性化溶液(pH 10)中, 异烟酸(INA)在Au电极表面的吸附取向和结构. 结果表明: －0.5～0.2 V (vs. SCE)间INA阴离子(INA^－)通过其羧酸根上的两个氧原子垂直吸附在Au电极表面; 特性吸附Cl^－对上述吸附结构无实质影响. 进一步的表面增强拉曼光谱的测试表明即使在－0.8～－0.5 V, 极少量吸附的INA^－很可能仍维持上述基本构型.     

Electrochemical Behavior of Irreversibly Adsorbed Sb on Au Electrode

The electrochemical processes of irreversibly adsorbed antimony (Sb_ad) on Au electrode were investigated by cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM). CV data showed that Sb_ad on Au electrode yielded oxidation and reduction features at about 0.15 V (vs saturated calomel electrode, SCE). EQCM data indicated that Sb_ad species were stable on Au electrode in the potential region from −0.25 to 0.18 V (vs SCE); the adsorption of Sb inhibited the adsorption of water and anion on Au electrode at low electrode potentials. Sb₂O₃ species was suggested to form on the Au electrode at 0.18 V. At a potential higher than 0.20 V the Sb₂O₃ species could be further oxidized to Sb(V) oxidation state and then desorbed from Au electrode.     

Electrochemical evaluation of lectin-sugar interaction on gold electrode modified with colloidal gold and polyvinyl butyral

In this work, ConA and CramoLL lectins were immobilized on gold nanoparticles (AuNp) with polyvinyl butyral (PVB), and adsorbed on the surface of gold (Au) electrodes. Electrochemical impedance spectroscopy (EIS), in the frequency range from 100mHz to 100KHz, and cyclic voltammetry (CV), from -0.2 to 0.7V, were performed on these electrodes, in phosphate buffer (PBS) solution containing 10mM K(3)[Fe(CN)(6)]/K(4)[Fe(CN)(6)] (1:1) mixture as a redox probe. EIS and CV measurements showed that redox probe reactions on the modified Au electrodes were partially blocked due to the adsorption of AuNp-ConA-PVB and AuNp-CramoLL-PVB. SEM images showed the presence of aggregates of AuNp-ConA on PVB spherules in a tridimensional structure on the surface of the Au electrode. Bovine serum albumin (BSA) was adsorbed on the AuNp-Lectin-PVB modified electrode in order to block the remaining free gold sites. Both EIS and CV techniques yielded results that confirm positive responses of the lectins to ovalbumin agglutination. These results indicate an improvement of the sensitivity for detection of sugars that can be applicable to construction of a biosensor sensitive to glycoproteins in solution.     

Surface poisoning during electrocatalytic monosaccharide oxidation reactions at gold electrodes in alkaline medium

In the present study, the surface poisoning of electrocatalytic monosaccharide oxidation reactions at gold electrodes were investigated. In the cyclic voltammetric studies, the electrocatalytic oxidation of aldohexose and aldopentose type monosaccharides, aminosugars, acetyl-glucosamine and glucronamide were observed at gold plate electrodes in alkaline medium. However, in controlled-potential electrolytic studies ranging −0.3 to −0.2 V in reaction solutions, current flows during electrolyses decreased quickly with time, except when glucosamine was used as a substrate.Results from surface enhanced infrared adsorption (SEIRA) spectroscopic measurements at an evaporated gold electrode for the electrocatalytic oxidation of glucose in 0.1 mol dm⁻³ NaOH at −0.3 V and Gaussian simulated spectra indicated that the gluconic acid as a 2-electron oxidation product and/or its analogs adsorbed onto the gold surface. Electrochemical quartz crystal microbalance (EQCM) measurement results, along with surface adsorption results from surface poisoning at the gold electrode during electrolytic reactions, suggested that gluconic acid and/or its analogs adsorbed vertically onto electrode surfaces in a full monolayer packing-like conformation. In the case of the electro oxidation of glucosamine in 0.1 mol dm⁻³ NaOH at −0.2 V, the obtained SEIRA spectra and EQCM results, clearly indicated that the glucosaminic acid as a 2-oxidation glucosamine product did not strongly bind onto the gold electrode surface.     

Spectroelectrochemical examination of the interaction between bacterial cells and gold electrodes

The interaction between bacterial cells of Pseudomonas fluorescens (ATCC 17552) and gold electrodes was analyzed by cyclic voltammetry (CV) and attenuated total reflection-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). The voltammetric evaluation of cell adsorption showed a decrease in the double-layer capacitance of polyoriented single-crystal gold electrodes with cell adhesion. As followed by IR spectroscopy in the ATR configuration, the adsorption of bacterial cells onto thin-film gold electrodes was mainly indicated by the increase in intensity with time of amide I and amide II protein-related bands at 1664 and 1549 cm(-1), respectively. Bands at 1448 and 2900 cm(-1) corresponding to the scissoring and the stretching bands of CH2 were also detected, together with a minor peak at 1407 cm(-1) due to the vs COO- stretching. Weak signals at 1237 cm(-1) were due to amide III, and a broad band between 1100 and 1200 cm(-1) indicated the presence of alcohol groups. Bacteria were found to displace water molecules and anions coadsorbed on the surface in order to interact with the electrode intimately. This fact was evidenced in the SEIRAS spectra by the negative features appearing at 3450 and 3575 cm-1, corresponding to interfacial water directly interacting with the electrode and water associated with chloride ions adsorbed on the electrode, respectively. Experiments in deuterated water confirmed these assignments and allowed a better estimation of amide absorption bands. In CV experiments, an oxidation process was observed at potentials higher than 0.4 V that was dependent on the exposure time of electrodes in concentrated bacterial suspensions. Adsorbed bacterial cells were found to get closer to the gold surface during oxidation, as indicated by the concomitant increment in the main IR bacterial signals including amide I, a sharp band at 1240 cm(-1), and a broad one at 1120 cm(-1) related to phosphate groups in the bacterial membranes. It is proposed to be due to the oxidation of lipopolysaccharides on the outermost bacterial surface.