Pt电极表面及附近水行为的现场红外反射吸收光谱电化学初探

本文用现场红外反射吸收光谱电化学方法和循环伏安法研究了Pt电极表面及附近水的行为.据不同范围内得到的SNIFTIRS 谱中水峰的变化提出了三种可能的解释:(A)电极上水的吸附取向的改变;(B)电极附近水分子的长程有序的变化;(C)电极上水的氧化及还原,Pt-O化合物的形成导致薄层中水量的减少。     

Pt(111)单晶电极上乙二醇解离吸附反应动力学

运用电化学循环伏安和程序电位阶跃方法研究了乙二醇在Pt(111)单晶电极上的解离吸附过程.动力学研究的定量结果指出,乙二醇解离吸附反应的平均速率随电极电位变化呈火山型分布,其最大值在0.10 V(vs SCE)附近.测得在含2×10－3 mol•L－1乙二醇的溶液中,最大初始解离速率vi为4.35×10－12 mol•cm-－2•s－1.     

萘乙酸在多壁碳纳米管-离子液体复合修饰电极上的电催化氧化及电分析方法

运用循环伏安法(CV),计时库仑法(CC),计时电流法(CA)研究了萘乙酸(NAA)在玻碳电极(GCE),多壁碳纳米管修饰玻碳电极(MWCNTs/GCE)和多壁碳纳米管-离子液体修饰玻碳电极(MWCNTs-IL/GCE)上的电化学行为及电化学动力学性质.实验结果表明,NAA在GCE电极上于1.00V附近有一不可逆氧化峰...     

阴离子特性吸附和Pt(111)电极表面结构对乙二醇解离吸附动力学的影响

运用电化学循环伏安和程序电位阶跃方法研究了阴离子特性吸附和Pt(111)电极表面结构对乙二醇解离吸附反应动力学的影响. 结果表明, 阴离子特性吸附显著影响乙二醇的解离吸附, 在高氯酸介质中(无特性吸附)测得乙二醇解离吸附反应的初始速率vi以及解离吸附物种(DA)的饱和覆盖度均明显大于硫酸溶液(发生SO2-4/HSO-4特性吸附)中的相应值; 其平均速率v随电极电位的变化呈类似火山型分布, 最大值位于0.22 V(vs SCE)附近. 还发现通过不同处理获得的Pt(111)电极的不同表面结构对这一表面过程也具有显著的影响.     

双席夫碱铜配合物修饰玻碳电极用于碳酸饮料中苯甲酸的测定

利用溶液法制备双席夫碱铜配合物(M),采用电沉积法将制备的M沉积在玻碳电极(GCE)上制备了双席夫碱铜配合物修饰电极(M/GCE),用于测定碳酸饮料中的苯甲酸的含量。元素分析和红外光谱结果显示,试验成功制备了M;电沉积过程循环伏安曲线变化结果显示M已成功沉积在了GCE表面;扫描电镜(SEM)结果显示M/GCE表面已形成了一层聚合物膜。三电极体系选用M/GCE(工作电极)、饱和甘汞电极(参比电极)、铂丝电极(辅助电极);支持电解质采用0.1mol·L~(-1) KCl溶液;电化学方法选用循环伏安法(CV),扫描速率为50mV·s~(-1)。结果表明,苯甲酸在M/GCE上的氧化峰电位和还原峰电位分别位于-0.007,-0.359V附近,电极反应可逆性良好,受扩散控制。苯甲酸浓度与其对应的氧化峰电流在0.001 0～2.000 0mmol·L~(-1)内呈线性关系,检出限(3S/N)为0.27μmol·L~(-1)。将电极在4℃下放置7d后,苯甲酸氧化峰电流下降了4.8%。以雪碧样品为基质进行了加标回收试验,回收率为97.6%～102%,测定值的相对标准偏差(n=5)为1.2%。     

聚腺嘌呤核苷酸在金电极上的吸附氧化

采用微电极循环伏安法和吸附转移溶出伏安法研究了单链多聚腺嘌呤核苷酸Poly(A)在金电极上的伏安行为。重点了考察了Poly(A)的吸附和氧化过程。发现Poly(A)分子在金电极表面能够形成多种状态的特性吸附。影响吸附态和吸附强度的主要因素是吸附电势, 吸附时间和溶液浓度。在负电位区, 随着吸附时间(t~s)的变化, Poly(A)分子在金电极表面发生不同状态的以腺嘌呤碱基为吸附位点的强吸附, 这种以腺嘌呤碱基吸附的Poly(A)分子能够在零伏附近给出很强的氧化电流峰和对应的还原峰。     

钙钛矿型氧化物电极极化过程中的导电特性

研究了La_(0.5)Sr_(0.5)CoO_3等钙钛矿型氧化物电极的极化性质及它们对氧电化学还原的催化活性。发现在阴极极化过程中氧化物电极发生还原时,其电催化活性降低,电极阻抗明显增加,而在阳极极化过程中电极阻抗减小。讨论了影响钙钛矿型氧化物导电的因素及电极阻抗变化对电极性能的影响。     

聚腺嘌呤核苷酸在金电极上的吸附氧化

采用微电极循环伏安法和吸附转移溶出伏安法研究了单链多聚腺瞟吟核苷酸Poly(A)在金电极上的伏安行为.重点考察了Poly(A)的吸附和氧化过程.发现Poly(A)分子在金电极表面能够形成多种状态的特性吸附.影响吸附态和吸附强度的主要因素是吸附电势,吸附时间和溶液浓度.在负电位区,随着吸附时间(T_s)的变化,Poly(A)分子在金电极表面发生不同状态的以腺嘌呤碱基为吸附位点的强吸附,这种以腺嘌呤碱基吸附的Poly(A)分子能够在零伏附近给出很强的氧化电流峰和对应的还原峰.     

3,3′-四亚甲基-双-(1-苯基-5-吡啶酮-4-羧酸酯)极谱行为的研究

TPPC在0.08mol/L CH_3COONa和0.4mol/L CH_3COOH(NaAc-HAc下同)底液条件下,在电位 —1.57 V(υs.SCE)附近产生一尖锐的导数波,峰高在3.7×10~(-6)～5.6×l0~(-5)mol/L范围内呈线性关系.同时,讨论了极谱波的性质及电极反应机理.     

Cu(CMQA)(H2O)配合物修饰电极作为识别和测定变性核酸的电化学探针

合成了N-羧甲基-L-蛋氨酸-N'-8-喹啉酰胺与铜(Ⅱ)的配合物[Cu(CMQA)(H2O)],并将它修饰于玻碳电极上.用循环伏安法检验了该修饰电极的电化学特性,发现在pH 5.0的乙酸盐缓冲底液中,电极对变性核酸(ssDNA)具有电化学活性;在循环伏安图上于(Epa)180 mV及(Epc)320 mV处出现氧化还原电位峰;并发现ssDNA的浓度变化引起其峰电流的变化.当用差示脉冲伏安法(DPV)试验ssDNA浓度与峰电流的关系时,结果表示随ssDNA浓度的增加,峰电流(ip)也随之增加,且ssDNA浓度在0.05～9.0 mg·L-1范围内与ip值的增加呈线性关系.但以小牛胸腺DNA(ctDNA)及鱼精RNA(yRNA)作试验时,其浓度变化不引起峰电流的变化,在此基础上建立了一种测定ssDNA的新方法.应用于合成试样分析时,根据结果算得方法的检出限(3σ)为25μg·L-1,回收率在95%～105%之间.     

Surface-enhanced Raman scattering at the silver electrode/ionic liquid (BMIPF6) interface

This is the first report of in situ SER spectra of chemical species adsorbed on a Ag/room temperature ionic liquid (RTIL) interface. We have investigated the dependence of the SERS intensity of the RTIL derived from 1-n-butyl-3-methylimidazolium hexafluorophosfate (BMIPF6) adsorbed on a silver electrode. It has been shown that the BMI+ adsorbs on the silver electrode for potentials more negative than -0.4 V vs a Pt quasireference electrode (PQRE). In the -0.4 to -1.0 V potential range the SER spectra are similar to the Raman spectrum of the RTIL BMIPF6. At potentials more negative than -1.0 V some imidazolium ring vibrational modes and N-CH3 vibrations are enhanced, suggesting that the imidazolium ring is parallel to the surface and for potentials <-2.8 V the BMI+ is reduced to the BMI carbene. The potential dependence of the SERS intensities of Py adsorbed on a silver electrode in BMIPF6 has also been investigated. The results have shown that at potentials less negative than -0.8 V (vs PQRE) Py adsorbs at an end-on configuration forming an Ag-N bond. In the -0.9 to -1.4 V potential range Py molecules lie flat on the electrode surface and at potentials <-1.4 V Py is replaced by the BMI+. The electrochemical and SERS results have shown that Py has the effect of changing the oxidation of silver in that medium as well as the reduction of BMI+ to the BMI carbene. In the presence of Py the BMI+ reduction is observed at potentials near -2.4 V. The Ag electrode has presented SERS activity from 0.0 to -3.0 V.     

铂电极上苯和苯磺酸吸附定向的现场红外反射吸收光谱电化学方法研究

本文用现场红外反射吸收光谱电化学方法和循环伏安法研究铂电析上苯和苯磺酸的吸附定向。对于苯/铂势系, 电势在-0.6至0.0V(相对饱和甘汞电极)内, 苯主要以垂直方式吸附; 在0.0至0.8V内则主要以平躺方式吸附。对于苯磺酸/铂体系,电势在-0.4V至0.0V内, 苯磺酸分子中的苯环主要呈垂直吸附且SO~3H基团远离电极表面; 在0.0至1.0V内则主要以倾斜平躺方式吸附, SO~3H基团通过其中的两个氧原子吸附于电极表面上。     

Redox transformations of adsorbed NO molecules on a Pt(100) electrode

The electrochemical behavior of adsorbed NO molecules on a Pt(100) electrode has been studied in perchloric acid solutions by means of cyclic voltammetry. According to the literature data, a saturated NO adlayer with a coverage of ～0.5 monolayers (MLs) is formed under open circuit conditions in an acidic nitrite solution as a result of a disproportionation reaction. The saturated adlayer is stable in the potential range of 0.4–0.9 V vs. a reversible hydrogen electrode in 0.1 M HClO₄. NO molecules are oxidized at 0.9–1.1 V with the formation of adsorbed nitrite anions, and they can be reduced to ammonia at potentials less than 0.4 V. In this paper it has been shown that the adlayer stability depends on the surface coverage and extent of ordering. An unsaturated NO adlayer demonstrates NO ? NH₃ redox transformations at 0.5–0.8 V.     

离子液体中硫氰根在铂电极上吸附行为的SERS研究

利用表面增强拉曼光谱(SERS)研究了室温离子液体1-丁基-3-甲基咪唑氟硼酸盐([BMIM]BF4)中SCN-在Pt电极表面的吸附行为. 研究结果表明, 离子液体中SCN-在较宽的电位范围内吸附在Pt电极上, 且SCN-的吸附方式随着电位区间的变化而变化, 在不同的电位区间内检测到了不同的Stark位移: -0.9~0.4 V约为34 cm-1/V, 对应于S端吸附; -1.6~-1.2 V约为40 cm-1/V, 该区间以N端吸附为主, 中间电位区间为吸附方式的转变区, 且Pt电极在离子液体[BMIM]BF4中的零电荷电位约为-1.1 V(vs. Pt ).     

Gold twin-electrodes in thin-layer electrochemistry

The characteristics of a gold twin-electrode system in a thin-layer cell containing 0.1 M perchloric acid, and varying amounts of sodium chloride, were investigated by triangular sweep voltammetry. The “adsorbed oxygen” layer starts to form above 1 V, and the peak from reduction of this layer shifts from 0.88 V to 0.65 V on changing the turn-around potential from 1.02 to 2.0 V. A distinct adsorption peak appears at 0.5 V, with cathodic peaks at 0.4 V and -0.1 V. Chloride adsorption is observed at 0.6 V, with desorption at 0.4 V. The dissolution of the gold electrode to gold(III) chloride occurs at 1.1 V; but this reaction is blocked above 1.2 V by the formation of the “adsorbed oxygen” layer. The peak from the reduction of the gold(III) chloride is located at 0.7 V and is separable from the “adsorbed oxygen” reduction peak. The electrode surface obtained from the reduction of gold(III) chloride shows characteristics different from those obtained by the reduction of the “adsorbed oxygen” layer.     

Scanning tunneling microscopy of sulfur and benzenethiol chemisorbed on Ru(0001) in 0.1 M HClO4

In situ scanning tunneling microscopy (STM) combined with linear sweep voltammetry was used to examine spatial structures of sulfur adatoms (SA) and benzenethiol (BT) molecules adsorbed on an ordered Ru(0001) electrode in 0.1 M HClO4. The Ru(0001) surface, prepared by mechanical polishing and electrochemical reduction at -1.5 V (vs RHE) in 0.1 M HClO4, contained atomically flat terraces with an average width of 20 nm. Cyclic voltammograms obtained with an as-prepared Ru(0001) electrode in 0.1 M HClO4 showed characteristics nearly identical to those of Ru(0001) treated in high vacuum. High-quality STM images were obtained for SA and BT to determine their spatial structures as a function of potential. The structure of the SA adlayer changed from (2 x mean square root of 3)rect to domain walls to (mean square root of 7 x mean square root of 7)R19.1 degrees and then to disordered as the potential was scanned from 0.3 to 0.6 V. In contrast, molecules of BT were arranged in (2 x mean square root of 3)rect between 0.1 and 0.4 V, while they were disordered at all other potentials. Adsorption of BT molecules was predominantly through the sulfur headgroup. Sulfur adatoms and adsorbed BT molecules were stable against anodic polarization up to 1.0 V (vs RHE). These two species were adsorbed so strongly that their desorption did not occur even at the onset potential for the reduction of water in 0.1 M KOH.     

Adsorption of calf thymus DNA on Au(110) studied by reflection anisotropy spectroscopy

Reflection anisotropy spectroscopy (RAS) was used to investigate the adsorption of single-stranded (ss-) and double-stranded (ds-) calf thymus DNA on Au(110) in an electrochemical cell. Both types of DNA form ordered structures for electrode potentials in the range from +0.6 to -0.4 V. Both types of DNA desorb at -0.6 V and may start desorbing at lower negative potentials. When adsorbed at +0.6 V, both forms give rise to a similar RAS signal and adsorb through the phosphate groups. As the potential is reduced, the RAS intensity observed from ss-DNA increases to roughly twice that observed from ds-DNA, a result that is interpreted as due to a change in the adsorption of the ss-DNA from sites involving the phosphate groups to sites involving the bases.     

铂电极上吡啶吸附及其取向的现场红外反射吸收光谱研究

用电化学和现场红外反射吸收光谱方法研究了Pt电极上吡啶的吸附取向。结果表明,在-0.80～0.80 V(vs SCE)范围内皆存在吡啶吸附,在较负电势下(约-0.80～-0.20 V),吡啶环可能以2种方式吸附于电极表面上,随电势变正(约-0.20～0.80V)由垂直取向向平躺取向转变,该平躺吸附降低了电极表面及其附近水分子结构的有序性。     

In situ scanning tunneling microscopy of 1,6-hexanedithiol, 1,9-nonanedithiol, 1,2-benzenedithiol, and 1,3-benzenedithiol adsorbed on pt(111) electrodes

Cyclic voltammetry (CV) and in situ scanning tunneling microscopy (STM) were used to examine four dithiol molecules, including 1,6-hexanedithiol, 1,9-nonanedithiol, 1,2-benzenedithiol, and 1,3-benzenedithiol, adsorbed on well-ordered Pt(111) electrodes in 0.1 M HClO(4). The open-circuit potential (OCP) of Pt(111) electrodes decreased substantially from 0.95 to 0.3 V (versus reversible hydrogen electrode) upon the adsorption of dithol molecules, which indicates that these adsorbates injected electrons into the Pt electrode. For all dithiol molecules, ordered adlattices of p(2 x 2) and (square root 3 x square root 3)R30 degrees were formed when the dosing concentration was lower than 150 microM and the potential of Pt(111) was more negative than 0.5 V. Raising the potential of Pt(111) from 0.1 to 0.4 V or more positive values could transform p(2 x 2) to (square root 3 x square root 3)R30 degrees before it turned disarray. The insensitivity of the structure of dithiol adlayers with their chemical structures was explained by upright molecular orientation with the formation of one Pt-S bond per dithiol molecule. This molecular orientation was independent of the coverage of dithiol molecules, as nucleation seeds produced at the beginning of adsorption were also constructed with p(2 x 2). The triangular-shaped STM molecular resolution suggested 3-fold binding of sulfur headgroup on Pt(111). All dithiols were adsorbed so strongly on Pt(111) electrodes that switching the potential negatively to the onset of hydrogen evolution in 0.1 M HClO(4) or water reduction in 1 M KOH could not displace dithiol admolecules.     

自组装金团簇电极库仑台阶现象和电化学阻抗谱研究

采用示差脉冲伏安法研究了自组装单层保护金纳米团簇(C8AuMPC)在常温下二氯甲烷溶液中的量子化电容充电效应. 研究结果表明, 该团簇在-0.8~0.8 V 电位范围内有4 对明显的量子化电容充电峰. 同时采用电化学阻抗谱对C8AuMPC修饰金电极体系的界面结构进行了表征, 研究结果表明, MPC自组装层存在两个界面, 即金电极-MPC层界面和MPC层-溶液界面; 这两个界面的界面电容在MPC的零电荷电位(ca.-0.2 V)附近均基本保持不变, 随着电位正移或负移到一定程度, 界面电容发生变化. 进一步利用双隧道结金属岛库仑阻塞效应理论讨论了已有报道中对MPC量子化电容充电的理论分析结果, 并证明电化学阻抗谱也是研究MPC量子化电容充电效应的有效方法. 另外, 用示差脉冲伏安法及循环伏安法研究了电活性物种二茂铁对C8AuMPC量子化电容充电的影响, 发现溶液中的电活性物种对MPC层-溶液界面的电子传递的贡献可以忽略, 表明该界面的电子传递主要发生在纳米粒子之间.