水在Ag电极上取向与结构的SERS研究──不同电极电位和NaClO4浓度的影响

将特殊的ORC方法、薄层溶液技术和差谱方法相结合,在较宽的电位区间(-0.7-2.0V),获得了不含任何(类)卤素离子的NaClO₄/Ag体系中水的SERS谱.结果表明,不同浓度的NaClO₄体系中,尽管体相水的结构有很大差别,但电极表面的吸附水有相似的结构特征,即由于电场作用而使有序性较高;并且随电极电位由极负电位向零电荷电位(PZC)变化时可能都经历着由单氢端吸附转变为双氢端吸附,继而又转向氧端吸附的取向变化过程.利用SERS技术特有的检测表面物种的高灵敏度,可观察到NaClO₄浓度引起的表面水的SERS谱的一些细微差异,依此较详细讨论了NaClO₄浓度对表面水的结构和取向变化过程的影响.     

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.     

离子液体中Fe电极界面结构的SERS光谱研究

采用高灵敏度的表面增强拉曼光谱(SERS)技术, 结合不同长度的探针分子, 通过电化学调控研究了Fe电极在离子液体中的表面增强因子、零电荷电位、界面吸附及界面双电层结构. 利用壳层隔绝纳米粒子增强拉曼光谱(SHINERS)技术提高表面吸附物种的拉曼信号, 降低高浓度本体的信号干扰, 研究了1-丁基-3-甲基咪唑四氟硼酸盐([BMIm]BF₄)离子液体本身在Au@SiO₂修饰的Fe电极表面的吸附行为. 结果表明,[BMIm]BF₄在Au@SiO₂修饰的Fe电极表面的吸附行为随电位变化而变化. 在-1.3 V以正区间, 咪唑阳离子以垂直吸附为主, 随电位负移逐渐倾斜甚至平躺吸附于电极表面; 当电位负至-2.3 V, 咪唑阳离子还原成卡宾. 再分别以不同分子长度的硫氰根(SCN^-)和4-氰基吡啶(4-CNPy)为探针分子, 发现SCN^-在[BMIm]BF₄中以N端吸附在纯Fe电极上, 三键频率随电位变化的速率, 即Stark系数为17 cm^-1/V; 4-CNPy以吡啶环上的N垂直吸附于Fe电极上, 频率保持不变, 即Stark系数接近零. 以上结果表明, 在离子液体中电极界面双电层与水体系的差别较大, 电位主要分布在电极紧密层中, 几乎无分散层存在. 此外, 还计算了[BMIm]BF₄中Fe电极的增强因子约为1.5×10².     

时间分辨表面增强拉曼光谱(TRSERS)研究硫脲衍生物与ClO4^-的共吸附行为

运用时间分辨表面增强拉曼光谱(TRSERS)结合电位双阶跃的方法, 研究了硫脲衍生物甲基硫脲(MTU)和烯丙基硫脲(ATU)在银电极表面与ClO4^-离子的共吸附行为, SERS强度-时间曲线表明它们各自相应的SERS谱峰强度随电位阶跃的响应速率不同, 离电极表面较近的基团的特征谱峰强度的响应速率较快; MTU以S端且垂直吸附在电极表面,ATU也以S端和表面发生化学吸附, 但整个分子斜躺吸附在电极表面上。     

银电极上4-氨基安替比林原位表面增强拉曼光谱电化学

在银电极表面4-氨基安替比林(4-AAP)分子自组装,形成单分子膜层.应用表面增强拉曼散射(SERS)光谱原位考察不同电位下4-AAP在电极表面的吸附机理及其组装液pH值对组装分子与银作用方式的影响.依据密度泛函数(DFT)理论预测4-AAP分子振动模式及其SERS光谱归属.结果表明:在开路电位下,组装层中的4-AAP分子以N15和O3为位点,由苯环倾斜和比林环垂直的方式吸附在银表面;但随着外加电位负移,4-AAP分子的苯环趋于垂直吸附而比林环则逐渐以平行方式靠近银表面.在-0.8V电位下,4-AAP分子从银表面脱附.酸性溶液中组装,形成的4-AAP膜层以N15和O3为位点吸附于银表面,比林环倾斜而苯环直立;碱性条件下,分子的吸附位点不变,比林环呈平行取向,而苯环倾斜于银表面.     

胞嘧啶吸附在粗糙金电极上的表面增强拉曼光谱

应用电化学伏安法和表面增强拉曼光谱(SERS)研究在-1.0 V~0 V电位区间内胞嘧啶于粗糙金电极表面的吸附行为.结果表明,在本实验的电位区间,胞嘧啶是以其N3位垂直吸附在粗糙金电极表面的.在负电位区间环呼吸振动模的强度出现极大值,与其它振动模强度相比,作者认为电磁场的增强和电荷转移均使该谱峰的拉曼信号增强.胞嘧啶的环呼吸振动频率随着电位负移而红移,这意味着它与金电极的成键作用减弱.同时也表明SERS谱可用于研究生物分子在金属电极表面的吸附行为.     

2,2′-联吡啶与锌电极作用的表面增强拉曼光谱研究

利用表面增强拉曼光谱(SERS)对2,2′-联吡啶分子在锌电极表面的吸附进行了研究. 实验表明, 2,2′-联吡啶和锌电极有较强的相互作用, 2,2′-联吡啶和锌表面的氧物种存在竞争吸附, 起始电位较正时, 氧物种的吸附使2,2′-联吡啶吸附电位负移；起始电位较负时, 2,2′-联吡啶的吸附抑止氧物种的吸附, 使其吸附电位正移, 且相同电位下氧化种的吸附量大大减少. 同时当电极电位由正往负移时, 吸附在锌表面的2,2′-联吡啶会发生构型转化, 在－1.3 V下以顺式构型垂直吸附, 而当电位负移至－1.4 V时则以反式构型吸附；而电极电位由负往正移时, 在研究电位区间内2,2′-联吡啶都以反式构型吸附, 不存在构型的转化.     

锌电极上2-巯基吡啶自组装单层的原位表面增强拉曼光谱电化学观察

利用原位表面增强拉曼散射(SERS)技术, 观察了2-巯基吡啶在锌电极上单层吸附和脱附行为. SERS实验结果表明, 2-巯基吡啶分子主要通过巯基上的硫原子垂直吸附于锌表面. 原位SERS光谱电化学发现, 当外加电位达到－1.4 V vs. SCE时, 分子开始从表面脱附, 并伴随吸附构型变化, 在－1.6 V时发生完全脱附.     

铂电极上吸附芳香分子的表面增强红外光谱研究

应用衰减全反射表面增强红外吸收光谱法分别研究了0.1 mol•L^－1 HClO₄中对硝基苯甲酸(PNBA)和0.1 mol•L^－1 KClO₄中吡啶(Py)在铂电极上的吸脱附. 结果表明在较高电位下(0.3～0.7 V vs. SCE) PNBA是通过其羧基脱质子后羧酸根的两个氧原子等位吸附在Pt电极表面, 而随着电位的负移, 除PNBA逐步脱附外, 还呈现出单个氧原子吸附的谱学特征. 光谱强度与电位的关系表明PNBA在铂电极表面吸脱附的中间电位约为0.2 V vs. SCE. 吡啶的吸附主要是通过氮原子的孤对电子及脱氢后的α碳原子与Pt电极表面键合. 在较宽的电位区间(0.4～－0.4 V vs. SCE)吡啶的吸附方式和取向基本维持不变.     

电化学方法和表面增强拉曼光谱技术研究钴电极表面咪唑的吸附和缓蚀行为

利用电化学和表面增强拉曼光谱方法研究了咪唑和钴电极的相互作用. 分析并指认了不同电极电位下咪唑溶液中钴电极上的表面增强拉曼光谱(SERS), 发现随电极电位的变化, 在钴电极表面存在三种表面物种并且可以在一定程度上相互转化. 在较负电位(−1.2~−0.9 V)区间, 咪唑在钴电极表面以吸附物种为主, 随电位正移, 吸附取向由通过吡啶N垂直吸附逐渐向C2=N3双键倾斜; 在较正电位区间(−0.8~−0.7 V)内, 吸附咪唑的信号逐渐减弱乃至消失, 而钴和咪唑的络合物信号逐渐增强; 开路电位(−0.6 V)下出现很强的钴的氧化物谱峰. 同时, 文中比较了钴电极表面在空白溶液和加入咪唑后的溶液中的极化曲线, 发现咪唑对钴电极的缓蚀作用较为明显. 该研究结果表明, 联合表面增强拉曼光谱技术和电化学方法使得人们可以从分子水平上了解表面物种和电极表面间复杂的相互作用.     

硫脲与多种阴离子共吸附行为的拉曼光谱研究

在电化学的研究与应用中，因硫豚（1’川可用作电镀添加剂、金属的缓蚀剂和一些电极反应的催化剂［‘］而受到人们的广泛重视．早在三十年代初就开展了有关水溶液和非水溶液体系中硫豚在不同金属电极表面的吸附行为的研究【’，’］、随着光谱电化学技术的建立、发展和不断完善     

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.     

硫脲及其衍生物的SERS和量子化学研究

Adsorption of thiourea (TU) and ethylthiourea(ETU) on roughened silver electrode was investigated using in- situ surface enhanced Raman spectroscopy(SERS). Using quantum chemistry and HSAB theories, the influences of electrode potential and the different substituent groups on SERS were discussed. TU is chemisorbed perpendicularly by Ag-S bond on silver at E=-0.3 V and adsorption of TU turns into a parallel orientation at E=-0.9 V. ETU is always chemisorbed at an angle from Ag. The adsorption of ETU is through C=C and C=O groups at E=-0.3 V, and mainly through C=C at E=-0.9V.     

Orientation of 6-mercaptopurine SAMs at the silver electrode as studied by Raman mapping and in situ SERS

Self-assembled monolayers (SAMs) of 6-mercaptopurine (6MP) on a silver electrode in acid and alkaline media were investigated by a combination protocol of the SERS technique with Raman mapping, and it was found that the adsorption mode of 6MP SAMs changed with the pH value of the environment. Quantum calculations for the vibrational mode were performed by the BLYP/6-31G method. 6MP was adsorbed on the silver electrode with a tilted orientation via S, N1, and N7 atoms in acid medium, while the SAMs adopted head-on adsorption modes with the S atom and the N1 atom anchoring the silver surface in alkaline medium. However, 6MP SAMs turned to the same upright orientation on the electrode through the S and N7 atoms when either acid or basic solution was removed. Stability of 6MP SAMs was observed by in situ SERS spectroelectrochemical measurements. The results reveal that the desorption potentials of 6MP SAMs formed under acid and alkaline conditions from the Ag electrode were at ca. -1.3 V and -1.6 V vs SCE, respectively.     

SERS谱峰对电极电位阶跃的不同响应速率的证据

八十年代以来,人们除继续研究表面增强拉曼散射(SERS)效应的复杂机理和发现有关新体系外,逐渐将注意力集中在将SERS 技术应用于生物、分析和电化学研究,以获得固/液体系的界面结构和吸     

Adsorption of enantiomeric and racemic cysteine on a silver electrode--SERS sensitivity to chirality of adsorbed molecules

The adsorption of both (L- and D-) enantiomeric forms of cysteine on the silver electrode surface was studied by surface-enhanced Raman scattering spectroscopy (SERS) as a function of electrode potential and pH value of the solution. It was demonstrated that at potentials more positive than -0.7 V (for pH 3) or -0.8 V (for pH 2 or lower), in acidic environment L-cysteine molecules are adsorbed mainly as P(H) (gauche) conformer, in zwitterionic form with the COO- groups close to the surface. At more negative potentials, NH3+ groups deprotonate at the surface with simultaneous weakening of the interaction of the carboxylic groups with the surface. Spectroscopic evidence for at least partial protonation of the COO- groups at strongly acidic solutions was given by observing the C=O stretching band at frequency lowered by about 30 cm(-1) in comparison with that observed for crystalline cysteine hydrochloride. It points to the considerable enhancement of the strength of hydrogen bonds and may be ascribed to the formation of cyclic L-cysteine dimers at the electrode surface. In neutral and alkaline solutions, adsorbed L-cysteine molecules have deprotonated amino groups at wide potential range. Similar spectroelectrochemical experiments were performed for D-cysteine and for a racemic mixture of D,L-cysteine. As expected, results for D-cysteine were similar to those for L-cysteine. However, for racemic mixture at acidic pH, the spectral effects corresponding to potential-induced transition from adsorbed zwitterions to neutral molecule were considerably smaller. This effect was discussed in terms of stereoselective dimerization of cysteine molecule at the electrode surface.     

Raman Spectroscopic Studies on the Complexation and Adsorbed Behaviour of Thiourea

Raman spectroscopic studies on thiourea (TU) in highly acidic media (e. g. >3 mol/L HC1O4) show that TU as a solution species is protonated through its sulphur atom and forms complex with anions. However, as an adsorbed species, TU is protonated via the nitrogen atom and adsorbed at the silver electrode surface through the sulphur atom. The distinct effects of pH and anions of the solution on the surface enhanced Raman (SER) spectra of TU were investigated. In acidic and neutral solutions, TU is coadsorbed with anions through its NH3 and - NH2 groups respectively.     

表面增强拉曼光谱研究稳定剂TAI在银上的吸附

用表面增强拉曼光谱的方法研究 4-羟基--甲基-1,3,3a,7-四氮茚(TAI)在金属银上的吸附.实验表明TAI分子是通过分子上的N原子以化学吸附的方式吸附在银电极上.电极处理的氧化-还原循环次数并不影响振动频率,但在一定范围内对表面增强拉曼光谱的吸收强度有明显影响.     

苯胺在银和金电极上的表面增强拉曼光谱

聚苯胺作为性能较好的导电高聚物有很大的应用潜力,有关其聚合和导电机理的研究受到广泛重视。表面增强拉曼光谱(SERS)能现场(in situ)检测表面吸附分子、提