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.     

pH值对2-(2-吡啶基)咪唑荧光光谱的影响研究

合成了2-(2-吡啶基)咪唑,并通过稳态荧光光谱研究了它在溶液中的光物理行为及溶液酸碱度的影响.发现2-(2-吡啶基)咪唑化合物存在分子内光诱导电子转移反应(PET),并且这一过程强烈地依赖于溶液的pH值,但是氮原子的质子化会影响PET过程.     

In situ SERS and SHINERS study of electrochemical hydrogenation of p-ethynylaniline in nonaqueous solvents

Surface-enhanced Raman spectroscopy (SERS) studies of electrode/solution interfaces are important for understanding electrochemical processes. However, revealing the nature of reactions at well-defined single crystal electrode surfaces, which are SERS-inactive, remains challenging. In this work, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was used for the first time to study electrochemical adsorption and hydrogenation reactions at single crystal surfaces in nonaqueous solvents. A roughened Au surface was also studied for comparison. The experimental results show that the hydrogenation of adsorbed p-ethynylaniline (PEAN) on roughened Au electrode surfaces occurred at very negative potentials in methanol because of the catalytic effect of surface plasmon resonance (SPR). However, because “hot electrons” were blocked by the silica shell of Au@SiO₂ nanoparticles and aprotic acetonitrile was an ineffective hydrogen source, surface reactions at Au(111) were inhibited in the systems studied. Density functional theory (DFT) calculations revealed that the PEAN triple bond opened, allowing adsorption in a flat configuration on the Au(111) surface via two carbon atoms. This work provides an advanced understanding of electrochemical interfacial processes at single crystal surfaces in nonaqueous systems.     

铂钌电极上乙醇解离吸附与氧化行为的原位SERS研究

应用电化学循环伏安法和原位表面增强拉曼光谱研究了乙醇在Pt-Ru电极上的解离吸附与氧化行为,首次获得了酸性介质中乙醇在Pt-Ru电极上解离吸附的表面拉曼光谱.实验表明:乙醇在粗糙铂和Pt-Ru电极上均能自发地解离出强吸附中间体CO,而且在Pt-Ru电极上,强吸附中间体CO氧化的过电位比在粗糙铂电极上降低了约140mV.初步证实酸性介质中乙醇在Pt-Ru电极上的氧化遵从双途径机理.本研究结果说明,表面增强拉曼光谱技术能拓展到有实用价值的电催化体系.     

苯在铑电极上吸附的表面增强拉曼散射光谱研究

利用成熟的电极处理方法成功地获得了苯在粗糙铑电极上电化学吸附的拉曼谱图.详细探讨了电极电位、电解质等因素对苯的电化学吸附的影响.结果表明,苯分子吸附到粗糙铑电极上后,表面拉曼谱图与纯苯本体谱图的差别很大,说明吸附后的苯分子在几何及电子结构上发生了巨大变化.苯分子可能以1,3-环己二烯的结构吸附于铑电极表面.     

纯锌电极上的表面增强拉曼光谱研究

通过化学刻蚀、电化学沉积和电化学氧化还原等粗糙方法,寻找合适的条件对锌电极表面进行预处理,以期获得吡啶在纯锌电极上的表面增强拉曼光谱(SERS).实验证明,电化学氧化还原处理是最佳的选择.以0.5mol/LNaClO4中性溶液作为电解质溶液,分别进行电化学氧化还原循环和电位阶跃两种处理.结果表明,将还原电位和氧化电位分别控制在-1.6和-0.7V时,利用共焦显微拉曼系统成功地得到了粗糙锌电极表面吸附吡啶的SERS信号.     

Effects of electrolytes used in roughening gold substrates by oxidation–reduction cycles on surface-enhanced Raman scattering

In this work, the effects of electrolytes used in roughening gold substrates by electrochemical methods on surface-enhanced Raman scattering (SERS) were first investigated. First, gold substrates were roughened by triangular-wave oxidation–reduction cycles (ORC) in aqueous solutions containing different kinds of 0.1 M electrolytes. Then Rhodamine 6G (R6G) was used as Raman probe to examine this effect of electrolytes used on the SERS observed. The result indicates that the highest intensity of SERS of R6G was obtained on the roughened Au substrate prepared in 0.1 M NaCl, which was less used in the literature. Meanwhile, it was also found that the rougher surface morphology observed, which is contributive to the higher SERS obtained, is corresponding to the smaller cathodic peak area shown in the cyclic voltammograms for roughening the Au substrate.     

乙醇在不同介质中电氧化的原位表面增强拉曼光谱研究

采用常规电化学伏安技术和电化学原位表面增强拉曼光谱(in-situ SERS)技术研究了不同介质中乙醇在粗糙铂电极上的电催化氧化行为. 发现不论在酸性、中性还是碱性介质中, 乙醇均能在粗糙铂电极上自发氧化解离生成强吸附中间体CO; 碱性介质中, CO在粗糙铂电极上基本氧化完全的电位(0.20 V)比中性和酸性介质中(0.50 V)负移了约0.30 V. 而乙醇在粗糙铂电极上CV正向扫描的氧化峰电位(-0.20 V)比酸性介质中(0.65 V)负移了约0.85 V. 比较不同介质中乙醇和CO在粗糙铂电极上的氧化峰电流和峰电位可以发现, 粗糙铂电极在碱性介质中对乙醇和CO的电催化氧化活性比中性和酸性介质中更强; 可以推测, 不论在酸性、中性还是碱性介质中, 乙醇在粗糙铂电极上的氧化过程均按双途径机理进行.     

Ultraviolet Raman study of thymine on the Au electrode

We record the potential-dependent Raman spectra of thymine adsorbed on the roughened Au electrode by ultraviolet (UV) excitation at 325 nm, and we find that the surface-enhanced Raman spectra of thymine changed intensely with the negative shift of the applied potential. When the vibrational mode changes, the resonance potential (potential of maximum intensity) varies accordingly, indicating that the thymine molecules were chemisorbed on the roughened Au surface. The charge transfer (CT) mechanism could probably explain the experiment results in the present work.     

乙醇在粗糙铂电极上解离吸附与氧化的原位SERS研究

采用循环伏安法和原位表面增强拉曼光谱（SERS）研究了乙醇在粗糙铂电极上的吸附和氧化行为,获得了乙醇在粗糙铂电极上解离吸附的表面增强拉曼光谱.研究表明,在酸性介质中,乙醇能在粗糙铂电极上自发地解离出强吸附物种CO,在低波数区检测到桥式和线性吸附CO的铂碳键的伸缩振动信息;乙醇在粗糙铂电极上的氧化反应受扩散步骤控制;从分子水平初步证实乙醇的氧化是通过双途径机理进行的.     

银电极表面异亮氨酸单分子膜结构和表面性质的表面增强拉曼光谱研究

利用表面增强拉曼光谱(SERS)技术研究了在粗糙化银电极表面吸附的异亮氨酸自组装单层膜结构及其表面性质随溶液酸碱性和电极电位改变的特征.研究结果表明溶液pH值的变化并没有显著改变异亮氨酸分子在银电极表面以去质子化羧基吸附为主的特征.借助于高氯酸根离子这一SERS光谱探针,对异亮氨酸单分子膜的表面酸碱性质进行了表征和分析.而就电位改变对该单分子膜结构的影响而言,在所研究的电位范围内,单分子膜中的异亮氨酸分子是通过去质子化羧基与氨基两个位点而吸附的,且吸附作用随电位负移而呈现有规律的变化.     

电化学方法获得具有表面增强拉曼活性镍电极的研究

利用纯电化学手段获得了具有较强表面增强拉曼活性的镍电极, 改进了原有的镍电极表面预处理方法. 结果表明, 在0.5 mol/L的NaClO4溶液中, 结合电化学阶跃技术和循环伏安技术, 可以得到合适的粗糙镍电极; 同时, 还得到了探针分子吡啶在该粗糙镍电极表面随电极电位变化的表面增强拉曼光谱(SERS), 此时谱峰强度获得了极大的增强; 还研究了粗糙镍电极的扫描电子显微镜(SEM)图像, 并估算出其SERS增强因子约为104, 此结果比以前的镍电极表面粗糙方法所能达到的增强因子高一个数量级.     

Surface-enhanced Raman scattering studies on the adsorption of p-nitrobenzoic acid at Au electrode under different potential with ultraviolet excitation

The potential-dependent surface-enhanced Raman spectrum of adsorbed p-nitrobenzoic acid (PNBA) on the roughened Au electrode has been obtained by using ultraviolet (UV) excitation at 325 nm. The surface-enhanced Raman spectra of PNBA intensely changed when the voltage was in the rang of negative value, and the electrode potential at which the resonance (potential of maximum intensity) occurs varied when the vibrational mode changes, indicating that the PNBA molecules were chemisorbed on the roughened Au surface. The charge transfer (CT) mechanism could probably explain the experiment results in the present work.     

Electrochemical and surfaced-enhanced Raman spectroscopic investigation of CO and SCN- adsorbed on Au(core)-Pt(shell) nanoparticles supported on GC electrodes

Core-shell Au-Pt nanoparticles were synthesized by using a seed growth method and characterized by transmission electron microscopy, X-ray diffraction, and UV-vis spectroscopy. Au(core)-Pt(shell)/GC electrodes were prepared by drop-coating the nanoparticles on clean glassy carbon (GC) surfaces, and their electrochemical behavior in 0.5 M H2SO4 revealed that coating of the Au core by the Pt shell is complete. The electrooxidation of carbon monoxide and methanol on the Au(core)-Pt(shell)/GC was also examined, and the results are similar to those obtained on a bulk Pt electrode. High quality surface-enhanced Raman scattering (SERS) spectra of both adsorbed CO and thiocyanate were observed on the Au(core)-Pt(shell)/GC electrodes. The potential-dependent SERS features resemble those obtained on electrochemically roughened bulk Pt or Pt thin films deposited on roughened Au electrodes. For thiocyanate, the C-N stretching frequency increases with the applied potential, yielding two distinctly different dnu(CN)/dE. From -0.8 to -0.2 V, the dnu(CN)/dE is ca. 50 cm(-1)/V, whereas it is 90 cm(-1)/V above 0 V. The bandwidth along with the band intensity increases sharply above 0 V. At the low-frequency region, Pt-NCS stretching mode at 350 cm(-1) was observed at the potentials from -0.8 to 0 V, whereas the Pt-SCN mode at 280 cm(-1) was largely absent until around 0 V and became dominant at more positive potentials. These potential-dependent spectral transitions were attributed to the adsorption orientation switch from N-bound dominant at the negative potential region to S-bound at more positive potentials. The origin of the SERS activity of the particles is briefly discussed. The study demonstrates a new method of obtaining high quality SERS on Pt-group transition metals, with the possibility of tuning SERS activity by varying the core size and the shell thickness.     

循环伏安法对铜(Ⅱ)-1,10-二氮杂菲配合物电化学性质的研究

铜(Ⅱ)-1,10-氮杂菲[Cu(phen)x]^2 (x=1,2,3)的水溶液体系是以铜：二氮杂菲为1：1,1：2和1：3为组成的混合配合物体系,根据水溶液中该配合物的平衡常数.     

电极表面Ag(δ+)-NH3络合物的表面增强拉曼散射效应

本文采用氧化还原循环处理电极首次得到Ag/0.1 mol L~(-1)NH_3+0.1 mol L~(-1)NH_4Cl体系中吸附在银电极上氨分子的表面增强拉曼散射(SERS)效应。按氨分子在电极表面上的吸附量为每平方厘米8×10~(15)计算, 增加因子为1.2×10~5。谱峰强度及位置随电极电位改变。吸附氨分子的SERS谱与Ag(NH_3)_2~+的正常拉曼光谱类似。本文结果表明电极表面上存在Ag(δ+)络合物, 它可能是SERS效应的活性中心, 用这个概念可较好地解释本文实验结果。通过谱图分析给出了Ag(δ+)表面络合物的可能结构模式。     

苯骈噻唑类化合物在银电极表面上的SERS

自七十年代中期,吸附在银电极表面上的吡啶的表面增强拉曼散射效应被发现以来,大量的有关表面增强拉曼散射效应的研究集中在含氮有机化合物上.对含硫化合物,尤其是对含硫和氮的杂环化合物的研究较少.在六十年代中期,Califano,Sbrana 和Davidovics 等人及其合作者分别研究了噻唑和异噻唑的红外和拉曼谱.本文研究了含巯基化合物,即系列的苯骈噻唑类化合物的普通拉曼谱(NRS)及其吸附在银电极表面上所产生的表面增强拉曼谱(SERS),并讨论了噻唑杂环上不同取代基对谱图的影响.     

氧化乐果的振动光谱及其表面增强拉曼散射研究

采用ATR-FTIR、FT-拉曼表征了氧化乐果在酸、碱、中性条件下的振动光谱,获得了氧化乐果分子较为全面的结构振动信息;以金/银核-壳粒子为基底,获得了不同浓度及其酸碱条件下氧化乐果的表面增强拉曼散射(SERS)光谱,考察了其分子在该基底表面的吸附状态及其酸碱影响,推测了氧化乐果的SERS机理;结果表明:νas(NH),νas(CH3),Amide Ⅰ,ν( POC ),ν( PO ),ν(C-S)为氧化乐果分子特征振动;中性条件下,氧化乐果浓度低于2.0×10-2 mol/L已无明显SERS,酸、碱条件下,在2.0×10-10 mol/L氧化乐果分子与基底的作用仍显著,尤其酸性的SERS更强;氧化乐果主要以磷酸酯结构与基底表面作用,探讨了酸碱条件下的不同水解历程对该作用的影响,为研究有机磷农药的形态变化提供了参考.     

Rh和Pt超薄层电极上的CO吸附行为(英文)

利用沉积在粗糙金电极上的过渡金属超薄层电极技术 ,我们获得了氢及一氧化碳在Rh和Pt表面上吸附的拉曼信号 ,并对两者之间的相互作用进行了分析 ..我们还进行了二氧化碳在这两种金属表面的还原行为的初步研究 ,以及对不同方式获得的一氧化碳吸附拉曼信号的特点进行了分析 .     

SERS study of the interaction of thiourea with a copper electrode in sulphuric acid solution

The electrochemical interaction of thiourea with a copper electrode in sulphuric acid solution was investigated using Fourier transform Raman and in situ surface-enhanced Raman scattering (SERS) spectroscopy. SERS spectra of thiourea at a copper electrode were obtained in solutions containing greater than 5 ppm thiourea; the spectra obtained were consistent with adsorption of the molecule on the copper electrode via the sulphur atom. The SERS spectra provide evidence of complex formation involving thiourea and sulphate species at the electrode surface.