pH值对4-氰基吡啶吸附行为影响的SERS研究

采用现场表面增强拉曼光谱(SERS)研究了4-氰基吡啶在不同pH值下铂电极上的吸附行为.结果表明,pH对4-氰基吡啶的吸附原子没有影响,均以吡啶环上的氮吸附在电极表面,但分子的取向不同.酸性条件下,4-氰基吡啶在正于0.6 V(SCE)的电位区间倾斜吸附,在0.6V到-0.2V以相对垂直方式吸附,而在负于-0.4V的电...     

电化学体系中吸附在金电极表面吡啶的紫外拉曼光谱研究

观察到波长为325nm的紫外光激发下吸附在金电极表面的吡啶的表面增强拉曼光谱(SERS)。结合其SERS谱随电位的变化关系,分析了其中的增强机制并表明随电位的负移吡啶的吸附方式发生改变。     

非水体系中镍表面Raman光谱研究新进展

本文利用共焦显微拉曼系统 ,获得有机乙醇溶剂中吡啶分子吸附在硝酸刻蚀镍电极表面的拉曼光谱 ,与水体系相比谱峰强度有所降低。根据表面拉曼光谱中吡啶分子环呼吸振动峰 ν1向高波数方向移动 (与液态吡啶分子相比 )推测吡啶分子通过氮原子以垂直 (或略微倾斜 )方式作用于镍电极表面 ,且随电位负移其与镍表面的作用逐渐减弱。     

吡啶,苯甲酸共存体系在Ag溶胶表面上的SERS研究

本文研究了吡啶、苯甲酸共吸附在Ag溶胶表面上的SERS谱,发现吡啶、苯甲酸加入顺序的不同对体系的SERS谱的影响不大,且苯甲酸的SERS谱相对强度大于吡啶的相对强度,说明苯甲酸的吸附能力强于吡啶。SERS谱中吡啶的环呼吸振动谱带从正常拉曼谱中的991cm~(-1)位移至1008cm~(-1),并且少量加入苯甲酸对环呼吸振动有进一步的影响,据此定性地讨论了吡啶的吸附取向。     

纯钛电极上的表面增强拉曼光谱研究

采用机械粗糙、电化学氧化还原、化学刻蚀等方法对纯钛电极表面进行粗糙,在钛基底上获得了表面增强拉曼光谱(SERS)信号。初步的实验结果表明,采用机械粗糙和电化学氧化还原方法能够获得具有一定粗糙度的电极表面,但是该表面并不具有SERS活性。而采用氢氟酸化学刻蚀方法能够获得具有SERS活性的表面,并且成功检测到吡啶分子的表面增强拉曼信号。实验尝试了在不同条件下进行刻蚀,对酸的刻蚀浓度、刻蚀时间、外接电位等影响因素作了研究,结果发现基底的SERS活性随氢氟酸浓度增大而出现最佳条件,即氢氟酸浓度0.33 Wt%,刻蚀时间为5 min时的拉曼信号最好。实验以0.01 mol·L-1吡啶为探针分子,0.1 mol·L-1 KCl为电解质,在开路电位下成功地观察了钛电极上的表面增强拉曼光谱。     

吡啶在银胶体溶液中的表面增强拉曼散射——存在平面吸附状态的可能性

自Fleischmann等在1973年首次发现吡啶在银电极上的表面增强拉曼散射(SERS)以来,人们先后研究了许多体系的SERS。如有人在真空中将苯、1,3,5-三嗪蒸汽沉积在低温银表面,观察SERS,发现苯是平躺在银上;1,3,5-三嗪在覆盖度较高时是竖立吸附,它和表面的作用是通过氮原子上的孤对电子实现。然而,大多数分子更倾向于以π键即平躺方式     

非水体系中吡啶和乙腈在铂电极上竞争吸附的表面增强拉曼光谱研究

继非水体系中CO在过渡金属表面吸附的表面增强拉曼光谱（SERS）研究之后，本文是又一篇关于非水体系中过渡金属表面SERS研究的文章。从拉曼谱峰的变化结果发现，吡啶在Pt电极表面是强烈的化学吸附，并且由于其吸附的量和吸附取向随电位在不断地变化，与水体系中吡啶（Py)在Pt电极表面的吸附相比较，SERS谱峰除了强度较低之外，在可研究的电位区间、谱峰位置以及其随电位变化等方面都存在着不同，这缘于结构较为复杂的有机溶剂分子在电极表面组成了更为复杂的界面结构，造成固／液界面的电迁移等电极动力学过程发生了变化，为了说明这一现象，文中还采用强吸附离子I^-进行研究，得到相似的结果。     

电位平均SERS技术研究二巯基嘧啶与银电极的作用

采用电位平均表面增强拉曼散射(PASERS)新方法研究二巯基嘧啶(2MP)在不同电极电位下与银电极的作用,PASERS 谱的获得是在快速调制两个电极电位的同时记录 SERS 谱。研究表明2MP在—1.1V 以正的电极电位下,通过硫原子以竖立方式作用于银电极表面,在—1.1V 以负的电位下发生电化学还原反应。     

银电极表面上C60薄膜的表面增强拉曼光谱研究

在银电极表面形成一层C60薄膜,分别在乙腈溶液和水溶液中进行表面增强拉曼光谱(SERS)研究并将两者进行比较,从而消除了溶液中的C60干扰表面吸附C60的SERS谱图的可能性.研究结果表明,C60分子对称性的降低导致SERS谱峰发生了分裂;表面电磁场的作用使得光谱选律在SERS效应中被拓宽,产生了新的拉曼谱峰.该结果与团簇吸附在粗糙银电极表面的C60分子的研究结果相似.与之不同的是在乙腈溶液和水溶液中的SERS谱图的低波数区内分别在348和311 cm-1左右出现一个新峰,经过分析可认为该峰与C60-金属基底的相互作用有关.     

吸附在铂电极上茄尼醇分子的SERS研究

本文首次报道了茄尼醇分子的常规拉曼光谱 (RRS)及该分子在铂电极上的表面增强拉曼散射(SERS)谱 ,并对它的谱带进行了初步指认。从其常规拉曼光谱和SERS谱的对比和分析推断 ,茄尼醇分子是通过CC等键吸附在铂电极表面的。这种分子RRS和SERS谱的明显差异表明 ,该分子与铂电极表面发生了强的相互作用。这种相互作用对吸附在铂电极上的茄尼醇分子结构发生了很大的扰动。     

Adsorption of Bipyridine Compounds on Gold Nanoparticle Surfaces Investigated by UV‐Vis Absorbance Spectroscopy and Surface Enhanced Raman Scattering

Adsorption behaviors of 2,2′‐bipyridine (2,2′‐BiPy), 2,4′‐bipyridine (2,4′‐BiPy), and 4,4′‐bipyridine (4,4′‐BiPy) on gold nanoparticle surfaces have been comparatively investigated by means of UV‐vis absorbance spectroscopy and surface‐enhanced Raman scattering (SERS). The three bipyridine compounds are assumed to have a standing geometry on Au surfaces as indicated from several spectral features and relative vibrational intensity factors on the basis of the electromagnetic (EM) selection rule. 2,4′‐BiPy appears to adsorb on Au surfaces via the 4‐pyridyl nitrogen atom as suggested from the stronger enhancement of the vibrational bands ascribed to the 4‐pyridyl ring. The SERS intensities for the three bipyridine compounds on Au could be ascribed to both the electromagnetic (EM) and charge transfer (CT) enhancement mechanism. The charge transfer is assumed to be dissimilar for 2,2′‐BiPy, 2,4′‐BiPy, and 4,4′‐BiPy due to their different positions of the nitrogen atoms as indicated from the disparate ν_8a band enhancements upon adsorption on surfaces.     

Adsorption of 4,4′‐thiobisbenzenethiol on silver surfaces: surface‐enhanced Raman scattering study

Adsorption of 4,4′‐thiobisbenzenethiol (4,4′‐TBBT) on a colloidal silver surface and a roughened silver electrode surface was investigated by means of surface‐enhanced Raman scattering (SERS) for the first time, which indicates that 4,4′‐TBBT is chemisorbed on the colloidal silver surface as dithiolates by losing two H‐atoms of the S H bond, while as monothiolates on the roughened silver electrode. The different orientations of the molecules on both silver surfaces indicate the different adsorption behaviors of 4,4′‐TBBT in the two systems. It is inferred from the SERS signal that the two aromatic rings in 4,4′‐TBBT molecule are parallel to the colloidal silver surface as seen from the disappearance of ν_{C H} band (3054 cm⁻¹), which is a vibrational mode to be used to determine the orientation of a molecule on metals according to the surface selection rule, while on the roughened silver electrode surface they are tilted to the surface as seen from the enhanced signal of ν_{C H}. The orientation of the C‐S bond is tilted with respect to the silver surface in both cases as inferred from the strong enhancement of the ν_{C S}. SERS spectra of 4,4′‐TBBT on the roughened silver electrode with different applied potentials reveal that the enhancement of 4,4′‐TBBT on the roughened silver electrode surface may be related to the chemical mechanism (CM). More importantly, the adsorption of 4,4′‐TBBT on the silver electrode is expected to be useful to covalently adsorb metal nanoparticles through the free S H bond to form two‐ or three‐ dimensional nanostructures. Copyright © 2007 John Wiley & Sons, Ltd.     

锌电极表面氧化成膜过程的现场拉曼光谱研究

利用电化学氧化还原法获得了具有SERS活性的粗糙锌电极,现场检测了其在不同浓度氢氧化钾溶液中随电位变化的表面拉曼光谱。锌氧化物拉曼信号在不同浓度氢氧化钾溶液中存在着很大的差异,说明氢氧根离子浓度对锌的氧化过程有很大的影响。根据所得拉曼谱图,作者尝试着给出不同浓度氢氧化钾溶液中锌的成膜过程及机理。     

溶液酸碱性对金纳米粒子在端基功能化单分子膜表面组装影响的SERS光谱研究

在4,4’-二硫联吡啶在Au表面形成自组装单分子层膜的基础上,采用表面增强拉曼散射光谱(SERS)研究了在不同pH值条件下金纳米粒子在4,4’-二硫联吡啶自组装单分子膜/Au体系表面的组装。研究结果表明,由于处于单分子膜表面的吡啶环中氮原子的质子化程度随溶液环境中pH值的变化而变化,使得金纳米粒子与单分子膜表面间的结合作用程度不同,由此会引起金纳米粒子在单分子膜表面的覆盖度存在差异,并最终导致所观测到的4-巯基吡啶自组装单分子膜的SERS光谱强度存在明显的差异。而且,令人感兴趣的是,所观测到的SERS谱峰强度随金纳米粒子组装时pH值的变化呈现出明显的规律性。结合分子结构特征的分析,初步阐明了SERS谱峰强度随pH值这一组装条件的改变而发生规律性变化的内在原因。     

The role of surface electronic states in surface enhanced raman scattering

The dependence of the surface enchanced Raman scattering (SERS) intensity on the electrode potential is considered in terms of the nonresonant adiabatic charge-transfer mechanism. Surface electronic states of a substrate metal are proposed to be responsible for the observed potential dependence of the SERS signal. The contribution of surface states to the nonlinear metal polarizability was found from electroreflectance spectra of silver single-crystals. Good agreement between the measured and calculated potential behaviour of the SERS signal was found for pyridine absorbed on the silver electrode.     

Vibrational Spectra of 2,6-Diphenyl Pyridine, 2,2′:6′,2″-Terpyridine and Meta-terphenyl

The Raman and infrared spectra of 2,6-diphenyl pyridine, m-terphenyl and 2,2′:6′,2″-1erpyridine have been analysed as metadisubstituted benzene or pyridine molecules. Complete vibrational assignment shows that some modes in the case of internal vibrations of substituents appear in pairs. The splitting of these modes have been attributed to the in-and out-of-phase motions arising out of interaction between phenyl or pyridine rings, as the case may be. In the case of meta terphenyl and terpyridine, two probable cases of Fermi resonance have been observed.     

Spectroscopic investigations and computational study of sulfur trioxide–pyridine complex

The Fourier transform infrared (FT‐IR) and FT‐Raman spectra of sulfur trioxide‐pyridine complex were recorded and analyzed. The potential‐dependent surface‐enhanced Raman scattering (SERS) was recorded from an electrochemically roughened silver electrode. The vibrational wave numbers of the compound were computed using the Hartree–Fock/6‐31G* basis and compared with the experimental values. The presence of strong pyridine ring vibrations in the SERS spectrum reveals the interaction between the pyridine ring and the silver surface. The molecule is adsorbed on the silver surface with the pyridine ring in a tilted orientation. The direction of charge‐transfer contribution to the SERS is discussed from the frontier orbital theory. The value of the calculated first hyperpolarizability is comparable to those reported for similar structures, which makes this molecule an attractive object for future studies of nonlinear optics. The optimized geometrical parameters of the title compound are in agreement with similar reported structures. Copyright © 2011 John Wiley & Sons, Ltd.     

苯丙氨酸桥联金属双卟啉的诱导圆二色光谱研究

本文报道了邻位和对位桥联苯丙氨酸锌双卟啉的合成，考查了双卟啉的分子结构对诱导圆二色性的影响。结果表明，两个卟啉环之间的π－π堆积和手性激子偶合作用是影响此类双卟啉圆二色光谱的主要因素。     

The interaction of iron and metal‐free meso‐tetra (4‐sulfonatophenyl) porphines with CVD graphene: a comparative Raman spectroscopy study

In this work, a non‐covalent interaction of iron and metal‐free meso‐tetra (4‐sulfonatophenyl) porphines (FeTPPS and TPPS, respectively) with high‐quality single‐layer graphene is studied by Raman spectroscopy. Such a kind of graphene functionalization is promising for a development of novel optoelectronic devices and sensors. Our results show that the central metal atom of porphyrin macrocycle, iron particularly, plays an important role in the integrity of FeTPPS on graphene surface; however, the predicted Raman enhancement is not significant. The interaction of metal‐free TPPS with graphene leads to the deprotonation of TPPS molecules and higher Raman enhancement values. Moreover, initially deprotonated TPPS solutions after the adsorption onto the graphene surface demonstrate the appearance of new Raman bands and significantly enhanced Raman signals. We propose that a strong interaction between deprotonated TPPS and graphene is realized through pyrrole and desulfonated phenyl rings of closely located planar TPPS molecules on the graphene surface. The results show that both the protonation of porphyrin macrocycle and the existence of central metal atom are crucial for a formation of nanocomposites with defined electronic properties. Copyright © 2014 John Wiley & Sons, Ltd.     

密度泛函理论研究过渡金属对吡啶的拉曼光谱强度的影响

本文采用杂化密度泛函理论计算了过渡金属M -Py分子的基态振动频率和拉曼光谱强度。计算结果表明过渡金属对Py分子的振动频率影响较小 ,但对Py分子的A1 振动模式的拉曼谱强度影响较大。对于A1 对称性的非C -H伸缩振动模 ,吡啶分子环呼吸振动和高频的C -C对称伸缩振动有较大的拉曼散射因子 ,我们还将此结果与典型的SERS活性金属 (铜族金属 )进行了比较