共查询到20条相似文献,搜索用时 31 毫秒
1.
Mengtao Sun Lixin Xia Maodu Chen 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(2):509-514
Self-assembled dynamics of silver nanoparticles and self-assembled dynamics of 1,4-benzenedithiol (1,4-BDT) adsorbed on silver nanoparticles were investigated experimentally with surface-enhanced Raman scattering (SERS) and theoretically with density functional theory (DFT) and finite difference time domain (FDTD) method. The absorption spectroscopy of 1,4-BDT in silver sol at different time intervals was measured, which give the indirect evidence of self-assembled dynamics of silver nanoparticles and self-assembled dynamics of 1,4-benzenedithiol (1,4-BDT) adsorbed on silver nanoparticles. To obtain the direct evidence of self-assembled dynamics of silver nanoparticles and self-assembled dynamics of 1,4-benzenedithiol (1,4-BDT) adsorbed on silver nanoparticles, the SERS of 1,4-BDT were measured experimentally and investigated theoretically. The appearances of S–S stretching band (revealing the formation of multilayers of 1,4-BDT), and strongly enhanced S–C stretching, C–C ring stretching vibrational modes clearly show self-assembled dynamics of 1,4-BDT. 相似文献
2.
The adsorption behaviors of 4-mercaptobenzoic acid on silver and gold nanoparticles were studied by surface-enhanced Raman scattering (SERS) and density functional theory. The silver and gold films by electrodeposition have the same excellent characteristics as SERS-active substrates. At the same, the SERS spectra indicate that 4-mercaptobenzoic acid molecules are adsorbed on the surfaces of gold nanoparticles through the S atom, and that the carboxyl group is far away from surface of gold nanoparticles, and that there is a certain angle between the plane of benzene ring and gold film. However, 4-mercaptobenzoic acid molecules are adsorbed on the surfaces of silver nanoparticles through the carboxyl group, and the S atom is far away from surface of silver nanoparticles, and there is also a certain angle between the plane of benzene ring and the surface of silver nanoparticles. Here it is demonstrated the calculated Raman frequencies are in good agreement with experimental values, and the calculated Raman frequencies are also helpful to infer the adsorption behaviors of 4-mercaptobenzoic acid molecules. 相似文献
3.
The adsorption behavior of 1,4-benzenedithiol (1,4-BDT) on colloidal gold and silver surfaces has been investigated by means of surface-enhanced Raman scattering (SERS). 1,4-BDT chemisorbed dissociatively on both gold and silver surfaces but as mono- and dithiolate, respectively. Regardless of the bulk concentration of 1,4-BDT, only a monolayer was assembled on the silver surface with a flat orientation by forming two Ag–S bonds. On the gold surface, the monothiolate species,1,4-BDT−1, appeared to assume a rather flat orientation at a very low surface coverage, but as the surface coverage was increased, the adsorbate took a perpendicular orientation. Furthermore, when the bulk concentration of 1,4-BDT was close to that required for a full-monolayer coverage limit, a band assignable to the S–S stretching vibration appeared at 536 cm−1 in the gold sol SERS spectra. A separate ellipsometry measurement performed with vacuum-evaporated gold substrates revealed that up to tetralayers could be assembled on gold in 1 mM n-hexane solution of 1,4-BDT while at best a bilayer formed in either methanol or ethanol solution. The different adsorbate structure of 1,4-BDT on gold and silver was overall quite comparable to that of p-xylene-α,α′-dithiol. 相似文献
4.
B Pergolese A Bigotto 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(6):1191-1197
The SER spectra of 1H-indazole adsorbed on silver hydrosol were recorded in the 1800-100 cm(-1) and in the 3200-2800 cm(-1) regions. The SERS data were interpreted on the basis of previous vibrational assignments, with the help of the results of DFT calculations carried out using the 6-31G** basis. From the comparison of SER and normal Raman spectra it can be deduced that 1H-indazole is non-dissociatively adsorbed on metal surface and that it interacts with silver sol via nitrogen atoms and ring pi-system. The molecular plane assumes a tilted orientation with respect to the silver surface. The effect of varying the concentration of adsorbate was also evaluated. The observed changes of the relative intensities of some enhanced bands suggest that the molecule assumes a more tilted orientation upon lowering the concentration of the adsorbate. 相似文献
5.
《Vibrational Spectroscopy》2006,40(1):127-132
Surface enhanced Raman spectroscopy has been used to study the potential controlled behavior of 2-thiouracil adsorbed on silver, gold and copper electrodes. Comparison of the normal Raman and SER spectra shows that the molecule adsorbs chemically to the metallic surfaces through its deprotonated sulfur atom. The position of the molecular aromatic ring in respect to the surface normal under potential modulation was analyzed using the electromagnetic theory's selection rules. Our data indicate that for all electrodes the surface potential induces a molecular reorientation leading to a more upright or tilted position. 相似文献
6.
Tian Zhongqun 《高等学校化学研究》1989,(3)
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. 相似文献
7.
Cao Y Li YS Tseng JL Desiderio DM 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(1):27-34
The oxidative stability of self-assembled monolayer (SAM) of thiols on silver was examined with matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS). A benzenesulfinate (BS) monolayer on silver was also prepared and investigated with MALDI-TOF-MS and surface-enhanced Raman scattering (SERS). The presence of sulfinate, sulfonate, and thiosulfonate fragment ions reveals that thiolate monolayers oxidize in the air. The relative abundance of C6H5SO2- and C6H5SO3- species in the mass spectra of the monolayer with different air-exposure times provides an estimation of the oxidation progress. In the vibrational spectrum, the large red shift of v(SOO-), combined with the lack of a shift of v(C-S) upon adsorption, indicates its bidentate O-coordination. The orientation of the confined molecules, based on the Raman surface selection rules, was derived from the preferential enhancement of the different functional groups. The benzene ring of BS was found almost normal to the metal surface as a result of the intermolecular forces; that geometry excludes the possibility of the pi-system of the benzene ring from participating as another binding site. The SER spectra of BS obtained via a selective etching process confirms these observations. 相似文献
8.
9.
Theoretical Vibrational Raman and Surface‐Enhanced Raman Scattering Spectra of Water Interacting with Silver Clusters 下载免费PDF全文
Marta Sanchéz‐Lozano Marcos Mandado Ignacio Pérez‐Juste Dr. Jose M. Hermida‐Ramón 《Chemphyschem》2014,15(18):4067-4076
In this study, we analyzed the Raman spectrum of a water molecule adsorbed on a cluster of 20 silver atoms, and the plasmonic electromagnetic effect of the silver surface was also considered to give a theoretical prediction of the surface‐enhanced Raman scattering spectrum. The calculations were performed at the density functional theory (DFT) level by using both frozen and unfrozen silver clusters. Two different models were used to consider the plasmonic enhancement; one of them was a modified classical (dipole) model and the other was the coupled perturbed Hartree–Fock method with excitation frequencies obtained from time‐dependent DFT calculations and with proper detuning of these frequencies. The importance of small geometrical distortions of the silver surface in the orientation of the adsorbed water was shown. Moreover, it was shown how the symmetry of the transition dipole moment and the symmetry of the vibrational modes influence the Raman intensities of the SERS spectrum. 相似文献
10.
Santos VO Alves MB Carvalho MS Suarez PA Rubim JC 《The journal of physical chemistry. B》2006,110(41):20379-20385
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. 相似文献
11.
V. T. Joy T. K. K. Srinivasan 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1999,55(14):2899
Adsorption of thiourea, N,N′-diphenylthiourea (DIPTU), N-ethyl-N′-phenylthiourea (ETPTU) and N-(p-nitrophenyl)thiourea (NPTU), from acidic and neutral solutions, on chemically deposited silver film substrates are investigated using Fourier transform surface-enhanced Raman scattering (FT-SERS) technique. A strong band in the low frequency region, around 230 cm−1 in the FT-SERS spectra of all these systems, assigned to Ag–S stretch, indicates a preferential adsorption through the sulfur atom. The frequencies and bandwidths of benzene ring vibrational modes in ETPTU as well as DIPTU are almost unaffected by adsorption indicating that benzene rings do not interact directly with the silver surface. A cis-cis conformation (both imino H-atoms cis with respect to thione sulfur atom) is proposed for DIPTU and ETPTU on the silver surface. In the case of NPTU, an additional interaction through the benzene ring is also observed as shown by the frequency shifts and band broadening of some benzene ring modes and weak intensity of the C–H stretching band. 相似文献
12.
Panicker CY Varghese HT Philip D Nogueira HI Castkova K 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,67(5):1313-1320
Methyl(2-methyl-4,6-dinitrophenylsulfanyl)ethanoate was prepared by nucleophilic substitution. FT-IR and FT-Raman spectra of methyl(2-methyl-4,6-dinitrophenylsulfanyl)ethanoate were recorded and analyzed. Surface-enhanced Raman scattering (SERS) spectrum was recorded on a silver colloid. The vibrationl wavenumbers were computed by density functional theoretical (DFT) computations at the B3LYP/6-31G* level and they were found to be in good agreement with the experimental values. The molecule is adsorbed on the silver surface with the benzene ring in a 'tilted orientation'. 相似文献
13.
GU Wei LIU Guokun REN Bin WU Deyin GU Renao & TIAN Zhongqun . Department of Chemistry College of Chemistry Chemical Engineering Suzhou University Suzhou China . State Key Laboratory for Physical Chemistry of Solid Surfaces Department of Chemistry College of Chemistry Chemical Engineering Xiamen University Xiamen China 《中国科学B辑(英文版)》2005,48(6):497-503
As one of the most widely used transition-metals, Co plays an important role in the study of metal mate-rials. The alloys of Co are often used as magnetic ma-terials because of their intense magnetism[1,2]. As an active metal and owing to high catalytic a… 相似文献
14.
Abdelsalam M Bartlett PN Russell AE Baumberg JJ Calvo EJ Tognalli NG Fainstein A 《Langmuir : the ACS journal of surfaces and colloids》2008,24(13):7018-7023
In situ electrochemical surface enhanced Raman spectra (SERS) for an immobilized monolayer of a flavin analogue (isoalloxazine) at nanostructured silver surfaces are reported. Unique in the present study, the flavin is not directly adsorbed at the Ag surface but is attached through a chemical reaction between cysteamine adsorbed on the Ag surface and methylformylisoalloxazine. Even though the flavin is held away from direct contact with the metal, strong surface enhancements are observed. The nanostructured silver surfaces are produced by electrodeposition through colloidal templates to produce thin (<1 microm) films containing close-packed hexagonal arrays of uniform 900 nm sphere segment voids. The sphere segment void (SSV) structured silver surfaces are shown to be ideally suited to in situ electrochemical SERS studies at 633 nm, giving stable, reproducible surface enhancements at a range of electrode potentials, and we show that the SER spectra are sensitive to subfemtomole quantities of immobilized flavin. Studies of the SER spectra as a function of the electrode potential show clear evidence for the formation of the flavin semiquinone at the electrode surface at cathodic potentials. 相似文献
15.
Surface-enhanced Raman scattering (SERS) of 2-benzoylpyridine (2-BP) adsorbed on silver hydrosols has been investigated. It has been observed that with a small change in the adsorbate concentration, the SER spectra of 2-BP show significant change in their features, indicating different orientational changes of the different part of the flexible molecule on the colloidal silver surface with adsorbate concentration. The time dependence of the SER spectra of the molecule has been explained in terms of aggregation of colloidal silver particles and co-adsorption and replacement kinetics of the adsorbed solute and solvent molecules on the silver surface. The broad long-wavelength band in the absorption spectra of the silver sol due to solute-induced coagulation of colloidal silver particles is found to be red-shifted with the increase in adsorbate concentration. The surface-enhanced Raman excitation profiles indicate that the resonance of the Raman excitation radiation with the new aggregation band contributes more to the SERS intensity than that with the original sol band. 相似文献
16.
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. 相似文献
17.
18.
Sajan D Fischer A Joe IH Jayakumar VS 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,64(3):580-585
The surface geometry of (RS)-phenylsuccinic acid molecule was studied by analysis of the SERS spectra of aromatic dicarboxylic acid adsorbed on silver colloid surfaces. For a reliable analysis of the SERS spectrum, we also performed density functional theoretical calculations. The SERS spectral features indicated that the RSPSA molecules should bound to the silver as dicarboxylate, with a strongly tilted orientation with respect to the normal to the surface. Such a tilted orientation was presumed to occur by the simultaneous sigma and pi-type coordination of carboxylate groups to silver surface caused by the steric hindrance and electrostatic repulsion between the two carboxylate groups, and thereby RSPSA on silver was easily displaced with aromatic carboxylic acids. A sigma-type coordination therefore seemed to be more important than a pi-type coordination for aromatic carboxylic acid derivatives to assemble on a silver surface. The large enhancement of in-plane bending, out of plane bending and ring breathing modes in the surface-enhanced Raman scattering spectrum indicates that the molecule is adsorbed on the silver surface in a 'at least vertical' configuration, with the ring perpendicular to the silver surface. 相似文献
19.
SERS活性光纤光谱微探针研究 总被引:2,自引:0,他引:2
用真空蒸镀银岛膜和银溶胶自组装膜两种方法对光纤探针进行表面增强拉曼(SERS)活性修饰,构造了圆锥型SERS活性光纤光谱微探针.选取几个有代表性的分子作为检测样品,得到了低浓度样品的SERS光谱,对样品BVPP的检测下限达到10-9mol/L.比较两种修饰光纤探针的检测结果可知,银溶胶自组装膜修饰更有优势. 相似文献
20.
本文利用线性电势扫描的方法研究了几种苯并噻唑类化合物及巯基苯基四氮唑在银上的吸附机理。结果表明:2.巯基苯并噻唑和巯基苯基四氮唑以化学吸附方式,通过分子上巯基与银表面的作用形成分子紧密排列的吸附层。25℃下,PMT可以在银表面形成紧密单层。这种吸附在较高吸附温度下可以转化为多层,且完全覆盖银表面。在含Br-的溶液中,它可以阻碍Br-与表面的接触。在较大的浓度下,2-甲基苯并噻唑和苯并噻唑也可以在银表面的某些位置,通过杂环上的S原子(或N原子)形成松散的吸附,但这种吸附层不能完全覆盖银表面。电镜实验也表明以上物质在银表面发生了作用。 相似文献