FT-Raman, FT-IR and surface enhanced Raman scattering spectra of sodium salicylate

FT-IR and FT-Raman spectra of sodium salicylate were recorded and analysed. Surface enhanced Raman scattering (SERS) spectrum was recorded is silver colloid. Comparisons of the SERS spectrum with the spectra in solution and of the solid sample are made. Sodium salicylate (an O donor ligand) is thought to adsorb in a somewhat 'tilted side on orientation' with respect to the silver surface.     

IR, Raman and SERS spectra of disodium terephthalate

The IR and Raman spectra of disodium terephthalate were recorded and analysed. Surface enhanced Raman scattering (SERS) spectrum was recorded in silver colloid. The vibrational wavenumber of the compound have been computed using the Hartree-Fock/6-31G* basis and compared with the experimental values. SERS studies suggest a flat orientation of the molecule at the metal surface.     

IR, Raman and SERS spectra of 2-phenoxymethylbenzothiazole

The FT-IR and FT-Raman spectra of 2-phenoxymethylbenzothiazole were recorded and analyzed. The surface enhanced Raman scattering (SERS) spectrum was recorded in a silver colloid. The vibrational wavenumbers of the compound have been computed using the Hartree–Fock/6-31G* basis and compared with the experimental values. The appearance of the Ag–O stretching mode at 237 cm⁻¹ in the SERS spectrum along with theoretically calculated atomic charge density, leads us to suggest that the molecule is adsorbed through the oxygen atom with the molecular plane tilted on the colloidal silver surface. The direction of charge transfer contribution to SERS has been discussed from the frontier orbital theory.     

IR, Raman and SERS studies of methyl salicylate

The IR and Raman spectra of methyl salicylate (MS) were recorded and analysed. Surface enhanced Raman scattering (SERS) spectrum was recorded in silver colloid. The vibrational wave numbers of the compound have been computed using the Hartree-Fock/6-31G* basis and compared with the experimental values. SERS studies suggest a flat orientation of the molecule at the metal surface.     

Experimental and theoretical surface enhanced Raman scattering study of 2-amino-4-methylbenzothiazole adsorbed on colloidal silver particles

The adsorption of 2-amino-4-methylbenzothiazole (2-AMBT) on colloidal silver particles has been investigated by a surface enhanced Raman scattering (SERS) study. The SERS spectra of the 2-AMBT molecule at varied adsorbate concentrations recorded in different time domains are compared with its Fourier transform infrared (FTIR) spectrum and normal Raman spectrum (NRS) in the bulk and in solution. The experimentally observed SERS spectra are compared with the theoretically modeled surface complexes using ab initio restricted Hatree-Fock (RHF) and density functional theory (DFT) calculations. The most favorable adsorptive sites of the 2-AMBT molecule have been estimated by natural population analysis (NPA) using the above-mentioned high level of theories. The enhancement of the in-plane modes together with the appearance of Ag-N stretching frequency at 215 cm(-1) indicates that the 2-AMBT molecule is adsorbed on the silver surface through the lone pair electrons of both nitrogen atoms with the molecular plane nearly vertical to the surface.     

FT-IR, FT-Raman and FT-SERS spectra of 4-aminosalicylic acid sodium salt dihydrate.

FT-IR, FT-Raman and FT-SERS spectra of 4-aminosalicylic acid sodium salt dihydrate (4ASAS) have been recorded and analysed. The vibrational bands due to NH2, OH, carboxyl group, and the benzene ring are identified. The CX ipb(17a, 17b), CC ipb(6,18a) and CH ipb (3,14a, 14b) bands are more enhanced in SERS. Broadening of the inplane carboxyl bend indicates interaction with the silver surface. Further the vC=O, v(C-O)c and v(C-O)h are intense in the SERS spectrum. The rocking and wagging modes of NH2 also show up in SERS. The molecule (O, N donor ligand) is thought to adsorb through the carboxyl oxygen atom with the benzene ring in a 'perpendicular side on orientation' with respect to the silver surface.     

Vibrational spectroscopy of betulinic acid HIV inhibitor and of its birch bark natural source

Raman and IR spectra of betulinic acid (BA) (3beta-hydroxy-20(19) lupaen-28 oic acid) and of the natural birch bark have been successfully recorded and discussed. A high selectivity of the Raman technique was remarked for evidencing the betulin in the birch bark. Surface enhanced Raman spectrum (SERS) of BA on colloidal silver has been obtained. The presence and shifting of the symmetric stretching mode of the COO group in the SERS spectrum suggests a chemisorption of the steroid structure on the metallic particles.     

Surface enhanced Raman spectra of carbonate,hydrocarbonate, and substituted acetic acids on silver hydrosols

The SERS spectra of carbonate, hydrocarbonate and several substituted acetic acids absorbed on silver hydrosols are recorded. The greatest enhancement of E′ modes is shown in the spectrum of carbonate, from which the carbonate is deduced to be absorbed in an “end on” configuration, rather than flat on the surface. The spectrum of the hydrocarbonate solution shows the most enhanced bands at about 925 and 620 cm⁻¹, which cannot be explained clearly. All the substituted acids have a most enhanced bands at about 1630 cm⁻¹, revealing that the acids are initially adsorbed in a single bonding state through the carboxyl group. The change in the SERS spectra of the acids with time indicates that a bidentate bridging adsorbed state may be formed after some time.     

FT-IR, FT-Raman and SERS spectra of Vitamin C

FT-IR and FT-Raman spectra of Vitamin c have been recorded and analysed. SERS spectrum was recorded is silver colloid. The molecule is thought to adsorb with the lactone ring in a tilted side on orientation with respect to the silver surface.     

Surface enhanced Raman scattering of ammonia

A surface enhanced Raman scattering (SERS) spectrum of 0.5 M NH₃ in 4.0 M KCl has been observed on a silver electrode. An approximate enhancement factor of 3 × 10⁵ is calculated, and additional evidence for the enhanced nature of the spectrum is provided by the observation that totally symmetric vibrations are depolarized and by the strong potential dependence of the intensity of surface lines. Assignments have been given to the SERS lines with the low-frequency lines assigned to a AgCl and AgN stretch. The positive shift of the maximum of the intensity versus voltage curve with a lower laser excitation frequency is taken as evidence for the occurrence of a charge transfer process from ammonia to the silver electrode. The fact that the SERS spectrum of NH₃ on Ag can only be observed at large electrolyte concentrations is attributed to the breaking of hydrogen bonding at the electrode-solution interface.     

银纳米粒子簇的设计、 制备和表面增强拉曼光谱

通过匹配激光光斑直径与胶体微球的尺寸, 设计制备了银纳米粒子的表面增强拉曼散射(SERS)基底, 并将其用于研究单个银纳米粒子簇的表面增强拉曼光谱. 在制备纳米粒子的过程中, 考察了等离子体刻蚀时间与银沉积厚度对“单”银纳米粒子结构与形貌的影响. 将吡啶、 巯基苯和罗丹明R6G作为SERS探针分子, 研究了其SERS效应, 通过荧光共振能量转移(FRET)机理, 实现了染料分子在单银纳米粒子簇上的SERS效应. SERS光谱测试与相关计算结果表明, 单个银纳米粒子簇的拉曼增强因子能够达到约10⁶.     

Surface enhanced vibrational spectra of thymine

Surface-enhanced vibrational spectroscopy (SEVS) is discussed using 5-methyluracil (thymine) as a model compound. Surface-enhanced Raman scattering (SERS) and surface-enhanced infrared (SEIR) are reported and a characterization of thymine adsorbed onto silver island films is provided. The thymine SERS spectra obtained using silver colloids, silver roughened electrodes and silver island films are remarkably different due to several binding possibilities of thymine during chemical adsorption onto a silver surface. It is shown that laser induced photo dissociation may lead to further changes in the recorded spectra of the adsorbate. The surface enhanced-infrared (SEIR) spectra of thymine on silver island are reported here for the first time. The infrared spectra of thymine films were also been obtained to help the assignment of molecular vibrations in the surface enhanced spectra.     

卟啉H2TSPP和Ag(II)TSPP吸附在均分散Fe3O4胶体上的拉曼光谱

Surface Enhanced Raman Scattering (SERS) of tetrasodium meso-tetrakis (4-sulfonatophenyl) porphine (H2TSPP) and silver tetraphenylporphyrin (Ag(Ⅱ)TSPP) adsorbed spontaneously on uniform Fe3O4 colloids are recorded. The enhancement of Raman bands is approximately 30. An analysis of the SERS spectrum shows that on the Fe3O4 surface H2TSPP takes its diacid form H42+TSPP.     

SERS spectroscopy and SERS imaging of Shewanella oneidensis using silver nanoparticles and nanowires

Facile and reproducible SERS signals from Shewanella oneidensis were obtained utilizing silver nanoparticles (AgNPs) and silver nanowires (AgNWs). Additionally, SERS images identify the distribution of SERS hot-spots. One important observation is the synergistically enhanced SERS signal when AgNPs and AgNWs are used in conjunction, due to constructively enhanced electromagnetic field.     

Solid-liquid-liquid extraction as an approach to the sensitive detection of a hydrophobic pollutant through surface-enhanced Raman spectroscopy

Surface-enhanced Raman scattering (SERS) spectra of thiram (tetramethylthiuram disulfide), a dimethyl dithiocarbamate fungicide, were recorded after the adsorption on plasmonic silver nanowires from a system of water, organic solvent and nanoparticles. As organic solvents dichloromethane and 1-octanol were involved. A method for measuring the adsorption constant of thiram as a model molecule to the silver surface by studying its partition phenomena in a binary solvent system is presented. The method is based on the extraction of a hydrophobic molecule from an organic solvent by an aqueous suspension of silver anisotropic nanoparticles. The obtained results demonstrate the effectiveness of SERS methodology for the sensitive analysis of compounds with low aqueous solubility, and a reliable SERS spectrum of thiram was obtained with excellent signal/noise ratio at low concentrations. In addition, for vibrational assignments, Density Functional Theory (DFT) was used for the simulation of the Raman and SERS spectra of thiram and its complexes with silver considering the following two models: a single silver atom and an Ag₂₀ cluster.     

SERS approach for Zn(II) detection in contaminated soil

Soil contamination by metals is a common problem encountered in many industrialized countries. In this work we present a new approach for heavy metals detection by using surface-enhanced Raman scattering (SERS) spectroscopy. Zn(II) can be clearly determined by SERS in contaminated soil by using 4-(2-pyridylazo) resorcinol (PAR) as chelating molecule for the metal ion. The SERS spectra of PAR, of its metal chelates and of the soil extract-PAR mixture were recorded using a hydroxylamine reduced silver colloid. An excellent match of the PAR-contaminated soil extracts SERS spectrum to the Zn(PAR)₂ SERS spectrum can be observed, demonstrating the presence of Zn(II) in the soil probes. Density functional theory (DFT) based calculations were also performed for a reliable assignment of SERS spectra.     

钩藤生物碱中一对异构体的TLC-FT-SERS研究

傅立叶变换表面增强喇曼光谱（FT－SERS）可高灵敏度检测单一组分的分子结构住处,金、银等金属的米粒子具有表面增强活性^[1],薄层色谱（TLC）可将微量混合物有效分离但不具备指纹检测功能,若将TLC与FT－SERS技术联用,则可使天然药物等提取得到高灵敏度分离与特征光谱检测,这项研究在国内外仅有补步报道^[2~5],钩藤为常用中草药,其有效成分生物碱具有改善心脑血液循环和脑功能的作用及清除自由基抗衰老活性,本文应用TLC－FT－SERS技术对天然药物钩藤中的生物碱进行高灵敏度的分析和特征喇曼光检测,在硅胶色谱板的钩藤碱与异钩藤碱与钩藤碱班点原位分别滴淋灰银胶,直接测得FT－SERS光谱。     

Monitoring Phosphorylation and Dephosphorylation Reactions by Surface-Enhanced Raman Scattering (SERS) in Model Compounds

Abstract

Raman and Surface-Enhanced Raman Scattering (SERS) spectra of phosphates, polyphosphates, and various phosphate complexes have been recorded. Bands of the vibrational spectra were assigned. The comparison of SERS spectra obtained by using colloidal silver with the corresponding Raman spectrum reveals enhancement and shifts in some bands, suggesting a possible partial charge-transfer mechanism in the SERS effect. Phosphorylation and dephosphorylation reactions brought about by the reactions of cobalt (III) bis trimethylenediamine phosphate/pyrophosphate complexes with nitrophenol/nitrophenyl phosphates are described.     

Evaluation of the potential of surface enhancement Raman spectroscopy for detection of tricyclic psychotropic drugs. Case studies on imipramine and its metabolite

The potential use of surface Raman enhanced spectroscopy (SERS) for confirmatory identification and the semi-quantitative analysis of selected tricyclic antidepressants (TCAs) is examined utilizing a conventional silver colloid. Raman and SERS spectra of aqueous solutions of imipramine (Imi) and its metabolite, desipramine (Des), were recorded as the function of concentration using NIR excitation. A good linear correlation is observed for the dependence of the SERS signal at 684 cm(-1) (R(2) = 0.9997) on Imi concentration over the range of 0.75-7.5 μM. The limit of detection of imipramine in the silver colloidal solution is 0.98 μM. SERS spectra of Imi and Des were also recorded for blood plasma samples without prior purification as well as after the use of standard solid phase extraction. All spectra show the characteristic spectral profile of the molecules and moreover, stronger signal enhancement is observed for Imi in the "raw" samples as opposed to Imi extracted from a biological matrix.     

Raman and surface enhanced Raman microscopy of microstructured polyethylenimine/DNA multilayers

We analyze microstructured multilayer films of poly(ethyleneimine) (PEI) and DNA by employing Raman and surface enhanced Raman spectroscopy (SERS). The microstructuring of the samples allows a simultaneous measurement of signal and reference in a single analytic process. Silver nanoparticles are implemented in the microstructured multilayers for SERS measurements. The recorded SERS spectra of PEI/DNA are dominated by the Raman bands of the DNA bases which show a larger mean enhancement than bands belonging to DNA backbone vibrations. Our results show that the combination of SERS and microstructured multilayer films provides an adapted way to characterize the polyelectrolytes as well as to measure the enhancement factor and the distance dependence for the SERS active silver nanoparticles. Furthermore, microstructured polyelectrolyte films containing SERS active nanoparticles are used for sensing molecules.