Correlation of SERS with cyclic voltammetry for cyanide complexes adsorbed on Cu electrodes

The growth and decay of surface enhanced Raman scattering (SERS) from cyanide complexes adsorbed on a Cu electrode have been measured with an optical multichannel analyzer during an electrochemical oxidation-reduction cycle. The Raman data are correlated with the chemical reactions indicated by cyclic voltammetry. Discrete vibrational SERS peaks of the adsorbed Cu-cyanide complexes were observed for wavelengths longer than 575 nm, while voltage dependent continuum inelastic scattering was detected for wavelengths as short as 457.9 nm.     

Chemical contribution to surface-enhanced Raman scattering

We present a new mechanism for the chemical contribution to surface-enhanced Raman scattering (SERS). The theory considers the modulation of the polarizability of a metal nanocluster or a flat metal surface by the vibrational motion of an adsorbed molecule. The modulated polarization of the substrate coupled with the incident light will contribute to the Raman scattering enhancement. We show that for a metal cluster and for a flat metal surface this new chemical contribution may enhance the Raman scattering intensity by a factor of approximately 102 and approximately 104, respectively. The new SERS process is determined by the electric field parallel to the surface of the metal substrate at the molecular binding site.     

结晶紫在混合正、负电性银胶上的表面增强拉曼散射

利用化学还原的方法分别制备了具有正、负电性的纳米银胶 ,通过测定结晶紫分子在正、负电性银胶以及混合银胶体系的表面增强拉曼光谱的变化 ,探讨了不同电性银胶基底对结晶紫分子表面增强拉曼活性的影响。结果表明 ,混合银胶体系能有效的改进单银胶体系的表面增强拉曼活性。     

SERS activity of carbon nanotubes modified by silver nanoparticles with different particle sizes

A two-dimensional (2D) surface-enhanced Raman scattering (SERS) substrate is fabricated by decorating carbon nanotube (CNT) films with Ag nanoparticles (AgNPs) in different sizes, via simple and low-cost chemical reduction method and self-assembling method. The change of Raman and SERS activity of carbon nanotubes/Ag nanoparticles (CNTs/AgNPs) composites with varying size of AgNPs are investigated by using rhodamine 6G (R6G) as a probe molecule. Meanwhile, the scattering cross section of AgNPs and the distribution of electric field of CNTs/AgNPs composite are simulated through finite difference time domain (FDTD) method. Surface plasmon resonance (SPR) wavelength is redshifted as the size of AgNPs increases, and the intensity of SERS and electric field increase with AgNPs size increasing. The experiment and simulation results show a Raman scattering enhancement factor (EF) of 10⁸ for the hybrid substrate.     

Bacterial mixture identification using Raman and surface‐enhanced Raman chemical imaging

The ability of normal Raman and surface‐enhanced Raman scattering (SERS) to identify and detect bacteria has shown great success in recent studies. The addition of silver nanoparticles to bacterial samples not only results in an enhanced Raman signal, but it also suppresses the native fluorescence associated with biological material. In this report, Raman chemical imaging (RCI) was used to analyze individual bacteria and complex mixtures of spores and vegetative cells. RCI uses every pixel or a binned pixel group (BPG) of the Raman camera as an independent Raman spectrograph, allowing collection of spatially resolved Raman spectra. The advantage of this technique resides primarily in the analysis of samples in complex backgrounds without the need for physically isolating or purifying the sample. Using a chemical imaging Raman microscope, we compare normal RCI to SERS‐assisted chemical imaging of mixtures of bacteria. In both cases, we are able to differentiate single bacterium in the Raman microscope's field of view, with a 60‐fold reduction in image acquisition time and a factor of 10 increase in the signal‐to‐noise ratio for SERS chemical imaging over normal RCI. Copyright © 2010 John Wiley & Sons, Ltd.     

The origin of ultrasensitive SERS sensing beyond plasmonics

Plasmon-free surface-enhanced Raman scattering (SERS) substrates have attracted tremendous attention for their abundant sources, excellent chemical stability, superior biocompatibility, good signal uniformity, and unique selectivity to target molecules. Recently, researchers have made great progress in fabricating novel plasmon-free SERS substrates and exploring new enhancement strategies to improve their sensitivity. This review summarizes the recent developments of plasmon-free SERS substrates and specially focuses on the enhancement mechanisms and strategies. Furthermore, the promising applications of plasmon-free SERS substrates in biomedical diagnosis, metal ions and organic pollutants sensing, chemical and biochemical reactions monitoring, and photoelectric characterization are introduced. Finally, current challenges and future research opportunities in plasmon-free SERS substrates are briefly discussed.     

用SERS研究一种新的钌(Ⅱ)联吡啶配合物及其与DNA的作用机理

着重讨论了用ＳＥＲＳ研究Ｒｕ（ｂｐｙ）２ｄｐｐｚ配合物及其与ＤＮＡ作用的机理。当这种钌配合物与ＤＮＡ发生作用时,只是它的ｄｐｐｚ配体插入了ＤＮＡ双链的碱基对中,与碱基对形成了共轭体系,影响了Ｒｕ配合物的ＭＬＣＴ跃迁,产生了荧光,同时也在拉曼谱图和电子吸收谱图上有所表现。     

氯化亚锡抑制吡啶分子表面增强拉曼光谱测定中的碳化现象

碳化是表面增强拉曼光谱中难以避免的干扰现象,特别是对于活性有机和生物分子的检测。作为一种最常用的探针分子,吡啶同样也存在碳化的问题。然而,作者发现通过引入SnCl2,可以有效地抑制表面增强拉曼光谱测定中吡啶分子的碳化现象。该方法操作简单,所引入的SnCl2只在谱图低波段处出现少而易区分的特征峰,不干扰被测样品的光谱分析。有别于文献中所采用的真空、惰性气氛、低温和低激光功率等物理方法,此法是解决碳化问题的一种崭新的化学方法,可望应用于其他易碳化的有机和生物分子的表面增强拉曼光谱检测。     

Surface‐enhanced Raman spectra of dimethoate and omethoate

Surface‐enhanced Raman scattering (SERS) spectra are presented and analyzed for two important organophosphate pesticides, dimethoate (DMT) and omethoate (OMT). Very detailed SERS spectra were obtained by aggregated Ag hydrosols, both in aqueous suspension and dried on a glass substrate. The SERS and ordinary Raman spectra of DMT do not resemble each other, suggesting that a chemical reaction immediately occurs when DMT is adsorbed onto the metal surface. We propose that the reaction product is OMT, which is the oxygen analog of DMT, on the basis of the Raman and SERS spectra of OMT. Further support is derived from the calculated Raman spectra of DMT and OMT. Minor wavenumber and intensity differences that are observed between the SERS spectra of DMT reaction product and those of OMT could be related to different metal/adsorbate interaction modes. The results can be useful in the development of new analytical methods for the determination of pesticide residues in food. Copyright © 2010 John Wiley & Sons, Ltd.     

内吞金纳米粒子的鼻咽癌细胞SERS光谱

采用内吞方法将金纳米粒子引入细胞内,测试分析单个活性CNE-1鼻咽癌细胞的常规拉曼光谱和SERS光谱,并对其进行初步谱峰归属。CNE-1细胞的常规拉曼光谱有6个主要的拉曼峰:718,1001,1123,1336,1446和1660cm-1;沉积于细胞内的金纳米粒子强烈地增强了细胞内生化物质拉曼信号,在内吞金纳米粒子的CNE-1细胞的拉曼光谱中出现了20多个SERS拉曼信号,主要拉曼峰的强度明显高于常规拉曼信号。DNA骨架振动(1026,1097,1336和1585cm-1)证明金纳米粒子通过内吞作用而进入细胞核内。结果表明,基于胶体金SERS技术可能为活性鼻咽癌细胞内生化物质的探测提供一种高灵敏的方法。     

Surface-enhanced Raman scattering study of silver deposition on thin Alq3 layers

Surface-enhanced Raman scattering (SERS) spectroscopy is applied to study in situ the interface formation of silver on thin Alq₃ films. The changes in the frequencies of Alq₃ vibrational modes are moderate and their line-shape is preserved upon Ag deposition. Moreover, a good correspondence appears between the SERS and powder spectra and frequencies predicted by density functional calculations for the meridianal isomer. The behaviour of Raman spectra indicates that no chemical interaction occurs between the Ag atoms and Alq₃ molecules.     

Visible light response of silver 4‐aminobenzenethiolate and silver 4‐dimethylaminobenzenethiolate probed by Raman scattering spectroscopy

Silver thiolate is a layered compound with a Raman spectrum that is known to change with time, becoming the same as the surface‐enhanced Raman scattering (SERS) spectrum of the parent thiol molecule adsorbed on Ag nanoparticles. On this basis, the Raman scattering characteristics of silver 4‐aminobenzenethiolate (Ag‐4ABT) compounds were investigated to determine whether certain peaks that are identifiable in the SERS spectrum of 4‐aminobenzenethiol (4‐ABT) but absent in its normal Raman spectrum were also apparent in the Ag salt spectrum. For comparative purposes, the Raman scattering characteristics of silver 4‐dimethylaminobenzenethiolate (Ag‐4MABT) were also examined. Raman spectra acquired while spinning the sample were typified by only a₁‐type vibrational bands of Ag‐4ABT and Ag‐4MABT, whereas in the static condition, several non‐a₁‐type bands were identified. The spectral patterns acquired in the static condition were similar to the intrinsic SERS spectra of 4‐ABT or 4‐dimethylaminobenzenethiol (4‐MABT) adsorbed on pure Ag nanoparticles. Notably, the CH₃ group vibrational bands were observable for Ag‐4MABT irrespective of the sample rotation. In addition, no decrease in intensity during irradiation with a visible laser was observed for any of the bands, suggesting that no chemical conversion actually took place in either 4‐ABT or 4‐MABT. The preponderance of evidence led to the conclusion that the non‐a₁‐type bands observable in the SERS spectra must be associated with the chemical enhancement mechanism acting on the Ag nanoparticles. The chemical enhancement effect was more profound at 514.5 nm than at 632.8 nm, and was more favorable for 4‐ABT than 4‐MABT at both wavelengths. Copyright © 2012 John Wiley & Sons, Ltd.     

低维光电材料缺陷与界面增强拉曼散射

近年来,一系列新型低维光电材料相继涌现,展现出优异的性能.这些光电材料与表面增强拉曼散射(SERS)技术相结合,显示出巨大的应用潜力,有望成为高灵敏SERS活性基底.缺陷与界面调控是低维光电材料SERS应用的重要策略,本文将重点介绍新型低维光电材料缺陷与界面增强拉曼散射的种类和增强机理.通过对缺陷与界面增强拉曼散射的应...     

表面增强拉曼光谱检测水中微量的芬太尼

通过化学法合成了具有表面增强拉曼散射(SERS)活性的银胶体,利用透射电子显微镜和紫外可见光谱仪分别对银胶体的形貌和光学性质进行了表征;采用这种衬底对水相中微量的芬太尼进行了SERS检测研究,并对芬太尼的SERS信号进行了归属,考察了各种实验条件对SERS检测的影响。实验结果表明,增大银胶体浓度有利于芬太尼SERS信号的检测;随着团聚剂氯化钠浓度增大芬太尼的SERS信号强度会先增大后减小,即团聚剂浓度存在一个最佳值;在优化的实验条件下芬太尼的检测限可以达到0.1ppm量级。     

Nanostructured gold surfaces as reproducible substrates for surface‐enhanced Raman spectroscopy

Raman spectroscopy is a common tool for the qualitative and quantitative chemical analysis of molecules. Although the unique identification of molecules is possible via their vibrational lines, high concentrations (mmol/l) are needed for their nonresonant excitation owing to their low scattering cross section. The intensity of the Raman spectra is amplified by the use of the surface‐enhanced Raman scattering (SERS) technique. While the use of silver sols results only in a limited reproducibility of the Raman line intensities, lithographically designed, nanostructured gold surfaces used as SERS‐active substrates should, in principle, combine the high sensitivity with better reproducibility. For this purpose, we have produced gratings of gold dots on Si(001) surfaces by means of electron beam lithography. Qualitative and quantitative investigations of crystal violet (CV) performed using nanostructured surfaces give high reproducibility and enhancement of the Raman lines. The substrates are reusable after cleaning; all results presented could be obtained from a single SERS substrate. For the experiments very low laser powers were used. Copyright © 2006 John Wiley & Sons, Ltd.     

Application of surface‐enhanced Raman scattering in cell analysis

In surface‐enhanced Raman scattering (SERS), the scattered intensity is drastically increased due to a resonant interaction with surface plasmons of coin metals. SERS is a nondestructive spectroscopic method applied also to biomedical samples. It inherits the advantages of normal Raman spectroscopy and at the same time overcomes the inherent low sensitivity problem. These properties endow SERS with exciting opportunities to be a successful analytical tool for cell analysis. SERS can be used to detect only molecules located on or close to the metallic nanostructures which can support surface plasmon resonances for the enhancement of the Raman signals. Therefore, these metallic nanostructures play a key role in the application of SERS in cell analysis. By incorporating the SERS substrates into the biosamples, molecular structural probing and cellular imaging become possible. In the past decade, analysts worldwide have developed many schemes to study the chemical changes and component distribution in cells by using SERS. In this paper, the application of SERS in cell analysis is reviewed. Copyright © 2011 John Wiley & Sons, Ltd.     

Surface‐enhanced Raman scattering of hydroxyproline

Surface‐enhanced Raman scattering (SERS) spectra of hydroxyproline and one deuterated analogue are reported. In this work, we tackled the problem of SERS reproducibility by employing gold colloids instead of the usual silver sols to achieve plasmon enhanced Raman scattering. We slightly modified modified a previously published procedure to obtain to obtain the colloid, and concentrated the gold particles by centrifugation. The SERS spectra show distinctive bands of hydroxyproline, assigned by comparison to normal Raman spectra and density functional theory calculations. Repeated measurements using this procedure showed reproducible SERS spectra. Copyright © 2011 John Wiley & Sons, Ltd.     

Engineering of SERS Substrates Based on Noble Metal Nanomaterials for Chemical and Biomedical Applications

Abstract

Surface-enhanced Raman scattering (SERS) has attracted great interest due to its remarkable enhancement, excellent sensitivity, and the “fingerprinting” ability to produce distinct spectra for detecting various molecules. Noble metal nanomaterials have usually been employed as SERS-active substrates because of their strong SERS enhancement originated from their unique surface plasmon resonance (SPR) properties. Because the SPR property depends on metal material's size, shape, morphology, arrangement, and dielectric environment around metal nanostructures, the key to wider applications of SERS technique is to develop plasmon-resonant structures with novel geometries to enhance Raman signals and to control the periodic ordering of these structures over a large area to obtain reproducible Raman enhancement. This review presents a general view on the theory background of SERS effect and several basic concepts and focuses on recent progress in engineering metallic nanostructures with various morphologies using versatile methods for improving SERS properties. Their potential applications in the field of chemical detection and biological sensing are overviewed.     

Vibration spectroscopic study of the interaction of tris-(8-hydroxyquinoline) aluminum (Alq3) with potassium

The interaction between Alq₃ and potassium was studied by using Raman and infrared spectroscopies. Infrared reflection absorption spectroscopy (IRRAS) spectra of Alq₃ films show significant changes after potassium deposition, such as the appearance of new bands and changes in relative intensity. Surface-enhanced Raman scattering (SERS) spectra obtained using the 413.1 nm line of a Kr⁺ laser reveal similar changes. Changes are even more obvious when the 530.9 nm line was used for excitation. Changes in the SERS for excitation with the 413.1 nm line are less obvious due to a strong photoluminescence. The vibrational pattern of potassium-doped Alq₃ cannot be explained by the formation of radical anion by simple charge transfer, indicating the excess electron is not delocalized over the molecule. The observed spectral change suggests that the potassium atom interacts with both nitrogen and oxygen atoms of Alq₃ molecule.     

金纳米粒子组装体系的表面增强拉曼光谱特性研究——表面粒子密度与拉曼光谱强度的关系

利用纳米粒子组装制备了金基底———巯基苯胺自组装膜偶联层———金纳米粒子的“三明治”结构,研究了表面粒子密度与偶连层分子的拉曼光谱强度的关系。实验结果显示,该结构对偶连层分子的拉曼光谱有很好的增强效应,增强因子可达１０５。在表面粒子密度较低时,拉曼光谱强度与表面粒子密度曲线呈线形,随着表面粒子密度的增加,曲线出现负偏差并在粒子密度较高区域出现一个平台。