对痕量羊角材料降解产物的表面增强拉曼光谱研究

将一定浓度的硝酸银与柠檬酸三钠混合后,利用微波加热法制备纳米银溶胶,该方法加热速度快、温度分布均匀、反应条件易控制。采用准弹性激光散射技术检测其粒度大小及分布状态的信息,测得其平均粒度为(53.27±2.65)nm,粒度大小集中分布在56 nm左右。然后以之作为表面增强拉曼光谱(SERS)的活性基底,研究测定羊角痕量降解产物的SERS光谱。结果发现,羊角降解产物的表面增强拉曼效应显著,尤其在659,830,850,929,999,1 028,1 280,1 439,1 599 cm-1等多处出现了明显的拉曼振动峰,这些谱峰反映了羊角降解产物的生化成分信息。并且通过对所获得的羊角降解产物SERS信号进行的谱峰归属分析表明,羊角降解产物主要为氨基酸与多肽类物质。运用表面增强拉曼光谱检测角材料的降解产物,获得较高的灵敏度,可测定浓度低至ppm水平的痕量降解产物,本研究表明,SERS可能为羊角等角材料降解产物的检测提供一种快速、直观、准确的新方法。     

生地当归药队煎剂的表面增强拉曼散射光谱

为揭示单味煎剂与方剂间的关系,分别测试分析了生地当归药队、单味药生地和单味药当归煎剂的表面增强拉曼散射(surface-enhanced Raman scattering, SERS)光谱,并对其进行谱峰归属。本文主要针对存在于三种煎剂中的17个拉曼信号(538,622,732,761,835,876,959,1 145,1 245,1 276,1 326,1 402, 1 456,1 470,1 518,1 546和1 605 cm-1)进行讨论。生地当归药队煎剂SERS光谱在538,732,761,835,876,959,1 145,1 245,1 276,1 326,1 402,1 456,1 470,1 518和1 605 cm-1处,出现15个明显的拉曼信号;生地煎剂SERS光谱在538,761,835,876,959,1 145,1 245,1 276,1 326,1 402,1 470,1 518和1 546 cm-1处,出现13个明显的拉曼信号;当归煎剂SERS光谱在538,622,732,761,835,876,959,1 245,1 326和1 402 cm-1处,出现10个明显的拉曼信号。生地当归药队煎剂SERS光谱保留了和未观察到生地和当归单味煎剂的某些拉曼峰,且产生了生地和当归单味煎剂中所没有的拉曼信号(1 456和1 605 cm-1),即产生新药物成分。生地当归药队煎剂所包含的药物成分并非是生地和当归单味药物煎剂所含药物成分的简单相加。结果表明,SERS光谱可能为方剂研究提供一种高灵敏度、快速准确和操作简单的检测方法。     

Raman and surface enhanced Raman scattering of a black dyed silk

The Raman and surface enhanced Raman scattering (SERS) spectra of a black dyed silk sample (BDS) were registered. The spectral analysis was performed on the basis of Raman and SERS spectral data of isolated samples of Bombyx mori silk fibroin, its motif peptide component (GAGAGS) and the synthetic reactive black 5 dye (RB5). The macro FT‐Raman spectrum of the silk sample is consistent with a silk II‐Cp crystalline fraction of Bombyx mori silk fibroin; the SERS spectrum is highly consistent with conformational modifications of the fibroin due to the interactions with the Ag nanoparticles. The GAGAGS peptide sequence dominates the Raman spectrum of the silk. The SERS spectrum of the peptide suggests a random coil conformation imposed by the surface interaction; the serine residue in the new conformation is exposed to the surface. Quantum chemical calculations for a model of the GAGAGS–Ag surface predict a nearly extended conformation at the Ag surface. The Raman spectrum of the dye was analysed, and a complete band assignment was proposed; it was not possible to propose a preferential orientation or organization of the molecule on the metal surface. Quantum chemical calculations for a model of the dye interacting with a silver surface predict a rather coplanar orientation of the RB5 on the Ag metal surface. The Raman spectrum of the BDS sample is dominated by signals from the dye; the general spectral behaviour indicates that the dye mainly interacts with the silk through the sulphone (–SO₂–) and sulphonate (–SO₂–O–) groups. Besides the presence of dye signals, mainly ascribed to the sulphone and sulphonate bands, the SERS spectrum of the BDS sample also displays bands belonging to the amino acids alanine, glycine, serine and particularly tyrosine. Copyright © 2013 John Wiley & Sons, Ltd.     

Surface‐enhanced Raman scattering of protoberberine alkaloids

Quaternary protoberberine alkaloids are a class of natural dyes characterized by bright colors ranging from yellow to orange. As they present a strong fluorescence emission, their analysis by Raman spectroscopy is limited to specific techniques such as Fourier transform (FT)‐Raman and spectral shift Raman techniques such as shifted subtracted Raman difference spectroscopy (SSRDS) and shifted excitation Raman difference spectroscopy (SERDS). In a previous article, we successfully used surface‐enhanced Raman scattering (SERS) in the analysis of the alkaloid dye berberine in an ancient textile. The examination of the Raman and SERS spectra of berberine in combination with density functional theory (DFT) calculations indicated a flat adsorption geometry of the molecule on the Ag surface. In this article we extend that work to the study of related protoberberine alkaloids, palmatine, jatrorrhizine, and coptisine. The same adsorption geometry as in berberine was deduced. We found that the four alkaloids, although minimally different in their chemical structures, could be differentiated by the position of marker bands. Those bands are the most enhanced ones in the SERS spectra, which appear in the 700–800 cm⁻¹ region. Copyright © 2008 John Wiley & Sons, Ltd.     

Understanding tip‐enhanced Raman spectra of biological molecules: a combined Raman,SERS and TERS study

Although conventional Raman, surface‐enhanced Raman (SERS) and tip‐enhanced Raman spectroscopy (TERS) have been known for a long time, a direct, thorough comparison of these three methods has never been carried out. In this paper, spectra that were obtained by conventional Raman, SERS (on gold and silver substrates) and TERS (in ‘gap mode’ with silver tips and gold substrates) are compared to learn from their differences and similarities. Because the investigation of biological samples by TERS has recently become a hot topic, this work focuses on biologically relevant substances. Starting from the TER spectra of bovine serum albumin as an example for a protein, the dipeptides Phe–Phe and Tyr–Tyr and the tripeptide Tyr–Tyr–Tyr were investigated. The major findings were as follows. (1) We show that the widely used assumption that spectral bands do not shift when comparing SER, TER and conventional Raman spectra (except due to binding to the metal surface in SERS or TERS) is valid. However, band intensity ratios can differ significantly between these three methods. (2) Marker bands can be assigned, which should allow one to identify and localize proteins in complex biological environments in future investigations. From our results, general guidelines for the interpretation of TER spectra are proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

Photochromic Properties and Surface Enhanced Raman Scattering Spectra of Indoline Spiropyran in Silver-Based Nanocomposite Films

The structure and photochromic transformations of composite organometallic nanosystems composed of Ag nanoparticles covered with a layer of indoline-spiropyran (ISP) molecules from solutions were studied by spectrophotometry, surface Raman scattering spectroscopy (SERS) and quantum chemistry. Analysis of experimental data showed that studied nanostructured systems have photochromic properties, manifested in the reversible photo-induced changes both of the electronic-absorption spectra and of the relative intensity of the SERS bands. The open form of ISP, formed in the organometallic nanostructured film as a result of photochromic transformations, has an adsorption geometry, and, possibly, a conformation different from that formed as a result of chemisorption of ISP molecules on silver colloids.     

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。     

Raman and SERS study of metoclopramide at different pH values

Conjugate acid–base forms of the drug metoclopramide were investigated by Raman spectroscopy in aqueous solutions and by surface‐enhanced Raman scattering (SERS), when the molecules were adsorbed on colloidal silver surfaces. Raman spectra were recorded at pH values below 8, metoclopramide being poorly water soluble at higher pH values. The SERS spectra of metoclopramide were recorded in the 3–11 pH range, even in spite of its low solubility at basic pH values. The Raman and SERS spectra were assigned by means of density functional theory (DFT) calculations. By monitoring several SERS marker bands, the protonated, neutral or the coexistence of both molecular species adsorbed on the colloidal silver particles could be evidenced. The adsorbate orientation was deduced to be perpendicular to the metal surface for the protonated molecular species and tilted for the neutral metoclopramide molecular species. Copyright © 2009 John Wiley & Sons, Ltd.     

Applications of Raman and Surface-Enhanced Raman Scattering Techniques to Humic Substances

This paper highlights the use of Raman, FT-Raman and surface-enhanced Raman scattering (SERS) techniques for the study of humic substances. In contrast to other technologies which reveal information only about the average compositions and the kinds of functional groups present in humic substances, Raman and especially FT-Raman spectroscopies characterize the building blocks of humic substances and their changes in derivation and separation processes. Furthermore, surface-enhanced Raman scattering (SERS) techniques are able to readily detect humic substances and co-existing organic species at low concentrations typically found in natural environments and reveal definitive information about the specific groups in humic substances that bind on metal electrodes. Further applications of both Raman and SERS techniques can be extended to complicated systems as well as real environmental samples. Experiments have demonstrated: (1). the backbones of humic substances are structurally disordered carbon networks in most cases; (2). The backbones of humic substances from different sources and types are similar to each other; (3). Normal Raman spectroscopic study of humic substances should concentrate on the use of near-IR laser(s) resulting from strong fluorescence background and self-adsorption under the excitation with visible laser irradiation; (4). FT-Raman spectroscopy is the required analytical method to assess the effectivity of fractionation methods; (5). SERS spectra of humic substances on metal colloids and films are in most aces very similar to the corresponding Raman spectra of neutralized samples; (6). SERS techniques are very sensitive and highly selective, also both visible lasers and near-IR lasers can be used for SERS study; (7). SERS spectra on metal electrodes may provide additional information about the binding sites and adsorption mechanisms of humic substances on metal surfaces.     

Laser Raman Spectra of Transition Metal Oxides and Catalysts

Abstract

During recent years the study of the vibrational structure of catalysts by laser Raman spectroscopy (LRS) and of the interfacial properties of adsorbed species on solid surfaces by resonance Raman spectroscopy (RRS) and surface-enhanced Raman spectroscopy (SERS) have comprised one of the major research activities in the area of Raman spectroscopy [1–10] as applied to catalysts [11, 12].     

Strategy for improved analysis of peptides by surface‐enhanced Raman spectroscopy (SERS) involving positively charged nanoparticles

A strategy for improved surface‐enhanced Raman spectroscopy (SERS) measurements that extends the variety of analytes accessible to SERS analysis is developed. The strategy involves inducing aggregation by mixing positively charged nanoparticles which form SERS‐active clusters when mixed with negatively charged silver nanoparticles fabricated using the Lee–Meisel process. To make positively charged nanoparticles, silver nanoparticles using the traditional Lee–Meisel process are fabricated and coated with a thin layer of silica and the silica modified with silane chemistry. Analytes with a significant amount of negative charge exhibit strong Raman bands when the strategy using these fabricated, positively charged nanoparticles for inducing cluster formation is used, enabling their detection and analysis. We envision the use of positively charged nanoparticles in cluster formation for expanding the range of analytes that can be detected using SERS and hence the range of applications SERS can play a role in. Copyright © 2008 John Wiley & Sons, Ltd.     

Characterization of sodium alginate and its block fractions by surface‐enhanced Raman spectroscopy

The surface‐enhanced Raman scattering (SERS) of sodium alginates and their hetero‐ and homopolymeric fractions obtained from four seaweeds of the Chilean coast was studied. Alginic acid is a copolymer of β‐D ‐mannuronic acid (M) and α‐L guluronic acid (G), linked 1 → 4, forming two homopolymeric fractions (MM and GG) and a heteropolymeric fraction (MG). The SERS spectra were registered on silver colloid with the 632.8 nm line of a He Ne laser. The SERS spectra of sodium alginate and the polyguluronate fraction present various carboxylate bands which are probably due to the coexistence of different molecular conformations. SERS allows to differentiate the hetero‐ and homopolymeric fractions of alginic acid by characteristic bands. In the fingerprint region, all the poly‐D ‐mannuronate samples present a band around 946 cm⁻¹ assigned to C O stretching, and C C H and C O H deformation vibrations, a band at 863 cm⁻¹ assigned to deformation vibration of β‐C₁ H group, and one at 799–788 cm⁻¹ due to the contributions of various vibration modes. Poly‐L ‐guluronate spectra show three characteristic bands, at 928–913 cm⁻¹ assigned to symmetric stretching vibration of C O C group, at 890–889 cm⁻¹ due to C C H, skeletal C C, and C O vibrations, and at 797 cm⁻¹ assigned to α C₁ H deformation vibration. The heteropolymeric fractions present two characteristic bands in the region with the more important one being an intense band at 730 cm⁻¹ due to ring breathing vibration mode. Copyright © 2009 John Wiley & Sons, Ltd.     

Characterization of polycyclic aromatic hydrocarbons using Raman and surface‐enhanced Raman spectroscopy

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous atmospheric pollutants and food contaminants, which exhibit potent carcinogenicity, mutagenicity, and teratogenicity. Vibrational spectroscopy techniques, especially Raman spectroscopy and surface‐enhanced Raman spectroscopy (SERS), can be potentially used as an alternative technique to liquid and gas chromatography in PAH analysis. However, there is limited information on the intrinsic Raman and SERS fingerprints of PAHs. In this study, we have acquired the Raman and SERS spectra of seven PAH compounds and compared their experimental spectra with theoretical Raman spectra calculated by density function theory (DFT). The vibrational modes corresponding to the Raman peaks have also been assigned using DFT. Characteristic Raman and SERS peaks have been identified for five PAH compounds, and the limits of detection were estimated. Such information could be useful for developing SERS assays for simple and rapid PAH identification. Copyright © 2014 John Wiley & Sons, Ltd.     

IR,Raman and SERS spectra of 5‐sulphosalicylic acid dihydrate

IR, Raman and surface‐enhanced Raman scattering (SERS) spectra of 5‐sulphosalicylic acid were recorded and analysed. The vibrational wavenumbers were computed by density functional theoretical (DFT) method using B3LYP/6–31G* basis. The bands due to the stretching modes CO, C S and SO₂ are intense in the SERS spectrum. The C H stretching mode also appears in the SERS spectrum. The molecule is found to adsorb through both the carboxyl and sulphonyl groups. A possible tilted orientation of the molecule is suggested. Copyright © 2006 John Wiley & Sons, Ltd.     

活血化瘀汤药队的表面增强拉曼散射光谱研究

在中药治疗过程中,以方剂为载体,注重整体,采用辨证论治的方法。为揭示方剂的药队规律,根据药队协同效应设计法,将活血化瘀汤方剂拆分为“调和”、“化瘀生新”、“活血止痛”、“补气”四个药队方剂。由于银纳米粒子可与煎剂产生强交互作用,并极大地增强拉曼信号,获取活血化瘀汤、调和药队煎剂、化瘀生新药队煎剂、活血止痛药队煎剂和补气药队煎剂五种方剂煎剂的表面增强拉曼散射(SERS)光谱,并对所有SERS谱峰进行归属。主要针对各煎剂中的18个拉曼信号(523,538,622,647,732,959,977,1 003,1 048,1 077,1 145,1 245,1 326,1 402,1 456,1 470,1 518和1 605 cm-1)进行讨论。活血化瘀汤SERS光谱中保留了药队煎剂的某些拉曼峰,如：538,622,647,732,959,1 003,1 048,1 326,1 402,1 456,1 470,1 518和1 605 cm-1。药队煎剂SERS光谱的某些拉曼峰并未在活血化瘀汤中出现,如：1 077,1 145和1 245 cm-1。在活血化瘀汤SERS光谱中,出现了新的拉曼峰,如：523和977 cm-1。新的拉曼峰出现说明新物质的产生。实验结果表明,活血化瘀汤所包含的药物成分并非是各药队煎剂所含药物成分的简单相加,SERS光谱可为方剂药队规律研究提供一优异、有效和准确的检测方法。     

Thiol‐immobilized silver nanoparticle aggregate films for surface enhanced Raman scattering

We report a novel method for the fabrication of films of silver nanoparticle aggregates that are strongly attached to Si substrates (Thiol‐immobilized silver nanoparticle aggregates or TISNA). The attachment is achieved by chemically modifying the surface of a Si(100) surface in order to provide SH groups covalently linked to the substrate and then aggregating silver nanoparticles on these thiol covered surfaces. The transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) characterization show a high coverage with single nanoparticles or small clusters and a partial coverage with fractal aggregates that provide potential hot spots for surface enhanced Raman scattering (SERS). We have confirmed the SERS activity of these films by adsorbing rhodamine 6G and recording the Raman spectra at several concentrations. By using the silver‐chloride stretching band as an internal standard, the adsorbate bands can be normalized in order to correct for the effects of focusing and aggregate size, which determine the number of SERS active sites in the focal area. This allows a quantitative use of SERS to be done. The adsorption–desorption of rhodamine 6G on TISNA films is reversible. These features make our TISNA films potential candidates for their use in chemical sensors based on the SERS effect. Copyright © 2008 John Wiley & Sons, Ltd.     

Biocompatible gold/silver nanostars for surface‐enhanced Raman scattering

Raman‐enhancing properties of chitosan (CS)‐coated gold/silver nanostars (Au/AgNSs) were demonstrated by using them as a surface‐enhanced Raman scattering (SERS) probe. Based on the energy‐dispersive X‐ray spectroscopy element distribution maps and highly enhanced SERS spectra, we suggest that the incorporation of silver into the NS tips leads to a stronger SERS behavior. The SERS spectra of the proteins adsorbed on the NS surface greatly differ from their respective Raman spectra in both the band positions and relative intensities, indicating that the protein molecules penetrate through the CS coating layer and interact closely with the NS surface. Raman and SERS spectra of Chlamydia trachomatis protease/proteasomelike activity factor are reported for the first time, demonstrating the potential of these NSs for the development of a diagnosis method for Chlamydia based on SERS. The results showed a good SERS performance of the Au/AgNSs and their potential for SERS detection of biomolecules. Copyright © 2016 John Wiley & Sons, Ltd.     

Sensitive Raman spectroscopy of lipids based on drop deposition using DCDR and SERS

Raman spectroscopy is widely used for study of lipids and membrane models. A severe limitation of this technique lies in the low Raman cross section requiring high sample concentrations. We report sensitive detection of synthetic 1,2‐dimyristoyl‐3‐trimethylammonium‐propane (DMTAP) lipid employing two Raman techniques with improved sensitivity: drop coating deposition Raman (DCDR) and surface‐enhanced Raman scattering (SERS) spectroscopies. DCDR provided well‐reproducible DMTAP spectra without considerable loss of its solution properties if measured from the ‘coffee ring’ pattern of a drop dried on a SpectRIM^TM plate. DMTAP was detected at ~10 μM initial solution concentration, which is about three orders of magnitude lower than that for conventional Raman spectroscopy. Moreover, SERS spectra from dried ring of Ag hydrosol/DMTAP system were obtained down to ~0.3 μM DMTAP concentration, which means that sensitivity of SERS is about five orders of magnitude higher than that of conventional Raman spectroscopy. In contrast to the DCDR technique, good SERS spectra of DMTAP were obtained only from some spots of the ring containing big nanoparticle aggregates, and the structural properties of DMTAP were significantly perturbed by adsorption on the Ag nanoparticles. Copyright © 2013 John Wiley & Sons, Ltd.     

Surface‐enhanced Raman scattering from polystyrene on gold clusters

Surface‐enhanced Raman scattering (SERS) constitutes a spectroscopic method of rapidly growing importance, and polystyrene is a widely used compound of great industrial importance. In this work, SERS data were obtained from polystyrene samples prepared by vapor deposition of gold and plasma‐induced polymerization of styrene gas. A thorough examination of this data is presented. The relationships between sample preparation parameters, gold‐cluster morphology, and SERS intensity were elucidated. Using Wilson's notation, vibrations were assigned to all bands between 250 and 1750 cm⁻¹ in the ordinary Raman and SERS spectra of polystyrene. The correct assignment of these bands would be a significant achievement because they have been controversial in the literature for ∼30 years. Our assignments were made by reviewing the literature and comparing the assignments found there to spectral data acquired during this study; they were confirmed using density functional theory (DFT) calculations performed on the styrene monomer. The orientation of polystyrene's phenyl ring, relative to the gold surface, was determined. It has been suggested that reactions involving silver catalyze polystyrene degradation during SERS, but we found that silver is not necessary for the degradation to occur. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman and surface‐enhanced Raman spectroscopic studies of the 15‐mer DNA thrombin‐binding aptamer

Aptamers are single‐stranded oligonucleotides that selectively bind to their target molecules owing to their ability to form secondary structures and shapes. The 15‐mer (5′‐GGTTGGTGTGGTTGG‐3′) DNA thrombin‐binding aptamer (TBA) binds to thrombin following the formation of a quadruplex structure via the Hoogsten‐type G–G interactions. In the present study, Raman and SERS spectra of TBA and thiolated TBA (used to facilitate covalent bonding to metal nanoparticle) in different conditions are investigated. The spectra of the two analogs exhibit vibrations, such as the C8N7 H2 deformation band at ∼1480 cm⁻¹ of the guanine tetrad, that are characteristic of the quadruplex structure in the presence of K⁺ ions or at low temperature. Interestingly, SERS spectra of the two analogs differ markedly from their respective normal Raman spectra, possibly due to changes in the conformation of the aptamer upon binding, as well as to the specific interaction of individual vibrational modes with the metal surface. In addition, the SERS spectra of the thiolated aptamer show significant changes with different concentrations, which may be due to different orientation of the molecule with respect to the metal surface. This study provides useful information for the development of label‐free aptamer‐based SERS sensors and assays. Copyright © 2009 John Wiley & Sons, Ltd.