表面增强拉曼散射活性基底

表面增强拉曼散射(SERS)是人们将激光拉曼光谱应用到表面科学研究中所发现的异常表面光学现象。它可以将吸附在材料表面的分子的拉曼信号放大106到1014倍,这使其在探测器的应用和单分子检测方面有着巨大的发展潜力。由于分子所吸附的基底表面形态是SERS效应能否发生和SERS信号强弱的重要影响因素,所以分子的承载基体是很关键的,因而SERS活性基底的研究一直是该领域的研究热点之一。本文总结了形态各异的表面增强拉曼散射活性基底,分析了最新发展并对其未来作一展望。     

Surface-enhanced Raman spectroscopy toward application in plasmonic photocatalysis on metal nanostructures

Among photothermal, photovoltaic and photochemical techniques, photochemistry is superior in energy storage and transportation by converting photons into chemical fuels. Recently plasmonic photocatalysis, based on localized surface plasmon resonance (LSPR) generated from noble metal nanostructures, has attracted much attention. It promotes photochemical reaction efficiency by optimizing the solar spectrum absorption and the surface reaction kinetics. The deeper understanding is in urgent need for the development of novel plasmonic photocatalysts. Surface-enhanced Raman spectroscopy (SERS), which is also originated from the LSPR effect, provides an excellent opportunity to probe and monitor plasmonic photoreactions in situ and in real-time, with a very high surface sensitivity and energy resolution. Here, fundamentals of plasmonic photocatalysis and SERS are first presented based on their connections to the LSPR effect. Following by a validity analysis, latest studies of SERS applied for the plasmon mediated photochemical reaction are reviewed, focusing on the reaction kinetics and mechanism exploration. Finally, limitations of the present study, as well as the future research directions, are briefly analyzed and discussed.     

Surface-enhanced Raman spectroscopy for classification of testosterone propionate and nandrolone residues in chicken

There is a critical need for a rapid and simple screening method of androgens in chicken. In this study, we evaluated surface-enhanced Raman spectroscopy (SERS) coupled with multivariate techniques for the classification of two androgens (i.e., testosterone propionate and nandrolone) in chicken from 294 samples. Raw Raman spectra were pretreated by using the methods of baseline correction, normalization and second derivative. Support vector machines (SVM) model using the score values of the first four principal components as the inputs was developed to classify all the chicken samples into the four groups (i.e., control, nandrolone, testosterone propionate, and testosterone propionate combined with nandrolone groups) with accuracy of 96.9%. Furthermore, the particle swarm optimization (PSO) was adopted to automatically optimize the penalty parameter C and the kernel parameter g of SVM model for improving the classification accuracy. The experimental results demonstrated that SERS, in combination with multivariate methods, could be utilized as a rapid and simple classification assay of androgens in chicken and exhibited great potential in practical applications as a screening tool to better serve customers.     

Surface-enhanced femtosecond CARS spectroscopy (SE-CARS) on pyridine

Surface-enhanced Raman scattering (SERS) has become an integral part of spectroscopy. The inelastic scattering process is enhanced by several orders of magnitude when molecules are in close contact to nano-structured coin metals. However, the use of surface enhancement in combination with nonlinear spectroscopy is by far not as common as in linear spectroscopy even though a more drastic effect could be expected. In our work, we report the observations we made from the preliminary studies on surface enhancement mechanisms in combination with coherent anti-Stokes Raman scattering (CARS) using femtosecond laser pulses. Silver colloids were used as enhancement medium. Molecules, which show conventional SERS were selected for the experiments. Femtosecond CARS was performed on these molecular systems in the presence and absence of silver colloids. The scattered CARS signal was collected both in the forward and sideward directions. From the analysis of the results general observations were made about the factors affecting the performance of SE-CARS.     

pH值对2-(2-吡啶基)咪唑荧光光谱的影响研究

合成了2-(2-吡啶基)咪唑,并通过稳态荧光光谱研究了它在溶液中的光物理行为及溶液酸碱度的影响.发现2-(2-吡啶基)咪唑化合物存在分子内光诱导电子转移反应(PET),并且这一过程强烈地依赖于溶液的pH值,但是氮原子的质子化会影响PET过程.     

表面增强拉曼光谱结合乘子效应模型对血浆和药片中甲巯咪唑的定量检测

将表面增强拉曼散射(Surface-enhanced raman scattering,SERS)技术与乘子效应模型结合,采用2-巯基异烟酸作为内标,以银纳米颗粒为SERS增强基底,对血浆和药片样本中甲巯咪唑的进行准确的定量分析.实验结果表明,本方法对血浆样本中甲巯咪唑的平均相对预测误差为5.1％,检出限为32 nmol/L;对药片中甲巯咪唑的定量结果与LC-MS/MS方法基本一致,其加标回收率在93.3％ ～ 110.9％之间.     

Surface-enhanced Raman studies of bradykinin using colloidal gold

In this paper, bradykinin (BK), an endogenous peptide hormone, which is involved in a number of physiological and pathophysiological processes was deposited onto the colloidal Au nanoparticles. The surface-enhanced Raman spectroscopy (SERS) was used to determine the adsorption mode of BK under different environmental conditions, including: excitation wavelengths (514.5 nm and 785.0 nm), pH of aqueous sol solutions (from pH = 3 to pH = 11), and size of the colloidal nanoparticles (10, 20, and 50 nm). The metal surface plasmon of the colloidal suspended Au nanoparticles was examined by ultraviolet-visible (UV–vis) spectroscopy. The results showed that the C-terminal part of BK plays a crucial role in the adsorption process onto the colloidal suspended Au particles. The Phe^5/8 and Arg⁹ residues of BK mainly participate in the interactions with the colloidal Au nanoparticles. At acidic pH of the solution (pH = 3), the BK COO⁻ terminal group through the both oxygen atoms strongly binds to the Au nanoparticles. The Phe⁵/Phe⁸ rings adopt tilted orientation with respect to the colloidal Au nanoparticles with diameters of 10 and 20 nm. As the particle size increases to 50 nm, the flat orientation of the Phe ring(s) with respect to the Au nanoparticles is observed.     

Surface-enhanced Raman scattering as a tool to probe cytochrome P450-catalysed substrate oxidation

Surface-enhanced Raman scattering was used as a spectroscopic tool to investigate the changes brought upon cytochrome P450BSß after fatty acid binding. Differences in the spectra of substrate-free and substrate-bound enzyme were observed indicating the potential for this method to be used in the screening of P450 substrates. In particular, the binding characteristics of myristic acid, an inherent substrate, and hydroxylauric acid, a product of fatty acid oxidation, towards P450BSß in the presence of H₂O₂ were investigated. Specific spectral changes could be assigned to changes in the heme environment only for myristic acid, indicating an occurrence of oxidation process characteristic for the enzymatic substrate.     

咪唑对锌缓蚀机理的表面增强拉曼光谱研究

利用电化学现场表面增强拉曼光谱技术(SERS)研究了咪唑在锌表面的成膜和缓蚀行为, 讨论了电位和pH值对咪唑分子和金属表面作用的影响. 锌电极上的表面拉曼光谱研究结果表明, 中性溶液中咪唑对锌的缓蚀作用明显, 它通过氮端垂直吸附在锌表面, 从而阻止锌的腐蚀, 其吸附取向不随电位的变化而改变; 在碱性溶液中咪唑和锌的作用较弱, 而且电位变化可以使其吸附取向发生改变, 在较正电位下咪唑以氮端垂直吸附, 在较负电位下以咪唑环倾斜吸附.     

表面增强拉曼光谱法快速定量分析食品中福美双、二氰蒽醌和灭蝇胺的残留

基于表面增强拉曼光谱(SERS)技术,以Au@SiO2和Au纳米增强粒子建立了食品中福美双、二氰蒽醌和灭蝇胺的快速定量分析方法,3种农药的检出限分别为1.4μg/L、0.020mg/L和0.030mg/L。采用加标回收试验对方法进行评价,福美双在生活饮用水和碳酸梨汁饮料中的回收率在104.5%~107.1%之间,相对标准偏差为4.0%~6.2%;二氰蒽醌在生活饮用水中的回收率在81.1%~100.0%之间,相对标准偏差为4.1%~7.8%,灭蝇胺在碳酸饮料和果皮中测定的相对标准偏差均小于11.0%,结果表明该方法准确可靠,精密度高。方法成功用于加标碳酸果汁饮料、果皮表面二氰蒽醌及灭蝇胺的检测,为快速定量检测食品中农残提供了SERS方法。     

表面增强拉曼光谱法同时检测奶粉中三聚氰胺和二聚氰胺

本文建立了奶粉中同时检测三聚氰胺及二聚氰胺的表面增强拉曼光谱法.奶粉样品经15％三氯乙酸溶液提取,中性氧化铝吸附杂质后进行拉曼光谱检测.三聚氰胺线性范围为0.0050～0.075 mg/L,检出限为0.0015 mg/L,回收率在79.5％～124％之间,相对标准偏差小于8.8％(n=5);二聚氰胺线性范围为0.50～l0mg/L,检出限为0.15 mg/L,回收率在76.5％～112％之间,相对标准偏差小于9.4％(n=5).该方法相比常规表面增强拉曼光谱法,仅通过一种样品前处理手段即可对奶粉中的三聚氰胺或二聚氰胺进行定性检出及定量分析,相比色谱等检测方法具有样品前处理过程简单、耗时短等优点,在奶粉质量监控方面具有良好的应用前景.     

纳米颗粒银层的电沉积机理及SERS效应

研究了大面积均匀平整的纳米颗粒银层电沉积的机理, 优化了制备工艺, 探索了其在表面增强拉曼光谱检测中的应用. 结果表明, 该纳米颗粒银层的电沉积随着电极电势的负移, 逐步由连续成核转向瞬时成核机理, 在电流密度为1.0 A/dm², 阴阳极面积比为1∶10, 以及20~30 ℃条件下, 银层具有更强的表面增强效应. XRD测试表明, (111)晶面为银电沉积层的择优取向面; 扫描电子显微镜表征表明, 银的颗粒尺度为6~11 nm. 该电沉积层作为表面增强拉曼光谱的活性基底, 具有灵敏度高及检测限低的特点, 对罗丹明6G 分子的检测限低至1.0×10^-12 mol/L, 同时在大范围内的拉曼增强效果均匀, 展现了良好的应用前景.     

银纳米枝的合成及表面增强拉曼效应

利用硝酸银与铜之间发生置换反应原理, 在铜箔上得到了有序的银纳米枝结构, 用十二烷基磺酸钠(SDS)为表面活性剂, 通过调控前驱体硝酸银的浓度, 可在铜箔上得到不同密度的银纳米枝. 表面拉曼增强实验结果表明, 当分别以对巯基苯胺(4-ATP)、腺嘌呤和罗丹明G6为探针分子时, 有序的银纳米枝结构比无序的银纳米粒子具有更好的拉曼增强活性; 且随银纳米枝密度的增加, 表面拉曼增强活性有所提高. 该有序的银纳米枝结构是较好的表面增强拉曼(SERS)活性基底, 在有机分子和生物分子的SERS检测方面将具有一定的应用前景.     

基于表面增强拉曼光谱快速检测纺织品禁用染料

基于表面增强拉曼光谱(SERS)技术, 发展了一种纺织品中染料定性检测的快速方法. 以国家明确禁止使用的致癌染料碱性红9(Basic red 9)和分散黄23(Disperse yellow 23)为模型分子, 利用一步法快速制备的银纳米粒子为SERS基底并进行优化. 通过在纺织品表面直接滴加银纳米粒子的方法实现了纺织品中染料的快速SERS鉴别. 研究结果表明, 该方法不需要复杂的样品前处理过程, 能够直接实现纺织品中染料的快速定性, 且灵敏度高, 对纺织品上两种禁用染料碱性红9和分散黄23的检测限分别为0.16和0.24 mg/kg, 超出了国家标准的要求, 有望成为一种实用的纺织品安全性评估技术.     

Advances in surface-enhanced Raman spectroscopy for analysis of pharmaceuticals: A review

Recently, Raman spectroscopy become a popular and potential analytical technique for the analysis of pharmaceuticals as a result of its advancement. The innovation of laser technology, Fourier Transform-Raman spectrometers with charge coupled device (CCD) detectors, ease of sample preparation and handling, mitigation of sub-sampling problems using different geometric laser irradiance patterns and invention of different optical components of Raman spectrometers are contributors of the advancement of Raman spectroscopy. Transmission Raman Spectroscopy is a useful tool in pharmaceutical analysis to address the problems related with sub-sampling in conventional Raman back scattering. More importantly, the development of surface-enhanced Raman scattering (SERS) has been a prominent advancement for Raman spectroscopy to be applied for pharmaceuticals analysis as it avoids the inherent insensitivity and fluorescence problems. As the active pharmaceutical ingredients (APIs) contain aromatic or conjugated domains with strong Raman scattering activity, Raman spectroscopy is an attractive alternative conventional analytical method for pharmaceuticals. Coupling of Raman spectroscopy with separation techniques is also another advancement applied to reduce or avoid possible spectral interferences. Therefore, in this review, transmission Raman spectroscopy, SERS, and SERS coupled with various separation techniques for pharmaceutical analysis are presented.     

In-situ surface-enhanced Raman scattering and FT-Raman spectroscopy of black prints

The black inkjet and laser prints were analysed with regard to application in forensic analysis of questioned documents. The purpose of this work was to study spectral properties and compare the suitability of surface-enhanced Raman scattering (SERS) with Fourier transform Raman spectra of prints. This work aimed to find optimal surface-enhanced Raman spectroscopic approach for the future analysis of documents using statistical methods. In this work, we analysed eight prints of four laser and four inkjet devices. The samples were measured using two dispersive Raman devices; (DXR Raman microscope with excitation line 532 nm, Foram 685-2 spectrometer − 685 nm) and FT-Raman device (Bruker Spectrometer MultiRAM with excitation line 1064 nm). The silver nanoparticles (AgNPs) colloid for SERS experiment were synthesised and checked by UV–vis spectroscopy and scanning electron microscopy (SEM). The remarkable differences caused by centrifugation of silver colloid were observed just in the SEM images. The main contribution of this paper is to propose the novel approach achieving sufficient SERS signal intensity of black prints using the both, laser and inkjet printers. Moreover, this method is based on just a single metal colloid, and the analysis can be performed in-situ, i.e. directly on the printed sample surface. We consider the SERS could by highly promising and universal for applications in the forensic analysis of printed documents with the combination of statistical method when conventional methods are not effective.     

Determination of primary aromatic amines using immobilized nanoparticles based surface-enhanced Raman spectroscopy

Primary aromatic amines(PAAs) are substances with toxicity and suspected human carcinogenicity. A facile method for highly sensitive detection of PAAs using surface-enhanced Raman spectroscopy(SERS)is reported. The immobilization of Au nanoparticles(AuNPs) on the glycidyl methacrylate–ethylene dimethacrylate(GMA-EDMA) materials makes the substrate a closely packed but not aggregated AuNP arrays which provides a prominent SERS enhancement. Four PAAs with different substituent groups,namely, p-toluidine, p-nitroaniline, benzidine and 4,4-methylene-bis-(2-chloroaniline) have been successfully identified and quantified. High sensitivity and good linear relationship between SERS signals and concentrations of PAAs are obtained for all four PAAs.     

银纳米粒子有序自组装体中偶联分子的表面增强拉曼光谱研究

采用自组装方法,分别以1,4-二巯基苯和对巯基苯胺为偶联分子,在光滑银基底表面上构筑了银纳米粒子的单层和双层有序结构.表面增强拉曼光谱研究表明,在有序银纳米粒子组装体中偶联分子的拉曼散射得到很大增强,其中1,4-对巯基苯的拉曼散射增强效应主要来自光滑银基底表面与单层银纳米粒子间的电磁耦合,而对巯基苯胺的拉曼散射增强效应则主要由两层银纳米粒子之间耦合作用所致.两种不同的耦合作用所产生的增强效应大致相近.     

Density functional theory and surface-enhanced Raman spectroscopy studies on endocrine-disrupting chemical,dimethyl phthalate

A method to monitor endocrine-disrupting chemical contamination phthalate esters (PAEs) by surface-enhanced Raman scattering (SERS) spectroscopy has been investigated. The molecular structure and assignment of the vibrations of dimethyl phthalate (DMP), forming short chains in PAEs, has been studied by density functional theory (DFT) calculations. The structure of DMP with the dihedral angles of 1C-6C-11C-13O and 4C-5C-18C-20O being 133.78° and −24.00°, respectively, has the lowest energy. Theoretical vibrational frequencies using B3LYP/6-31 + G(d) (after scaling) show excellent agreement with the experimental normal Raman spectrum. In the region 200–1800 cm⁻¹, SERS spectra of DMP were measured using ordered gold nanosubstrates. All except the weak signals in the normal Raman spectrum of DMP were successfully enhanced. These results demonstrate that SERS technology could be developed as a rapid method for screening of DMP.