表面增强拉曼光谱基底研究进展

表面增强拉曼光谱(SERS)由于具有拉曼峰强、检测灵敏度高、能够无损分析等特点,在生物传感、表面吸附、储能、转化、文物等领域应用广泛,而制备出均匀分散并且高稳定性和重现性SERS基底是SERS技术的前提.对表面增强拉曼光谱技术的基底以及机理进行了综述.     

金纳米双锥体的制备及对食品污染物的快速检测

制备了一种新颖、可靠、快速的检测平台用于检测食品中多种化学污染物。通过种子两步生长法合成出金纳米双锥体,采用消耗诱导分离法获得纯度接近100%的金纳米双锥体,利用液-液界面自组装法制备出大面积致密的金纳米双锥体表面增强拉曼散射（SERS）活性基底。研究表明,以结晶紫（CV）作为拉曼探针分子,该基底具有较好的SERS灵敏性和重复性;而且对抗生素孔雀石绿（MG）、农药残留福美双（THR）和塑化剂邻苯二甲酸卞酯（BBP）的检测灵敏性较高,检测限分别达到10^-9、10^-9、10^-8 mol/L,对酒中BBP的检测限为1.3 mg/kg。     

表面增强拉曼散射在癌症检测中的应用进展

表面增强拉曼散射(Surface-Enhanced Raman Scattering,SERS)由于特异性强、灵敏度高,在生物医学领域有着广泛的应用。癌症是目前人类健康的主要杀手之一,及时的诊断与治疗是提高癌症患者生存率的最佳方式。SERS光谱能够准确给出被检测的癌细胞分子层面的信息,运用表面增强拉曼散射技术准确检测癌症成为生命科学和纳米材料领域研究的热点。本文对表面增强拉曼散射原理及在癌症检测方面最新的研究进展进行了综述。     

表面增强拉曼光谱定量分析技术几种方法的探讨

表面增强拉曼光谱(SERS)技术增强了拉曼光谱的检测信号和灵敏度,拓宽了拉曼光谱在实际中的应用范围.因SERS技术具有现场快速分析等优点,被应用于农药、医药、环境、食品等领域的定量检测.但SERS在实际分析过程中,存在再现性欠佳、信号易受实验测试条件和基底干扰等因素而限制了其发展,其定量分析技术仍亟待提高和完善.阐述了...     

有序阵列SERS基底的发展和模板法制备

表面增强拉曼散射(Surface enhanced Raman scattering,SERS)增强基底的性能决定着检测信号的灵敏性和稳定性。本文综述了SERS基底的发展,并分类总结了模板法制备有序阵列基底的现状,对基底的制备方向和商业前景进行了展望。有序阵列结构基底的制备是SERS领域中的一个重要的研究课题,对SERS技术的发展和应用具有重要的意义。     

表面增强拉曼散射基底的研究进展

表面增强拉曼光谱(SERS)由于其高的灵敏度、抗干扰能力强等优点,被广泛应用在表面科学、分析化学、物理学等领域,是研究表面和界面过程的重要工具,是定性鉴定化学组成相近化合物的有力手段.因此,高品质、高活性的SERS基底一直是科研工作者们追求和研究的重点.本文对SERS活性基底的发展进行了介绍,从金、银金属纳米粒子作为基底的拉曼效应的科学研究,又进一步总结了非金属纳米粒子ZnO、TiO₂、ZnS、Cu₂O、CdTe、CdS等SERS基底.今后,将贵金属与半导体纳米材料复合将是SERS基底的研究热点.SERS光谱目前可以在液相色谱分析的检测器、医学检测仪器、刑侦分析检测等众多领域得到应用.     

两种卟啉化合物在Ag溶胶表面的紫外－可见吸收光谱和表面增强拉曼散射光谱研究

两种卟啉化合物在Ａｇ溶胶表面的紫外－可见吸收光谱和表面增强拉曼散射光谱研究王传义,刘春艳,阎晓斌,何建军,张曼华,沈涛（中国科学院感光化学研究,北京１００１０１）关键词卟啉,Ａｇ溶胶,表面增强拉曼光谱,紫外吸收光谱表面增强拉曼散射（ＳＥＲＳ）自１９７...     

自组装纳米阵列SERS基底的发展及应用进展

表面增强拉曼散射(SERS)的谱峰窄以及分子指纹特性使其在分析化学、环境检测、生物医药及食品安全等领域具有广泛应用。而稳定、均一、重复性好的SERS活性基底的制备至关重要。自组装法可制备出均一、稳定、高度有序、可控的纳米阵列,提高SERS检测的重现性和灵敏度。本文对自组装纳米阵列技术制备SERS活性基底及SERS的应用进行了综述。     

疏水性钯纳米团簇的合成及其作为表面增强拉曼散射基底的应用

以醋酸钯为前体、有机氢硅烷为还原剂开发了一种简单温和的疏水性钯纳米颗粒制备方法。通过调节前体、保护剂和还原剂的配比,在氯仿溶液中室温条件下合成了疏水性的钯纳米团簇和钯纳米球。运用透射电子显微镜（TEM）、X射线衍射（XRD）、光学接触角测试仪、循环伏安法（CV）、表面增强拉曼光谱（SERS）对这两种钯纳米材料进行了测试表征。TEM观察表明这两种钯纳米材料粒径分布均匀,分散性良好。接触角测试表明钯纳米团簇与钯纳米球均具有疏水性。CV测定结果显示这两种钯纳米材料具有良好的电催化稳定性,钯纳米团簇比钯纳米球对乙醇氧化具有更突出的电催化性能,表明钯纳米团簇结构稳定并具有更大的比表面积。SERS测试表明钯纳米团簇是一种优良的疏水性表面增强拉曼散射基底,利用这种基底对疏水性致癌物3,4-苯并芘和联苯胺进行了SERS快速检测,检测限为0.1mg/mL。     

多级结构银微-纳米晶的制备及其性能

采用液相还原法,通过调控氧化剂硝酸银与还原剂抗坏血酸的摩尔比例制备出具有多级结构的花状及枝状银微-纳米晶,考察了反应介质对形貌及尺寸的影响。利用扫描电子显微镜（SEM）、X射线衍射仪（XRD）、表面增强拉曼光谱（SERS）、紫外-可见（UV-Vis）漫反射光谱等方法,对样品的形貌、微晶结构、光学及催化性能进行了研究。结果表明：花状及枝状多级结构银微-纳米晶均具有面心立方晶体结构,且（111）晶面为主要曝露晶面;表面增强拉曼光谱表明花状及枝状银微-纳米晶为基底时均表现出优异的表面增强拉曼效应;微结构上的差异使枝状银在紫外-可见漫反射光谱上352 nm处有较强的吸收峰;在银催化硼氢化钠还原4-硝基苯酚的实验中,多级结构枝状银表现出最优良的催化活性。     

Microwave-assisted green synthesis of Ag/reduced graphene oxide nanocomposite as a surface-enhanced Raman scattering substrate with high uniformity

A nanocomposite of silver nanoparticles/reduced graphene oxide (Ag/rGO) has been fabricated as a surface-enhanced Raman scattering (SERS) substrate owing to the large surface area and two-dimensional nanosheet structure of rGO. A facile and rapid microwave-assisted green route has been used for the formation of Ag nanoparticles and the reduction of graphene oxide simultaneously with L-arginine as the reducing agent. By increasing the cycle number of microwave irradiation from 1 and 4 to 8, the mean diameters of Ag nanoparticles deposited on the surface of rGO increased from 10.3 ± 4.6 and 21.4 ± 10.5 to 41.1 ± 12.6 nm. The SERS performance of Ag/rGO nanocomposite was examined using the common Raman reporter molecule 4-aminothiophenol (4-ATP). It was found that the Raman intensity of 4-ATP could be significantly enhanced by increasing the size and content of silver nanoparticles deposited on rGO. Although the Raman intensities of D-band and G-band of rGO were also enhanced simultaneously by the deposited Ag nanoparticles which limited the further improvement of SERS detection sensitivity, the detectable concentration of 4-ATP with Ag/rGO nanocomposite as the SERS substrate still could be lowered to be 10⁻¹⁰ M and the enhancement factor could be increased to 1.27 × 10¹⁰. Furthermore, it was also achievable to lower the relative standard deviation (RSD) values of the Raman intensities to below 5%. This revealed that the Ag/rGO nanocomposite obtained in this work could be used as a SERS substrate with high sensitivity and homogeneity.     

High-density metallic nanogaps fabricated on solid substrates used for surface enhanced Raman scattering

The Raman signal of adsorbed molecules can be significantly enhanced by utilizing metallic structures with high-density Raman hot spots used as surface enhanced Raman scattering (SERS) substrates. In this work, we develop a simple, convenient and tunable method to fabricate high-density Ag or Au nanogaps on Si wafers. These nanogaps can serve as Raman hot spots, leading to dramatic enhancement of the Raman signal. The high-density nanogaps can be formed by repeating the electroless deposition of Ag NPs (or Au NPs) and coating of p-aminothiophenol (PATP, a Raman probe) on the deposited Ag NPs (or Au NPs) through the self-assembly process. After removal of PATP by O(2) plasma, the as-fabricated SERS substrate can be reused for the detection of other molecules.     

Enhanced sensitivity of a direct SERS technique for Hg(2+) detection based on the investigation of the interaction between silver nanoparticles and mercury ions

Mercury which is a very important pollutant has drawn significant attention in recent research. So far, among the various detection methods, the strategies based on surface-enhanced Raman scattering (SERS) are quite attractive because of the high sensitivity, and especially as it is reported that Hg(2+) can be directly detected by SERS without tagging. However, the procedure for the direct SERS detection of mercury is still unclear with little experimental evidence, limiting further development of Hg(2+) detection by SERS. Herein, we performed a simple method based on SERS for the detection of mercury ions in water without tagging. It is established that in only 2 min, low concentration of Hg(2+) can be recognized based on the decrease of SERS intensity. The detection procedure is investigated by multiple characterizations and the mechanism proven by the obtained data provides a practical way to further improve the sensitivity of the SERS detection. It is demonstrated that the interaction between Hg(2+) and Ag nanoparticles (Ag NPs) could occur in a short time, which includes the complexation of Hg(2+) with citrate and the formation of amalgam due to the reduction of Hg(2+). This interaction influences the surface plasmon resonance (SPR) property of Ag NPs and thereby decays the electromagnetic enhancement of Ag NPs; meanwhile the interaction also causes the zeta potential decrease of Ag NPs and accordingly affects the adsorption of Raman reporter molecules on the surface of Ag NPs. Therefore, the weakness of SERS intensity in the presence of Hg(2+) should be mainly attributed to the interaction between Hg(2+) and Ag NPs. From the mechanism demonstrated, it can be speculated that using fewer Ag NPs in the detection could improve the sensitivity, because at low Hg(2+) concentration the interaction becomes stronger since every Ag nanoparticle acts with more Hg(2+) ions. Accordingly, we establish that 90.9 pM (18.2 ppt) Hg(2+) is detected in 18 μM Ag NPs, which is much lower than that in reported papers.     

Self-assembly of gold nanoparticles to silver microspheres as highly efficient 3D SERS substrates

Herein we report a simple, one-pot, surfactant-free synthesis of 3D Ag microspheres (AgMSs) in aqueous phase at room temperature. The 3D AgMSs act as supports to fix the gold nanoparticles (GNPs) in 3D space via the interaction between the carboxyl groups of GNPs and the Ag atoms of AgMSs. The ensemble of AgMSs@GNPs with high surface-enhanced Raman scattering (SERS) activity and sensitivity can be an ideal 3D substrate choice for practical SERS detection applications. The simple self-assembly strategy may be extended to other metallic materials with great potentials in SERS, catalysis, and photoelectronic devices.     

Noble metal nanocrystals: plasmon electron transfer photochemistry and single-molecule Raman spectroscopy

The excited electronic states of noble metal Au and Ag nanocrystals are very different than those of molecules. Ag and Au nanocrystal optical transitions (plasmons) in the visible can be so intense that they significantly modify the local electromagnetic field. Also, coherent elastic Rayleigh light scattering is stronger than normal electronic absorption of photons for larger nanocrystals. These two facts make Au and Ag nanocrystals ideal nanoantennas, in that they focus incident light into the local neighborhood of subwavelength size. Surface-enhanced Raman scattering (SERS), in which the Raman scattering rate of nearby molecules increases by many orders of magnitude, is a consequence of this nanoantenna effect. Metallic nanocrystals also have no band gap; this makes them extraordinarily polarizable. Their electronic transitions sense the local environment. An extreme case is the interaction of two 30 nm Ag nanocrystals separated by a 1 nm gap. Their mutual polarization completely transforms the nature of the metallic excited electronic state. Single particles have an excited state uniformly distributed throughout the interior, while the nanocrystal dimer has its excited state localized on the metal surface in the junction. This creates an electromagnetic "hot spot" in the junction, enabling the observation of single-molecule SERS. The fact that surface molecules are typically chemisorbed and exchange electrons with the metal has interesting chemical consequences. First, the enhanced Raman intensities are controlled by quantum mechanical coupling of the molecular lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) with the optically excited electrons in the metal. Second, charge-transfer photochemistry can result from metal plasmon excitation. In crystalline Ag nanocrystals the photochemistry quantum yield can be high because the nanocrystal surface dominates plasmon nonradiative relaxation. Colloidal Ag nanocrystals stabilized by sodium citrate build up a photovoltage under visible excitation, caused by irreversible "hot hole" photo-oxidation of adsorbed citrate anion. This creates a driving force for photochemical transformation of round 8 nm Ag seeds into 70 nm single-crystal disk prisms under room lights, in a novel type of light-driven Ostwald ripening.     

Fabrication and evolution of multilayer silver nanofilms for surface-enhanced Raman scattering sensing of arsenate

Surface-enhanced Raman scattering (SERS) has recently been investigated extensively for chemical and biomolecular sensing. Multilayer silver (Ag) nanofilms deposited on glass slides by a simple electroless deposition process have been fabricated as active substrates (Ag/GL substrates) for arsenate SERS sensing. The nanostructures and layer characteristics of the multilayer Ag films could be tuned by varying the concentrations of reactants (AgNO₃/BuNH₂) and reaction time. A Ag nanoparticles (AgNPs) double-layer was formed by directly reducing Ag⁺ ions on the glass surfaces, while a top layer (3rd-layer) of Ag dendrites was deposited on the double-layer by self-assembling AgNPs or AgNPs aggregates which had already formed in the suspension. The SERS spectra of arsenate showed that characteristic SERS bands of arsenate appear at approximately 780 and 420 cm^-1, and the former possesses higher SERS intensity. By comparing the peak heights of the approximately 780 cm^-1 band of the SERS spectra, the optimal Ag/GL substrate has been obtained for the most sensitive SERS sensing of arsenate. Using this optimal substrate, the limit of detection (LOD) of arsenate was determined to be approximately 5 μg·l^-1.     

Naturally inspired SERS substrates fabricated by photocatalytically depositing silver nanoparticles on cicada wings

Densely stacked Ag nanoparticles with an average diameter of 199 nm were effectively deposited on TiO₂-coated cicada wings (Ag/TiO₂-coated wings) from a water-ethanol solution of AgNO₃ using ultraviolet light irradiation at room temperature. It was seen that the surfaces of bare cicada wings contained nanopillar array structures. In the optical absorption spectra of the Ag/TiO₂-coated wings, the absorption peak due to the localized surface plasmon resonance (LSPR) of Ag nanoparticles was observed at 440 nm. Strong Surface-enhanced Raman scattering (SERS) signals of Rhodamine 6G adsorbed on the Ag/TiO₂-coated wings were clearly observed using the 514.5-nm line of an Ar⁺ laser. The Ag/TiO₂-coated wings can be a promising candidate for naturally inspired SERS substrates.     

负载有Ag纳米粒子的TiO2准一维复合材料制备及其SERS效应

采用紫外光还原法和种子法制得了不同含量Ag纳米粒子负载的锐钛矿型TiO2纳米带复合材料。用各种测试技术对产物的物相、形貌、Ag负载情况以及SERS性质进行了一系列表征。测试结果表明,以紫外光还原法获得的产物中Ag完全负载在TiO2纳米带表面,其粒径主要处在10～50 nm间,且Ag负载量随着还原次数增多而缓慢增加。在此基础上,以种子法制得的产物中Ag负载量则显著增大,覆盖率可达80 %以上。这种含Ag纳米复合材料具有检测吡啶分子的SERS活性,其Ag负载量越多,SERS效应越明显。     

银/铂双金属中空纳米颗粒的制备及光学性质研究

通过以Ag纳米颗粒为模板的置换和沉积反应，制备了Ag／Pt双金属复合纳米颗粒、用透射电子显微镜（TEM）对颗粒的形貌、尺寸和结构进行了表征，发现复合颗粒具有中空结构．紫外可见吸收光谱（UV-Vis）研究表明，Ag／Pt双金属中空复合纳米颗粒具有单峰的表面等离子共振吸收特征，随着反应溶液中氯铂酸和硝酸银摩尔比的增加，吸收峰先红移后蓝移．表面增强拉曼光谱实验结果表明，Ag／Pt双金属复合纳米颗粒对吡啶分子具有较好的增强效果．     

离子交换法在钠钙硅酸盐玻璃中原位合成银纳米颗粒的研究

采用离子交换结合热处理法,在商用钠钙硅酸盐平板玻璃中原位形成2～7nm的银纳米颗粒。利用电子探针、X射线吸收近边结构谱、透射电子显微镜和高分辨透射电子显微镜研究了银离子在玻璃中的扩散、还原和生长机理。结果表明：玻璃中同时存在2价和3价铁离子,2价铁离子的存在有利于银离子被还原成中性银原子。银原子在玻璃中成核并生长成纳米颗粒。银纳米颗粒可以在离子交换时形成。提高热处理温度比延长热处理时间更有利于颗粒长大。特别当热处理温度高于玻璃转变温度时,出现Ostwald生长,导致银颗粒迅速长大,密度降低。大部分银纳米颗粒为十四面体单晶,少量为孪晶结构。