表面增强拉曼散射强度与金纳米粒子粒径关系

表面增强拉曼散射（SurfaceenhancedRamanscattering,简称SERS）的增强机理主要分为两类’‘－‘’：电磁增强和化学增强．通常SERS活性表面的获得需要粗糙化．MOSkovitS最先提出,可将粗糙化的SERS活性表面模型化为平整金属基底上排列的金属胶体粒子“’．这样的模型与实际体系比较符合,同时给理论处理提供了便利．在这一模型基础之上,人们提出了一系列SERS电磁增强的理论计算方法’‘－“．在这些理论计算中,大多包含有SERS强度与粒径关系的结果．粒径对SERS强度的影响体现在两方面：1）SERS与粗糙度有关,粒径可视为粗…     

在铜箔上电辅助制备纳米银及其SERS应用研究

在电化学工作站上以铜箔为工作电极,以硝酸银和PVP混合液作为前驱溶液,利用循环伏安法电辅助制备了纳米银,得到在铜箔上紧密均匀分布的纳米银颗粒聚集体作为SERS基底。通过X射线粉末衍射、X射线光电子能谱、扫描电子显微镜等表征手段,对铜箔上负载的银纳米颗粒进行了形貌和成分的表征,探讨了PVP及电辅助方法对纳米银形貌及基底SERS活性的影响。以4-巯基吡啶和罗丹明6G为探针溶液研究了制备基底的SERS活性,同时还对基底的均匀性进行了研究,结果表明所制备的SERS基底具有良好的性能。     

Plasmonic Colloidosomes as Three‐Dimensional SERS Platforms with Enhanced Surface Area for Multiphase Sub‐Microliter Toxin Sensing

Colloidosomes are robust microcapsules attractive for molecular sensing because of their characteristic micron size, large specific surface area, and dual‐phase stability. However, current colloidosome sensors are limited to qualitative fluorogenic receptor‐based detection, which restrict their applicability to a narrow range of molecules. Here, we introduce plasmonic colloidosome constructed from Ag nanocubes as an emulsion‐based 3D SERS platform. The colloidosomes exhibit excellent mechanical robustness, flexible size tunability, versatility to merge, and ultrasensitivity in SERS quantitation of food/industrial toxins down to sub‐femtomole levels. Using just 0.5 μL of sample volumes, our plasmonic colloidosomes exhibit >3000‐fold higher SERS sensitivity over conventional suspension platform. Notably, we demonstrate the first high‐throughput multiplex molecular sensing across multiple liquid phases.     

Theoretical Investigation on SERS of Pyridine Adsorbed on Cn Clusters Induced by Charge Transfer: A Hint that SERS Could be Applied on Many Materials

The SERS spectra of pyridine–C_n (n=1–6) complexes are investigated theoretically. The obtained enhancement factors of about 10²–10³ in the pre‐resonance Raman spectrum calculations are attributed to charge‐transfer transitions from the carbon clusters to pyridine, where a good match of band structures between substrates and probe molecules is essential.     

贵金属纳米颗粒杂化囊泡的制备及拉曼增强效果研究

以超支化聚合物囊泡为模板制备了贵金属纳米颗粒表面功能化的杂化囊泡.模板囊泡通过多巴胺修饰的超支化聚醚HSP-DA在水中自组装形成.在碱性条件下,囊泡表面的多巴胺自聚合生成聚多巴胺,实现囊泡的交联.由于聚多巴胺具有强黏附特性,因此可以将HSP-PDA交联囊泡分别与Au纳米溶胶、Ag纳米溶胶直接混合,得到Au纳米颗粒或Ag纳米颗粒功能化的杂化囊泡.分别测定了2种杂化囊泡的拉曼光谱,发现杂化囊泡产生了明显的表面增强的拉曼光谱(SERS)信号,清晰显示了对应于囊泡模板分子的拉曼信号,表明可以通过SERS来原位检测囊泡的组成.Ag纳米颗粒杂化囊泡展示出更高的SERS灵敏度,可进一步作为探针检测水中浓度为10-7mol/L罗丹明6G分子,得到了显著增强的拉曼光谱,证明所制备的Ag纳米颗粒杂化囊泡可用于目标分子的痕量检测.     

Long‐Term Stable Silver Subsurface Ion‐Exchanged Glasses for SERS Applications

We report on the formation of silver subsurface ion‐exchanged metal oxide (silver SIMO) glasses and their surface‐enhanced Raman scattering (SERS) activity. The samples were prepared by a combined thermal and chemical three‐step methodology and characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), environmental electron scanning microscopy (ESEM), and UV/Vis spectroscopy. This unique method provides SERS substrates with protection against contamination and strong, reliable and reproducible SERS enhancement. The Raman enhancement factors of the long‐term stable SIMO glasses were estimated to approximately 10⁷.     

Facile Fabrication of Multi‐targeted and Stable Biochemical SERS Sensors

The direct transfer of single‐crystalline Au nanowires (NWs) onto Au substrates was achieved by a simple attachment and detachment process. In the presence of a lubricant, Au NWs grown vertically on a sapphire substrate were efficiently moved to an Au substrate through van der Waals interactions. We demonstrate that the transferred Au NWs on the Au substrate can act as sensitive, reproducible, and long‐term‐stable surface‐enhanced Raman scattering (SERS) sensors by detecting human α‐thrombin as well as Pb²⁺ and Hg²⁺ ions. These three biochemically and/or environmentally important analytes were successfully detected with high sensitivity and selectivity by Au NW‐SERS sensors bound by a thrombin‐binding aptamer. Furthermore, the as‐prepared sensors remained in working order after being stored under ambient conditions at room temperature for 80 days. Because Au NWs can be routinely transferred onto Au substrates and because the resultant Au NW‐SERS sensors are highly stable and provide with high sensitivity and reproducibility of detection, these sensors hold potential for practical use in biochemical sensing.     

Tailoring Size and Coverage Density of Silver Nanoparticles on Monodispersed Polymer Spheres as Highly Sensitive SERS Substrates

Silver nanoparticles (AgNPs) were deposited onto the monodispersed carboxylic polystyrene (CPS) spheres by an improved in situ reduction method. The size and coverage density of the AgNPs on the surface of CPS spheres could be easily tailored by tuning the concentrations of carboxylic functional groups and silver precursor. The morphologies and structures of the resulting CPS/Ag hybrid particles were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), UV‐Vis‐NIR spectrometer and X‐ray photoelectron spectroscopy (XPS), etc. The surface enhanced Raman scattering (SERS) performances of the resulting uniform CPS/Ag hybrid particles were investigated using 4‐aminobenzenethiol (4‐ABT) as the probe molecule. The optimized CPS/Ag hybrid particles show high enhancement factor (EF) of 2.71×10⁷, low limit of detection (LOD) of 10^?10 m and good reproducibility with relative standard deviation (RSD) of 9.64 %. The good SERS improvement properties demonstrate these hybrid particles could be employed as simple and effective substrates in the SERS spectroscopy.     

SERS decoding of micro gold shells moving in microfluidic systems

In this study, in situ surface‐enhanced Raman scattering (SERS) decoding was demonstrated in microfluidic chips using novel thin micro gold shells modified with Raman tags. The micro gold shells were fabricated using electroless gold plating on PMMA beads with diameter of 15 μm. These shells were sophisticatedly optimized to produce the maximum SERS intensity, which minimized the exposure time for quick and safe decoding. The shell surfaces produced well‐defined SERS spectra even at an extremely short exposure time, 1 ms, for a single micro gold shell combined with Raman tags such as 2‐naphthalenethiol and benzenethiol. The consecutive SERS spectra from a variety of combinations of Raman tags were successfully acquired from the micro gold shells moving in 25 μm deep and 75 μm wide channels on a glass microfluidic chip. The proposed functionalized micro gold shells exhibited the potential of an on‐chip microfluidic SERS decoding strategy for micro suspension array.     

Doping and metallic‐support effect evidenced on SERS spectra of polyaniline thin films

Surface‐enhanced Raman scattering (SERS) is a process with origins, electromagnetic and chemical. The electromagnetic enhancement consists of the excitation of surface plasmons in the metallic support of the thin film. With only the electromagnetic enhancement mechanism, the surface spectra should not differ from volume Raman spectra. However, between SERS and volume Raman spectra, there are differences resulting from the chemical reactions taking place at the polymer/metal interface, intermediated by solvent molecules, that finally depend on the types of polymers and metallic supports. Polyaniline (PAN) is an excellent material to emphasize the chemical component of SERS. This is due to its particular structure with a repeating unit that contains two entities at different weights—a reduced state and an oxidized state–that, in turn, react differently with a metallic substrate. SERS spectra depend on the oxidizing properties of the metal surface, which involves an intermediate compound of the types Ag₂O and Au₂O₃ when N‐methyl‐2‐pyrrolidinone is used as the solvent. This article presents new results concerning the surface chemical effects that produce variations of the PAN SERS spectra. The SERS spectra of the PAN emeraldine base (PAN‐EB) layered on Au support are characterized by a semiquinoid structure that we believe is induced on the intermediate compound Au₂O₃. In the presence of H₂SO₄, the SERS spectra change gradually as the degree of acid protonation doping increases. The SERS spectra of the fully protonated PAN‐EB are identical to those obtained on PAN emeraldine salt (PAN‐ES) synthesized by cyclic voltammetry in an acid medium and are invariable with the type of metallic support. The SERS spectra show that the emeraldine salt can be partially or totally deprotonated with water or NH₄OH. The deprotonation is complete for the Ag support and partial for the Au support. The SERS spectra of the fully protonated PAN‐EB are characterized by a double band with maxima at about 1330 and 1370 cm⁻¹. Although the generation process of positive charge on the macromolecular chain of PAN‐EB doped in the presence of (C₄H₉)₄NBF₄ is similar to that due to protonic acid doping, involving cation addition (C₄H or H⁺ ions, respectively) in SERS spectra, the complex band situated at about 1330–1370 cm⁻¹ no longer appears. The doping of PAN‐EB with FeCl₃ produces two polymer forms: a salt type characterized by a protonated structure similar to that found for PAN‐ES and a base type similar to the leucoemeraldine form. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2599–2609, 2000     

铬酸根离子的SERS检测及磁分离研究

介绍了一种基于表面增强拉曼光谱技术(SERS)的简单快速检测低浓度铬酸根离子的方法. 通过介质中水与铬酸根离子以及修饰在金基底和金纳米粒子表面的羧酸根形成氢键而构建“巯基苯甲酸-金基底/铬酸根-水/巯基苯甲酸-金纳米粒子”三明治结构. 通过检测标记分子的SERS信号判断溶液中是否存在铬酸根离子. 研究表明标记分子的SERS强度与铬酸根离子的浓度有关, 随浓度增加SERS强度呈非线性增强, 在10^－9 mol/L出现转折点. 利用以上三明治结构, 通过引入功能化的Fe₂O₃@Au核壳磁性纳米粒子, 利用外加磁场可富集分离溶液中的铬酸根离子, 经SERS 检测表明10^－5 mol/L的铬酸根离子磁分离后其浓度降低了约4～6个数量级.     

Enantioselective Discrimination of Alcohols by Hydrogen Bonding: A SERS Study

Efficient and generic enantioselective discrimination of various chiral alcohols is achieved by using surface‐enhanced Raman scattering (SERS) spectroscopy through charge–transfer (CT) contributions. The relative intensities of the peaks in the SERS spectra of a chiral selector are strongly dependent on the chirality of its surroundings. This highly distinct spectral discrepancy may be due to the tendency of chiral isomers to form intermolecular hydrogen‐bonding complexes with the chiral selector in different molecular orientations, resulting in different CT states and SERS intensities of the adsorbates in the system. This study opens a new avenue leading to the development of novel enantiosensing strategies. A particular advantage of this approach is that it is label‐free and does not employ any chiral reagents, including chiral light.     

Surprisingly Long‐Range Surface‐Enhanced Raman Scattering (SERS) on Au–Ni Multisegmented Nanowires

Very long range surface‐enhanced Raman scattering is observed from a nickel nanowire that is separated by 120 nm from a pair of gold nanodisks. The excitation of the surface‐plasmon resonance (SPR) from the gold nanodisk pair generates an enhanced electromagnetic field near the nickel segment (SEM, left), leading to Raman intensity greater than the nickel alone (right).

     

Biocompatible Triplex Ag@SiO2@mTiO2 Core–Shell Nanoparticles for Simultaneous Fluorescence‐SERS Bimodal Imaging and Drug Delivery

Herein, we report the synthesis of biocompatible triplex Ag@SiO₂@mTiO₂ core–shell nanoparticles (NPs) for simultaneous fluorescence‐surface‐enhanced Raman scattering (F‐SERS) bimodal imaging and drug delivery. Stable Raman signals were created by typical SERS tags that were composed of Ag NPs for optical enhancement, a reporter molecule of 4‐mercaptopyridine (4‐Mpy) for a spectroscopic signature, and a silica shell for protection. A further coating of mesoporous titania (mTiO₂) on the SERS tags offered high loading capacity for a fluorescence dye (flavin mononucleotide) and an anti‐cancer drug (doxorubicin (DOX)), thereby endowing the material with fluorescence‐imaging and therapeutic functions. The as‐prepared F‐SERS dots exhibited strong fluorescence when excited by light at 460 nm whilst a stable, characteristic 4‐Mpy SERS signal was detected when the excitation wavelength was changed to longer wavelength (632.8 nm), both in solution and after incorporation inside living cells. Their excellent biocompatibility was demonstrated by low cytotoxicity against MCF‐7 cells, even at a high concentration of 100 μg mL^?1. In vitro cell cytotoxicity confirmed that DOX‐loaded F‐SERS dots had a comparable or even greater therapeutic effect compared with the free drug, owing to the increased cell‐uptake, which was attributed to the possible endocytosis mechanism of the NPs. To the best of our knowledge, this is the first proof‐of‐concept investigation on a multifunctional nanomedicine that possessed a combined capacity for fast and multiplexed F‐SERS labeling as well as drug‐loading for cancer therapy.     

Facile Synthesis of Multi-Branched Gold Nanostructures through a TBAB-Assisted Route in Aqueous Solution and Their SERS Property

Facile synthesis of multi‐branched gold nanostructures by using the tetrabutyl ammonium bromide (TBAB) as a capping agent is described. The reaction is carried out in a one‐step process at mild temperature. Gold nanostructures with more than six sharp branches ranging from 70 to 130 nm in length are synthesized in high yield. It is proposed that the relative weak adsorption capacity of TBAB leads to the incompletely covered gold surface and the growth of nanoparticles occurs on the uncovered gold surface, and therefore short branches appear consequently. Then positively charged TBAB layers on the gold surfaces prevent the branches from aggregating with each other which stimulates the branch growth. The prepared branched gold nanoparticles show efficient surface‐enhanced Raman scattering (SERS) properties. Low temperature (4°C) is unfavorable to the formation of multi‐branched gold nanostructures, and only thin small irregular plate‐like nanoparticles are produced. The addition of SDS in TBAB aqueous solution results in forming SDS micelles at much lower concentration of SDS (0.4 mmol/L) as compared to that in pure water, and short branched gold nanoparticles are obtained in the SDS‐TBAB system.     

Magnetism and application of NiFe@Au nanoparticles

This report describes the synthesis of magnetic NiFe@Au (i.e., NiFe core with Au shell) nanoparticles as functional spectroscopic probes. Both of the magnetic NiFe nanoparticles and its composite NiFe@Au particles were synthesized in aqueous solution. It is more analogous with the biological organism environment. The composite nanoparticles were dispersible in aqueous solution and could be directed by a magnetic field. Such NiFe@Au nanoparticles have been shown to function as magnetic and spectroscopic nanoprobes for surface enhanced Raman scattering (SERS) detection of molecules attached to the surface of the nanoparticles. It shows more potential functional SERS nanoprobes for biomolecular separation and detection.     

Silver nanocrystals with concave surfaces and their optical and surface-enhanced Raman scattering properties

Shaped and dimpled: Silver nanocrystals enclosed by concave surfaces and thus high-index facets have been prepared by simply controlling the growth habit of Ag cubic seeds. Four types of concave nanocrystals, including octahedron, cube, octapod, and trisoctahedron, were obtained (see picture).