Single-molecule surface-enhanced Raman scattering: Current status and future perspective

The single-molecule surface-enhanced Raman scattering （smSERS） has been extensively studied after the initial observation in 1997, yet there still exist unsettled issues in the fundamental mechanism of smSERS. In this review, we survey some of the recent breakthroughs in the mechanism of smSERS and its application.     

Quantum simulation of ‘zitterbewegung' in a single trapped ion under conditions of parity-keeping and parity-breaking

The motional trembling(‘zitterbewegung’)of a relativistic electron governed by Dirac equation was originally predicted by Schr¨odinger in the early days of quantum mechanics and simulated in a recent experiment with a single trapped ultracold ion.We investigate stable and instable confinements of a single trapped ion in a Paul trap under different conditions relevant to parity.Since our treatment involves neither restriction of Lamb-Dicke limit nor rotating-wave approximation,we may demonstrate different quantum dynamics of the single trapped ion in a wide range of the trapping parameters.We discuss the origin of the zitterbewegung which is relevant to the stability of the ion trapping.     

Surface-enhanced Raman spectroscopy of morphine in silver colloid

We report the surface-enhanced Raman （SERS） spectra of morphine in silver colloid, and study the silver colloid enhanced effects on the Raman scattering of morphine. The Raman bands of morphine are assigned to certain molecule vibrations. The broad band in the long-wavelength region of the electronic absorption spectra of the sol with added adsorbent at certain concentrations has been explained in terms of the ag- gregation of the colloidal silver particles. The potential applications of SERS in quantitative measurement of the morphine samples are demonstrated. By using a proper Raman band of morphine, the detection limit of morphine in silver sol is found to be 1.5 ng/ml. The result suggests that it is of great significance to use SERS in illicit drug morphine inspection.     

Laser-Induced Silver Nanoparticles Deposited on Optical Fiber Core for Surface-Enhanced Raman Scattering

We report on surface-enhanced Raman scattering （SERS） probes based on silver nanopaxtieles which axe deposited on the core of the distal end of standard single mode fibers, by means of the very simple, versatile, and lowcost laser-induced nanoparticle technique. The morphological features of the Ag nanoparticles vary according to the experimental conditions such as laser power, illumination time, and concentration of the reaction solution. The SERS activity of the probes is demonstrated with the detections of rhodamine 6G aqueous solutions. The detections are made from both ends of the probes, i.e., in direct detection mode from the end with nanoparticles and in remote detection mode from the distal end, respectively.     

Λ_b~0-baryon production in pp collisions in the general-mass variable-flavour-number scheme,and comparison with CMS and LHCb data

We calculate the next-to-leading-order cross section for the inclusive production ofΛ_(b )baryons in pp collisions in the general-mass variable-flavor-number scheme.We use realistic evolved non-perturbative fragmentation functions obtained from fits to B-meson production in e~+e~-annihilation and compare our results for transversemomentum and rapidity distributions with recent experimental data from the CMS and the LHCb collaborations at the CERN LHC.We find satisfactory agreement in general,with some indication for the need to modify the available fragmentation functions at larger values of the scale variable.     

Semiclassical Approach to Non-Sequential Double Ionization of Diatomic Molecules in Strong Laser Field

We develop a semiclassical model to describe the non-sequential double ionization of diatomic molecules in an intense linearly polarized field, achieving insight into the two-electron correlation effect in the ionization dynamics. Compared to the experimental data of nitrogen molecules, our model shows a good agreement in the tunnelling regime and a qualitative agreement in the over-barrier regime. We find that the classical collisional trajectories are the main source of the double ionization in the tunnelling regime. As a prediction of our theory, we also calculate the double ionization ratios of H2^2＋/H2^＋ for hydrogen molecules and predict a ratio less than that of nitrogen molecules.     

Investigation on activating individual living monocytic U937 cell by interleukin-6 using Raman tweezers

We investigate the activation of living monocytic U937 cells induced by interleukin-6 （IL-6） at the single cell level. We employ home-built Raman tweezers to measure the Raman spectra of living U937 cells with and without IL-6 at the single cell level. Raman peaks of amide III, amide I, DNA backbone, as well as guanine and adenine in U937 cells, change at 1312, 1652, 1090, and 1576 cm ？1 , respectively, shortly after IL-6 is added in the medium. The change is a dynamic temporal process. In the activation process of U937 cells induced by IL-6, the protein signals recover in 20 min, while the nucleic acid signals continue to increase for 20 min. The results reveal that the biochemical cascades of activation in signal transduction induced by IL-6 can be investigated in situ at the single cell level.     

Metal-dielectric-metal plasmonic waveguide devices for manipulating light at the nanoscale

We review some of the recent advances in the development of subwavelength plasmonic devices for manipulating light at the nanoseale, drawing examples from our own work in metal-dielectric-metal （MDM） plasmonic waveguide devices. We introduce bends, splitters, and mode converters for MDM waveguides with no additional loss. We also demonstrate that optical gain provides a mechanism for on/off switching in MDM plasmonic waveguides. Highly efficient compact couplers between dielectric waveguides and MDM waveguides are also introduced.     

Biocompatible and stable core/shell drug nanocarrier with high surface-enhanced Raman scattering activity

<正>A novel drug carrier based on SiO_2-coated silver nanoparticle aggregates and antitumor drug is successfully synthesized.The surface-enhanced Raman scattering(SERS) spectra of the antitumor drug in living cells are obtained.By using silver nano-aggregates as SERS substrates instead of dispersed silver particles, a great improvement of SERS signal intensity is achieved.It is found that the chemical stability of the drug carrier can also be increased with the existence of SiO_2 shell.The adsorbing effect between antitumor drug 9-aminoacridine(9AA) and silver particles is investigated to optimize the SERS signal. The core/shell structure of the drug carrier is characterized by ultraviolet-visible(UV-Vis) spectroscopy and transmission electron microscopy(TEM) pictures.The experimental results show that the drug carrier offers biocompatibility,stability,and high SERS activity,holding the potential for realizing the intracellular drug tracing.     

Controllable optical activity of non-spherical Ag and Co SERS substrate with different magnetic field

We experimentally fabricate a non-spherical Ag and Co surface-enhanced Raman scattering(SERS) substrate, which not only retains the metallic plasmon resonant effect, but also possesses the magnetic field controllable characteristics.Raman detections are carried out with the test crystal violet(CV) and rhodamine 6G(R6G) molecules with the initiation of different magnitudes of external magnetic field. Experimental results indicate that our prepared substrate shows a higher SERS activity and magnetic controllability, where non-spherical Ag nanoparticles are driven to aggregate effectively by the magnetized Co and plenty of hot-spots are built around the metallic Ag nanoparticles, thereby leading to the enhancement of local electromagnetic field. Moreover, when the external magnetic field is increased, our prepared substrate demonstrates excellent SERS enhancement. With the 2500 Gs and 3500 Gs(1 Gs = 10~(-4)T) magnetic fields, SERS signal can also be obtained with the detection limit lowering down to 10~(-9)M. These results indicate that our proposed magnetic field controlled substrate enables us to freely achieve the enhanced and controllable SERS effect, which can be widely used in the optical sensing, single molecule detection and bio-medical applications.     

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.     

微流控SERS芯片及其生物传感应用

由于微流控芯片具有优异的集成性和灵活的可操作性,基于芯片上的检测方法被大量开发,发展十分迅速。其中,表面增强拉曼光谱（SERS）凭借其超高的灵敏度、独一无二的指纹谱和窄峰宽等特点成为一种广泛采用的检测手段。SERS微流控芯片集SERS检测技术与微流控芯片的优势于一体,一方面为SERS检测方法的重复性和可靠性提供了一个高效平台,另一方面推动了微流控芯片的功能拓展,在生物分子探测、细胞捕获乃至组织模拟等领域具有广阔的应用前景。本文在简要介绍SERS的原理及其生物传感应用的基础上,重点概述了SERS微流控芯片的构建及其在生物传感及检测中的应用,最后探讨了该研究方向存在的问题及发展方向。     

溶液酸碱性对腺嘌呤分子吸附构型影响的SERS光谱研究

核酸碱基是构成核酸的基本单元,有关核酸碱基结构的研究是核酸研究工作的重要基础。本研究借助于表面增强拉曼散射技术,对不同pH值条件下腺嘌呤分子在金表面的吸附构型及其变化特征进行了研究。研究结果表明,随着溶液酸性的增强、腺嘌呤分子质子化程度的增大,腺嘌呤分子在金表面的吸附态倾向于由通过氨基和嘌呤环上7位的氮原子作为结合点的直立吸附转变为分子平躺的吸附形式。这一转变过程通过腺嘌呤的环呼吸全对称伸缩振动的特征谱峰其强度有规律的显著变化而得以表征。有关这一谱峰的增强作用可以通过表面增强拉曼散射的电荷传递(CT)机理来加以说明。     

用于SERS基底的Au-Pd核壳纳米颗粒和银纳米立方颗粒的制备及表征(英文)

本文研究了尺寸可控的Au -Pd核壳纳米粒子和银纳米立方颗粒的表面增强拉曼散射(SERS)活性。发现Au-Pd核壳纳米粒子的增强能力要比粗糙的钯电极强;银纳米立方颗粒的增强能力和粗糙的银电极相当。更为重要的是,银纳米立方颗粒既具有原子级平整的小单晶面又处于纳米尺度,因而它们可以作为粗糙表面和结构确定的单晶表面之间的桥梁,对其SERS效应的研究可以加深人们对SERS机理的认识。     

Understanding SERS of bacteria

Surface‐enhanced Raman spectroscopy (SERS) has been suggested as a powerful tool to identify bacteria, drawing from its high fingerprint (vibrational) information content, its extreme sensitivity (down to the single molecule level) and its obliviousness to the aqueous environment intrinsic to biological systems. We review here in a comparative manner the various studies that attempted to utilize SERS for this important goal in light of the work carried out by our own group over the past 10 years or so. We show that SERS has an additional major advantage, namely, it introduces a new dimension of selectivity, which, on the one hand, makes it even more suitable as an analytical tool, but on the other hand, it requires gaining control of the precise manner in which the SERS‐active metal centers are produced and brought into contact with the micro‐organism. Our emphasis in this review is on understanding the spectra in terms of the nature of the SERS‐active centers and their placement within the bacterium. On the interpretation and assignment of the spectra, we constantly keep in mind the final goal of bacteria identification. Copyright © 2008 John Wiley & Sons, Ltd.     

铂纳米立方体的合成及其SERS活性研究

本文用氢气还原氯亚铂酸钾,以聚丙烯酸钠作表面活性剂合成了铂纳米立方体,得到的铂纳米立方体的边长约为15nm。将铂纳米立方体组装到玻碳电极表面上可以作为SERS基底。以SCN-作为探针分子,初步研究铂纳米立方体的SERS效应。从铂纳米立方体上得到的SERS信号强度比粗糙的铂电极强,这表明铂纳米立方体具有更高的SERS活性。     

微流控SERS及其在生物医学应用的研究进展

微流控芯片以其对微量样品的精确操控能力而引起特别关注,表面增强拉曼光谱(SERS)作为一种超灵敏的光谱检测技术近年来在痕量检测上应用广泛。微流控芯片与SERS相结合的系统可对微量生物样品进行无损、快速、高灵敏度且高通量的检测分析,在生物医学领域有巨大的应用潜力,是当前的研究热点之一。本文介绍了微流控SERS系统近年的发展情况,包括微流控芯片的制作加工和流体操控,以及微流控芯片中SERS基底的集成;并重点介绍了近年来SERS微流控芯片系统在生物医学上的应用,如生物分子的检测、细胞分析、药物监测和筛选、疾病诊断,以及在环境和食品健康安全方面的检测应用。     

Three-dimensional noble-metal nanostructure: A new kind of substrate for sensitive,uniform, and reproducible surface-enhanced Raman scattering

Surface-enhanced Raman spectroscopy(SERS) is a powerful vibrational spectroscopy technique for highly sensitive structural detection of low concentration analyte. The SERS activities largely depend on the topography of the substrate.In this review, we summarize the recent progress in SERS substrate, especially focusing on the three-dimensional(3D)noble-metal substrate with hierarchical nanostructure. Firstly, we introduce the background and general mechanism of3 D hierarchical SERS nanostructures. Then, a systematic overview on the fabrication, growth mechanism, and SERS property of various noble-metal substrates with 3D hierarchical nanostructures is presented. Finally, the applications of 3D hierarchical nanostructures as SERS substrates in many fields are discussed.     

金纳米粒子聚集体系的制备及其SERS效应表征

以Na2S作为金纳米粒子的还原制备与聚集剂制备了金纳米粒子聚集体系。在制备过程中通过紫外可见光谱对制备条件进行了优化。TEM表征显示聚集体系中的金纳米粒子均为球形,且聚集状态呈现出较好的均匀性。将这一聚集体系作为SERS基底应用于若干氨基酸分子的SERS光谱表征与分析。初步的研究表明Na2S-金纳米粒子聚集体系可有效地应用于生物分子的SERS光谱表征与分析。