New Tools for Investigating Electromagnetic Hot Spots in Single‐Molecule Surface‐Enhanced Raman Scattering

Surface‐enhanced Raman scattering (SERS) is quickly growing as an analytical technique, because it offers both molecular specificity and excellent sensitivity. For select substrates, SERS can even be observed from single molecules, which is the ultimate limit of detection. This review describes recent developments in the field of single‐molecule SERS (SM‐SERS) with a focus on new tools for characterizing SM‐SERS‐active substrates and how they interact with single molecules on their surface. In particular, techniques that combine optical spectroscopy and microscopy with electron microscopy are described, including correlated optical and transmission electron microscopy, correlated super‐resolution imaging and scanning electron microscopy, and correlated optical microscopy and electron energy loss spectroscopy.     

Recent strategies toward microfluidic‐based surface‐enhanced Raman spectroscopy

Surface‐enhanced Raman spectroscopy (SERS) is an extremely powerful analytical tool, which not only yields information about the molecular structure of the analyte in the form of characteristic vibrational spectrum but also gives sensitivities approaching those in fluorescence spectroscopy. The SERS measurement on the microfluidic platform provides possibility to manufacture the device with design perfectly fulfilling the needs of the application with minimal sample consumption. This review aims at describing basic strategies for SERS measurement in microfluidic devices published in the last decade and covers current trends in microfluidics with SERS detection in the field of bioanalysis and approaches toward on‐line coupling of liquid‐based separation techniques with SERS detection.     

Ultrafast plasmon dynamics and evanescent field distribution of reproducible surface-enhanced Raman-scattering substrates

Surface-enhanced Raman scattering (SERS) is a potent tool in bioanalytical science because the technique combines high sensitivity with molecular specificity. However, the widespread and routine use of SERS in quantitative biomedical diagnostics is limited by tight requirements on the reproducibility of the noble metal substrates used. To solve this problem, we recently introduced a novel approach to reproducible SERS substrates. In this contribution, we apply ultrafast time-resolved spectroscopy to investigate the photo-induced collective charge-carrier dynamics in such substrates, which represents the fundamental origin of the SERS mechanism. The ultrafast experiments are accompanied by scanning-near field optical microscopy and SERS experiments to correlate the appearance of plasmon dynamics with the resultant evanescent field distribution and the analytically relevant SERS enhancement. Figure Ultrafast time-resolved differential absorption spectroscopy combined with scanning near-field optical microscopy (left) and atomic force microscopy (right) yields insight into the photoinduced charge-carrier dynamics in innovative reproducible SERS-substrates Dana Cialla and Ronald Siebert contributed equally to this work.     

Surface- and resonance-enhanced micro-Raman spectroscopy of xanthene dyes: from the ensemble to single molecules.

Surface-enhanced resonance Raman scattering (SERRS) spectra of various rhodamine dyes, of pyronine G and thiopyronine adsorbed on isolated silver clusters were recorded at the ensemble level and at the single-molecule level with a high-resolution confocal laser microscope equipped with a spectrograph and a CCD-detector. Comparing single-molecule spectra with ensemble spectra, various inhomogeneous spectral features, such as line splitting, spectral wandering, spectral diffusion and abrupt spectral jumps between different metastable spectral states, are revealed positions and the relative intensities of the vibronic bands. Resonance enhancement is investigated with respect to single-molecule surface-enhanced Raman scattering (SERS) spectroscopy and is found to be responsible for approximately three orders of magnitude in sensitivity. A significant influence of the substituents on the single-molecule SERRS sensitivity is found, showing that various chemical effects are responsible for surface enhancement in addition to the electromagnetic enhancement effect.     

Functionalization of Ag nanoparticles with dithiocarbamate calix[4]arene as an effective supramolecular host for the surface-enhanced Raman scattering detection of polycyclic aromatic hydrocarbons

We report the use of 25,27-diethyl-dithiocarbamic-26,28-dihydroxy-p-tert-butylcalix[4]arene in the functionalization of Ag nanoparticles for pyrene detection by surface-enhanced Raman scattering (SERS). SERS spectra provided information about the calixarene orientation on the metal surface and the interaction mechanism with pyrene. Thus, in this work, we have combined a powerful spectroscopy technique such as SERS, the electronic plasmon-based properties of nanostructured metals, the molecular size-selective recognition of calixarene, and the strong chelating properties of the dithiocarbamate group toward the metal surface in the detection of polycyclic aromatic hydrocarbons.     

生物活性分子的拉曼光谱电化学研究(英文)

本文概述了采用电化学现场拉曼光谱技术研究氧化物歧化酶在L 半胱氨酸修饰金电极表面的电子迁移反应以及腺嘌呤共存条件下超氧化物歧化酶在金电极表面的电子迁移反应和不同电位下银电极表面烟酰胺腺嘌呤二核苷酸的吸附等体系的反应吸附特性 .所得结果对于分析和研究生物活性分子电化学过程机理具有重要意义 .     

Surface-enhanced Raman spectroscopy: benefits,trade-offs and future developments

Surface-enhanced Raman spectroscopy (SERS) is a vibrational spectroscopy technique with sensitivity down to the single molecule level that provides fine molecular fingerprints, allowing for direct identification of target analytes. Extensive theoretical and experimental research, together with continuous development of nanotechnology, has significantly broadened the scope of SERS and made it a hot research field in chemistry, physics, materials, biomedicine, and so on. However, SERS has not been developed into a routine analytical technique, and continuous efforts have been made to address the problems preventing its real-world application. The present minireview focuses on analyzing current and potential strategies to tackle problems and realize the SERS performance necessary for translation to practical applications.

Surface-enhanced Raman spectroscopy (SERS) is a vibrational spectroscopy technique with sensitivity down to the single molecule level that provides fine molecular fingerprints, allowing for direct identification of target analytes.     

Detection of SERS active labelled DNA based on surface affinity to silver nanoparticles

Developments in specific DNA detection assays have been shown to be increasingly beneficial for molecular diagnostics and biological research. Many approaches use optical spectroscopy as an assay detection method and, owing to the sensitivity and molecular specificity offered, surface enhanced Raman scattering (SERS) spectroscopy has become a competitively exploited technique. This study utilises SERS to demonstrate differences in affinity of dye labelled DNA through differences in electrostatic interactions with silver nanoparticles. Results show clear differences in the SERS intensity obtained from single stranded DNA, double stranded DNA and a free dye label and demonstrate surface attraction is driven through electrostatic charges on the nucleotides and not the SERS dye. It has been further demonstrated that, through optimisation of experimental conditions and careful consideration of sequence composition, a DNA detection method with increased sample discrimination at lower DNA concentrations can be achieved.     

Progress in plasmonic engineering of surface-enhanced Raman-scattering substrates toward ultra-trace analysis

This review describes advances made toward the application of surface-enhanced Raman scattering (SERS) in sensitive analysis and diagnostics. In the early sections of this review we briefly introduce the fundamentals of SERS including a discussion of SERS at the single-molecule level. Applications relevant to trace analysis, environmental monitoring, and homeland security and defense, for example high explosives and contaminant detection, are emphasized. Because the key to wider application of SERS analysis lies in the development of highly enhancing substrates, in the second half of the review we focus our attention on the extensive progress made in designing innovative soluble, supported, and ordered SERS-active nano-architectures to harness the potential of this technique toward solving current and emerging analytical tasks. No attempt or claim is made to review the field exhaustively in its entirety nor to cover all applications, but only to describe several significant milestones and progress made in these important areas and to provide some perspective on where the field is quickly moving.Dedicated to the memory of Wilhelm Fresenius     

Resonance scattering particles as biological nanosensors in vitro and in vivo

Recently dark-field microscopy and Rayleigh scattering spectroscopy have emerged as complementary technologies for ultrasensitive biological detection and imaging with high spatial and temporal resolution. Plasmonic resonant nanoparticles are key nano-scale probes for these technologies that have enabled single-molecule sensitivity and imaging. In this tutorial review, we focus on the use of plasmonic probes as single-particle biological nanosensors in vitro and in vivo. The progress in this field over the last decade will be highlighted.     

SERS-based mercury ion detections: principles,strategies and recent advances

Mercury ion (Hg²⁺), known as one of the highly toxic and soluble heavy metal ions, is causing serious environmental pollution and irreversible damage to the health. It is urgent to develop some rapid and ultrasensitive methods for detecting trace mercury ions in the environment especially drink water. Surface-enhanced Raman scattering (SERS) is considered as a novel and powerful optical analysis technique since it has the significant advantages of ultra-sensitivity and high specificity. In recent years, the SERS technique and its application in the detection of Hg²⁺ have become more prevalent and compelling. This review provides an overall survey of the development of SERS-based Hg²⁺ detections and presents a summary relating to the basic principles, detection strategies, recent advances and current challenges of SERS for Hg²⁺ detections.     

Simultaneous High Throughput Single Molecule Electrophoresis and Single Molecule Spectroscopy

Single molecule detection (SMD) has developed rapidly in recent years, especially high-throughput single molecule detection. Such research facilitated several fundamental studies at the single molecule level. In the fixture, SMD may be successfully applied to biological, clinical and medical research for DNA sequencing and single-molecule scans for disease detection. Presently, single-molecule identification of DNA and proteins is performed using fluorescence intensity, mobility or hybridization with a selective probe. In some cases, such methods are insufficient for confident single-molecule identification. Therefore, we invented a high-throughput combination single-molecule spectroscopy/imaging technique for monitoring the spectroscopic differences of several different individual molecules while they migrate in solution. The technique can offer three-dimensional data for each molecule:mobility, fluorescence intensity and spectroscopy information. Two sample systems were selected as test cases. In the first case, λ DNA is labeled with YOYO-Ⅰ,POPO-Ⅲ and a combination of the two dyes. Many individual λ DNA molecules are simultaneously imaged and identified by their spectroscopic differences. In the second case, a biotinylated 2.1 kb PCR product (also labeled with YOYO-Ⅰ) was reacted with avidin-conjugated R-phycoerythrin. The individual reactants and products are also simultaneously imaged and identified by their spectroscopic differences. This technique can be used for high-throughput DNA screening, molecular identification and monitoring intermolecular interactions with a speed of over 2,000,000 molecules per second. The existing method is the highest and most powerful single-molecule screening method available to date. Such technology is expected to have a great impact on single-molecule diagnosis and monitoring molecular interaction at the single molecule level and will be beneficial to early detection and diagnosis of disease (e.g. cancer, HIV). Furthermore, this technique allows one to directly observe and evaluate the data without any complicated calculations.     

Recent directions of electrospray mass spectrometry for elemental speciation analysis

A brief survey is given of the last 2 years’ literature on electrospray mass spectrometry (ESI-MS) for speciation analysis. As observed for many years, the main recent applications in this field concern arsenic and selenium species, especially in studies encompassing combined use of molecular and element mass spectrometry. A further application field is the stoichiometric characterization of metal complexes by ESI-MS, which in some studies was assisted by nuclear magnetic resonance spectroscopy. A few examples are presented to illustrate arsenic species involved in metabolic pathways, sulfur species in oils and bitumen, and aluminum complexes. On the basis of this review, we also give an outlook of expected future developments and trends in this research field.     

Monitoring the electrochemistry of single molecules by surface-enhanced Raman spectroscopy

Coherent control of chemical species in complex systems is always subject to intrinsic inhomogeneities from the environment. For example, slight chemical modifications can decisively affect transport properties of molecules on surfaces. Hence, single-molecule (SM) studies are the best solution to avoid these problems and to study diverse phenomena in biology, physics, and chemistry. Along these lines, monitoring SM redox processes has always been a "holy grail" in electrochemistry. To date, claims of SM electrochemistry by spectroscopy have come only from fluorescence quenching of polymers and redox-fluorescent molecules. In unconnected developments, the potential of the bianalyte surface-enhanced Raman scattering (SERS) method as a technique with SM sensitivity has been demonstrated. Raman spectroscopy has the potential to explore SM detection of any molecule, independent of its chemical nature. We provide definitive proof of SM events following redox cycles using SERS. The superior sensitivity and spectral richness of SERS makes it general enough to study, in principle, SM electron transfer of any (label-free) molecule.     

基于CiteSpace的磁性SERS检测技术研究态势分析

表面增强拉曼光谱(SERS)具有灵敏度高、特异性强、操作简便、快速等优点,已成为近年来最有前景的分析工具之一。磁性纳米材料将贵金属的独特性能和磁性结合在一起,作为SERS基底检测痕量目标物被广泛研究。本文以1990～2020年间WOS核心数据库在SERS磁性纳米基底这一领域检索到的805条记录为研究对象,运用文献计量可视化工具CiteSpace软件,对磁性纳米基底领域的核心作者、机构、期刊和国家进行共现分析、共被引分析、聚类分析,对文章进行共被引分析、高被引分析,对关键词和科学领域进行聚类分析、突现分析等研究。本研究目的是发现SERS磁性纳米基底技术检测痕量目标物这一研究领域的热点研究课题和趋势,为环境污染物分析提供参考。     

Bioanalytical applications of SERS (surface-enhanced Raman spectroscopy)

Surface-enhanced Raman scattering (SERS) is a powerful technique for analyzing biological samples as it can rapidly and nondestructively provide chemical and, in some cases, structural information about molecules in aqueous environments. In the Raman scattering process, both visible and near-infrared (NIR) wavelengths of light can be used to induce polarization of Raman-active molecules, leading to inelastic light scattering that yields specific molecular vibrational information. The development of surface enhancement has enabled Raman scattering to be an effective tool for qualitative as well as quantitative measurements with high sensitivity and specificity. Recent advances have led to many novel applications of SERS for biological analyses, resulting in new insights for biochemistry and molecular biology, the detection of biological warfare agents, and medical diagnostics for cancer, diabetes, and other diseases. This trend article highlights many of these recent investigations and provides a brief outlook in order to assess possible future directions of SERS as a bioanalytical tool.     

From single to multiple microcoil flow probe NMR and related capillary techniques: a review

Nuclear magnetic resonance (NMR) spectroscopy is one of the most important and powerful instrumental analytical techniques for structural elucidation of unknown small and large (complex) isolated and synthesized compounds in organic and inorganic chemistry. X-ray crystallography, neutron scattering (neutron diffraction), and NMR spectroscopy are the only suitable methods for three-dimensional structure determination at atomic resolution. Moreover, these methods are complementary. However, by means of NMR spectroscopy, reaction dynamics and interaction processes can also be investigated. Unfortunately, this technique is very insensitive in comparison with other spectrometric (e.g., mass spectrometry) and spectroscopic (e.g., infrared spectroscopy) methods. Mainly through the development of stronger magnets and more sensitive solenoidal microcoil flow probes, this drawback has been successfully counteracted. Capillary NMR spectroscopy increases the mass-based sensitivity of the NMR spectroscopic analysis up to 100-fold compared with conventional 5-mm NMR probes, and thus can be coupled online and off-line with other microseparation and detection techniques. It offers not only higher sensitivity, but in many cases provides better quality spectra than traditional methods. Owing to the immense number of compounds (e.g., of natural product extracts and compound libraries) to be examined, single microcoil flow probe NMR spectroscopy will soon be far from being sufficiently effective as a screening method. For this reason, an inevitable trend towards coupled microseparation–multiple microcoil flow probe NMR techniques, which allow simultaneous online and off-line detection of several compounds, will occur. In this review we describe the current status and possible future developments of single and multiple microcoil capillary flow probe NMR spectroscopy and its application as a high-throughput tool for the analysis of a large number of mass-limited samples. The advantages and drawbacks of different coupled microseparation–capillary NMR spectroscopy techniques, such as capillary high-performance liquid chromatography–NMR spectroscopy, capillary electrophoresis–NMR spectroscopy, and capillary gas chromatography–NMR spectroscopy, are discussed and demonstrated by specific applications. Another subject of discussion is the progress in parallel NMR detection techniques. Furthermore, the applicability and mixing capability of tiny reactor systems, termed “microreactors” or “micromixers,” implemented in NMR probes is demonstrated by carbamate- and imine-forming reactions.     

The asilomar conference on ion spectroscopy,October 16–20, 2009

The ASMS conference on ion spectroscopy brought together at Asilomar on October 16–20, 2009 a large group of mass spectrometrists working in the area of ion spectroscopy. In this introduction to the field, we provide a brief history, its current state, and where it is going. Ion spectroscopy of intermediate size molecules began with photoelectron spectroscopy in the 1960s, while electronic spectroscopy of ions using the photodissociation “action spectroscopic” mode became active in the next decade. These approaches remained for many years the main source of information about ionization energies, electronic states, and electronic transitions of ions. In recent years, high-resolution laser techniques coupled with pulsed field ionization and sample cooling in molecular beams have provided high precision ionization energies and vibrational frequencies of small to intermediate sized molecules, including a number of radicals. More recently, optical parametric oscillator (OPO) IR lasers and free electron lasers have been developed and employed to record the IR spectra of molecular ions in either molecular beams or ion traps. These results, in combination with theoretical ab initio molecular orbital (MO) methods, are providing unprecedented structural and energetic information about gas-phase ions.     

Single-molecule SERS detection of C60

Single-molecule Surface-Enhanced Raman Scattering (SERS) detection of buckminsterfullerene (C(60)) is achieved by using different isotopologues of the molecule with a distribution around an average isotopic substitution ((12)C → (13)C) of ~30%. The distribution of different isotopologues creates a broad (~20 cm(-1)) average SERS signal within which single-molecule SERS spectra of individual isotopic realizations of the molecule can be distinguished. The SERS enhancement factors for SM-SERS C(60) events are typically in the range of ~10(8), suggesting a limitation imposed by either photobleaching or surface interactions with the (Ag) metallic colloids to reach the highest SERS hot-spots (which can typically have larger maximum enhancements). SM-SERS signals of isotopically substituted C(60) also show broader peaks (FWHM ≈ 4 cm(-1)) than equivalent signals in natural C(60). The latter feature suggests a contribution to the homogeneous broadening coming from isotopic disorder in the molecule; a feature that can only be observed with the ability to detect single-molecule spectra.     

Spectroscopic studies of molecular interaction at the liquid–liquid interface

The development of techniques to study the liquid–liquid interface is a major challenge. Spectroscopy in all its forms provides a powerful method of investigation, especially when combined with other optical techniques. Over the last 30 years, there have been significant developments in the methods for studying heterogeneous interfaces. As technology progresses, the sensitivity of existing techniques has been improved but there are major challenges still to be met, such as the measurement of interfacial dielectric constant and viscosity. This paper aims to summarise the use of spectroscopy to study molecular interactions at the liquid–liquid interface.