Facile electrochemical surface-alloying and etching of Au wires to enable high-performance substrates for surface enhanced Raman scattering

Surface-enhanced Raman Spectroscopy(SERS)is a nondestructive technique for rapid detection of analytes even at the single-molecule level.However,highly sensitive and reliable SERS substrates are mostly fabricated with complex nanofabrication techniques,greatly restricting their practical applications.A convenient electrochemical method for transforming the surface of commercial gold wires/foils into silver-alloyed nanostructures is demonstrated in this report.Au substrates are treated with repetitive anodic and cathodic bias in an electrolyte of thiourea,in a one-pot one-step manner.X-rays absorption fine structure(XAFS)spectroscopy confirms that the AuAg alloy is induced at the surface.The unique AuAg alloyed surface nanostructures are particularly advantageous when served as SERS substrates,enabling a remarkably sensitive detection of Rhodamine B(a detection limit of 10^(-14)M,and uniform strong response throughout the substrates at 10^(-12)M).

STUDY ON PHOTO-INDUCED ORIENTATION OF A NOVEL PHOTO-ALIGNMENT FILM WITH SURFACE ENHANCED RAMAN SCATTERING (SERS) SPECTROSCOPY

Surface enhanced Raman scattering (SERS) spectroscopy was first utilized to study the photo-orientation behaviour of the photoreactive groups on a novel photo-alignment film surface and elucidate the generation mechanism of pretilt angle. The novel photo-alignment film was prepared by spin-coating a solution of ladderlike polysiloxane (LPS) bearing dual photoreactive group on an ITO surface and by irradiation with linear-polarized ultraviolet (LPUV) light A Si—H terminal compound (M) containing an identical photosensitive part has been used to fabricate a model film for SERS investigation.

Role of Raman spectroscopy and surface enhanced Raman spectroscopy in colorectal cancer

Colorectal cancer(CRC) is the fourth most commoncancer in the United Kingdom and is the second largest cause of cancer related death in the United Kingdom after lung cancer.Currently in the United Kingdom there is not a diagnostic test that has sufficient differentiation between patients with cancer and those without cancer so the current referral system relies on symptomatic presentation in a primary care setting.Raman spectroscopy and surface enhanced Raman spectroscopy(SERS) are forms of vibrational spectroscopy that offer a nondestructive method to gain molecular information about biological samples.The techniques offer a wide range of applications from in vivo or in vitro diagnostics using endoscopic probes,to the use of micro-spectrometers for analysis of biofluids.The techniques have the potential to detect molecular changes prior to any morphological changes occurring in the tissue and therefore could offer many possibilities to aid the detection of CRC.The purpose of this review is to look at the current state of diagnostic technology in the United Kingdom.The development of Raman spectroscopy and SERS in clinical applications relation for CRC will then be discussed.Finally,future areas of research of Raman/SERS as a clinical tool for the diagnosis of CRC are also discussed.

Application of Monodisperse Thermo-Responsive Composite Microgels with Core-Shell Structure Based on Au@Ag Bimetallic Nanorod as Core in Surface Enhanced Raman Spectroscopy Substrate

The monodisperse Au@Ag bimetallic nanorod is encapsulated by crosslinked poly( N-isopropylacrylamide)( PNIPAM) to produce thermo-responsive composite microgel with well-defined core-shell structure( Au@ Ag NR@ PNIPAM microgel)by seed-precipitation polymerization method using butenoic acid modified Au @ Ag NRs as seeds. When the temperature of the aqueous medium increases from 20℃ to 50℃,the localized surface plasmon resonance( LSPR) band of the entrapped Au @ Ag NR is pronouncedly red-shifted because of the decreased spatial distances between them as a result of shrinkage of the microgels,leading to their plasmonic coupling. The temperature tunable plasmonic coupling is demonstrated by temperature dependence of the surface enhanced Raman spectroscopy( SERS) signal of 1-naphthol in aqueous solution. Different from static plasmonic coupling modes from nanostructured assembly or array system of noble metals,the proposed plasmonic coupling can be dynamically controlled by environmental temperature. Therefore, the thermo responsive hybrid microgels have potential applications in mobile LSPR or SERS microsensors for living tissues or cells.

Sensitive and Label-Free Detection of Protein Secondary Structure by Amide Ⅲ Spectral Signals using Surface-Enhanced Raman Spectroscopy

Proteins and peptides perform a vital role in living systems, however it remains a challenge for accurate description of proteins at the molecular level. Despite that surface-enhanced Raman spectroscopy (SERS) can provide the intrinsic fingerprint information of samples with ultrahigh sensitivity, it suffers from the poor reproducibility and reliability. Herein, we demonstrate that the silver nanorod array fabricated by an oblique angle deposition method is a powerful substrate for SERS to probe the protein secondary structures without exogenous labels. With this method, the SERS signals of two typical proteins (lysozyme and cytochrome c) are successfully obtained. Additionally, by analyzing the spectral signals of the amide Ⅲ of protein backbone, the influence of concentration on the folding status of proteins has been elucidated. With the concentration increasing, the components of α-helix and β-sheet structures of lysozyme increase while the secondary structures of cytochrome c almost keep constant. The SERS method in this work offers an effective optical marker to characterize the structures of proteins.

Self-assembly 2D plasmonic nanorice film for surface-enhanced Raman spectroscopy

As an ultrasensitive sensing technology,the application of surface enhanced Raman spectroscopy(SERS)is one interesting topic of nano-optics,which has huge application prospectives in plenty of research fields.In recent years,the bottleneck in SERS application could be the fabrication of SERS substrate with excellent enhancement.In this work,a two-dimensional(2D)Ag nanorice film is fabricated by self-assembly method as a SERS substrate.The collected SERS spectra of various molecules on this 2D plasmonic film demonstrate quantitative detection could be performed on this SERS substrate.The experiment data also demonstrate this 2D plasmonic film consisted of anisotropic nanostructures has no obvious SERS polarization dependence.The simulated electric field distribution points out the SERS enhancement comes from the surface plasmon coupling between nanorices.And the SERS signals is dominated by molecules adsorbed at different regions of nanorice surface at various wavelengths,which could be a good near IR SERS substrate for bioanalysis.Our work not only enlarges the surface plasmon properties of metal nanostructure,but also exhibits the good application prospect in SERS related fields.

Fast Quantification of the Mixture of Polycyclic Aromatic Hydrocarbons Using Surface-Enhanced Raman Spectroscopy Combined with PLS-GA-BP Network

To realize the fast and accurate quantitative analysis of the mixture of polycyclic aromatic hydrocarbons(PAHs),surface-enhanced Raman spectroscopy(SERS)coupled with multivariate calibrations were employed.In this study,three kinds of calibration algorithms were used to quantitative analysis of the mixture of naphthalene(Nap),phenanthrene(Phe),and pyrene(Pyr).Firstly,partial least squares(PLS)algorithm was used to select characteristic variables,then the global search capability of genetic algorithm(GA)was used for the determining of the initial weights and thresholds of back propagation(BP)neural network so that local minima was avoided.The PLS-GA-BP model exhibited superiority to quantify PAHs mixture,which achieved R2=0.9975,0.9710,0.9643,ARE=10.07%,19.28%,16.72%and RMSE=13.10,5.40,5.10 nmol L−1 for Nap,Phe,Pyr(in the PAHs mixture)concentration prediction respectively.The forecast error,ARE and RMSE have been reduced more than 50%and 60%respectively compared with the whole spectral BP model.The study indicates that accurate quantitative spectroscopic analysis of the mixture of PAHs samples can be achieved through the combination of SERS technique and PLS-GA-BP algorithm.

Surface-enhanced resonance Raman scattering spectroscopy of single R6G molecules

Surface-enhanced resonance Raman scattering （SERRS） of Rhodamine 6G （R6G） adsorbed on colloidal silver clusters has been studied. Based on the great enhancement of the Raman signal and the quench of the fluorescence, the SERRS spectra of R6G were recorded for the samples of dye colloidal solution with different concentrations. Spectral inhomogeneity behaviours from single molecules in the dried sample films were observed with complementary evidences, such as spectral polarization, spectral diffusion, intensity fluctuation of vibrational lines and even ＂breathing＂ of the molecules. Sequential spectra observed from a liquid sample with an average of 0.3 dye molecules in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1 or 2 molecules. Difference between the SERRS spectra of R6G excited by linearly and circularly polarized light were experimentally measured.

Rapid Identification of Legionella Pathogenicity by Surface-Enhanced Raman Spectroscopy

Objective To establish Surface-enhanced Raman Spectroscopy（SERS） can be used as a rapid and reliable method to distinguish virulent strain and mild strain of L. pneumophila. Methods We isolated and characterized of bacterial strains from ATCC and water samples strains, while we analyzed data from SERS technology using gold nanoparticles as a base and cell infections were employed to rapidly detect L. pneumophila strains. Origin 8.0 was used to collect Raman spectra, smooth and homogenize data, and to contrast spectra. Principal component analysis（PCA） was conducted to discriminate differences between groups using the multivariate analysis package Py Chem 3.0.5. Results Our results indicated that the peaks of high virulence strains reached ≥4000. This criterion was verified by subsequent cell experiments. In addition, we also conducted SERS rapid identification on the virulence of several collected clinical strains and obtained accurate results. Conclusion The present study indicates that the established SERS protocol can be used as a rapid and reliable method to distinguish virulent and mildly virulent strains of L. pneumophila, which can be further used in clinical samples.

Monitoring the penetration and accumulation of gold nanoparticles in rat skin ex vivo using surface-enhanced Raman scattering spectroscopy

Contamination by accidental cutaneous contact with the commercial products and the air pol-hutants raised a considerable health and safety issue.This study aimed to trace the dynamics of the 20 nm gold nanopartide(GNP)penetration and accumulation in rat skin tissues using a surface-enhanced Raman scattering(SERS)techmique.After the topical application of GNPs on rat skin surface,the SERS spectra were recorded for every 15 pum to an overall depth of 75 pum from skin surface for 150 min.The processes of GNP penetration in rat skin were accompanied by aggregation of GNPs,which affected SERS spectra.The results revealed that 20 nm GNPs can penetrate through stratum corneum layer,viable epidermis layer,and then into dermis layer.This study demonstrated for the first time the potential of SERS spectroscopy to monitor the penetration and accumulation of GNPs in rat skin.

THE CHARACTERIZATION OF SILVER SUBCOLLOID USED IN SURFACE ENHANCED RAMAN SPECTROSCOPY

A clear light-yellow silver sol which has the visible spectral absorption at 390 nm, when adsorbed phenylmercaptotetrazole(PMT) or mercaptobenzothiazole(MBT), has a new absorption at 510-550 nm. It was found that the adsorption of halide ions competes with PMT and MBT. However, halide ions have a completely different influence from PMT and MBT on the spectral absorption of the silver sol. The differences may result from the change of the properties of the surface of the silver subcolloidal particles and from the bond forms combining adsorbates with the substrates.

柠檬汁还原法制备AgNPs用于果蔬农药残留的SERS快速检测

[目的/意义]为满足目前市场上对农产品农药残留的快速灵敏检测需求,报道一种基于柠檬汁还原制备银纳米粒子(AgNPs)的方法。[方法]首先将新鲜柠檬汁经滤纸过滤,稀释成2%的柠檬汁水溶液,再配制一定浓度的AgNO3溶液、50 mM的NaOH溶液,放置室温保存。然后在室温下,将10 mL的ddH2O、2mL的NaOH、2mL的2%柠檬汁和5 mL的AgNO3溶液混合,待溶液颜色变为澄清的黄色时,溶液离心即可获得AgNPs。[结果和讨论]该方法制备的AgNPs,其颗粒形貌大小基本均一,约为20 nm,具有很好的表面增强拉曼散射(Surface Enhancement of Raman Scattering,SERS)增强效应,即良好的SERS信号稳定性,较强的SERS增强性能。该胶体中AgNPs分散较均匀,并且具有较长时间储存的稳定性,因此可用于微量农残检测。柠檬汁中主要还原成分抗坏血酸、葡萄糖和果糖,其含量分别为395.76μg/mL、5.95 mg/mL和5.90 mg/mL。将柠檬汁还原法制备的AgNPs用于果蔬表面农残检测,对于百草枯、多菌灵的检出限分别最低至3.90 ng/kg及0.22μg/kg。[结论]这项工作为果蔬农残快检提供了一种绿色、便捷的SERS材料制备方法,为实现农产品农药残留的快速、灵敏检测提供一种新的途径。

EFFECT OF SOLVENT ON SURFACE ENHANCED RAMAN SCATTERING SPECTRA OF COLLOIDAL SILVER

The effect of solvent on surface enhanced Raman scattering [SERS) of colloidal silver has been studied. Experiments show that the intensity of SERS is related to the polarity and molecular constitution of the solvent. The influence of solvent is due to the change of the adsorption quantity and adsorption intensity.

Raman and Surface-enhanced Raman Scattering of Chlorophenols

Raman spectrum is a powerful analytical tool for determining the chemical information of compounds. In this study, we obtained analytical results of chlorophenols（CPs） molecules including 4-chlorophenol（4-CP）, 2,6-dich- lorophenol（2,6-DCP） and 2,4,6-trichlorophenol（2,4,6-TCP） on the surface of Ag dendrites by surface-enhanced Raman scattering（SERS） spectra. SEM images indicate that the SERS substrate of Ag dendrites is composed of a large number of polygonal nanocrystallites, which self-assembled into a 3D hierarchical structure. It was found that there were distinct differences for those three molecules from Raman and SERS spectra. This indicates that SERS could be a new tool of detection technique regarding trace amounts of CPs.

Controllable Silver Plating on Silica for Surface-enhanced Raman Scattering

We proposed a facile and rapid method for preparing silica-silver core-shell（SSCS） substrates to use Ag electroless plating on SiO2@Au-seed particles.UV-Vis-NIR absorption spectrometer and SEM were employed to monitor the reaction process of the formation of Ag on the surfaces of silica beads,and the optical resonance of the substrate could shift from visible to NIR region.It has been found that surface-enhanced Raman scattering（SERS） enhancement changes with the electroless plating time and the SSCS substrate with the plating time of 90 s（90SSCS） shows the strongest SERS response under the laser excitation at 514.5 nm.Signals collected over multiple spots and substrate of rhodamine 6G（R6G） resulted in a relative standard deviation（RSD） of 9.75%.The calculated enhancement factor（EF） was approximately 105 ＂106.SSCS substrate exhibits high SERS performance,which is due to electromagnetic SERS enhancement with additional localization field within closely packed Ag nanoparticles decorated on the SiO2 nanoparticles.And this substrate presents tunable and broad localized surface plasmon resonance（LSPR）,so this method may open a new way for SERS studies with other laser excitation.

Molybdenum Nanoscrews:A Novel Non-coinage-Metal Substrate for Surface-Enhanced Raman Scattering

For the first time, Mo nanoscrew was cultivated as a novel non-coinage-metal substrate for surface-enhanced Raman scattering(SERS). It was found that the nanoscrew is composed of many small screw threads stacking along its length direction with small separations. Under external light excitation, strong electromagnetic coupling was initiated within the gaps, and many hot-spots formed on the surface of the nanoscrew, which was confirmed by high-resolution scanning near-field optical microscope measurements and numerical simulations using finite element method. These hotspots are responsible for the observed SERS activity of the nanoscrews. Raman mapping characterizations further revealed the excellent reproducibility of the SERS activity. Our findings may pave the way for design of low-cost and stable SERS substrates.

SERS光谱技术在结直肠癌诊断中的应用效果

选取扬州大学附属江都人民医院收集的50例结直肠癌组血清和50例健康组血清。以金纳米星(AuNS)为基底,利用Renishaw inVia Reflex激光共焦Raman光谱仪,对血清样本的表面增强Raman散射(SERS)光谱进行测定。借助Origin 2021对Min-Max归一化后平均光谱的特征峰分析,并用主成分分析(PCA)-K最邻近(KNN)模型对关键特征提取、分类。结果表明AuNS基底具有良好的均匀性、灵敏度和洁净性。结直肠癌患者在572、633、873、1065、1314、1417和1655 cm^(-1)特征峰处强度明显高于健康组,在1000和1536 cm^(-1)特征峰处强度低于健康组。PCA-KNN模型的准确率达到95%,灵敏度、特异性和曲线下的面积(AUC)分别达到90.0%、96.7%和0.933。结合PCA-KNN模型和SERS光谱技术可实现对结直肠癌快速、准确的识别,为诊断结肠癌提供了一种探索性的新方法。

基于水凝胶表面增强拉曼光谱(SERS)基底检测研究进展

表面增强拉曼光谱(SERS)具有超高灵敏度、指纹信息、少量样本和无损检测等独特优势,设计和制备具有优异重现性和稳定性的SERS基底是实现SERS检测技术进一步发展的关键因素。水凝胶是一种新型的封装材料,其交联聚合物网络具有能够保留大量水分的三维分层结构,并且对杂质具有良好的阻隔作用和强大的抗干扰能力。水凝胶SERS基底具有低成本、高灵敏度、快速检测、高通量等诸多优点,在这篇综述中,主要从SERS基底研究进程,水凝胶SERS基底优点,水凝胶SERS基底在食品、生物、环境检测领域的应用三个方面进行综述,以期为水凝胶SERS基底制备提供新的参考。首先,针对SERS基底研究进程,早期的固定金属纳米粒子(MNPs)刚性固态基底中,MNPs倾向于氧化和聚集,SERS基底重现性差,无法对表面粗糙样品进行分析;柔性支撑材料上修饰MNPs的SERS基底中,MNP s检测过程中容易分离,SERS基底灵敏度和稳定性差。为获得具有良好均匀性和稳定性的S ERS基底,将水凝胶与等离子体纳米结构结合,水凝胶作为MNPs的保护层为SERS分析提供了可靠的尺寸和电荷选择性,同时保持了高渗透性。其次,水凝胶SERS基底可以无需样品预处理对待测物实现原位检测,生物相容性复合水凝胶可以直接体内检测,DNA水凝胶可以精确识别,修饰多重抗体的水凝胶可以同时检测多种分析物,可调网孔尺寸的微凝胶对目标物具有选择筛分作用,三维纳米结构的水凝胶提供更多吸附热点。目前,制备的水凝胶SERS微粒、芯片、贴片等在食品安全、生物医药,环境监测的现场痕量分析方面显示出巨大的潜力。综上,水凝胶SERS基底的制备具有很好的发展前景,能够为今后的分析检测领域提供新的借鉴。

基于Ni纳米颗粒的SERS基底制备及其性能

以Ni纳米材料为研究对象,提出了一种新的基于超声辅助的表面增强Raman散射(SERS)基底的制备方法,以实现对生物分子罗丹明6G(R6G)的高灵敏检测。首先,通过超声辅助法制备Ni纳米溶液,然后,采用旋涂法制备SERS基底,以R6G为探针分子,研究了基底的SERS活性、重复性以及在基底制备过程中加入表面活性剂甲基丙烯酸甲酯(MMA)对基底SERS活性的影响。结果表明,在加入MMA的实验条件下,基底表面的纳米颗粒分散更加均匀,能提供的SERS热点更多,有助于增强基底的SERS强度。该SERS基底对R6G的最低检测限(LOD)为1×10^(-6)mol/L,增强因子约为2.56×10^(4),重复性测试的相对标准偏差为10.19%(R6G浓度为1×10^(4)mol/L)。该方法经济、简单、快速、有效,可以作为未来生物传感应用的候选方法。

液相剥离自组装法制备AgNPs/MoS_(2)复合SERS基底及其性能

二维纳米材料因其原子级厚度、可调的带隙以及高比表面积等特点,在表面增强拉曼散射(SERS)领域展现出巨大的应用潜力。当二维材料与金属纳米颗粒结合时,其SERS性能显著增强。本工作提出一种简便的复合基底制备方法,结合银纳米颗粒(AgNPs)优异的导电性能,良好的透光性和弯曲柔韧性,采用天然二硫化钼粉末作为原料,通过一步法实现二维材料直接液相剥离与AgNPs原位合成。通过单因素分析法确定硝酸银与二硫化钼的质量比、机械搅拌转速、超声时间的影响范围,再利用响应面分析法设计优化实验条件。当硝酸银和二硫化钼的质量比为5∶1、机械搅拌转速为1000 r/min、超声时间为3 h时,所制备的SERS基底在检测低浓度孔雀石绿时表现出高的灵敏度和良好的线性关系,增强因子达到四个数量级。