Surface-Enhanced Raman Scattering on Template-Embedded Gold Nanorod Substrates

Surface-enhanced Raman scattering (SERS) of rhodamine 6G was investigated on template-embedded gold nanorods produced by anodic aluminum oxide template-assisted nanofabrication. A signal enhancement of about 10⁶ was obtained. Two-dimensional arrays of gold nanospheres with different diameters and gap sizes were used as simplified model systems. SERS substrate design principles were investigated in order to achieve maximum electromagnetic enhancement of both the incident and Raman scattered fields.     

Highly Ordered Arrays of Particle-in-Bowl Plasmonic Nanostructures for Surface-Enhanced Raman Scattering

A highly ordered particle-in-bowl (PIB) nanostructure array is designed and fabricated to achieve large field enhancement for the surface-enhanced Raman scattering (SERS) application. This new type of PIB structure is composed of an Ag particle located at the bottom of an Au bowl, and the two are separated by a precisely controlled nanoscale dielectric layer. The fabrication of the PIB structure is based on the self-assembly of polystyrene spheres and atomic layer deposition (ALD), which allows good control of the metal particle size and gap distance, as well as large-scale ordering. Numerical simulation reveals a high enhancement of the local field at the nanogaps. The SERS performance of the PIB arrays, and the effects of the Ag particle size and the ALD dielectric layer thickness are characterized, results of which are in reasonable agreement with simulation. With Rhodmaine 6G as the probe molecule, the spatially averaged SERS enhancement factor is on the order of 3.8 × 10(7) and the local field enhancement from simulation can be up to 10(8) .     

Enhanced Raman Scattering from Benzene Condensed on a Silver Grating

Abstract

We study the Raman intensity from a benzene overlayer on a silver grating as a function of layer thickness both in theory and experiment. Numerical results are obtained using matrix formalism based on the Rayleigh method for a coated grating. The electromagnetic enhancement due to surface plasmon polariton resonances and multiple beam interferences for a p-polarized incident wave is discussed.     

Separation of Silver Nanocrystals for Surface-enhanced Raman Scattering Using Density Gradient Centrifugation

One-dimensional silver nanocrystals(AgNCs) have been prepared by a polyol process using sodium hydroxide and nitric acid at a constant silver source concentration.Results indicate that the aciditybasicity plays an important role in silver-nanocrystal formation.Different morphologies of AgNCs were synthesized by changing the NaOH or HNO_3 amount.We demonstrate that nearly monodisperse silver nanocrystals can be separated from polydisperse samples using density gradient centrifugation separation(DGCS).We also demonstrate that the separated AgNCs can be used as substrates for surfaceenhanced Raman scattering(SERS) spectroscopy.The separation approach provides a method of improving the nanocrystal quality produced by large-scale synthetic methods.     

Volume‐Enhanced Raman Scattering Detection of Viruses

Virus detection and analysis are of critical importance in biological fields and medicine. Surface‐enhanced Raman scattering (SERS) has shown great promise in small molecule and even single molecule detection, and can provide fingerprint signals of molecules. Despite the powerful detection capabilities of SERS, the size discrepancy between the SERS “hot spots” (generally, <10 nm) and viruses (usually, sub‐100 nm) yields poor detection reliability of viruses. Inspired by the concept of molecular imprinting, a volume‐enhanced Raman scattering (VERS) substrate composed of hollow nanocones at the bottom of microbowls (HNCMB) is developed. The hollow nanocones of the resulting VERS substrates serve a twofold purpose: 1) extending the region of Raman signal enhancement from the nanocone surface (e.g., surface “hot spots”) to the hollow area within the cone (e.g., volume “hot spots”)—a novel method of Raman signal enhancement, and 2) directing analyte such as viruses of a wide range of sizes to those VERS “hot spots” while simultaneously increasing the surface area contributing to SERS. Using HNCMB VERS substrates, greatly improved Raman signals of single viruses are demonstrated, an achievement with important implications in disease diagnostics and monitoring, biomedical fields, as well as in clinical treatment.     

SrWO4晶体的紫外受激拉曼散射

使用提拉法生长了高光学质量的SrWO₄晶体,尺寸为22mm×40mm,重72.3g.测量了SrWO₄ 晶体的透过光谱,其短波截止边为263nm,长波截止边大于3200nm,因此可在较宽波长范围内实现拉曼频移.采用无腔的单次通过方式,在SrWO₄晶体中实现了紫外光激发的受激拉曼散射.当抽运光为355nm皮秒激光脉冲时获得了3级斯托克斯谱线（366.44、379.25、392.98nm）,其中一级斯托克斯线的抽运阈值仅为169.76MW/cm²,相应的拉曼增益高达49.09cm/GW.实验表明,SrWO₄具有透光波段宽、抗光损伤能力强、拉曼阈值低、增益系数大等优点,在紫外激光的拉曼变频方面表现出良好应用前景.     

纳米颗粒自组装SERS基底的发展及应用进展

表面增强拉曼散射(SERS)技术作为一种分析手段,因其高灵敏度、高选择性、及对样品的非破坏性等,在生物医药、环境检测、分析化学及食品安全等领域获得了广泛应用。金属纳米颗粒阵列因具有较强的局部表面等离子共振效应,能构造出高性能的SERS基底。自组装技术作为可制备出高度有序、可重复性高且结构可控的纳米阵列的方法,迄今仍是SERS基底构造研究领域中的热点。简单介绍了自组装技术的方法及其在SERS基底制备中的发展及应用,并对其未来发展趋势做出展望。     

银纳米粒的合成及其在有机磷农药检测中的应用研究

以硝酸银、柠檬酸钠为原料,硼氢化钠为还原剂合成了柠檬酸盐封端的银纳米粒,采用紫外光谱、X射线衍射仪、透射电镜对合成的银纳米粒进行表征,并成功将其应用于水样中敌百虫的分析。结果表明:合成的银纳米粒呈球形、具有良好的分散性,平均粒径25 nm,在398 nm处有最大紫外吸收峰,A398 nm/A522 nm的吸光度比与浓度在0.20~18.0 ng/m L范围内的敌百虫线性相关,检测限为0.12 ng/m L,为简单而快速地分析有机磷农残建立了新方法。     

One-step Synthesis of Shape-controllable Gold Nanoparticles and Their Application in Surface-enhanced Raman Scattering

Gold nanoparticles（NPs） of various shapes were synthesized by a one-step method at ambient temperature in the presence of NaCI.2-mercaptosuccinic acid（MSA） was used as both reducing agent and stabilizing agent.The shapes of gold NPs were controllable by simply tuning S/Au ratio（S is from MSA molecule,and S/Au ratio is controlled by tuning the volume of added MSA solution）,and triangle,polygonal and spherical nanoparticles were obtained.This result suggested a new way to consider the effects of MSA on the growth of nanoparticles,which showed that MSA is a strong capping agent and facilitates more uniform growth of nanoparticles in every dimension.And other important factors on nanoparticles growth including NaCI and temperature were discussed.Furthermore,a typical probe molecule,4-aminothiophenol（4-ATP） was used to test the surface-enhanced Raman scattering（SERS） activity of these gold NPs and the results indicated good Raman activity on these substrates.And the enhancement factor（EF） at 1078 cm^-1（a₁） was estimated to be as large as 6.3×10⁴ and 5.5×10⁴ for triangular plates and truncated particles,respectively.     

用于表面增强拉曼散射的石墨烯/纳米粒子复合基底材料的研究现状

表面增强拉曼散射(Surface enhanced Raman scattering,SERS)自从被发现以来在单分子检测、生物医学体系、环境科学、纳米材料以及传感器等领域获得了广泛的应用,而其SERS增强因子、物质吸附能力等性能的好坏主要取决于SERS的基底材料及结构。相比于纳米粒子的SERS基底,石墨烯/纳米粒子复合材料的SERS基底由于石墨烯额外的化学增强作用、表面分子富集和荧光淬灭等功能而受到各国研究人员的重视。首先分析了石墨烯/纳米粒子复合材料的SERS增强机理,然后从材料制备和基底结构两个方面综述了石墨烯/纳米粒子复合材料在SERS上的研究现状,最后对其未来的发展方向进行了展望。     

Near-Field Surface-Enhanced Raman Imaging of Dye-Labeled DNA with 100-nm Resolution

Raman chemical imaging on a scale of 100 nm is demonstrated for the first time. This is made possible by the combination of scanning near-field optical microscopy (SNOM or NSOM) and surface-enhanced Raman scattering (SERS), using brilliant cresyl blue (BCB)-labeled DNA as a sample. SERS substrates were produced by evaporating silver layers on Teflon nanospheres. The near-field SERS spectra were measured with an exposure time of 60 s and yielded good signal-to-noise ratios (25:1). The distinction between reflected light from the excitation laser and Raman scattered light allows the local sample reflectivity to be separated from the signal of the adsorbed DNA molecules. This is of general importance to correct for topographic coupling that often occurs in near-field optical imaging. The presented data show a lateral dependence of the Raman signals that points to special surface sites with particularly high SERS enhancement.     

Combined Visible Plasmons of Ag Nanoparticles and Infrared Plasmons of Graphene Nanoribbons for High-Performance Surface-Enhanced Raman and Infrared Spectroscopies

Ag nanoparticles (NPs) modified graphene nanoribbons (GNRs) are proposed to function as the high-performance shared substrates for surface-enhanced Raman and infrared absorption spectroscopy (SERS and SEIRAS). This is realized by modulating the localized plasmonic resonances of Ag NPs in visible region and GNRs in mid-infrared region simultaneously, so as to selectively employ each resonance to acquire SERS and SEIRAS on a single substrate. As a proof of concept, shared substrates are prepared by fabricating GNRs on a Fabry–Pérot like cavity, followed by depositing a thin Ag film with annealing treatment to achieve Ag NPs. Complementary Raman and infrared active vibrational modes of rhodamine 6G molecules can be extracted from the SERS and SEIRAS spectra. By optimizing the dimension of Ag NPs, SERS enhancement factors at the order of 10⁵ can be achieved, which are comparable with or even larger than that of the reported shared substrates. Meanwhile, various polyethylene oxide vibrational modes can be recognized with maximum SEIRAS amplification up to 170 times, which is one order larger than that of the reported graphene plasmonic infrared sensors. Such plasmonic nanosensor with excellent SERS and SEIRAS performance exhibits promising potential for biosensing applications on an integrated lab-on-a-chip strategy.     

Silver nanoclusters films for single molecule detection using Surface Enhanced Raman Scattering (SERS)

A highly efficient Surface Enhanced Raman Scattering (SERS) substrate was prepared using a nanocluster deposition system that enabled detection of Crystal Violet molecules down to a single molecule level. The large SERS signal enhancement can be attributed to the presence of nano gaps on the surface of the nanoclusters which create abundant hot spots for electric field enhancement. Observed variations in the Raman peaks at very low molar concentrations in the range 4 × 10⁻¹⁴–3.2 × 10⁻¹⁸ M suggest that the spectra are due to a single molecule. Possible mechanisms for ultrahigh SERS sensitivity of the substrates are discussed. These substrates take the detection limit of CV down by two orders of magnitude as compared to those reported in literature.     

Reaction Kinetics‐Mediated Control over Silver Nanogap Shells as Surface‐Enhanced Raman Scattering Nanoprobes for Detection of Alzheimer's Disease Biomarkers

It is very challenging to accurately quantify the amounts of amyloid peptides Aβ40 and Aβ42, which are Alzheimer's disease (AD) biomarkers, in blood owing to their low levels. This has driven the development of sensitive and noninvasive sensing methods for the early diagnosis of AD. Here, an approach for the synthesis of Ag nanogap shells (AgNGSs) is reported as surface‐enhanced Raman scattering (SERS) colloidal nanoprobes for the sensitive, selective, and multiplexed detection of Aβ40 and Aβ42 in blood. Raman label chemicals used for SERS signal generation modulate the reaction rate for AgNGSs production through the formation of an Ag‐thiolate lamella structure, enabling the control of nanogaps at one nanometer resolution. The AgNGSs embedded with the Raman label chemicals emit their unique SERS signals with a huge intensity enhancement of up to 10⁷ and long‐term stability. The AgNGS nanoprobes, conjugated with an antibody specific to Aβ40 or Aβ42, are able to detect these AD biomarkers in a multiplexed manner in human serum based on the AgNGS SERS signals. Detection is possible for amounts as low as 0.25 pg mL^?1. The AgNGS nanoprobe‐based sandwich assay has a detection dynamic range two orders of magnitude wider than that of a conventional enzyme‐linked immunosorbent assay.     

SrWO4晶体的紫外受激拉曼散射

使用提拉法生长了高光学质量的SrWO₄晶体,尺寸为22mm×40mm,重72.3g.测量了SrWO₄ 晶体的透过光谱,其短波截止边为263nm,长波截止边大于3200nm,因此可在较宽波长范围内实现拉曼频移.采用无腔的单次通过方式,在SrWO₄晶体中实现了紫外光激发的受激拉曼散射.当抽运光为355nm皮秒激光脉冲时获得了3级斯托克斯谱线（366.44、379.25、392.98nm）,其中一级斯托克斯线的抽运阈值仅为169.76MW/cm²,相应的拉曼增益高达49.09cm/GW.实验表明,SrWO₄具有透光波段宽、抗光损伤能力强、拉曼阈值低、增益系数大等优点,在紫外激光的拉曼变频方面表现出良好应用前景.     

Ultrasensitive Telomerase Activity Detection by Telomeric Elongation Controlled Surface Enhanced Raman Scattering

Telomerase is now considered to be a valuable biomarker and therapeutic target in the diagnosis and treatment of cancerous diseases, which brings an urgent need in the development of fast and efficient telomerase detection strategies. Here, a new surface enhanced Raman scattering (SERS) based protocol using telomeric elongation controlled SERS (TEC‐SERS) effect for the ultrasensitive telomerase detection is presented. The TEC‐SERS protocol not only provides an unprecedented high sensitivity but also avoids laborious PCR procedures. The detection limit is ≈2–3 orders of magnitude lower than those of previously reported methods. This highly sensitive and straightforward TEC‐SERS protocol can be developed as a routine telomerase detection method, which would greatly facilitate the telomerase based ultra‐early diagnosis of malignant tumors and the fast screening of anti‐cancer drugs.     

Bactericidal Textile Productions from Cellulose with Silver Nanoparticles

Stabilized silver nanoparticles, in solutions sodium-carboxymethyl cellulose （Na-CMC）, were synthesized and their structure and physico-chemical properties were studied. The forms and sizes of silver nanoparticles were studied by atomic force microscopy and transmission electron microscopy methods, which silver nanoparticles are loaded in solutions CMC and grafted cotton fabrics. Investigations show that spherical silver nanoparticles with size 5-35 nm and with content of 0.0085% mass. in cotton fabrics has a high bactericidal activity. Stabilization of silver nanoparticles helps to save the bactericidal and bacteriostatic activity during washing the cotton fabrics and textiles on their basis.     

低对称性SiO2/Ag核壳复合纳米结构的银镜反应制备及表面增强拉曼散射活性研究

利用银镜反应在自组装的SiO2纳米粒子单层膜上制备了低对称性的SiO2/Ag核壳复合纳米结构.通过透射电镜(TEM)、扫描电镜(SEM)和紫外-可见分光光度计(UV-Vis)对核壳复合纳米结构的表面形貌和光学性质进行了表征.以亚甲基蓝作为探针分子,研究了低对称性SiO2/Ag核壳复合纳米结构的表面增强拉曼散射(SERS)活性.