Exploring How to Increase the Brightness of Surface‐Enhanced Raman Spectroscopy Nanolabels: The Effect of the Raman‐Active Molecules and of the Label Size

Due to the surface‐enhanced Raman scattering (SERS) effect, SERS labels based on noble‐metal nanoparticles loaded with Raman‐active molecules are good candidates for ultrasensitive multiplexed assays and in vitro/in vivo imaging. However, understanding how to maximize the brightness of such labels is of paramount importance for their widespread application. The effective differential Raman scattering cross‐section (dσ_R/dΩ) of SERS labels made of pegylated gold nanoparticles loaded with various Raman active molecules (Raman reporters) is studied. It is found that proper choice of the Raman reporter and of nanoparticle size can enhance the dσ_R/dΩ by several orders of magnitude. The experimental results are understood by considering the molecular cross‐section for resonant Raman scattering and the local electromagnetic enhancement factor (G_SERS) in the nearby of gold nanoparticles. These results are useful to guide the design of SERS labels with improved performances and to provide a reference for the comparison of the absolute value of the dσ_R/dΩ of SERS labels based on metal nanoparticles.     

水产品中孔雀石绿和结晶紫残留的拉曼光谱法快速检测

为实现水产品中孔雀石绿以及结晶紫残留的快速检测,建立了一种水产品中孔雀石绿以及结晶紫残留的表面增强拉曼光谱（SERS）快速检测方法。该方法通过乙腈提取、石油醚净化、硼氢化钾还原以及二氯二氰苯醌（DDQ）氧化等四步获取提取液,并通过单因素实验,确定了胶体金、提取液以及促凝剂的加入量。经研究,孔雀石绿拉曼特征位移为795、39、1215、1610 cm-1,结晶紫拉曼特征位移为795、939、1610 cm-1,根据其拉曼光谱特征峰及其强度,对孔雀石绿和结晶紫进行定性快速测定。结合检出概率模型（POD）,确定出孔雀石绿及结晶紫的虾、蟹类检出限为1.00 μg/kg,鱼、贝类检出限为0.50 μg/kg,灵敏性≥95%,特异性≥95%,假阴性≤5%,假阳性≤5%符合了快速检测定性的要求。该方法操作简单、快速准确,从样品前处理到结果显示仅需40 min,可用于水产品中的孔雀石绿和结晶紫的现场快速检测。     

Carbon nanotube-tipped endoscope for in situ intracellular surface-enhanced Raman spectroscopy

Gold nanoparticle-decorated carbon nanotubes (CNTs) are used to study intracellular environments in situ using surface-enhanced Raman spectroscopy (SERS). CNTs are decorated with gold nanoparticles and assembled onto the tips of pulled glass capillaries to form a SERS-enabled endoscope. The sub-micrometer size and high mechanical strength of the endoscope make it possible to penetrate the cell membrane for intracellular probing and remain positioned inside during lengthy SERS measurements without causing damage to the cell. Using the SERS-enabled endoscope, DNA and other biomolecules are detected in situ within the nucleus of a single human cervical carcinoma cell in a minimally invasive manner. The SERS-enabled endoscopes exhibit high selectivity and sensitivity for detecting trace amounts of analytes (≈1 pM) in biofluid environments, highlighting their capabilities as label-free, biological sensors for real-time in situ cellular diagnostics, biological detection, and pharmaceutical research.     

牛奶中阿莫西林含量表面增强拉曼光谱检测方法的建立

以香水百合花瓣绿色合成的银溶胶为表面增强拉曼散射（SERS）活性基底，建立了牛奶中阿莫西林含量的SERS检测方法。对SERS检测条件进行了优化，考察了银溶胶浓度、银溶胶与阿莫西林溶液的体积比和氯化钠溶液的添加与否对SERS检测的影响。试验结果表明：当银溶胶浓度为106.04 μg/mL、银溶胶与阿莫西林溶液的体积比为41且不添加氯化钠的条件下，获得的SERS信号最强。在该条件下，阿莫西林标准溶液的浓度与1 055 cm^-1 处拉曼特征峰的SERS信号强度在1～1 000 μg/mL 范围内有良好的线性关系，方法的最低检出浓度可达到1 μg/mL。3份加标牛奶中阿莫西林的加标回收率为84.51%～93.62%，相对标准偏差（RSD）为5.16%。该方法简单方便，可实现牛奶中一定浓度阿莫西林的检测。     

Diamond-like carbon thin films produced by femtosecond pulsed laser deposition of fullerite

Diamond-like carbon films have been deposited from a fullerite target by ultra-short pulsed laser deposition technique. The results indicate that the films morphology and structure, determined by scanning electron microscopy, atomic force microscopy and energy dispersive X-ray diffraction, depend strongly on the substrate temperature. X-ray photoelectron, X-ray Auger electron, Raman and surface enhanced Raman scattering spectra indicate that the fs-DLC films composition involves a mixed sp, sp² and sp³ carbon network consisting of aromatic rings and sp³ diamond-like structures linked by chains of different lengths and composition. The films deposited at room temperature, presenting the higher content of sp³ carbon (48%), also contain C₆₀ crystalline phase and show a very high hardness of 49 GPa.     

Surface-enhanced Raman scattering substrate of silver nanoparticles depositing on AAO template fabricated by magnetron sputtering

In this report, we describe a fabrication process of low-cost and highly sensitive SERS substrates by using a simple anodizing setup and a low-energy magnetron sputtering method. The structure of the SERS substrates consists of silver nanoparticles deposited on a layer of anodic aluminum oxide (AAO) template. The fabricated SERS substrates are investigated by a scanning electron microscope (SEM), a transmission electron microscope (TEM), and a confocal Raman spectroscope. We have verified from the surface morphology that the fabricated SERS substrates consist of high-density round-shape silver nanoparticles where their size distribution ranges from 10 to 30 nm on the top and the bottom of nanopores. The surface-enhanced Raman scattering activities of these nanostructures are demonstrated using methylene blue (MB) as probing molecules. The detection limit of 10⁻⁸ M can be achieved from this SERS substrate.