贵金属纳米颗粒/石墨烯复合基底SERS研究进展

由于贵金属纳米颗粒/石墨烯复合基底可为喇曼光谱分析技术提供灵敏度高、稳定性好、生物相容性好的基底而备受关注。首先从电磁原理和化学原理两个角度出发,系统地探讨了贵金属纳米颗粒/石墨烯复合基底表面增强喇曼散射(SERS)的机理,进而概述了石墨烯及贵金属纳米颗粒的制备方法及其性能特征,并详细介绍了化学气相沉积法制备石墨烯和物理法制备贵金属纳米颗粒的过程。在此基础上,对不同贵金属纳米颗粒/石墨烯复合基底SERS的国内外研究进展进行了综合的阐述和分析,主要介绍了贵金属Ag,Au和Pt的纳米颗粒复合体系,最后对贵金属纳米颗粒/石墨烯复合基底SERS技术在各个领域的应用及其发展前景进行了展望。     

两种基底对中药溶液喇曼光谱增强作用的比较

为了对比分析TiO₂-AgNPs薄膜与银胶纳米颗粒溶液两种表面增强喇曼光谱散射（SERS）基底对中药溶液样品的SERS增强效果，选取中药附子溶液作为实验样品，分别采用两种SERS基底通过喇曼散射实验取得其表面增量喇曼光谱，并进行了解析对比。结果表明，TiO₂-AgNPs薄膜与银胶纳米颗粒溶液两种SERS基底都对中药附子溶液的喇曼散射光谱起到了明显的增强作用；TiO₂-AgNPs薄膜的增强效果相对于银胶纳米颗粒溶液更为敏感，如在喇曼位移1398cm-1的相对峰强比，TiO₂-AgNPs薄膜基底为27.85%，银胶纳米颗粒溶液基底为11.97%，但其具有易氧化、可用时间短、制备难度大、可重复性不高等缺点，因此更适于样品成分的精确鉴定，银胶纳米颗粒溶液具有制备更简单、使用时间长、稳定性和重复性好等优点，适于大量样品成分确定对比的检测；两种基底对中药溶液样品的SERS增强各有优势。此结果对国内外利用SERS技术分析中药有效成分的基底选择有一定参考作用。     

硫化铅掺杂石英玻璃光纤喇曼增强特性研究

普通单模光纤的喇曼增益低,严重制约了喇曼放大器的发展。因此,研究高喇曼增益的光纤具有重要意义。研究了硫化铅掺杂石英玻璃光纤的喇曼散射增强特性。采用改进的化学气相沉积(MCVD)法分别制备出硫化铅掺杂石英玻璃光纤和普通单模光纤样品,并测得其传输损耗谱和喇曼光谱,实验结果表明:硫化铅掺杂石英玻璃光纤具有更强的喇曼散射强度。在不同的泵浦功率条件下,分别进行了喇曼放大实验,相比于普通单模光纤,硫化铅掺杂石英玻璃光纤具有更大的喇曼增益。     

级联喇曼光纤放大器

介绍了级联喇曼放大器的理论,并报道了最新的实验结果,分析了各种因素对放大器性能的影响,对未来的前景做了展望。     

蓝紫光的腔增强空气喇曼光谱

喇曼光谱是一种无损、快速检测物质成分的方法。为了提高监测灵敏度, 对408nm波段半导体激光器的腔增强自发喇曼散射进行了研究。利用输出功率500mW、线宽0.9nm的408nm半导体激光器作激发光, 把激光耦合入共焦球面镜腔, 两面共焦球面镜的反射率分别为96.5%和99.5%, 部分激光返回半导体激光器形成光反馈, 半导体激光器与共焦腔形成共振。对装置的光反馈过程进行了探讨, 并对外腔的模式匹配和频率匹配分别进行了分析。结果表明, 共焦腔内功率达到15W, 功率增强了30倍; 用90°探测构型收集喇曼信号, 完成了空气喇曼信号检测; 1s积分时间, 获得N₂信号900个计数。此共振增强腔大大增强了喇曼散射信号, 有潜力应用于多种气体的在线检测或高灵敏度检测。     

喇曼-原子力显微镜的研究进展

喇曼-原子力显微镜(Raman-AFM)是一种基于探针增强喇曼散射效应(TERS)的新型形貌表征与光电测试设备,能够在纳米尺度上对低维结构材料与器件进行喇曼研究.本文详细介绍了Raman-AFM的基本原理与关键技术特点,并展望了它的发展前景.     

喇曼分析仪

由海洋光学器件公司生产的R-3000喇曼分析仪系统可对水溶液、粉末、药片、凝胶和表面介质进行实时定性和定量光谱分析。这种分析仪系统的分析光谱范围为200cm~(-1)～2700cm~(-1),其激光分辨率优于10cm~(-1),     

基于差分喇曼光谱快速鉴别食品塑料包装袋

为了快速鉴别案件现场残留的食品塑料包装袋样本,采用差分喇曼光谱法结合系统聚类分析方法,对46个不同来源、不同系列的食品塑料包装袋样本进行了分析检验.结果表明,依据差分喇曼光谱图中特征峰的不同,可以有效区分不同来源的食品塑料包装袋样本;同时结合系统聚类分析法,可将46个样本分为17类.该方法不破坏检材、重现性好,实验结果...     

Surface-enhanced Raman spectroscopy chips based on two-dimensional materials beyond graphene

Surface-enhanced Raman spectroscopy (SERS) based on two-dimensional (2D) materials has attracted great attention over the past decade.Compared with metallic materials,which enhance Raman signals via the surface plasmon effect,2D materials integrated on silicon substrates are ideal for use in the fabrication of plasmon-free SERS chips,with the advantages of outstanding fluorescence quenching capability,excellent biomolecular compatibility,tunable Fermi levels,and potentially low-cost material preparation.Moreover,recent studies have shown that the limits of detection of 2D-material-based SERS may be comparable with those of metallic substrates,which has aroused significant research interest.In this review,we comprehensively summarize the advances in SERS chips based on 2D materials.As several excellent reviews of graphene-enhanced Raman spectroscopy have been published in the past decade,here,we focus only on 2D materials beyond graphene,i.e.,transition metal dichalcogenides,black phosphorus,hexagonal boron nitride,2D titanium carbide or nitride,and their heterostructures.We hope that this paper can serve as a useful reference for researchers specializing in 2D materials,spectroscopy,and diverse applications related to chemical and biological sensing.     

Comparative characteristics of the Raman scattering spectra of graphene films on conductive and semi-insulating 6H-SiC substrates

The raman scattering (RS) spectra of graphene on semi-insulating and conductive 6H-SiC substrates formed by preliminary and additional annealing of silicon carbide at various temperatures are studied. The degree of perfection of the graphene films and sizes of its clusters are estimated. It is shown that the temperature of additional annealing in the case of conductive substrates should be higher than that for semi-insulating substrates to obtain graphene layers with the same structural perfection.     

Raman analysis of epitaxial graphene on 6H-SiC(000) substrates under low pressure environment

This article investigates the formation mechanism of epitaxial graphene on 6H-SiC(0001) substrates under low pressure of 2 mbar environment.It is shown that the growth temperature dramatically affects the formation and quality of epitaxial graphene.The higher growing temperature is of great benefit to the quality of epitaxial graphene and also can reduce the impact of the substrate for graphene.By analyzing Raman data,we conclude that epitaxial graphene grown at 1600℃has a turbostratic graphite structure.The test from scanning electron microscopy (SEM) indicates that the epitaxial graphene has a size of 10μm.This research will provide a feasible route for fabricating larger size of epitaxial graphene on SiC substrate.     

激光偏振拉曼的CVD多晶石墨烯表征

石墨烯具有优异的物理化学性质,在MEMS器件、光电检测材料、柔性显示屏、新能源电池、复合材料等方面成为研究热点。目前大面积石墨烯制备主要依赖于化学气相沉积技术(chemical vapor deposition, CVD),但其生长的晶体质量直接影响到电化学特性和实际应用,因此需要一种快速而准确的表征方法。实验利用背向散射的偏振激光散射装置测量CVD生长的石墨烯拉曼光谱。通过分析实验获得的300 nm SiO2/Si基底上的单层、五层和十层左右的石墨烯角分辨偏振拉曼光谱,发现单层生长的石墨烯偏振特性与机械剥离单晶石墨烯一致;随着层数的增加,G峰偏振响应差异更加明显,表现出明显的椭圆特性;在不同石墨烯层数上的D峰也呈现出一定的偏振响应差异性。偏振拉曼测试结果表明目前CVD生长的缺陷和多晶特性与石墨烯层数呈现正相关特征。     

提高波前探测精度的高阶矩方法

夏克-哈特曼波前传感器测量畸变波前的探测精度主要取决于光斑质心的测量精度。提出了一种提高光斑质心探测精度的新方法,在优化的探测窗口内使用高阶矩方法计算光斑的质心。首先,在整个子孔径内,通过一阶矩方法获得光斑的近似中心,然后以这个近似中心为中心,包含整个光斑,建立一个矩形窗口,并在该窗口内通过高阶矩方法重新计算光斑的质心。通过该改进的方法,在优化的探测窗口外,噪声的影响基本被消除;在优化的探测窗口内,噪声的影响也因为光斑权值比重的增大而削弱。实验结果证明:与传统方法相比,新方法提高了光斑质心测量的精度、重复性和稳定性。     

低压环境下在6H-SiC(000-1)衬底上外延生长石墨烯的Raman光谱分析

本文探索在低压（2mbar）真空环境下在6H-Si(000-1)衬底上外延生长石墨烯的形成机理。结果显示,生长温度极大的影响着SiC热分解过程中石墨烯的形成和质量,更高的生长温度可以降低衬底对石墨烯的影响,也有利于高质量石墨烯的生成。通过对Raman光谱数据进行分析,表明在1600℃时生成的石墨烯具有turbostratic 石墨结构。扫描电子显微镜显示石墨烯的尺寸约在10微米左右,这为制备大尺寸的外延石墨烯提供新的方法。     

Raman analysis of epitaxial graphene on 6H-SiC (000(1)) substrates under low pressure environment

This article investigates the formation mechanism of epitaxial graphene on 6H-SiC (000(1)) substrates under low pressure of 2 mbar environment.It is shown that the growth temperature dramatically affects the formation and quality of epitaxial graphene.The higher growing temperature is of great benefit to the quality of epitaxial graphene and also can reduce the impact of the substrate for graphene.By analyzing Raman data,we conclude that epitaxial graphene grown at 1600 ℃ has a turbostratic graphite structure.The test from scanning electron microscopy (SEM) indicates that the epitaxial graphene has a size of 10μm.This research will provide a feasible route for fabricating larger size ofepitaxial graphene on SiC substrate.     

基于Simulink的某雷达天线伺服系统性能改进方法研究

为了满足高精度随动系统的精度要求,以一种高精度伺服系统作为研究对象,建立力矩电机驱动的伺服系统的数学模型,采用超前滞后校正和提高增益、引入滞后环节的控制方法,对系统进行建模和仿真,实验结果表明,超前滞后校正的控制方法可以提高系统响应的快速性,满足高精度要求,提高增益、引入滞后环节的控制方法可以显著改善伺服系统死区非线性对于系统的影响.     

基于异构关联的大数据价值密度提升方法

电信大数据通常分散存储在 DPI、OIDD、CRM 等多个系统中,且格式、表述和规则在各系统中互不相同;因而,同一对象在不同系统中的多类数据很难被有效识别及完整利用,大数据分析的样本规模和特征维度严重受限,导致分析结果可信度和准确率下降。提出了电信大数据的异构关联方法与实现架构,并进行了方法的流程举例和验证,从用户维度实现了多系统间的数据融合,优化了诸如用户画像等应用的数据样本空间,从而大幅提升电信大数据价值密度。     

Methods for improving the stability of electromagnetic geophysicalinversions

Two methods are presented for improving the stability of geophysical inversions. The first method uses the weighted-least-squares technique to reduce the effects of additive noise in the measurement data. This is accomplished by giving a lesser weight to those measurements that are thought to be more noisy. Some simulations are presented that demonstrate the effectiveness of this method. In addition, the authors explore the possibility of using postreconstruction image processing to reduce the effects of noise in the measurements. A novel technique, referred to as minimax partitioning, is developed. This method, in conjunction with image filtering is used to locate high-contrast anomalies in a region. Examples are presented that show the superiority of this partitioning scheme over other techniques