基于拉曼光谱的汽油牌号快速识别

提出了一种基于拉曼光谱的汽油牌号快速识别方法。该方法首先基于已知牌号的成品汽油样本进行建模,获取不同牌号成品汽油建模样本的拉曼谱图,经过谱图预处理后对谱图进行主成分分析(principal component analysis,简称PCA),获得载荷矩阵和得分矩阵,同时分别计算不同牌号汽油样本的平均得分向量,即不同牌号的得分中心坐标;然后对未知牌号汽油样本进行识别,先将未知牌号汽油样本拉曼谱图进行相同的谱图预处理,再计算该样品在载荷矩阵上的得分向量,根据PCA类中心最小距离法,计算该得分向量到不同牌号的得分中心坐标的欧式距离,依最小距离直接确定汽油牌号。针对45个取自国内不同炼油厂的成品汽油样本的实验结果表明这些汽油样本拉曼谱图经谱图预处理和PCA后,不同牌号汽油样本在主元得分空间上存在明显类间距,使用PCA类中心最小距离法可实现汽油牌号快速准确的分类。     

基于拉曼特征峰的甲醇汽油甲醇含量测定

采用拉曼光谱分析技术定量分析甲醇汽油中的甲醇含量。首先,对采集到的原始拉曼光谱进行平滑除噪、荧光背景消除、标准归一化等预处理;其次,根据甲醇含量与拉曼光谱的相关性分析找出甲醇含量的特征点;最后,建立了基于拉曼特征峰的甲醇含量一元线性回归模型。针对实验室配制的19个甲醇汽油样本的实验结果表明,该方法准确、稳健、所需训练样本少,可以应用于甲醇汽油中甲醇含量的快速测定。     

激光拉曼光谱仪的全系统校正

提出了一套对激光拉曼光谱仪进行全系统校正的完整方案，并在一台ＳＰＥＸ １４３０型双单色仪单道拉曼光谱仪上全面实现了这套校正，包括谱仪的波数精度及重现性，狭缝函数，光谱分辨率，功率传递系数，光谱响应，偏振光谱响应，偏振传递性能及寄生谱带检查。结果表明，在激光拉曼谱测量中许多源于光谱仪体系的测量误差实际上是不可避免的，因此对常用的谱仪要作日常的状态监控和至少一次全面系统校正，是激光拉曼谱学研究的先决条     

苯的激光拉曼光谱研究

采用激光拉曼光谱技术获得了苯的振动拉曼光谱,结合群论分析、退偏度测量和相关文献对其中8条拉曼谱线进行了分析.1550～1650cm-1区间内的两条谱线是由于费米共振而形成的.     

便携式拉曼光谱仪快速测定磷酸浓度

用便携式激光拉曼光谱仪测定磷酸浓度,利用P—O键对称伸缩振动峰(893—911cm-1)的峰值,以硝酸根特征峰为内标,建立了激光拉曼光谱法测定磷酸含量的模型,并对拉曼位移与磷酸浓度的关系进行了拟合。两种方法用于实际样品检测的结果准确度和精密度良好,均能够满足水体中磷酸含量测定的要求。     

拉曼光谱技术的汽油组分含量测定

为实现汽油中所含组分含量的快速测定,对93号、97号汽油,芳烃、烯烃、苯、甲醇、乙醇等几类物质,以及往汽油中添加几类物质后的410个汽油混合物进行拉曼光谱检测。将获取的原始拉曼光谱经过有效波段提取、平滑去噪、基线扣除、数据归一化等一系列预处理过程,最终提取出每个汽油混合样品光谱中所含的33个特征峰信息,依据现行的国标检测方法,以气相色谱法测定的汽油中各组分含量值为基础,结合化学计量学多重回归分析方法,建立了汽油组分含量测定模型。经过比较,使用多输出最小二乘支持向量回归机(MLS-SVR)建立的模型优于偏最小二乘(PLS)模型。MLS-SVR模型对汽油中芳烃、烯烃、苯、甲醇、乙醇测定精度均较好,预测均方根误差(RMSEP)分别为0.27%,0.30%,0.16%, 0.17%, 0.12%;相应的相关系数(r)为0.999 2,0.998 4,0.998 5,0.992 6,0.996 8。通过对未知混合汽油样品的测定,证明了该方法具有较好的推广预测精度,预测均方根误差不超过0.5%,能够满足工业中的测量需求。拉曼光谱结合多输出最小二乘支持向量机为汽油组分测定提供了一种高精确、快捷、方便的测定方法。     

基于LRS-Ⅲ型拉曼光谱仪检测黑色笔迹

拉曼光谱技术是一种发展时间不长的可靠的检测技术手段,能实现非破坏性物质鉴定。目前,发达国家已将该项技术应用于法庭中。本研究利用拉曼光谱仪对黑色字迹进行鉴定,为鉴别各种黑色笔迹提供科学依据。     

苯的激光拉曼光谱检测研究

为了对苯的质量分数进行快速准确的检测,采用拉曼光谱法进行检测.对苯的激光拉曼光谱进行了理论分析,进行了标准样品和不同质量分数苯样品的系列拉曼光谱实验.结果表明:苯的拉曼光谱特征峰值与苯的含量成正比,将最强的561.4 nm处的峰值代入线性回归公式,即可得到苯的质量分数,检出限达0.3%.得到一种新的苯质量分数检测方法.     

拉曼光谱结合偏最小二乘的甲醇汽油甲醇含量快速定量分析方法研究

甲醇汽油是一种用以替代传统汽油的新型燃料,其品质受到甲醇含量的严重影响.因此,甲醇汽油中甲醇含量的快速分析对其品质把控具有深远意义.基于拉曼光谱(Raman)结合偏最小二乘(PLS)建立了一种甲醇汽油中甲醇含量快速定量分析方法.采用激光拉曼光谱仪对49组甲醇汽油样品的Raman光谱进行采集,并进行光谱解析.比较了五种光...     

中红外光谱吸收法快速测定汽油中的苯含量

利用美国Thermo公司的傅里叶变换中红外光谱仪对汽油中的苯含量进行快速测定,并采用TQAnalystEZEdition(Nicolet)分析软件通过经典最小二乘法(CLS)进行了定量分析。结果表明,利用中红外光谱仪可以快速、准确地测量汽油中苯的含量,其再现性和重现性优于气相色谱法的要求。     

A vibrational study of liquid benzene through dispersive Raman spectroscopy using advanced optical elements

A compact experimental setup using advanced optical elements was designed to take Raman spectrum of liquid benzene. All seven Raman active vibrational modes were observed. A simplified mechanical model for two most intense in-phase modes, i.e., ring breathing and C–H stretching, shows that the vibrational contribution to the ratio of C–C and C–H bond strengths is a factor of ～1.66. A simulation of Raman spectrum with Gaussian vibrational bands, weighted by Planck distribution function, yields the vibrational line widths and the relative polarizability changes. A value of 0.74 is estimated for the ratio of change in polarizability of C–H bond to that of C–C bond upon laser excitation from a simple electrostatic calculation, which is comparable with the value of 0.6 obtained from the simulation.     

基于激光拉曼光谱的钻井液中含烃浓度定量识别研究

钻井液中的烃能够显示出地层的含油气情况，地层含油气浓度的检测对识别真假油气显示，特别是准确解释和评价油气层具有重要意义。基于激光拉曼光谱技术具有连续、快速、直接检测样品的独特优势，开展了激光拉曼光谱技术应用于钻井液中含烃浓度定量识别的研究。实验室条件下搭建的激光拉曼在线检测系统对C₇~C₁₄正构烷烃及苯进行了检测与振动模式指认，在水基钻井液中优选正辛烷作为标志烃，基于最小二乘法建立了水基钻井液中正辛烷不同特征峰数学模型，在1 298 cm-1频移处振动强度与正辛烷含量具有良好的线性关系；在柴油基钻井液中优选苯作为标志烃，基于最小二乘法建立了油基钻井液中苯的不同特征峰数学模型，在986 m-1频移处振动强度与添加苯含量具有良好线性关系。实验结果表明:激光拉曼光谱技术可用于钻井液中含烃浓度的检测，为反演地层含油气浓度，提高油气层判识精度提供了一种新的途径。     

激光拉曼光谱对苯的低浓度探测研究

激光拉曼光谱技术是基于拉曼散射理论的检测技术,具有快速、无损、样品无需预处理等优点。运用激光拉曼光谱技术对苯的25种不同浓度的样品进行了研究,结果表明,在184.8g/L~0.264g/L浓度范围内,苯的振动拉曼光谱强度与其浓度呈线性关系,利用最小二乘法拟合得到线性相关系数R=0.99626,检出限为0.223g/L。     

Fast single-photon avalanche diode arrays for laser Raman spectroscopy

We incorporate newly developed solid-state detector technology into time-resolved laser Raman spectroscopy, demonstrating the ability to distinguish spectra from Raman and fluorescence processes. As a proof of concept, we show fluorescence rejection on highly fluorescent mineral samples willemite and spodumene using a 128×128 single-photon avalanche diode (SPAD) array with a measured photon detection efficiency of 5%. The sensitivity achieved in this new instrument architecture is comparable to the sensitivity of a technically more complicated system using a traditional photocathode-based imager. By increasing the SPAD active area and improving coupling efficiency, we expect further improvements in sensitivity by over an order of magnitude. We discuss the relevance of these results to in situ planetary instruments, where size, weight, power, and radiation hardness are of prime concern. The potential large-scale manufacturability of silicon SPAD arrays makes them prime candidates for future portable and in situ Raman instruments spanning numerous applications where fluorescence interference is problematic.     

Blood analysis by Raman spectroscopy

Concentrations of multiple analytes were simultaneously measured in whole blood with clinical accuracy, without sample processing, using near-infrared Raman spectroscopy. Spectra were acquired with an instrument employing nonimaging optics, designed using Monte Carlo simulations of the influence of light-scattering-absorbing blood cells on the excitation and emission of Raman light in turbid medium. Raman spectra were collected from whole blood drawn from 31 individuals. Quantitative predictions of glucose, urea, total protein, albumin, triglycerides, hematocrit, and hemoglobin were made by means of partial least-squares (PLS) analysis with clinically relevant precision (r(2) values >0.93). The similarity of the features of the PLS calibration spectra to those of the respective analyte spectra illustrates that the predictions are based on molecular information carried by the Raman light. This demonstrates the feasibility of using Raman spectroscopy for quantitative measurements of biomolecular contents in highly light-scattering and absorbing media.     

基于近红外光谱技术成品汽油分类方法的研究

在研究成品汽油的分类方法过程中,首先采用判别式聚类分析方法比较了700~1 100和1 100~1 700 nm两个波段范围判别模型的准确性,然后在识别模型准确性较高的波段(1 100~1 700 nm)采用主成分分析法(PCA)结合自组织竞争神经网络方法,对90#,93#和97#成品汽油建立定性识别模型。在建立定性模型前先用PCA法对原始数据进行主成分压缩。主成分分析结果表明,前3个主成分的累积可信度已达97%,取前3个主成分的32个波长点的吸光度作为神经网络的输入,建立三层自组织竞争神经网络模型。神经网络模型的学习参数为0.01,网络训练迭代次数为500。结果表明,基于主成分分析结合自组织竞争神经网络方法建立的近红外光谱鉴别成品汽油的模型鉴别准确率高、方法可行。     

Disease-related proteins determination based on surface-enhanced Raman spectroscopy

Abstract

Surface-enhanced Raman spectroscopy (SERS) is a promising platform for simple, rapid, and economical protein quantitation and analysis and can achieve much lower detection limits for the ultrasensitive detection of proteins and a much wider linear concentration range for quantitative analysis than other methods can. In addition, SERS can provide a large amount of fingerprint information for the individual components of a mixture through SERS effects, which are sensitive and selective for different types of proteins and protein mixtures. In general, the occurrence and development of diseases are accompanied by changes in the content or structure of biomarkers (disease-related proteins). Here, we provide an overview of the SERS technique and its applications to disease-related protein determination. Different diseases, such as Alzheimer’s disease (AD), cardiac muscle tissue injury, and multicancer, are discussed and exhibit potential utility in biomarker detection and diagnosis. SERS opens a new path to the early diagnosis of critical diseases, which will effectively reduce human suffering and mortality.     

Surface-enhanced Raman spectroscopy based on ordered nanocap arrays

We fabricated the Ag cap array for surface-enhanced Raman scattering (SERS) by Ag deposition onto two dimensional polystyrene colloid sphere templates, and 4-mercaptopyridine (4-MPy) was used as the probing molecule. When the colloids with different size were chosen as the substrate for 20 nm Ag deposition, the film on 100 nm colloids gave the significant enhancement. SERS intensity increased with the increase of Ag thickness. When 20 nm Ag film was coated by Ta, the SERS signals decreased with the increase of Ta thickness, indicating the main effect from the top of cap structure. When Co layer was added under the Ag film, the SERS intensity decreased with the increase of Co thickness because the Co layer affects electromagnetic and plasmon resonance.     

Raman spectroscopy based on a single-crystal sapphire fiber

We demonstrate the advantages of using a single-crystal sapphire fiber to perform Raman spectroscopy over using a standard glass fiber. The narrow Raman peaks and the low background signal of a single-crystal sapphire fiber allow for the detection of weaker Raman signals or Raman signals much closer to the incident laser wavelength than with a standard glass fiber, which has a strong broadband Raman spectrum of its own. The Raman spectra of calcite, single-walled carbon nanotubes, and aqueous sodium carbonate solution were collected using a 50 cm long, 200 μm diameter sapphire fiber, and then they were compared with the results using a 50 cm long, 100 μm diameter glass fiber. The Raman spectrum of each tested material becomes indistinguishable due to the background Raman signal of the glass fiber but can easily be seen using the sapphire fiber, which has only a few narrow Raman peaks of its own.