Quantitative measurement of hydroxyl radical(OH) concentration in premixed flat flame by combining laser-induced fluorescence and direct absorption spectroscopy

An accurate and reasonable technique combining direct absorption spectroscopy and laser-induced fluorescence(LIF)methods is developed to quantitatively measure the concentrations of hydroxyl in CH_4/air flat laminar flame. In our approach, particular attention is paid to the linear laser-induced fluorescence and absorption processes, and experimental details as well. Through measuring the temperature, LIF signal distribution and integrated absorption, spatially absolute OH concentrations profiles are successfully resolved. These experimental results are then compared with the numerical simulation. It is proved that the good quality of the results implies that this method is suitable for calibrating the OH-PLIF measurement in a practical combustor.     

激光诱导水体频率上转换的荧光发射

用Nd：YAG的二倍频532 nm激光对几种不同水体的激光诱导荧光(LIF)光谱进行了测量,利用特征光谱荧光标记(SFS)技术指认出水体中溶解有机物(DOM)、叶绿素a(Chl a)及类胡萝卜素等物质的特征光谱带。指出在455 nm波长处具有较大强度的荧光峰是附属色素中抗氧化作用的类胡萝卜素(PPC)的贡献。提出了激光诱导PPC荧光频率上转换发射的动力学模型。     

基于二维相关荧光谱土壤中PAHs检测方法研究

传统荧光光谱技术已被用于土壤中多环芳烃(PAHs)的检测,但由于土壤体系的复杂性、PAHs污染物的多样化和微量化,传统的荧光光谱技术无法有效提取土壤中PAHs的特征信息。为了解决上述问题,提出并建立一种基于二维相关荧光谱土壤中多环芳烃的检测方法。以土壤中典型的多环芳烃蒽和菲为研究对象,配置38个蒽菲混合标准土壤样品(蒽和菲的浓度范围均为0.000 5～0.01 g·g-1),在激发波长265～340 nm,发射波长350～500 nm范围内采集了所有样品的三维荧光谱。以激发波长为外扰,对外扰变化的动态一维荧光谱进行相关计算,得到每一样品的同步二维相关荧光谱。研究了浓度均为0.005 g·g-1蒽菲混合土壤样品的三维荧光谱和同步二维相关荧光谱特性,在同步谱主对角线398,419,444和484 nm处存在自相关峰,其中,398和484 nm荧光峰来自土壤中的菲,419和444 nm荧光峰来自土壤中的蒽;在主对角线外侧,蒽和菲两组荧光峰之间存在负的交叉峰,进一步验证了其来源不同;同时,在(408,434) nm和(434,467) nm处出现交叉峰,其中408和434 nm荧光峰来自土壤中的菲,467 nm荧光峰来自土壤中的蒽。指出与三维荧光谱表征的信息相比,二维相关荧光谱不仅能提取更多的特征信息(408和467 nm的特征峰在三维荧光谱中未被表征),而且还能提供荧光峰之间的相互关系,对其来源进行有效解析。在上述研究二维相关荧光谱特性的基础上,基于同步相关谱矩阵(38×151×151)建立了定量分析土壤中蒽和菲污染物浓度的多维偏最小二乘(N-PLS)模型,对蒽的校正和预测相关系数分别为0.986和0.985,校正均方根误差(RMSEC)和预测均方根误差(RMSEP)分别为4.33×10-4和5.55×10-4 g·g-1;对菲的校正和预测相关系数分别为0.981和0.984,RMSEC和RMSEP分别为5.20×10-4和4.80×10-4 g·g-1。为了比较,基于三维荧光光谱矩阵(38×16×151)建立了定量了分析土壤中蒽和菲的N-PLS模型,对蒽的校正和预测相关系数分别为0.981和0.972,RMSEC和RMSEP分别为5.09×10-4和6.74×10-4 g·g-1;对菲的校正和预测相关系数分别为0.957和0.956,RMSEC和RMSEP分别为7.36×10-4和7.77×10-4 g·g-1。指出,对于土壤中的蒽和菲检测,基于二维相关荧光谱的N-PLS模型的相关系数r,RMSEC和RMSEP都要优于基于三维荧光谱的N-PLS模型。研究结果表明：所提出和建立的方法-二维相关荧光谱直接检测土壤中PAHs污染物不仅可行,而且能提供更好的分析结果。该研究为激光诱导荧光结合相关谱技术现场直接检测土壤中多环芳烃污染物提供了理论和实验基础,具有较好的应用前景。     

Detection of explosives with laser-induced breakdown spectroscopy

Our recent work on the detection of explosives by laser-induced breakdown spectroscopy (LIBS) is reviewed in this paper. We have studied the physical mechanism of laser-induced plasma of an organic explosive, TNT. The LIBS spectra of TNT under single-photon excitation are simulated using MATLAB. The variations of the atomic emission lines intensities of carbon, hydrogen, oxygen, and nitrogen versus the plasma temperature are simulated too. We also investigate the time-resolved LIBS spectra of a common inorganic explosive, black powder, in two kinds of surrounding atmospheres, air and argon, and find that the maximum value of the O atomic emission line SBR of black powder occurs at a gate delay of 596 ns. Another focus of our work is on using chemometic methods such as principle component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) to distinguish the organic explosives from organic materials such as plastics. A PLS-DA model for classification is built. TNT and seven types of plastics are chosen as samples to test the model. The experimental results demonstrate that LIBS coupled with the chemometric techniques has the capacity to discriminate organic explosive from plastics.     

南极海洋芳香烃低温降解微生物的拉曼光谱分析

激光镊子拉曼光谱技术可以实现在自然状态下对单个细胞或细胞器较长时间的观察研究.应用激光镊子拉曼光谱技术实时观察南极微生物低温降解芳香烃过程中单个南极细菌的细胞生长和胞内生物大分子的动态变化过程,收集、分析其拉曼光谱,结果发现:单细胞的拉曼光谱反映了其细胞内部的生命物质组成,南极动球菌 NJ41 和希瓦氏菌 NJ49 生...     

NO分子A2Σ→X2Π双光子激光感生荧光光谱

以Nd∶YAG激光器抽运光学参变振荡器 /光学参变放大器做为激发源 ,得到了NO分子在 2 2 0～ 35 0nm波长范围内的双光子激光诱导荧光光谱 ,并将其归属于A2 Σ(ν′ =0 )→X2 Π(ν″ =1～ 8)跃迁 ,用最小二乘法拟合获得NO分子X2 Π态振动常量″ωe =(190 4 .7± 7.3)cm-1,″ωe ″xe =(14 .2± 1.2 )cm-1,″ωe″ye=- (0 .0 2 18± 0 .0 0 91)cm-1,及平衡位置的力常量k =(1.5 99± 0 .0 12 )× 10 3 N·m-1。计算了所得跃迁谱带的弗兰克康登因子及相对荧光强度 ,结果与实验观测值相符。这可为用激光诱导荧光光谱技术探测大气污染物NO分子提供理论及实验参考     

土壤重金属铬元素的激光诱导击穿光谱定量分析研究

利用Nd ∶YAG脉冲激光器(波长:1064 nm)作为光源,在实验室自然大气环境下诱导产生土壤激光等离子体,通过等离子体原子发射光谱法定量分析了国家标准土壤样品中元素Cr的含量.实验上研究了在最佳实验条件下土壤中Cr的LIBS分析谱线,测定了Cr元素的定标曲线.实验结果表明,Cr元素浓度在(60—400)×10^-6范围内,元素含量与光谱线强度之间有较好的线性关系;元素Cr浓度分析测量的相对标准偏差(RSD)为7.89%,定量分析结果与标准值的相对偏差为5.3%,Cr元素的检测限为1 关键词： 土壤污染 定量分析 激光诱导击穿光谱 定标曲线     

利用特征光谱荧光标记与高斯拟合分析水体中有机物的特性

讨论了一种自然水体中有机物的快速分析方法,以激光诱导荧光(LIF)方法测量了水体的总荧光光谱(TLS);利用特征光谱荧光标记(SFS)技术对水体中溶解有机物(DOM)及叶绿素a(Chl a)的荧光光谱进行了正确的指认和提取。以最小二乘法-Gaussian拟合对水体的TLS进行了拟合,可有效地分离出拉曼散射及荧光光谱,拟合的相关系数优于0.996 4。结果表明,通过在TLS中利用SFS技术正确的指认特定污染物,并以Gaussian拟合进行有效地提取,可以进行水体污染物的快速、实时和在线监测。     

污泥内层和外层胞外聚合物的三维荧光光谱特性研究

运用三维荧光光谱技术对污泥LB-EPS和TB-EPS的荧光特性进行了研究.实验结果表明,在污泥LB-EPS和TB-EPS中都有三个明显的荧光峰,分别为Peak B(λex/λem=270～280 nm/345～360 nm),Peak C(λex/λem=330～340 nm/410～430 am)和Peak D(λex/λem=390 nm/450～470 nm).其中Peak B为类蛋白荧光(Protein-like)、Peak C为可见区类富里酸荧光(Visible fulvic-like)、Peak D为类腐殖酸荧光(Humic-like).从各荧光峰的荧光强度来分析,LB-EPS和TB-EPS中的主要成分都为类蛋白,然后依次为富里酸和腐殖酸.浓度和pH值对污泥LB-EPS和TB-EPS的三维荧光特性都有很大的影响,但影响程度略有区别,表明作为外层的胞外聚合物,LB-EPS表现出与TB-EPS不全相同的化学结构.     

Fluorescence Correlation Spectroscopy of Gold Nanoparticles

Diffusion dynamics of gold nanoparticles (GNPs) was studied by fluorescence correlation spectroscopy (FCS). The fluorescence was studied by exciting the particles by green laser (532 nm), which is far from longitudinal plasmon band of nanorods. Transmission electron microscope (TEM) and UV-Vis-NIR spectrometer were used to characterize the gold nanoparticles. Despite their low quantum yields, GNPs possess the native fluorescence. The excellent antiphotobleaching behavior of gold nanorods leads to prospects of using FCS for its detailed studies. Using FCS, dynamic information can be extracted from the fluorescence fluctuations in the system by autocorrelation function. Maximum entropy method (MEMFCS) was used to identify the number of distinct components present in the system. The particle sizes obtained from FCS were found to be higher (by few orders of magnitude) compared to TEM analysis. This might be due to the possible contributions from cetyltrimethyl ammonium bromide (CTAB) capping in the system.     

Laser-induced breakdown spectroscopy applied to the characterization of rock by support vector machine combined with principal component analysis

Laser-induced breakdown spectroscopy(LIBS) is a versatile tool for both qualitative and quantitative analysis.In this paper,LIBS combined with principal component analysis(PCA) and support vector machine(SVM) is applied to rock analysis.Fourteen emission lines including Fe,Mg,Ca,Al,Si,and Ti are selected as analysis lines.A good accuracy(91.38% for the real rock) is achieved by using SVM to analyze the spectroscopic peak area data which are processed by PCA.It can not only reduce the noise and dimensionality which contributes to improving the efficiency of the program,but also solve the problem of linear inseparability by combining PCA and SVM.By this method,the ability of LIBS to classify rock is validated.     

激光诱导荧光水体污染遥测数据定量分析方法

在紫外光的激发下,污染水体中的溶解有机物(DOM)会产生特定的荧光光谱,因此利用激光诱导荧光(LIF)可对水体中的溶解有机物的含量进行定量分析,从而可估计出水体富营养化的程度。提出了一种用于对水质遥测数据进行定量分析的方法,这是一种基于遗传算法(GA)的光谱分离算法。首先确定拉曼散射信号和溶解有机物的荧光在404nm波段的信号强度,然后再利用拉曼散射信号对DOM荧光光谱进行归一化处理。根据浓度校准曲线可得到水体中的溶解有机物的浓度。     

应用激光诱导击穿光谱检测土壤中的铅

应用激光诱导击穿光谱技术对模拟土壤中Pb进行快速定量分析。该模拟土壤由PbCl₂,CaCO₃,SiO₂,KBr化学纯试剂制备而成。通过实验得到信噪比随延时的增大呈先增后减的变化规律。利用实验光谱图建立了Pb含量的定标曲线。定量分析研究得到：该方法用于Pb含量定量分析的平均相对误差为8.33%,最低检测限为89μg/g。实验结果验证了激光诱导击穿光谱技术用于土壤中Pb含量测量的能力。     

常见食用油和煎炸食用油的激光诱导荧光光谱特性

为了实现地沟油的快速检测,利用激光诱导荧光探测技术搭建了食用油类快速检测系统。对多种食用油和煎炸食用油(地沟油的一种)进行了光谱采集,建立了多种食用油和煎炸食用油的荧光光谱数据库,发现煎炸食用油的特征荧光光谱与常见食用油之间存在较大差异,在此基础上利用主成分分析法和BP神经网络实现了油类识别、地沟油的快速检测,总体识别率高达97.5%。实验证明激光诱导荧光光谱技术具有快速非接触和灵敏度高等优点,与BP神经网络相结合能够实现油类的快速识别,成为地沟油快速检测的一种新方法。     

土壤湿度对多环芳烃荧光特性的影响

荧光光谱技术已被用于检测土壤中多环芳烃。但土壤湿度对多环芳烃的荧光强度产生很强的干扰,这对于荧光光谱技术的土壤多环芳烃快速实时检测技术的发展无疑是一种挑战。为了研究土壤湿度对多环芳烃荧光特性的影响,分别配置了八个不同湿度(含水量5%～40%,间隔5%)的菲土壤样品。采用美国PE公司的LS-55荧光分光光度计对不同湿度含量的菲土壤样品进行了检测,得到不同湿度含量下的一维动态荧光谱,以土壤湿度为外扰,研究了其二维相关荧光光谱特性,发现菲土在386,408和432 nm处荧光强度随着土壤中湿度的增大而增强,而333 nm处瑞利散射光强度却在减小,提出通过建立菲荧光强度、瑞利散射光强度与土壤湿度之间的关系,有可能实现土壤湿度对菲荧光强度影响的校正。同时,也研究了土壤湿度对定量分析菲浓度标准曲线的影响,指出土壤湿度极大影响着精准定量分析菲浓度标准曲线的建立。     

Effect of Host Medium on the Fluorescence Emission Intensity of Rhodamine B in Liquid and Solid Phase

In this work, we study the effect of concentration, host medium, PH and phase states on the fluorescence emission from the laser dye Rhodamine B pumped by UV laser as exited source. The polymethylmethacrylate PMMA is used as a host medium in case of solid phase samples while, ethanol and Tetrahydrofuran (THF) are used in case of a liquid one. Laser Induced Fluorescence (LIF) technique was used to study the fluorescence properties of both cases of liquid and thin film solid-state samples. In addition, the Dual Thermal Lens (DTL) technique was used to study the quantum yield of these samples. The concentrations of Rhodamine B in ethanol as solvent between 2 × 10⁻² M and 5 × 10⁻⁶ M were studied. The maximum fluorescence emission is observed at concentration of Rhodamine B C = 3 × 10⁻⁴ M. Comparison studies were investigated for different host medium such as ethanol, THF, PMMA in liquid phase state and PMMA in solid phase state. The measurements revealed that, the behavior of both phases state was analogous. Rhodamine B/PMMA thin film sample by ratio of 4:1 and thickness 0.12 mm was found to have the best photostability sample with a quantum yield about ≈0.82.     

Rapid Identification of Bacterial Species by Fluorescence Spectroscopy and Classification Through Principal Components Analysis

This work presents the development of a method for rapid bacterial identification based on the autofluorescence spectrum. It was demonstrated differences in the autofluorescence spectrum in three bacterial species and the subsequent separation, through the Principal Components Analysis (PCA) technique, in groups with high likeness, that could identify the bacteria in less than 10 min. Fluorescence spectra of 60 samples of 3 different bacterial species (Escherichia coli, EC, Enterococcus faecalis, EF and Staphylococcus aureus, SA), previously identified by automated equipment Mini API, were collected in 10 excitation wavelengths from 330 to 510 nm. The PCA technique applied to the fluorescence spectra showed that bacteria species could be identified with sensitivity and specificity higher than 90% according to differences that occur within the spectra with excitation of 410 nm and 430 nm. This work presented a method of bacterial identification of three more frequent and more clinically significant species based on the autofluorescence spectra in the excitation wavelengths of 410 and 430 nm and the classification of the spectra in three groups using PCA. The results demonstrated that the bacterial identification is very efficient with such methodology. The proposed method is rapid, ease to perform and low cost compared to standard methods.     

人工湿地中水溶性有机物三维荧光光谱特性的分析

采用三维荧光技术,结合荧光区域一体化积分的分析方法,研究了一个表面流+垂直流复合人工湿地处理两条污染河流废水中水溶性有机物的荧光特征变化,结果表明:(1)该人工湿地中水溶性有机物腐殖质的主要来源为生物代谢输入而非陆源输入;(2)在表面流人工湿地的后段,部分类蛋白类物质转化为类富里酸类物质,表明经过表面流人工湿地处理之后,水溶性有机物的组成成分发生显著变化,并且有机物结构趋于稳定。而垂直流人工湿地对类腐殖酸物质峰具有明显的削弱作用;(3)表面流人工湿地对水溶性有机物的结构转化意义重大,可以显著提高水溶性有机物的稳定性。表面流+垂直流的复合人工湿地工艺对水溶性有机物具有良好的去除效果。     

超声射流CCl2 自由基激光诱导荧光激发谱

用CCl4 /Ar混合气体脉冲直流高压放电产生CCl2 自由基 ,在超声射流冷却下获得了CCl2 A 1B1- X 1A14 40～ 5 80nm的K 结构分辨的激光诱导荧光激发谱 .通过K 结构分辨谱的分析 ,对 72 2条转动子谱带进行了归属 ,得到了激发态CCl2 A 1　B1的两个全对称振动模式的振动频率、非谐性常数和转动常数差值 ,即激发态的振动频率ω1=6 31.2 0cm-1,ω2 =30 2 .0 0cm-1,A′-B′ =3.476cm-1.     

Characterization of the globular oxide inclusion ratings in steel using laser-induced breakdown spectroscopy

Grade assessment of steel is generally performed via the metallographic method, which is timeconsuming and is not able to provide the elemental distribution information. In this paper, we present a method to measure the globular oxide inclusion ratings in steel using laser-induced breakdown spectroscopy (LIBS). The measurement is performed in two basic steps: steel samples are polished using metallographic sand paper and the Al₂O₃ inclusion number and size distribution in a marked area are observed using scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDS) for further LIBS scanning analysis. The threshold intensity that distinguishes soluble aluminum and insoluble aluminum inclusions is determined using LIBS combined with the SEM/EDS statistical data. Carbon steel (the sample number is S9256) and bearing steel (the sample number is GCr15) are analyzed in scanning mode, and the number of Al₂O₃ inclusions in different size ranges is obtained from the statistical information derived from the Al₂O₃ size calibration curve. According to heavy and thin series for globular oxide inclusions grade assessment, the method we propose is comparable to the traditional metallographic method in terms of accuracy; however, the process is simplified and the measurement speed is significantly improved.