激光拉曼光谱在高分子中的应用

论述了激光拉曼光谱对高分子结构、结晶形态和表征,反应动力学过程和取向的研究,还介绍了纵向声学模、共振、高温高压、光波导和付里叶拉曼光谱在高分子研究中的最新进展。     

激光分析的研究进展

激光分析是现代分析化学的前沿领域之一。本文基于激光与物质作用产生的发射、散射、吸收和电离等特性,对激光诱导荧光光谱、激光拉曼光谱、激光光声光谱、激光光热光谱和激光电离光谱等激光分析方法的研究进展和应用进行了综述。     

细胞功能分子的表面增强拉曼成像及其应用研究进展

表面增强拉曼光谱(surface-enhanced Raman spectroscopy, SERS)具有高灵敏、高通量的特性.基于SERS的拉曼成像技术是一种无损的生物成像技术,已被广泛应用于细胞表面与细胞内生物分子的检测和成像,如对聚糖、microRNA、蛋白质等分子的定量、结构分析与功能追踪等.这一技术也已用于细菌的快速检测、细胞或细菌间的信号通讯研究、细胞p H检测,并可通过活体肿瘤组织的边缘描绘指导手术切除. SERS成像可以规避生命体系中强的分子自荧光以及荧光成像中的光漂白现象,并可以利用不同拉曼信标的指纹光谱实现高灵敏、高通量的生物成像.通过与其他成像技术(如核磁共振成像、光声成像)的结合, SERS成像有望用于更复杂生命体系中生物分子的研究.本文综述了近年来细胞功能分子的表面增强拉曼成像及其应用方面的研究进展.     

PAMAM树形高分子等含氮有机物的荧光研究进展

近年来不具有典型荧光基团的PAMAM树形高分子等含氮有机物被发现可发射强烈荧光,引起了广泛的关注.实验结果表明多种因素,如分子结构、分子量、氧化、酸化、介质和陈化过程等,均对荧光的强度和荧光峰位置产生影响.与传统有机荧光物质相比,这类含氮有机物荧光物不仅具有生物相容性好和水溶性高的特性,还具有易于功能化改性和制备相对简...     

激光波长对拉曼光谱检测地质成分的影响

随着激光技术的不断发展,以激光为光源的拉曼光谱检测技术由于其快速、无损、无接触探测等优势,已成为地质样品成分鉴别的一种重要途径。由于激光波长是样品拉曼效应的重要决定因素之一,进一步明确其在地质样品成分检测中的影响,能够为开展行星矿物成分研究提供重要参考依据。本工作基于自主建立的532nm/785nm双色光源激光拉曼光谱探测系统,开展了不同激光波长对地质样品成分拉曼光谱的影响研究,获得了包括硝酸根、碳酸根、磷酸根、硅酸根等分子基团以及硫化物、氧化物等多种地质样品主要成分的拉曼特征光谱。通过对比表明,532nm激发光具有更高的光子能量,能够检测更多的样品成分,但荧光效应较强,785nm激发光存在拉曼信号强度较低问题,但是具有很好的荧光抑制效果,可根据实际样品种类进行最佳激发光波长的选择。     

天然高分子细胞培养基质的研究进展

天然高分子材料如壳聚糖、丝素蛋白和胶原蛋白等具有异体抗原性弱、生物相容性好、可生物降解且能促进细胞粘附、生长和增殖等优点。同人工合成高分子材料相比,天然高分子几乎不含有机溶剂和引发剂等物质,生物安全性高,是细胞培养基质的首选原材料。近年来,随着生物科技的发展,其新功能也不断被发现并受到学术界的广泛重视。本文综述了天然多糖类和天然蛋白质类高分子材料的理化性质及在细胞培养基质领域中的应用,对目前所存在的一些问题进行了描述并预测其发展动向。     

傅里叶交换拉曼光谱及其在化学中的应用

传统的激光拉曼光谱,由于采用光栅分光系统和可见激光为光源,使它存在几个固有缺点。试样本身和微量杂质受激光照射后产生的荧光很强,常常严重干扰拉曼光谱的测量。由于激发光位于可见区,很易使试样受热分解或光致解离。它的频率精度也较差,不适于做光     

拉曼镊子在生物单细胞中的应用与进展

拉曼镊子(Raman tweezers)是将激光光镊(Optical tweezers)与显微拉曼光谱(Raman spectroscopy)结合的光学技术,可以在接近自然状态下研究单个生物细胞或细胞器.因其有无直接接触、无损伤、快速识别、实时追踪等特点,广泛用于生物细胞的识别、探测、筛选等.研究显示,拉曼镊子在微观生物研究的应用中,可提高拉曼光谱的信噪比,也能实现生化动力学过程的实时跟踪,从而能深刻了解细胞内生物大分子的活动规律.本文着重介绍了拉曼镊子的起源、原理及其在单细胞中的应用以及展望.     

在线多通道拉曼光谱检测系统的建立及与毛细管电泳的联用

利用氩离子激光器和ICCD自组装了毛细管电泳-激光拉曼光谱联用分析系统,用已知拉曼谱图的苯和甲苯对系统进行调试,详细讨论了外光路系统对灵敏度的影响.用甲基橙和甲基红混合体系进行拉曼-毛细管电泳联用的实验研究,得到了较好的甲基橙和甲基红的在线电泳-时间分辨激光拉曼谱图.     

两种卟啉化合物在Ag溶胶表面的紫外-可见吸收光谱和表面增强拉曼散射光谱研究

表面增强拉曼散射(SERS)自1974年被Fleischmann等^[1]发现以来,日益受到人们的重视.通过SERS谱图分析,可以获得物质结构及其与基体作用的信息.由于SERS可使拉曼信号增强10⁵~10⁶倍^[2],并且在某些情况下银胶还能使表面吸附质的荧光猝灭^[3,4], SERS常用来检测一些普通拉曼光谱难以检测的样品和考察界面络合物的形成.     

On-line FT-Raman and dispersive Raman spectra database of artists’ materials (e-VISART database)

Raman spectroscopy has been widely applied in the analysis of different types of artwork. This technique is sensitive, reliable, non-destructive and can be used in situ. However, there are few references in the literature regarding specific Raman spectra libraries for the field of artwork analysis. In this paper, the development of two on-line databases with Fourier transform Raman (FT-Raman; 1064 nm) and dispersive Raman (785 nm) spectra of materials used in fine art is presented; both are implemented in the e-vibrational spectroscopic databases of artists materials database (e-VISART). The database provides not only spectra, but also information about each pigment. It must be highlighted that for each pigment or material several spectra are available from different dealers. Some of the FT-Raman spectra available in the e-VISART database have not been published until now. Some examples in which the e-VISART database has been successfully used are presented.     

Fourier transform Raman spectroscopic studies of a novel wood pulp bleaching system

The use of near-infrared (NIR) Fourier transform (FT) Raman spectroscopy for the study of lignocellulosic materials is discussed. An application utilizing NIR FT-Raman spectroscopy to study a novel chlorine-free process for the bleaching of wood pulps is presented in detail. The new process, still under development, entails the oxidation of residual lignin in wood pulps by vanadium-substituted polyoxometalates, and reoxidation of the reduced polyoxometalates by chlorine-free oxidants such as air, dioxygen, peroxides or ozone. Results from FT-Raman measurements of polyoxometalate-treated pulps are compared with those from chemical, spectroscopic and optical techniques commonly used in the pulp and paper industry.     

Step-scan near-infrared Fourier-transform Raman spectroscopy with 100 picosecond laser pulses

Time-resolved Fourier-transform Raman scattering with picosecond excitation is reported for the first time. The resonance Raman spectrum of 9,10-diphenylanthracene in its excited single state was obtained by Raman excitation at 1064 nm with 100 ps pulses, following photoexcitation at 355 nm. The implementation and characterization of time-resolved FT-Raman spectroscopy with a step-scan interferometer is discussed. FT-Raman spectra generated with continuous and mode-locked beams in the continuous-scan mode of the interferometer are compared with step-scan FT-Raman spectra generated with 2 kHz pulses.     

A comparison of Fourier transform infrared and near-infrared Fourier transform Raman spectroscopy for quantitative measurements: An application in polymorphism

Polymorphism in cortisone acetate, a synthetic adrenocortical steroid, and in a compound from a heart disease project has been studied with near-infrared Fourier transform Raman (NIR FT-Raman) spectroscopy. For cortisone acetate similar quantitative precision was obtained with both Raman and diffuse reflection IR measurements. The Raman measurements of the heart disease compound gave a calibration with a standard error of prediction of better than 2.5%. The combination of excellent precision with very convenient measurement of powders makes NIR FT-Raman spectroscopy a valuable tool for quantitative measurements of polymorphism.     

Quantitative aspects of near-infrared Fourier transform Raman spectroscopy

Three fundamental behaviors of vibrational spectroscopy data manipulation routinely associated with Fourier transform infrared (FTIR) spectroscopy are evaluated for near-infrared (NIR) Fourier transform Raman spectroscopy. Spectral reproducibility, spectral subtraction and sensitivity are examined relative to the NIR FT-Raman experiment. Quantitative predictive ability is compared for identical sets of samples containing mixtures of the three xylene isomers. Partial least-squares analysis is used to compare predictive ability. IR performance is found to be better than Raman, though the potential for method development using NIR FT-Raman is shown to be quite promising.     

Fourier transform Raman microspectroscopy

Summary This paper shows some preliminary results taken with a commercially available Raman microscope which is based on the Fourier Transform Raman technique using near infrared laser sources. The micro apparatus is described and measurement examples are given. A comparison between spectra taken with the microscope and a conventional macro sample device which is usually utilized in FT-Raman spectroscopy is carried out. Furthermore the differences of FT-Raman and FT-IR microanalysis are studied on the basis of practical results received from spectral data. Limitations due to the physical properties of infrared and Raman microspectroscopy are discussed.The data partly contained in this paper were first presented at the 12th Int. Raman conference, August 1990, Columbia, S.C.Dedicated to the 60th birthday of Professor Bernhard Schrader     

Applications of Fourier transform Raman spectroscopy in inorganic chemistry—a considered view

A sudy of a wide variety of coloured main group metal, transition metal coordination and transition metal organometallic complexes using Fourier transform Raman (FT-Raman) spectroscopy has demonstrated a high success rate (ca 50%) with good quality spectra obtained in short periods of time. It is suggested that FT-Raman spectroscopy should now be regarded as a routine spectroscopic tool for use in inorganic as well as organic research and teaching laboratories.     

New trends in telescopic remote Raman spectroscopic instrumentation

Raman spectroscopy is a powerful analytical technique in many areas of research for several reasons. These include the sensitivity to small structural changes, non-invasive sampling capability, minimal sample preparation, narrow line widths of Raman lines, and high spatial resolution in the case of micro-Raman spectroscopy. Advancements in lasers, spectrographs and holographic optical components have made Raman spectroscopy an effective tool for analyzing natural and synthetic materials. These advances have led to the development of both in situ Raman spectroscopy and telescopic remote Raman spectroscopy for a lander or rover for planetary exploration. A telescopic Raman spectroscopic system capable of measuring Raman spectra of minerals, inorganic and organic chemicals, and biogenic materials to radial distances in the range 10-100 m has been developed. In this work, the author reviews the current status of telescopic remote Raman spectroscopic instrumentation and examines new trends in the field of remote Raman spectroscopy and its combination with time-resolved remote laser-induced native fluorescence (LINF) and laser-induced breakdown spectroscopy (LIBS), and their applications in earth and planetary science.     

Anti-Stokes Yb3+ emission--valuable structure information in spectra of rare earth compounds measured with FT-Raman spectrometers

Raman spectroscopy is a powerful and simple method which proved to be very useful in studies of solids. The most widely used Raman spectrometers are FT-Raman instruments with YAG:Nd(3+) laser as an excitation source. However, in the case of samples containing rare earth elements, the quality of FT-Raman spectra is often low due to strong fluorescence effects. We show that, in such cases, anti-Stokes part of the Raman spectra often contains strong, well resolved bands identified as multiphonon-assisted emission bands of Yb(3+) present as an impurity. We show on several examples that analysis of these bands may provide useful structure information, similar to that obtained by "Eu structure probe" method in optical spectroscopy. The Yb(3+) emission can be also measured using standard luminescence detection systems. However, the application of FT-Raman system allows one to obtain good quality spectra in a much cheaper, easier and faster way (in times as short as a few seconds). Moreover, high-sensitivity of FT-Raman spectrometers allows to detect even very small amounts of Yb(3+) impurity.     

FT-Raman spectroscopy of biological molecules

Raman spectroscopy of biological molecules is often very difficult if not impossible due to a large fluorescence background from absorbing species, either from the molecule itself or an impurity. Photobleaching is occasionally successful in photochemically removing fluorescent impurities, but the majority of samples are not responsive to such treatment. Resonance enhancement of an absorbing species allows acquisition of Raman spectra in spite of competing fluorescence. However, the resonance Raman spectrum is characteristic of the chromophore only and little structural information is obtained from the spectrum about other parts of the molecule which are not resonantly enhanced. The newly developed technique of FT-Raman spectroscopy proves to be a solution to both of these problems for biological materials. Excitation with infrared wavelengths prevents electronic absorptions which give rise to fluorescence. In addition, the obtained spectra are completely nonresonant, allowing detection of vibrational modes of all parts of the molecule including the chromophore. We will present nonresonant, fluorescence free spectra of a range of biologically significant molecules including phospholipids and porphyrins.