拉曼光谱测量中的荧光抑制方法综述

拉曼光谱是物质的特征结构谱,但是在许多情况下,除了激发出拉曼散射光之外,还会激发出强度远大于拉曼散射的荧光,从而限制了拉曼光谱的应用。因此在拉曼检测中对荧光采取抑制措施是十分必要的。在过去的几十年里发展了多种荧光抑制方法,包括荧光淬灭剂法、光漂白法、红外/紫外激发法、偏振调制法、移频激发法、高频调制法、门控法、数值处理法、非线性效应法等。文中概括性地介绍了上述各种技术方法的原理,并扼要地分析比较了各自的性能特点。     

Detection and differentiation of biological species using microcalorimetric spectroscopy

We report on the application of infrared (IR) microcalorimetric spectroscopy ( micro -CalSpec) to the identification and detection of trace amounts of biological species. Our approach combines principles of photothermal IR spectroscopy with ultrasensitive microcantilever (MC) thermal detectors. We have obtained photothermal IR spectra for DNA and RNA bases and for Bacillus Cereus (an anthrax simulant) in the wavelength range of 2.5-14.5 micro m (4000-690 cm(-1)). The measurements are accomplished by absorbing biological materials directly on a MC thermal detector. The main advantage of the developed micro -CalSpec is its unprecedented sensitivity as compared to any of the previously explored IR techniques, including FTIR and photothermal FTIR methods. Our results demonstrate that <10(-9)g of a biological sample is sufficient to obtain its characteristic micro -CalSpec spectrum that contains information-rich chemical (vibrational) signatures. This opens up a new opportunity to create inexpensive high-throughput analytical systems for biochemical detection.     

Spectroscopic study of tribooxidation processes in modified PTFE

The effect of layered silicates on the structure and performance characteristics of polytetrafluoroethylene is studied using IR spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy, as well as tribological and physicomechanical testing. It has been shown that the filling of polytetrafluoroethylene with layered silicates leads to a substantial (up to 2500 times) decrease in its mass wear rate, while its strength characteristics remain similar to those of the original polymer. The use of IR spectroscopy and X-ray photoelectron spectroscopy to study structural transformations that occur during the friction of the polymer composite materials with various compositions of fillers has revealed the formation of intermediate products in the course of the oxidative destruction of polytetrafluoroethylene.     

Near-field photothermal microspectroscopy for adult stem-cell identification and characterization

The identification of stem cells in adult tissue is a challenging problem in biomedicine. Currently, stem cells are identified by individual epitopes, which are generally tissue specific. The discovery of a stem-cell marker common to other adult tissue types could open avenues in the development of therapeutic stem-cell strategies. We report the use of the novel technique of Fourier transform infrared near-field photothermal microspectroscopy (FTIR–PTMS) for the characterization of stem cells, transit amplifying (TA) cells and terminally differentiated (TD) cells in the corneal epithelium. Principal component analysis (PCA) data demonstrate excellent discrimination of cell type by spectra. PCA in combination with linear discriminant analysis (PCA–LDA) shows that FTIR–PTMS very effectively discriminates between the three cell populations. Statistically significant differences above the 99% confidence level between IR spectra from stem cells and TA cells suggest that nucleic acid conformational changes are an important component of the differences between spectral data from the two cell types. FTIR–PTMS is a new addition to existing spectroscopy methods based on the concept of interfacing a conventional FTIR spectrometer with an atomic force microscope equipped with a near-field thermal sensing probe. FTIR-PTMS spectroscopy currently has spatial resolution that is similar to that of diffraction-limited optical detection FTIR spectroscopy techniques, but as a near-field probing technique has considerable potential for further improvement. Our work also suggests that FTIR–PTMS is potentially more sensitive than synchrotron radiation FTIR spectroscopy for some applications. Microspectroscopy techniques like FTIR–PTMS provide information about the entire molecular composition of cells, in contrast to epitope recognition that only considers the presence or absence of individual molecules. Our results with FTIR–PTMS on corneal stem cells are promising for the potential development of an IR spectral fingerprint for stem cells.     

太赫兹技术对营养品中蛋白质含量的研究

采用太赫兹时域光谱(THz-TDS)和红外光谱分析技术,研究了3种奶粉、杏仁粉和白砂糖的光学性能和光谱特性。通过对比样品在1658 cm-1和1747 cm-1处的红外光谱吸收峰,可以判定蛋白质和脂肪含量的差别。对比样品在THz波段的吸收系数和折射率,蛋白质含量较高的样品其吸收系数和折射率较高。观察样品的红外吸收峰强度和位置难以定量分析样品的蛋白质含量,但可以利用样品在THz波段的吸收系数与折射率有效地判定营养品中蛋白质的含量。实验结果表明蛋白质在太赫兹波段比在红外波段有更好的区分性,THz-TDS技术有望为营养品中蛋白质含量检测提供一种有效的分析手段。     

红外光谱技术的近代进展及其应用

对红外光谱技术的近代进展,如漫反射、衰减全反射、联用技术、差谱技术和数据压缩等及其应用作了简单地介绍。     

红外分光仪信号漂移误差的自动跟踪

文章介绍一种红外分光仪的信号处理方法，对于克服漂移误差具有较好的效果。     

二羟基廿二酸的抗磨作用机理

四球机磨损试验表明,二羟基廿二酸具有良好的抗磨性,与传统的抗磨剂二烷基二硫代磷酸锌(ZDDP)比较接近。C22酸的抗磨性优劣次序为13,14－二羟基廿二酸(DHDA)＞13(14)－羟基廿二酸(MHDA) ＞廿二酸(DA),表明羟基的引入能显著地提高基础油的抗磨性。红外光谱说明DHDA和MHDA可能与摩擦表面起摩擦化学反应形成聚酯。俄歇电子能谱分析揭示DHDA在摩擦表面形成富氧保护膜,这与IR分析结果二羟基廿二酸能形成含氧较高的网状聚酯膜相一致。初步结果说明了二羟基廿二酸通过形成摩擦聚合物膜而起抗磨作用。     

岗梅与毛冬青的二维红外相关光谱鉴别研究

采用红外光谱法(FTIR)并结合二维相关光谱(Two-dimensionalInfrared CorrelationSpectrocopy)分析技术,对岗梅与毛冬青进行无损快速鉴别研究。岗梅与毛冬青皆为冬青属植物,其外形极其相似,加工成饮片后更易混淆,因此通过红外光谱对其进行无损快速鉴别研究。两种药材在一维谱上几乎没有显著差别,因此需要借助二阶导数谱和二维红外光谱对其进行进一步的研究。结果表明:通过岗梅与毛冬青的红外光谱并结合二维相关谱完全可以将其区别开来。该方法快速、准确,对中药的鉴别提供一种新的方法和手段。     

Transient two-dimensional IR spectrometer for probing nanosecond temperature-jump kinetics

We have developed a Fourier transform two-dimensional infrared (2D IR) spectrometer to probe chemical reactions and biophysical processes triggered by a nanosecond temperature jump (T jump). The technical challenges for such a spectrometer involve (1) synchronization of a nanosecond T-jump laser and femtosecond laser system, (2) overcoming the decreased signal-to-noise ratio from low repetition rate data acquisition, and (3) performing an interferometric measurement through a sample with a density and index of refraction that varies with time delay after the T jump. The first challenge was overcome by synchronizing the two lasers to a clock derived from the Ti:sapphire oscillator, leading to timing accuracy of 2 ns for delays up to 50 ms. The data collection time is reduced by using undersampling with the improved signal-to-noise ratio obtained from a balanced detection scheme with a dual stripe array detector. Transient dispersed vibrational echo and 2D IR spectroscopy are applied to N-methylacetamide and ubiquitin, as examples, and the spectral responses by a temperature elevation and by structural changes of the protein are compared. The synchronization of 2D IR spectroscopy with a nanosecond temperature jump without losing its sensitivity at a low repetition rate opens a new applicability of the nonlinear spectroscopy to probe a variety of molecular structure changes induced by a nanosecond perturbation.     

In-Contact IR Spectroscopy of Hydrocarbon Lubricants

This paper reviews the application of infrared (IR) spectroscopy to in-contact lubrication studies, details improvements to the method and reports initial results from the study of a simple hydrocarbon fluid. IR spectra have been taken from the Hertzian region of a sliding contact lubricated by poly-α-olefin fluids. Single reflection sampling was used with a spot size of 100 μm square. The spectral range was limited to the CH stretch region of 3100--2700 cm⁻¹. The results show that it is possible to obtain good quality IR spectra from hydrocarbon films of less than 50 nm. Spectra sampled from the contact zone show peak intensity changes, frequency shifts and shape changes. Analysis of these results indicate that in the high pressure region there is an increase in gauche defects in the alkyl chain implying a more globular molecule with a lower volume but higher energy. In thin lubricant films (<100 nm) there is evidence of fluid structuring close to the metal surface.     

Comparison of engine oil degradation observed in laboratory alteration and in the engine by chemometric data evaluation

The influence of ethanol in gasoline and its partial combustion products on the engine oil performance was investigated by joint use of IR spectroscopic data and chemometrics. Oil samples obtained from artificial alteration in the laboratory and engine alteration in a chassis dynamometer were compared. Quantification of residual amounts of antioxidant and antiwear additive (ZDDP) in the oil samples by FTIR spectroscopy showed depletion of phenolic antioxidant during engine alteration but ZDDP degradation during artificial alteration. Different chemometrical models using principal component analysis (PCA) elucidated similarities and differences between both alteration types, proving the findings of FTIR spectroscopy. Additionally, laboratory-based artificial alteration was mainly driven by oxidative processes whereas engine alteration showed higher amounts of both oxidation and nitration products.     

红外光谱在食品安全检测中的应用

本文对红外光谱在食品安全检测中的应用进行综述,简要介绍红外光谱分析技术,并着重阐述其在食品种类和产地鉴别、食品中有毒有害成分检测及食品中农药残留检测和食品掺假鉴定等方面的应用。红外光谱在食品安全检测中发挥重要的作用,且应用前景广阔。     

Effect of mechanical activation of ultra-high-molecular-weight polyethylene on its mechanical and triboengineering properties

The effect of mechanical activation of initial ultra-high-molecular-weight polyethylene powders on the pysicomechanical properties of the polymer is studied. Mechanical activation is found to raise the strain and strength properties, as well as the triboengineering characteristics of ultra-high-molecular-weight polyethylene. X-ray diffraction analysis, IR spectroscopy, and optical and electronic microscopy show that mechanoactivation of the initial powder defines the polymer’s structural organization.     

Friction and wear behaviour of liquid paraffin containing an S-P type additive and amine

Sulphurised olefin (SO) and dibutyl phosphite (DBP) are two popular antiwear and extreme-pressure additives for gear oils. Investigation of the effects of the weight ratio of SO to DBP in liquid paraffin, and the effects of dodecyl amine, on the friction and antiwear properties of oil, were conducted with a four-ball wear tester. The chemical composition of the film, formed was examined using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and reflecting infrared spectro-scopic (IR) microscopy. The four-ball test results indicate that the weight ratio of SO to DBP affects the friction and wear behaviour of the oil and, with a weight ratio of SO to DBP of 20:1, a stable friction coefficient, and the smallest wear scar, were observed. Wear tests also showed that dodecyl amine improves or reduces the antiwear ability of the oil at certain concentrations. AES profile analyses demonstrate a thick boundary film formed on the rubbed surface with the weight ratio of SO to DBP at 20:1. Both AES and IR results indicate that the addition of dodecyl amine to an S-P type oil results in competitive adsorption, and hinders the reaction of SO and DBP with the steel surfaces.     

野葛与粉葛的二维红外相关光谱鉴别

采用傅立叶变换红外(FTIR)光谱法并结合二维红外相关光谱(Two-dimensional Infrared Correlation Spectroscopy)分析技术,对野葛与粉葛进行无损快速鉴别研究。野葛和粉葛均为葛藤属植物,其外形极其相似,加工成粉末后更易混淆,但两种葛根的疗效并不完全相同,因此通过红外光谱法可对其进行无损快速鉴别研究。两种药材在一维红外光谱上略有差别,因此需要借助二阶导数光谱和二维红外光谱对其进行进一步的研究。结果表明,通过野葛与粉葛的红外光谱并结合二维相关光谱完全可以将其区别开来。该方法快速、准确,对中药的鉴别提供了一种新的方法和手段。     

FTIR spectroscopy and nanotribological comparative studies: influence of the adsorbed water layers on the tribological behaviour

Under ambient conditions, a water film is always present on a silica substrate and generates additional capillary forces between the nanotip and the studied surface. In the present paper, we report AFM measurements of pull-off and friction forces as a function of the temperature and a comparative FTIR spectroscopy study. The AFM results show a net decrease of the forces as the temperature increases, while the IR spectroscopy indicates that the liquid film is removed at high temperature. Consequently, we deduce that a liquid neck is created between the tip and the surface and that the forces measured are mostly capillary forces. The present work shows that temperature studies with AFM can be a useful way to probe the influence of the capillary force in turn to characterize surface properties.     

苯系列傅里叶变换红外(FT-IR)光谱的研究

从红外光谱学原理角度出发，将挥发性苯系列化合物的FT-IR谱图的性质加以分析，与仪器联用的计算机检索软件中的标准谱图进行了对比，列举了苯系列样品（色谱标准物）可能官能团的位置，并讨论了温度的影响。     

栽培与野生丹参的红外光谱三级鉴定研究

红外三级鉴定法可以区别和鉴定栽培和野生丹参,红外三级鉴定包括普通红外光谱、二阶导数谱和二维红外相关光谱,并且表观分辨率逐渐提高。栽培与野生丹参一维谱图峰形相似度很高,只是吸收峰波数有一定的差异。二阶导数谱则可看到在1500~1180cm-1波段栽培丹参在1410cm-1处有单峰,而野生丹参则出现分叉峰,分别在1420cm-1、1406cm-1处。在1180~850cm-1波段,栽培丹参在993cm-1、872cm-1处有比较强的吸收峰,而野生丹参在1032cm-1处有比较强的吸收峰。二维红外相关光谱中差异更明显,在1170~860cm-1波段,野生丹参在950cm-1处有很强的自动峰,而栽培丹参在此没有吸收峰;1500~1170cm-1波段野生丹参的峰强度要较栽培丹参大,依据自动峰的不同可以很容易的分辨出栽培与野生丹参。红外三级鉴定方法是一种快速有效的鉴定中药材的方法。     

Antifriction nanocomposites based on chemically modified UHMWPE. Part 1. Mechanical and tribological properties of chemically modified UHMWPE

The mechanical and tribological properties of chemically modified UHMWPE are studied. X-ray diffraction analysis, IR spectroscopy, scanning differential calorimetry, and electron emission are used to study the permolecular structure and friction surface of polymers with different amounts of copolymers UHMWPE and LDPE grafted with maleic anhydride. Addition of grafted UHMWPE is shown to have no effect on the viscoelastic properties of the polymer-polymer composite, while the addition of grafted LDPE noticeably improves its performance (ductility, plasticity) while retaining its strength. Chemical modification of UHMWPE significantly improves its wear resistance (two to three times), which is due to the features of polymer crystallization and the formation of a permolecular structure.