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光声位相理论及其在化学中的应用研究进展 总被引:2,自引:0,他引:2
光声位相作为光声光谱重要的一部分, 包含着很多有价值的信息, 对它的研究可以获得其它光谱甚至光声振幅谱都不能得到的信息。光声位相在测定样品的光学和热学性质、样品无辐射弛豫过程的研究以及深度剖面分析等方面显示了特有的能力。本文结合本实验室近几年的工作, 在光声光谱理论的基础上,对光声位相理论及其在化学中的应用作一综述。 相似文献
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近年来,用光声量热法(photoacoustic calorimetry,缩写PAC)测量液相体系中的光物理或光化学过程有了较快发展.这对于观测无辐射的瞬态粒子有重要意义。Peters及其同事曾分析过这种光声技术的原理.简言之,脉冲激光被体系吸收后将 相似文献
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设计了适于激光诱导光声流动检测的毛细管流动池,讨论了池的特点及其在分析化学中的应用,用该池检测Co~(2+),检测限相当于2×10~(-6)cm~(-1)光吸收。 相似文献
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Schmid T 《Analytical and bioanalytical chemistry》2006,384(5):1071-1086
Photoacoustic spectroscopy (PAS) is based on the absorption of electromagnetic radiation by analyte molecules. The absorbed
energy is measured by detecting pressure fluctuations in the form of sound waves or shock pulses. In contrast to conventional
absorption spectroscopy (such as UV/Vis spectroscopy), PAS allows the determination of absorption coefficients over several
orders of magnitude, even in opaque and strongly scattering samples. Small absorption coefficients, such as those encountered
during trace gas monitoring, can be detected with cells with relatively short pathlengths. Furthermore, PA techniques allow
absorption spectra of solid samples (including powders, chips or large objects) to be determined, and they permit depth profiling
of layered systems. These features mean that PAS can be used for on-line monitoring in technical processes without the need
for sample preparation and to perform depth-resolved characterization of industrial products. This article gives an overview
on PA excitation and detection schemes employed in analytical chemistry, and reviews applications of PAS in process analytical
technology and characterization of industrial products. 相似文献
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A novel photothermal phase-shift spectroscopy configuration based on the retro-reflected beam interference has been developed and its operational principle is described. The weak absorption measurement ability of this technique is experimentally proven with a water/ethanol solution of standard Pyronine G dye and the limit of detection is found to be 1.8 x 10(-6) absorbance. Potential applications of the technique are discussed. 相似文献
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Schilt S Vicet A Werner R Mattiello M Thévenaz L Salhi A Rouillard Y Koeth J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(14):35-3436
First investigations of photoacoustic (PA) spectroscopy (PAS) of methane using an antimonide semiconductor laser are reported. The laser fabrication is made in two steps. The structure is firstly grown by molecular beam epitaxy, then a metallic distributed-feedback (DFB) grating is processed. The laser operates at 2371.6 nm in continuous wave and at room temperature. It demonstrates single-mode emission with typical tuning coefficients of 0.04 nm mA(-1) and 0.2 nm K(-1). PA detection of methane was performed by coupling this laser into a radial PA cell. A detection limit of 20 ppm has been achieved in a preliminary configuration that was not optimised for the laser characteristics. 相似文献
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This paper summarizes the features and performances of optical detection systems currently applied in order to monitor separations
on microchip devices. Fluorescence detection, which delivers very high sensitivity and selectivity, is still the most widely
applied method of detection. Instruments utilizing laser-induced fluorescence (LIF) and lamp-based fluorescence along with
recent applications of light-emitting diodes (LED) as excitation sources are also covered in this paper. Since chemiluminescence
detection can be achieved using extremely simple devices which no longer require light sources and optical components for
focusing and collimation, interesting approaches based on this technique are presented, too. Although UV/vis absorbance is
a detection method that is commonly used in standard desktop electrophoresis and liquid chromatography instruments, it has
not yet reached the same level of popularity for microchip applications. Current applications of UV/vis absorbance detection
to microchip separations and innovative approaches that increase sensitivity are described. This article, which contains 85
references, focuses on developments and applications published within the last three years, points out exciting new approaches,
and provides future perspectives on this field. 相似文献
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Kumauchi M Kaledhonkar S Philip AF Wycoff J Hara M Li Y Xie A Hoff WD 《Journal of the American Chemical Society》2010,132(44):15820-15830
PAS domains form a divergent protein superfamily with more than 20?000 members that perform a wide array of sensing and regulatory functions in all three domains of life. Only nine residues are well-conserved in PAS domains, with an Asn residue at the start of α-helix 3 showing the strongest conservation. The molecular functions of these nine conserved residues are unknown. We use static and time-resolved visible and FTIR spectroscopy to investigate receptor activation in the photosensor photoactive yellow protein (PYP), a PAS domain prototype. The N43A and N43S mutants allow an investigation of the role of side-chain hydrogen bonding at this conserved position. The mutants exhibit a blue-shifted visible absorbance maximum and up-shifted chromophore pK(a). Disruption of the hydrogen bonds in N43A PYP causes both a reduction in protein stability and a 3400-fold increase in the lifetime of the signaling state of this photoreceptor. A significant part of this increase in lifetime can be attributed to the helical capping interaction of Asn43. This extends the known importance of helical capping for protein structure to regulating functional protein kinetics. A model for PYP activation has been proposed in which side-chain hydrogen bonding of Asn43 is critical for relaying light-induced conformational changes. However, FTIR spectroscopy shows that both Asn43 mutants retain full allosteric transmission of structural changes. Analysis of 30 available high-resolution structures of PAS domains reveals that the side-chain hydrogen bonding of residue 43 but not residue identity is highly conserved and suggests that its helical cap affects signaling kinetics in other PAS domains. 相似文献
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The improvement in hyphenated analytical techniques has significantly widened their applications to the analysis of biomaterials. In this article, we discuss recent advances in applications of hyphenated chromatographic techniques including capillary electrophoresis to the analyses of biological samples. As tools of separation, gas chromatography, high-performance liquid chromatography and capillary electrophoresis are considered with special emphasis on applications utilizing the hyphenation of these methods to mass spectrometry. Moreover, applications using other detection methods such as Fourier transform infrared spectroscopy hyphenated to gas chromatography and photodiode array detector combined with high-performance liquid chromatography or capillary electrophoresis are also discussed. Owing to their high sensitivity, luminescence-based detection systems such as laser-induced fluorescence and chemiluminescence are also included in this review. 相似文献
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Besson JP Schilt S Thévenaz L 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(14):312-3456
Multi-hydrogenated compounds detection based on photoacoustic (PA) spectroscopy is reported. Three near-infrared semiconductor lasers are used with a resonant PA cell operated in its first longitudinal mode to monitor methane, water vapour and hydrogen chloride in the parts per million range. The design of our cell results from simulations performed in order to optimise its performances. Influence of the buffer gas on the PA signal has also been analysed, both theoretically and experimentally. A reduction of the PA signal of almost one order of magnitude has been observed between N(2) and He, which demonstrates the importance of the buffer gas in PA spectroscopy. Finally, detection limits of 0.5 ppm of CH(4) and 3 ppm of HCl has been achieved experimentally in nitrogen and an H(2)O sensitivity of 0.2 ppm has been estimated. 相似文献
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Light emitting diode-based detectors Absorbance, fluorescence and spectroelectrochemical measurements in a planar flow-through cell 总被引:2,自引:0,他引:2
Purnendu K. Dasgupta In-Yong Eom Kavin J. Morris Jianzhong Li 《Analytica chimica acta》2003,500(1-2):337-364
Light emitting diodes (LEDs) were first used for chemical analysis three decades ago. They are finally making their appearance in commercial analytical systems and dedicated detectors. LEDs are the most energy-efficient means of producing monochromatic light, and provide a concentrated small cool emitter ideal for miniature analytical devices. Although they rank behind fluorescent and halogen discharge lamps in total conversion efficiency (lm/W), new efficiency records are being set every year such that by next decade broadband (white) LED sources are not only likely in analytical instrumentation, but for general illumination. This paper begins with a review of analytical use of LEDs that has been advanced in the last decade. LED-based absorbance measurement and its use in pedagogy, titrations, in providing immunity to refractive index and turbidity effects, in field and process analysis, in capillary electrophoresis (CE), in liquid–liquid extraction systems, in film and drop-based analytical systems and with liquid core waveguides (LCWs) are discussed. LED-based fluorescence and spectroelectrochemical detection follows next. Multipurpose LED-based analytical instrumentation and special analytical applications and general applications are discussed. A listing of (mostly web-based) resources for fabricating LED-based detectors is then provided. Detector circuits and available components are considered and different modes of driving LEDs are compared. The temperature dependence of LED characteristics and strategies to ameliorate this problem are discussed.
The review and general resource material is followed with the construction details, operation and performance observed for a simple-to-fabricate multipurpose cell that allows simultaneous multiwavelength absorbance, fluorescence and spectroelectrochemical detection. 相似文献