光纤光谱仪的多样化组装及应用——介绍一个仪器分析实验

介绍了一个本科生的仪器分析实验——光纤光谱仪的多样化组装及应用。利用光源、光纤和电荷耦合器件检测器等部件,组装出紫外-可见光谱仪、分子荧光光谱仪、近红外光谱仪、拉曼光谱仪和激光诱导荧光光谱仪。通过本实验,不仅能够拓展传统光学实验的内容,而且可以通过自己动手组装仪器,培养学生的专业实践能力和知识应用能力。     

基于高斯函数卷积的色散型拉曼光谱仪温度校正

色散型拉曼光谱仪易受到温度影响,使测得的光谱重复性变差。针对这个问题,本研究提出了基于高斯函数卷积的温度校正方法。利用标准物质获得光谱仪在不同温度下的仪器响应函数,并以此构造高斯函数,通过卷积运算对温度造成的波数漂移以及分辨率变化进行校正。本方法直接基于拉曼谱分析,机理性强,且无需测量大量样本。利用苯作标准物质,对间二甲苯与汽油样本的拉曼光谱进行温度校正。结果表明,本方法能有效去除温度对色散型拉曼光谱仪的影响,使得不同温度下测得的光谱一致性显著提高。     

Combined time- and space-resolved Raman spectrometer for the non-invasive depth profiling of chemical hazards

A time-resolved inverse spatially offset Raman spectrometer was constructed for depth profiling of Raman-active substances under both the lab and the field environments. The system operating principles and performance are discussed along with its advantages relative to traditional continuous wave spatially offset Raman spectrometer. The developed spectrometer uses a combination of space- and time-resolved detection in order to obtain high-quality Raman spectra from substances hidden behind coloured opaque surface layers, such as plastic and garments, with a single measurement. The time-gated spatially offset Raman spectrometer was successfully used to detect concealed explosives and drug precursors under incandescent and fluorescent background light as well as under daylight. The average screening time was 50 s per measurement. The excitation energy requirements were relatively low (20 mW) which makes the probe safe for screening hazardous substances. The unit has been designed with nanosecond laser excitation and gated detection, making it of lower cost and complexity than previous picosecond-based systems, to provide a functional platform for in-line or in-field sensing of chemical substances.     

Performance enhancement of a Fourier transform Raman microprobe

Improvements to an existing Fourier transform Raman microprobe are described which include the optimization of the spectrometer for use in the near-IR region, the laser input optics in the microscope and optics employed to couple the microscope to the spectrometer. Several examples are presented which demonstrate the effect of these improvements on the microprobe's spatial resolution, Rayleigh rejection and ability to analyze weak Raman scattering materials with moderate excitation powers. Polarized data from a single crystal and data from the use of holographic notch filters are also presented. Future improvements to the system are also discussed.     

AOTF Raman spectrometer for remote detection of explosives

A spectrometer based on acousto-optic tunable filters is developed for use in measuring Raman spectra as part of a detection system that is low-cost, reliable, and field-portable. The system is coupled with a fiber optic bundle to carry the excitation laser light to the sample and to collect the Raman scattered light. Spectra of the explosives trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine (HMX) and nitroguanidine (NQ) were obtained in very short times and are in good agreement with those taken with conventional Fourier transform Raman spectrometers. Spectra of mixtures of explosives were also obtained and show no overlap of their characteristic Raman bands.     

便携式三聚氰胺快速检测仪的研制与应用

自主研发了便携式三聚氰胺速检仪,利用纳米增敏表面增强拉曼光谱法,定量检出限为0.5 mg/kg;采用相对测量方式可有效克服测量不稳定性.用于原奶、消毒奶、酸奶、奶粉中三聚氰胺检测,线性关系良好.样品前处理步骤简单.通常情况,平均单样检测时间小于2 min,仪器检测时间小于30 s,尤其适用于现场快速分析.除了可应用于乳...     

Surface Enhanced Raman Scattering Sensing with Nanostructures Fabricated by Soft Nanolithography

The nanospike structures formed with femtosecond laser irradiations have been successfully replicated on the surface of a polyurethane (PU) polymer using a low cost soft nanolithography method. The surface enhanced Raman scattering (SERS) of rhodamine 6G (Rh6G) and dinitrotoluene (DNT) molecules have been measured with silver coated PU nanospike surfaces by a simple portable Raman spectrometer. Compared to a flat silver coated surface, where no Raman Scattering of the molecules can be detected by the simple portable Raman spectrometer, the Raman spectra are enhanced by more than 4 orders of magnitudes. This indicates that the high area/volume ratio and small size of the PU nanospikes can be used for SERS sensing.     

气/液界面Langmuir单分子膜的原位拉曼光谱

提出了一种原位测量气/液界面Langmuir单分子膜拉曼光谱的新方法, 即利用SERS技术, 通过降低亚相的方法来获得气/液界面Langmuir单分子膜的原位拉曼光谱. 利用这种方法, 用原位拉曼光谱测量系统得到了信噪比较好的十八胺及二棕榈酰磷脂酰胆碱单分子膜的拉曼光谱, 在分子水平上获取了单分子膜中的结构信息.     

InVia-Reflex显微共焦拉曼光谱仪的使用与管理维护

显微共聚焦拉曼光谱仪可有效分析物质的化学成分、微观结构、应力应变等特性,广泛应用于生命、医学、食品、化学、材料等领域,在拉曼研究中占有重要地位. 介绍了InVia-Reflex显微共焦拉曼光谱仪的工作原理及使用方法,对激光损伤样品、激光强度变化引起拉曼光谱特征改变、拉曼信号隐藏在强背底信号中等常见问题进行了分析,给出了相应的解决方案. 最后,详细阐述了如何有效地管理和维护设备,以提高仪器的使用效率,为同类型仪器的运行提供管理经验.     

Computer analysis of a spectrometer slit function

A method for the computer analysis of a spectrometer slit function, considered as a convolution of two limiting functions has been developed. An apllication of this method to the slit function of a Raman spectrometer is described.     

Thermal decomposition of liebigite

Summary A combination of high resolution thermogravimetric analysis coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of liebigite. Water is lost in two steps at 44 and 302°C. Two mass loss steps are observed for carbon dioxide evolution at 456 and 686°C. The product of the thermal decomposition was found to be a mixture of CaUO₄ and Ca₃UO₆. The thermal decomposition of liebigite was followed by hot-stage Raman spectroscopy. Two Raman bands are observed in the 50°C spectrum at 3504 and 3318 cm^-1 and shift to higher wavenumbers upon thermal treatment; no intensity remains in the bands above 300°C. Three bands assigned to the υ₁ symmetric stretching modes of the (CO₃)^2- units are observed at 1094, 1087 and 1075 cm^-1 in agreement with three structurally distinct (CO₃)^2- units. At 100°C, two bands are found at 1089 and 1078 cm^-1. Thermogravimetric analysis is undertaken as dynamic experiment with a constant heating rate whereas the hot-stage Raman spectroscopic experiment occurs as a staged experiment. Hot stage Raman spectroscopy supports the changes in molecular structure of liebigite during the proposed stages of thermal decomposition as observed in the TG-MS experiment.     

两种形貌GdPO_4纳米粒子的制备和光学性质研究

以Gd2O3、H3PO4为原料,聚乙二醇(PEG)为结构导向剂,通过改变沉淀剂NaOH的用量,制备了棒状、丝状的GdPO4纳米粒子,用X射线衍射仪(XRD)、X射线能量扩散光谱仪(EDS)、透射电子显微镜(TEM)、X射线光电子能谱仪(XPS)、富里叶变换红外光谱仪(FT-IR)对样品进行表征,研究了样品的激光拉曼散射光谱(Raman)、光致发光(PL)性质。结果表明,两种不同形貌的GdPO4纳米粒子具有不同的光学活性,PEG的浓度以及它和Gd3+、H+的配位作用对棒状GdPO4纳米粒子的形成有重要的影响。     

Fourier transform raman spectroscopy using a bench-top fourier transform infrared spectrometer

The use of a bench top FTIR spectrometer for near infrared Fourier transform Raman spectroscopy is demonstrated. The use of near infrared excitation results in fluorescence free Raman spectra allowing previously difficult samples to be measured.     

A compact collinear AOTF Raman spectrometer

A compact, lightweight, completely packaged, uncooled, fully-automated collinear acousto-optic tunable-filter (AOTF) based spectrometer has been used to measure Raman spectra of three organic energetic materials (NQ, HMX, and TNT) using argon-ion laser excitation. Even though the resolution of the AOTF spectrometer is modest (7.4 cm(-1)) and it was not specifically designed for measuring Raman spectra, it has performed impressively. Such an instrument is specially useful for remote sensing and field measurements. In this paper, we will describe this instrument, present the measured Raman spectra and their comparison with the corresponding FT-IR spectra.     

Monitoring of chemical reactions within microreactors using an inverted Raman microscopic spectrometer

An inverted Raman microscope spectrometer has been used to profile the spatial evolution of reactant and product concentrations for a chemical reaction within a microreactor operating under hydrodynamic flow control. The Raman spectrometer was equipped with a laser source at wavelength of 780 nm, confocal optics, a holographic transmission grating, and a charge-coupled device (CCD) detector. The microreactor consisted of a T-shaped channel network etched within a 0.5 mm thick glass bottom plate that was thermally bonded to a 0.5 mm thick glass top plate. The ends of the channel network were connected to reagent reservoirs that were linked to a syringe pump for driving the solutions by hydrodynamic pumping within the channels. The microchannels were 221 micro m wide and 73 micro m deep. The synthesis of ethyl acetate from ethanol and acetic acid was investigated as a model system within the microreactor as Raman scattering bands for each reactant and product species were clearly resolved. Raman spectral intensities of each band were proportional to concentration for each species and hence all concentrations could be quantitatively measured after calibration. By scanning specific Raman bands within a selected area in the microchannel network at given steps in the X-Y plane, spatially resolved concentration profiles were obtained under steady-state flow conditions. Under the flow conditions used, different positions within the concentration profile correspond to different times after contact and mixing of the reagents, thereby enabling one to observe the time dependence of the product formation. Raman microscopy provides a useful complementary technique to UV/VIS absorbance and fluorescence methods for the in situ monitoring and analysis of chemical reaction species having their lowest S(0)-S(1) absorption bands too far in the UV to be of use, due to their probable overlap with the bands from other reactant, product and solvent molecules.     

Computerized laser Raman spectrometer

A microprocessor computer specially designed for application in optical spectroscopy is described and the construction of a laser Raman spectrometer realized on its base is discussed. The computer exercises an active control over a high resolution double monochromator, a photon counting system and the exciting laser radiation. The spectral information can be visualized on an oscilloscope display, hardcopied on a XY recorder and stored on magnetic tape.     

Quantitative analysis using Raman methods

The feasibility of using a Fourier Transform Raman spectrometer employing back scattering optics, to obtain spectra with excellent reproducibility both in band positions and intensities, is demonstrated. Such a spectrometer affords the basis of quantitative chemical analysis via external intensity standards. The potential and application of the technique are reviewed.     

Remote-Raman spectroscopic study of minerals under supercritical CO2 relevant to Venus exploration

The authors have utilized a recently developed compact Raman spectrometer equipped with an 85 mm focal length (f/1.8) Nikon camera lens and a custom mini-ICCD detector at the University of Hawaii for measuring remote Raman spectra of minerals under supercritical CO(2) (Venus chamber, ～102 atm pressure and 423 K) excited with a pulsed 532 nm laser beam of 6 mJ/pulse and 10 Hz. These experiments demonstrate that by focusing a frequency-doubled 532 nm Nd:YAG pulsed laser beam with a 10× beam expander to a 1mm spot on minerals located at 2m inside a Venus chamber, it is possible to measure the remote Raman spectra of anhydrous sulfates, carbonates, and silicate minerals relevant to Venus exploration during daytime or nighttime with 10s integration time. The remote Raman spectra of gypsum, anhydrite, barite, dolomite and siderite contain fingerprint Raman lines along with the Fermi resonance doublet of CO(2). Raman spectra of gypsum revealed dehydration of the mineral with time under supercritical CO(2) at 423 K. Fingerprint Raman lines of olivine, diopside, wollastonite and α-quartz can easily be identified in the spectra of these respective minerals under supercritical CO(2). The results of the present study show that time-resolved remote Raman spectroscopy with a compact Raman spectrometer of moderate resolution equipped with a gated intensified CCD detector and low power laser source could be a potential tool for exploring Venus surface mineralogy both during daytime and nighttime from a lander.     

Polarized Raman Spectra X. Polarized Raman Spectra of Naphthalene Single Crystal

The polarized Raman spectra of naphthalene single crystal are recorded with a laser Raman spectrometer. Relative intensites of Raman lines in various polarizations are accurately measured by photon-counting technique. All the strong lines are polarized in the c′c′ and bb polarizations, and the polarization data alone are not sufficient to decide the symmetry of a Raman active vibration. The oriented gas model is found not adequate to fully understand the results. The polarization data have to be interpreted in terms of the electronic spectrum of naphthalene.     

两步法制备多孔硅及其表征I:恒电流法(英文)

本工作通过采用电化学极 -化学氧化两步法在 1:1氢氟酸和乙醇溶液中制备出孔径约为 1～ 2 μm ,厚度大经为 6～ 10 μm的多孔硅样品 .首先将 0 .0 3A/cm2 的恒电流施加到p( 10 0 )硅片一段时间 ,然后将该硅片浸到 2 0 %的硝酸溶液中氧化一段时间 .通过此方法获得的多孔硅结构再进一步用扫描电子显微镜和拉曼光谱仪进行表面形貌和光学性质的考察 .所有制备出的多孔硅结构均有光致发光现象 .老化的多孔硅样品 (在干燥器放置一年 )的光致发光谱峰强度明显增强 ,但分别经过苯乙烯和十六碳烯 ( 1)两种有机溶剂处理 1h后的老化多孔硅样品的光致发光强度却没有显著改变 .