低温拉曼光谱分析流体包裹体盐度的条件约束

流体包裹体盐度及类型是分析地质流体作用的重要地球化学参数。NaCl-H₂O体系是地质体中最常见的流体体系之一,其盐度通常由显微测温法获得,而盐水合物的低温拉曼光谱不仅可以用来计算流体包裹体盐度,还可以区分盐水类型。理论上讲,低温冷冻条件下的流体包裹体并非均匀体系,单一测点的拉曼光谱具有较强的局限性,由其计算的盐度并不能代表整个流体包裹体的盐度。为了更好地了解低温条件下流体包裹体的相变特征及其拉曼光谱对盐度的响应,本文通过配置五种不同浓度的NaCl溶液,研究了其在低温下的结晶过程及拉曼光谱特征。结果显示,在反复冷冻与升温过程中,冰晶首先形成,而水石盐的形成依赖于盐溶液的浓缩,多形成于冰晶间的缝隙中。水石盐的四个拉曼特征峰中,p₁[(3 402±1) cm-1]和p₂[(3 419±1) cm-1]相对强度稳定,p₃[(3 432±2) cm-1]和p₄[(3 535±4) cm-1]相对强度随盐度增加发生大幅度变化,从而导致相同盐度样品不同测点的拉曼特征比值随盐度增加而愈发离散。因此,传统的流体包裹体单一测点低温拉曼测盐误差较大,数据分析显示多点测试统计平均值才能更好的反映流体的真实盐度。相对于强度和半高宽,总峰面积与盐度相关性最好,是计算盐度的首选参数。该研究阐述了低温拉曼测盐的实验操作和数据处理方法,并阐明了其在流体包裹体分析中的应用条件。尽管操作过程较复杂,但其抗干扰强,应用盐度范围广,计算结果可靠,是重要的测盐方法。     

Micro‐Raman investigations on inclusions of unusual habit in a commercial tanzanite gemstone

The vibrational properties of submillimetre size inclusions of unusual habit in a commercial tanzanite gemstone were investigated by confocal Raman microspectroscopy with the aim of probing both their chemical composition and crystal structure. Highly contrasted Raman spectra were recorded in confocal conditions from several inclusions incorporated at different depths, ranging between a few microns to some tens of microns beneath the gemstone surface. The observed spectral features were identified as specific markers of hematite (α‐Fe₂O₃). Their unambiguous assignment has been inferred by comparing our experimental findings with the literature data recorded either in single crystals of hematite or in other iron oxides and oxyhydroxides. Our results rule out the presence of any pseudomorphic variety of hematite in the investigated gemstone, while confocal micro‐Raman spectroscopy definitively proved itself as a very reliable, relatively costless and noninvasive tool for unambiguous identification of subsurface regions of gemstones. Copyright © 2011 John Wiley & Sons, Ltd.     

原位低温拉曼光谱技术在储层流体包裹体分析中的应用

准确获取流体包裹体中盐的类型一直是包裹体研究的重要问题。采用原位低温拉曼光谱技术对民丰洼陷深部天然气储层流体包裹体进行了分析。常温拉曼光谱综合分析表明,包裹体中流体为含甲烷的盐水溶液。在—180℃下对包裹体进行了原位低温拉曼光谱分析,结果显示包裹体中含有NaCl,CaCl_2,MgCl_2等盐类,其中以NaCl为主,CaCl_2含量很少,MgCl_2含量极少。根据沉积成岩过程分析了包裹体中流体的成因,解释了储层成岩作用的机理。研究结果表明,原位低温拉曼光谱是获取储层包裹体中流体性质的一种有效方法。在包裹体原位低温拉曼光谱分析技术基础上,结合沉积成岩过程,可以给储层的成岩作用类型和成岩反应机理给出重要证据。     

Detection of small amounts of H2O in CO2‐rich fluid inclusions using Raman spectroscopy

Raman spectroscopic analysis at low (−100 °C) or high (100–200 °C) temperature is shown to be effective for detecting small amounts of H₂O in CO₂‐rich fluid inclusions from the deep lithosphere, which have previously been thought to be water‐free. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopy as a potential method for the detection of extremely halophilic archaea embedded in halite in terrestrial and possibly extraterrestrial samples

Evidence for the widespread occurrence of extraterrestrial halite, particularly on Mars, has led to speculations on the possibility of halophilic microbial forms of life; these ideas have been strengthened by reports of viable haloarchaea from sediments of geological age (millions of years). Raman spectroscopy, being a sensitive detection method for future astrobiological investigations onsite, has been used in the current study for the detection of nine different extremely halophilic archaeal strains which had been embedded in laboratory‐made halite crystals in order to simulate evaporitic conditions. The cells accumulated preferentially in tiny fluid inclusions, in simulation of the precipitation of salt in natural brines. FT‐Raman spectroscopy using laser excitation at 1064 nm and dispersive micro Raman spectroscopy at 514.5 nm were applied. The spectra showed prominent peaks at 1507, 1152 and 1002 cm⁻¹ which are attributed to haloarchaeal C₅₀ carotenoid compounds (mainly bacterioruberins). Their intensity varied from strain to strain at 1064‐nm laser excitation. Other distinguishable features were peaks due to peptide bonds (amide I, amide III) and to nucleic acids. No evidence for fatty acids was detected, consistent with their general absence in all archaea. These results contribute to a growing database on Raman spectra of terrestrial microorganisms from hypersaline environments and highlight the influence of the different macromolecular composition of diverse strains on these spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

拉曼面扫描无损鉴定矿物包裹体：以彩虹方柱石中的磁铁矿包裹体为例

如何利用拉曼光谱对矿物中的微小包裹体进行无损鉴定，是矿物学与宝石学研究中经常遇到的问题。彩虹方柱石是一种含有特殊包裹体的方柱石，其包裹体在反射光下呈现虹彩效应。本文利用超景深显微镜、电子探针、显微激光拉曼光谱、X射线粉晶衍射分析，特别是创新性运用拉曼光谱面扫描填图技术对彩虹方柱石中微小的磁铁矿包裹体进行了无损鉴定研究。显微特征显示，彩虹方柱石的包裹体可能和固溶体出溶有关，微小包裹体平行排列，形成了类似反射型衍射光栅的结构，导致其在反射光下出现彩虹色。根据电子探针测试结果，彩虹方柱石端元组分为Ma_68.2-69.7Me_30.3-31.8，属针柱石亚族。根据拉曼光谱测试结果，部分包裹体出现了位于661 cm-1处的弱拉曼峰。由于图谱信噪比普遍偏低且该峰并不会在所有测试位置出现，所以容易被忽略。为进一步探究该峰的来源，对包裹体部位进行拉曼面扫描，并选择630～680 cm-1范围的拉曼峰进行了相关性分析，确认了包裹体位置普遍存在位于661 cm-1处的弱拉曼峰。该拉曼峰可归属为磁铁矿的A_1g振动峰，从而确认了产生虹彩效应的针状包裹体中包含有更微小的磁铁矿包裹体。XRD测试结果表明，包裹体较多的样品存在位于2.51 Å处的磁铁矿（311）晶面衍射峰，进一步验证了拉曼光谱面扫描的结果。根据上述实验，拉曼面扫描技术或许可以成为鉴定矿物宝石中微小包裹体的有效辅助性手段。该研究创新性提出，如果矿物包裹体的拉曼信号很弱，可以将拉曼面扫描结果与包裹体的分布特征结合分析来判断该信号的有效性。同时为无损鉴定矿物中的包裹体提供了一种新的研究思路与方法。     

激光拉曼光谱测定流体包裹体成分研究进展

成矿流体研究是矿床学研究中的前沿地带,单个流体包裹体的成分分析更是其中的热点和难点,本文对现有的各种测试技术的优缺点进行了总结,揭示了各自的局限性。通过对与流体包裹体成分分析相关的激光拉曼分析技术的探索过程进行回顾和总结,试图对低温和常温下激光拉曼对流体包裹体成分分析的研究工作的方向进行展望：低温：(1)流体包裹体中常见水盐多元复杂体系的研究工作;(2)对天然流体包裹体成分进行定性、定量尝试;(3)目前常用的显微热台测包裹体盐度将第一次熔融温度作为低共熔温度的方法存在误差,应该做进一步研究;(4)低温下氯盐水合物的结构尚无定论。常温：(1)Fe3+,Zn2+,Cu2+等离子作为主要成矿金属离子在水溶液中与Cl-和H₂O是如何结合的;(2)NaCl,CaCl₂,MgCl₂,CuCl₂,ZnCl₂,FeCl₃含量高低造成水溶液拉曼光谱O—H伸缩振动区域(2 800～3 800 cm-1)的谱峰偏移的原因。     

Quantitative Determination of Gaseous Phase Compositions in Fluid Inclusions by Raman Microspectrometry

ABSTRACT

Raman microspectrometry has been revealed as a powerful technique for performing qualitative analysis and estimation of relative molar fractions of the gaseous species present in minerals fluid inclusions. In this work, the methodology and calibration procedures used for the quantification of the different species in fluid inclusions are described, paying special attention to the estimation of the CO₂ molar fraction. A discussion about the Fermi resonance of CO₂ vibrations (ν₁-2ν₂; 1285–1388 cm^?1) is also included.     

Sub‐picosecond Raman spectrometer for time‐resolved studies of structural dynamics in heme proteins

We describe a pump–probe Raman spectrometer based on a femtosecond Ti:sapphire laser, an optical parametric generator and two optical parametric amplifiers for time‐resolved studies, with emphasis on the structural dynamics in heme proteins. The system provides a 100‐fs pump pulse tunable in the range 500–600 nm and a transform‐limited sub‐picosecond probe pulse tunable in the range 390–450 nm. The spectrometer has spectral (25 cm⁻¹) and temporal (∼0.7 ps) resolutions which constitute an effective compromise for identifying transient heme protein species and for following their structural evolution by spontaneous Raman scattering in the time range 0.5 ps to 2 ns. This apparatus was applied to time‐resolved studies of a broad range of heme proteins, monitoring the primary dynamics of photoinduced heme coordination state and structural changes, its interaction with protein side‐chains and diatomic gaseous ligands, as well as heme vibrational cooling. The treatment of transient Raman spectra is described in detail, and the advantages and shortcomings of spontaneous resonance Raman spectroscopy for ultrafast heme proteins studies are discussed. We demonstrate the efficiency of the constructed spectrometer by measuring Raman spectra in the sub‐picosecond and picosecond time ranges for the oxygen‐storage heme protein myoglobin and for the oxygen‐sensor heme protein FixLH in interaction with the diatomic gaseous ligands CO, NO, and O₂. Copyright © 2010 John Wiley & Sons, Ltd.     

Characterization of 6‐propylthiouracil and its interaction with human serum albumin on Au surface by surface‐enhanced Raman scattering

In this study, surface‐enhanced Raman scattering (SERS) spectra of 6‐propylthiouracil (6‐PTU) on Au surface and the interaction between 6‐PTU and human serum albumin (HSA) were studied. The Raman bands were assigned by the density functional theory calculations at the B3LYP/6‐311++g(d,p) level. Furthermore, the effects of concentration on the SERS spectra of 6‐PTU were analyzed. It shows that with the changes of the concentrations of 6‐PTU, the SERS spectra of 6‐PTU present significant changes, and it can be concluded that with the changing of concentrations, the orientation of 6‐PTU on Au surface also changes. In addition, the SERS spectra of the interaction between 6‐PTU and HSA show that the binding sites of 6‐PTU to HSA are the functional groups N3H and CO. The information will not only be references to the study of the mechanism of the interaction between drugs and blood plasma or serum albumin but also a guidance to understand the metabolism of drugs in human body. Copyright © 2015 John Wiley & Sons, Ltd.     

Molecular structure,vibrational spectroscopic,first‐order hyperpolarizability and HOMO,LUMO studies of 3‐hydroxy‐2‐naphthoic acid hydrazide

The Fourier‐transform infrared spectrum of 3‐hydroxy‐2‐naphthoic acid hydrazide (3H2NAH) was recorded in the region 4000–400 cm⁻¹. The Fourier‐transform Raman spectrum of 3H2NAH was also recorded in the region 3500–10 cm⁻¹. Quantum chemical calculations of energies, geometrical structure and vibrational wavenumbers of 3H2NAH were carried out by density functional theory (DFT/B3LYP) method with 6‐31G(d,p) as basis set. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. The values of the electric dipole moment (µ) and the first‐order hyperpolarizability (β) of the investigated molecule were computed using ab initio quantum mechanical calculations. The UV spectrum was measured in ethanol solution. The calculation results also show that the 3H2NAH molecule might have microscopic nonlinear optical (NLO) behavior with non‐zero values. A detailed interpretation of the infrared and Raman spectra of 3H2NAH is also reported based on total energy distribution (TED). The calculated HOMO and LUMO energies shows that charge transfer occur within the molecule. The theoretical FT‐IR and FT‐Raman spectra for the title molecule have also been constructed. Copyright © 2009 John Wiley & Sons, Ltd.     

Hydrogen bonding in different pyrimidine–methanol clusters probed by polarized Raman spectroscopy and DFT calculations

We report on the hydrogen bonding between pyrimidine (Pd) and methanol (M) as H‐donor in this study. Hydrogen bonds between pyrimidine and methanol molecules as well as those between different methanol molecules significantly influence the spectral features at high dilution. The ring‐breathing mode ν₁ of the reference system Pd was chosen as a marker band to probe the degree of hydrogen bonding. Polarized Raman spectra in the region 970–1020 cm⁻¹ for binary mixtures of (pyrimidine + methanol) at 28 different mole fractions were recorded. A Raman line shape analysis of the isotropic Raman line profiles at all concentrations revealed three distinct spectral components at mole fractions of Pd below 0.75. The three components are attributed to three distinct groups of species: ‘free Pd’ (pd), ‘Pd with low methanol content’ (pd1) and ‘Pd with high‐methanol content’ (pd2). The two latter species differ considerably in the pattern and the strengths of the hydrogen bonds. The results of density functional theory calculations on structures and vibrational spectra of neat Pd and eight Pd/M complexes with varying methanol content support our interpretations of the experimental results. A nice spectra–structure correlation for the different cluster subgroups was obtained, similar to earlier results obtained for Pd and water. Apart from N···H and O···H hydrogen bonds between pyrimidine and methanol, O···H hydrogen bonds formed among the methanol molecules in the cluster at high methanol content also play a crucial role in the interpretation of the experimental results. Copyright © 2010 John Wiley & Sons, Ltd.     

Infrared versus light scattering techniques to monitor the gel to liquid crystal phase transition in lipid membranes

In this study, Fourier transform infrared, Raman and Brillouin spectroscopy have been used to study lipid phase behavior of hydrated as well as dried multilamellar l ‐α‐phosphatidylcholine assemblies, in order to compare limitations and potentials of the different techniques. Dried lipid samples have been studied in the presence and absence of trehalose, which is known to affect the phase behavior of these systems. The methylene C‐H stretching (2800–3000 cm⁻¹) region in infrared (IR) and Raman spectra provided mutually consistent information on the rearrangement of lipid acyl chains occurring at the lipid melting temperature. IR spectra have a higher signal‐to‐noise ratio, thus permitting a more precise evaluation of the melting temperature. In the hydrated lipid samples, the C‐H stretching region in the Raman spectra is less affected by the contribution of water compared with that in the IR spectra. Raman spectra are particularly suitable to simultaneously study both lipid and water contributions allowing to distinguish ice from non‐frozen water below 0 °C. Brillouin light scattering was used to probe the collective dynamics, i.e. the propagation velocity and the attenuation of longitudinal acoustic modes in the lipid samples. Lipid phase transitions are evident from a change in the temperature behavior of the acoustic velocity. Moreover, a strong relaxation process with a characteristic time of 14 ps was observed in the sample dried without trehalose with a maximum in acoustic attenuation at about 45 °C, which likely reflects the rearrangement of acyl chains. Copyright © 2015 John Wiley & Sons, Ltd.     

FT‐IR and FT‐Raman spectra and ab initio calculations of 3‐{[(2‐hydroxyphenyl) methylene]amino}‐2‐phenylquinazolin‐4(3H)‐one

Fourier transform infrared (FT‐IR) and Fourier transform (FT) Raman spectra of 3‐{[(2‐hydroxyphenyl)methylene]amino}‐2‐phenylquinazolin‐4(3H)‐one were recorded and analyzed. The vibrational wavenumbers of the title compound were computed using HF/6‐31G* and 6‐311G* basis sets and compared with experimental data. The assignments of the normal modes are done by potential energy distribution (PED)calculations. The prepared compound was identified by nuclear magnetic resonance (NMR) and mass spectra. Optimized geometrical parameters of the title compound are in agreement with reported structures. Shortening of CN bond lengths reveal the effect of resonance. The simultaneous IR and Raman activations of the CO stretching mode shows a charge transfer interaction through a π‐conjugated path. The first hyperpolarizability, infrared intensities and Raman activities are reported. The phenyl C C stretching modes are equally active as strong bands in both IR and Raman spectra, which are responsible for hyperpolarizability enhancement leading to nonlinear optical activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Vibrational spectroscopy and crystal structure analysis of two polymorphs of the di‐amino acid peptide cyclo(L‐Glu‐L‐Glu)

Cyclo(L ‐Glu‐L ‐Glu) has been crystallised in two different polymorphic forms. Both polymorphs are monoclinic, but form 1 is in space group P2₁ and form 2 is in space group C2. Raman scattering and FT‐IR spectroscopic studies have been conducted for the N,O‐protonated and deuterated derivatives. Raman spectra of orientated single crystals, solid‐state and aqueous solution samples have also been recorded. The different hydrogen‐bonding patterns for the two polymorphs have the greatest effect on vibrational modes with N H and CO stretching character. DFT (B3‐LYP/cc‐pVDZ) calculations of the isolated cyclo(L ‐Glu‐L ‐Glu) molecule predict that the minimum energy structure, assuming C₂ symmetry, has a boat conformation for the diketopiperazine ring with the two L ‐Glu side chains being folded above the ring. The calculated geometry is in good agreement with the X‐ray crystallographic structures for both polymorphs. Normal coordinate analysis has facilitated the band assignments for the experimental vibrational spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Vibrational spectroscopy investigation using density functional theory on 7‐chloro‐3‐methyl‐2H‐1,2,4‐ benzothiadiazine 1,1‐dioxide

The solid phase Fourier transform infrared (FTIR) and Fourier transform (FT) Raman spectral analysis of 7‐chloro‐3‐methyl‐2H‐1,2,4‐benzothiadiazine 1,1‐dioxide (diazoxide), an antihypertensive agent was carried out along with density functional computations. The optimized geometry, wavenumber and intensity of the vibrational bands of diazoxide were obtained by DFT‐B3LYP level of theory with complete relaxation in the potential energy surface using 6‐31G(d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The harmonic vibrational wavenumbers calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated wavenumbers are found to be in good agreement. The experimental spectra coincide satisfactorily with those of calculated spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

DFT study and quantitative detection by surface‐enhanced Raman scattering (SERS) of ethyl carbamate

Ethyl carbamate (EC), a potentially toxic compound, is found in alcoholic beverages and fermented foodstuff. A combined experimental and theoretical study of Raman on EC is reported in this work for the first time. The Raman bands observed for EC in solid phase are characteristic for the carbonyl group, C―C, C―H and N―H stretching and deformation vibrations. These spectral features coupled with a pKa study allowed establishing the neutral species of EC present in the aqueous solutions experimentally tested at different concentrations. In addition, by performing a density functional theory study in the gas phase, the calculated geometry, the harmonic vibrational modes, and the Raman scattering activities of EC were found to be in good agreement with our experimental data and helped establish the surface‐enhanced Raman scattering (SERS) behavior and EC adsorption geometry on the silver surfaces. The Raman peak at 1006 cm⁻¹, assigned to the υ_s(CC) + ω(CH) modes, the strongest and best reproducible peak in the SERS spectra, was used for a quantitative evaluation of EC. The limit of detection, which corresponds to a signal‐to‐noise ratio equal to 3, was found to be 2 × 10⁻⁷ M (17.8 µg l⁻¹). SERS spectra obtained by using hydroxylamine hydrochloride‐reduced silver nanoparticles provide a fast and reproducible qualitative and quantitative determination of EC in aqueous solution. Copyright © 2013 John Wiley & Sons, Ltd.     

Spectroscopic,structural and theoretical studies of 2‐methyl‐4‐nitroaniline (MNA) crystal. Electronic transitions in IR

Polarized FT‐IR, Raman, neutron scattering (IINS), and UV‐Vis‐NIR spectra of 2‐methyl‐4‐nitroaniline (MNA) crystal plates, powder, and solutions were measured in the 10–50 000 cm⁻¹ range. The FT‐IR spectrum of deuterated MNA (DMNA) in KBr pellet, the Raman spectrum of the DMNA powder as well as the EPR spectrum of the MNA powder were also recorded. Complete assignments of bands to normal vibrations have been proposed. Density functional theory (DFT) calculations of wavenumbers and potential energy distribution (PED) have been performed to strengthen the assignments. The analysis of vibrational and electronic spectra has revealed vibronic couplings in MNA molecules in solutions and in crystals. In the polarized FT‐IR spectra of the crystal five unusually large bands are observed in MIR and NIR regions. Their origin is discussed in terms of N H···O, C H···O, C H···H N hydrogen bonds, intermolecular charge transfers, electrostatic interactions, and ion radicals formation in the crystal. The role of a methyl group introduction to 4‐nitroaniline is analyzed. The crystal structure of MNA at the room temperature was re‐investigated. Copyright © 2008 John Wiley & Sons, Ltd.     

FT‐IR,FT‐Raman and DFT calculations of 3‐{[(4‐fluorophenyl)methylene]amino}‐2‐phenylquinazolin‐4(3H)‐one

Fourier transform (FT)‐Raman and Fourier transform infrared (FT‐IR) spectra of 3‐{[(4‐fluorophenyl)methylene]amino}‐2‐phenylquinazolin‐4(3H)‐one were recorded and analyzed. The vibrational wavenumbers of the title compound were computed using the B3LYP/6‐31G* basis and compared with the experimental data. The prepared compound was identified by NMR and mass spectra. The simultaneous IR and Raman activation of the CO stretching mode shows a charge transfer interaction through a π‐conjugated path. The first hyperpolarizability and infrared intensities are reported. The assignments of the normal modes are done by potential energy distribution (PED) calculations. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectra of selected mineral phases of the Morasko iron meteorite

Selected minerals from oval inclusions (nodules) in the Morasko IAB iron meteorite have been investigated by electron microprobe (EMP) and micro‐Raman spectroscopy. Collected spectra of quartz, forsterite‐rich olivine, chromite, kosmochlor (Na–Cr‐rich clinopyroxene) and Na‐feldspar (albite) were compared with corresponding measurements of earth minerals and used for fast identification of meteorite fragments not EMP characterized. Some structural conclusions concerning particular minerals, like solid‐state form or average crystallite size, were also drawn from the measured spectra. Copyright © 2013 John Wiley & Sons, Ltd.