Surface enhanced Raman scattering of trans‐p‐coumaric and syringic acids

The vibrational spectra of trans‐p‐coumaric acid (pCA) and syringic acid (SA) are discussed. The spectral fingerprints of the organic acids observed in the infrared and Raman spectra are assigned to fundamental vibrational wavenumbers supported by quantum chemical computations. The average surface‐enhanced Raman scattering spectra of both acids have been obtained on silver colloidal solutions and the interpretation of the spectra is presented based on complementary Raman spectra and computational results for the silver salts. Copyright © 2009 John Wiley & Sons, Ltd.     

基于溶剂化效应的BDE-15分子振动光谱增强特征振动研究

利用密度泛函与自洽反应场理论在B3LYP/6-31+G(d)水平下分别计算气态及24种不同极性溶剂中4,4’-二溴二苯醚(4,4’-dibrominated diphenyl ethers, BDE-15)的分子振动光谱(红外光谱、拉曼光谱),以气态分子振动光谱为基准,筛选出对溶剂极性敏感的特征振动作为指标构建溶剂对BDE-15振动光谱溶剂化效应指标体系,探究溶剂对BDE-15分子振动频率、红外/拉曼峰强溶剂化效应及综合效应,并寻求显著增强BDE-15分子特征振动频移/强度的溶剂。研究表明：从分子振动频率角度,溶剂极性敏感的(频移>1 cm-1)分子特征振动均为伸缩振和面外弯曲振,但24种溶剂对BDE-15分子振动频率溶剂化效应并不显著;从分子振动峰强角度,24种溶剂对BDE-15分子振动光谱峰强的增强效应主要发生在红外光谱的中低频区及拉曼光谱的高频区,其中起显著增强(红外/拉曼效应指标值分别大于6与5)的溶剂为醇类、乙腈、二甲亚砜、硝基苯;不同极性溶剂对BDE-15拉曼峰强溶剂化效应及综合效应指标值均表现出随溶剂介电常数增长由线性到对数的增长趋势,而红外峰强只保留低介电常数溶剂时的线性关系。利用上述BDE-15分子振动光谱峰强增强方法对BDE-153,BDE-154和BDE-209进行验证,醇类、乙腈、二甲亚砜、硝基苯对三者的振动光谱红外/拉曼峰强的效应指标值分别大于6与5,且最大峰强增倍数皆大于33,说明所建BDE-15分子振动光谱增强特征振动方法有助于进一步开展基于分子振动光谱的PBDEs同系物间辨识研究。     

李时珍石的红外与拉曼光谱

李时珍石是一种硫酸盐新矿物，理想分子式为：ＺｎＦｅ＿２（ＳＯ＿４）＿４·１４Ｈ＿（２）Ｏ。属三斜晶系。空间群Ｐ，Ｚ＝１。本文首次报导它的拉曼光谱，并结合红外光谱，以及与它的类质同象物─—粒铁矾的振动光谱对照，对李时珍石的振动光谱的主要谱带的归属作了探讨。     

枪晶石变温拉曼光谱及其固液相微结构研究

枪晶石在传统冶金连铸保护渣中起着十分重要的作用。采用紫外激光光源和电荷耦合器件(CCD)探测器,测定了枪晶石晶体和高温拉曼光谱(温度范围:298~1 723 K),观察了其在变温状态(升温和降温过程)下的特征谱变化。谱图结果显示,枪晶石熔态微结构单元与固态的相比更为多元化,表明熔体状态下多种团簇结构共存。同时,利用枪晶石晶胞结构模型,通过Dmol3密度泛函(DFT)理论计算了其分子振动频率,将其与实验值相结合,确定了特征谱峰的归属,为进一步采用拉曼光谱法原位研究保护渣中枪晶石的结构变化与行为特征提供了重要依据。     

Studies on paint cross sections of a glass painting by using FT‐IR and Raman microspectroscopy supported by univariate and hierarchical cluster analyses

Fourier transform infrared (FT‐IR) and Raman spectroscopy is used for the non‐destructive analysis of painting materials and ageing compounds in micrometric cross sections of a glass painting. The combination of both techniques in conjunction with imaging/mapping function provides the spatial distribution of chemical components identified in vibrational spectra. The aim of our work is to show the applicability of the FT‐Raman mapping technique in the detection of painting materials. We also compare Raman information gained by using two laser excitations at 532 and 1064 nm implemented in microspectrometers with different confocality and spatial resolution. In turn among FT‐IR imaging techniques, we compare chemical images recorded in external reflection and attenuated total reflection modes that give chemical images of different size and spatial resolution. Our FT‐IR and Raman imaging characterize a number of painting materials such as pigments, binders, fillers as well as degradation products. Raman maps are constructed by using the univariate analysis. In turn, a profile of IR images requires the use of a more complex methodology. Here, we compare FT‐IR images of the painting cross sections obtained by using the univariate and hierarchical cluster analysis. We clearly show that the multivariate approach is a powerful tool for the credible construction of IR images, providing the relevant chemical information on the multicomponent stratigraphy of the samples. Moreover, the combination of all the methods allows us to demonstrate their degree of utility for the study on the paint cross sections of the works of art. Copyright © 2013 John Wiley & Sons, Ltd.     

Spectral unmixing combined with Raman imaging,a preferable analytic technique for molecule visualization

This article reviews spectral unmixing used as a new method for Raman imaging. Raman spectroscopy explores the vibrational information about specific chemical bonds in molecules, which can be used for label-free molecular visualization. However, chemical bonds are usually shared among different molecules, which results in closed or mixed Raman peaks of many molecules. Therefore, the acquired spectra cannot be directly used to reconstruct the Raman images, as pure component spectra are hidden under the acquired spectra. Spectral unmixing is an effective method to provide a meaningful spectrum of each component with no priori spectral information and to also reconstruct the compositional distribution images. This article summarizes some representative spectral unmixing approaches used for Raman imaging and many related researches. This review strives to introduce the combination of spectral unmixing and Raman imaging as an efficient analytic technique to characterize various constituents and make subtle understanding of those complex structures.     

单脉冲喇曼散射技术测量高压燃烧场组分浓度

介绍了自发喇曼散射技术的基本原理、实验方法及对高压燃烧场的测量结果。利用Nd:YAG激光的三倍频输出激发振动喇曼散射,在单脉冲条件下测量了高压模拟燃烧室内不同化学配比条件下以氢气-空气预混燃烧场为主要组分(N2,O2,H2O,H2等)的喇曼光谱,获得了主要组分浓度随燃烧时间、燃烧场压力的变化规律。实验中利用偏振技术有效地提高了信噪比。通过优化激光光束形状及光路设计避免了等离子体光谱对喇曼信号的干扰。     

Infrared and Raman Spectra of Some Iodide-Bridged Complexes of Mercury (II)

The IR and Raman Spectra of pentaiododimercurate (II) and octaiodotrimercurate (II) anionic complexes have been obtained in the solid state and interpreted in terms of halogen-bridged structures. Spectroscopic and chemical evidences support a dimeric structure for the pentaiododimercurate (II) anion.

The addition of HgBr₂ and HgI₂ to tetraiodocadmate (II), mercurate (II) and tetrabromocadmate (II) species have also been studied. The vibrational spectra also support halogen-bridged structures for these new mixed binuclear complexes.     

自发喇曼散射技术对燃烧场的诊断

 介绍了利用Nd:YAG激光的三倍频激发自发振动喇曼散射技术对燃烧场的诊断及相关的实验原理，测量了不同配比条件下的CH₄-air预混火焰内的主要组分(N₂，O₂，H₂O，CH₄)及其相对浓度；并分别用分子浓度测温法和斯托克斯谱与反斯托克斯谱强度比法测量了火焰的温度；还对该技术测温、测浓度的不确定度进行了分析。将该技术应用到对复杂的固体燃剂燃烧场的诊断，取得了燃烧场中几种主要燃烧组分（N₂，H₂CO，CH₄，H₂O）的喇曼光谱，以及这些组分在燃烧过程中的变化信息。     

激光轰击过程中纳米碳管复合光限幅材料组成及结构的演变研究

光限幅材料在激光轰击过程中的稳定性将在很大程度上决定其实用化价值。文章采用红外(IR)光谱、拉曼(Raman)光谱、透射电子显微镜(TEM)及孔结构分析等测试方法对纳米碳管(CNTs)复合光限幅材料在激光轰击过程中组成、结构的演变进行跟踪研究。结果表明,在强激光轰击下,复合体系中二氧化硅(SiO₂)基质的组成未发生显著改变且网络结构趋于完整,具有较好的稳定性。掺杂CNTs石墨化程度提高,SiO₂凝胶玻璃基质对其起一定的保护作用。轰击过程产生的热效应使得SiO₂颗粒长大,由其堆积而成的孔随之增大。     

Structural-dynamic model of 2-biphenylmethanol in an anharmonic approximation

Using a density functional B3LYP/6-31G(d) method, the geometry, electro-optical parameters, quartic force field, and vibrational spectra (IR and Raman) of 2-biphenylmethanol have been calculated. A vibrational analysis was performed. The resulting IR and Raman spectra were interpreted in detail.     

吡喃酮类化合物与镱配合物的红外和拉曼光谱研究

采用非水体系中牺牲金属阳极的电化学方法分别合成了稀土金属镱与 3 羟基黄酮及 3 羟基 2 甲基 γ 吡喃酮的配合物。对配合物进行了IR和Raman光谱测定。两种光谱提供了互为补充的信息 ,配体经配位后—OH的伸缩振动谱峰消失 ,部分相关的谱峰频率发生了明显位移 ,特别是羰基伸缩振动红移十分明显 ,在Raman光谱的低波数区间检测到可指认为金属和配体键合的伸缩振动。根据这两种光谱的研究结果推断了所得配合物的可能结构。     

Crystal and molecular structure of 2‐amino‐5‐chloropyridinium hydrogen selenate—its IR and Raman spectra,DFT calculations and physicochemical properties

The new organic‐inorganic salt, 2‐amino‐5‐chloropyridinium hydrogen selenate, has been synthesised and characterised by means of FT‐IR, FT‐Raman and single crystal X‐ray crystallography. Its vibrational spectra have been discussed on the basis of quantum chemical DFT calculations using the B3LYP/6‐31G(d,p) approach. The crystal and molecular structures have been compared and the role of the intermolecular interactions in this crystal has been analysed. The N HO interactions between the hydrogen atoms of the organic cation and oxygen atoms of hydrogen selenate anion determine the supramolecular arrangement in three‐dimensional space. The possible application of the studied composite material as a Raman laser has been discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

A resonance Raman spectroscopic study of the protonation of Disperse Orange 25 in solution and adsorbed on oxide surfaces

The protonation of Disperse Orange 25 (DO25) in aqueous solution, and upon adsorption on oxide surfaces, was studied by resonance Raman (RR) spectroscopy. The neutral and protonated forms of DO25 were modelled by DFT calculations of the isolated molecules in the gas phase at the B3‐LYP/DZ level, enabling calculation of the vibrational spectra of these species, together with vibrational assignments. RR spectra show that DO25 is physisorbed on the SiO₂ surface, but its adsorption on SiO₂ Al₂O₃ or H‐mordenite results in protonation. This observation indicates the presence of Brønsted acidic sites on these oxide surfaces with pK_a values ⩽2.5. RR studies of the adsorption of DO25 can therefore provide useful information on the nature of surface acidity on oxides, which is complementary to that obtained from other probe molecules. Copyright © 2007 John Wiley & Sons, Ltd.     

4-N-甲基苯乙烯砒啶盐衍生物振动超极化率的理论研究

在双谐振子近似下，利用耦合微扰Hartree-Fock方法计算了4-N-甲基苯乙烯砒啶盐衍生物分子的静态振动第一超极化率和红外与拉曼光谱，给出了对静态振动第一超极化率起主导贡献的两种简正振动模式. 研究发现，标题分子的静态振动第一超极化率都比较大，且与静态电子第一超极化率呈较好的线性关系. 首次提出了利用红外与拉曼光谱特征峰标识的振动模来估算振动第一超极化率大小的少模方法. 结果表明，少模方法用于估算振动第一超极化率的大小是可行的.     

Molecular structure of alkali metal 4‐nitrobenzoates

The influence of lithium, sodium, potassium, rubidium, and cesium on the electronic system of the 4‐nitrobenzoic acid molecule was studied. The vibrational (FT‐IR, FT‐Raman) and NMR (¹H and ¹³C) spectra for 4‐nitrobenzoic acid salts of alkali metals were recorded. The assignment of vibrational spectra was done. Characteristic shifts of band wavenumbers and change in band intensities along the metal series were observed. Good correlation between the wavenumbers of the vibrational bands in the IR and Raman spectra for 4‐nitrobenzoates and ionic potential, electronegativity, atomic mass, and affinity of metals were found. The chemical shifts of protons and carbons (¹H, ¹³C NMR) in the series of studied alkali metal 4‐nitrobenzoates were observed too. Optimized geometrical structures of studied compounds were calculated by HF, B3PW91, B3LYP methods using 6‐311++G** basis set. The theoretical IR, Raman, and NMR spectra were obtained. The theoretical vibrational spectra were interpreted by means of potential energy distributions (PEDs) using VEDA 3 program. The calculated parameters were compared to experimental characteristic of studied compounds. Copyright © 2007 John Wiley & Sons, Ltd.     

Optical investigation of CdS quantum dots in Langmuir–Blodgett films

Structures with CdS quantum dots produced by the Langmuir–Blodgett (LB) technique were investigated by Raman, IR, and UV spectroscopies. The confinement effect of longitudinal optical (LO) phonons in CdS quantum dots was investigated by Raman spectroscopy. Surface vibrational modes of CdS quantum dots were observed in IR spectra. It was shown experimentally that the frequency of the surface vibrational modes depends on the properties of the surrounding media. An average size of CdS quantum dots of about 3–6.4 nm was obtained from the analysis of UV measurements. Received: 1 February 1999 / Accepted: 1 April 1999 / Published online: 19 May 1999     

Vibrational spectroscopy and DFT calculations of N,N′‐dicyclohexylcarbodiimide

Infrared (IR) and Raman spectra were obtained for N,N′‐dicyclohexylcarbodiimide (DCC) in the solid state and in CHCl₃ solution. Structures and vibrational spectra of isolated, gas‐phase DCC molecules with C₂ and C_i symmetries, computed at the B3‐LYP/cc‐pVTZ level, show that the IR and Raman spectra provide convincing evidence for a C₂ structure in both the solid state and in CHCl₃ solution. Using a scaled quantum‐chemical force field, these density functional theory calculations have provided detailed assignments of the observed IR and Raman bands in terms of potential energy distributions. Comparison of solid‐state and solution spectra, together with a Raman study of the melting behaviour of DCC, revealed that no solid‐state effects were evident in the spectra. Copyright © 2010 John Wiley & Sons, Ltd.     

Quantum chemical calculations of vibrational spectra of <Emphasis Type="Italic">para</Emphasis>-ethylbenzenesulfonic acid

Quantum chemical calculations of vibrational spectra of para-ethylbenzenesulfonic acid have been conducted by means of a non-empirical SCF MO LCAO method with the use of the 6-31G(d) basis set. Calculated IR and Raman frequencies are assigned to vibrations of specific atomic groups. It is shown that para-ethylbenzenesulfonic acid can serve as a reasonable quantum chemical model in calculations of vibrational spectra for polystyrene sulfonic resins of various degrees of hydration.     

Towards modelling the vibrational signatures of functionalized surfaces: carboxylic acids on H-Si(111) surfaces

In this work, we investigate the adsorption process of two carboxylic acids (stearic and undecylenic) on a H-Si(111) surface via the calculation of structural and energy changes as well as the simulation of their IR and Raman spectra. The two molecules adsorb differently at the surface since the stearic acid simply physisorbs while the undecylenic acid undergoes a chemical reaction with the hydrogen atoms of the surface. This difference is observed in the change of geometry during the adsorption. Indeed, the chemisorption of the undecylenic acid has a bigger impact on the structure than the physisorption of the stearic acid. Consistently, the former is also characterized by a larger value of adsorption energy and a smaller value of the tilting angle with respect to the normal plane. For both the IR and Raman signatures, the spectra of both molecules adsorbed at the surface are in a first approximation the superposition of the spectra of the Si cluster and of the carboxylic acid considered individually. The main deviation from this simple observation is the peak of the stretching Si-H (ν(Si-H)) mode, which is split into two peaks upon adsorption. As expected, the splitting is bigger for the chemisorption than the physisorption. The modes corresponding to atomic displacements close to the adsorption site display a frequency upshift by a dozen wavenumbers. One can also see the disappearance of the peaks associated with the C=C double bond when the undecylenic acid chemisorbs at the surface. The Raman and IR spectra are complementary and one can observe here that the most active Raman modes are generally IR inactive. Two exceptions to this are the two ν(Si-H) modes which are active in both spectroscopies. Finally, we compare our simulated spectra with some experimental measurements and we find an overall good agreement.