The structure of solvated halide ions in dimethyl sulfoxide studied by Raman spectroscopy and X-ray diffraction

The solvation structure of chloride, bromide, and iodide ions, X⁻, in dimethyl sulfoxide (DMSO) has been investigated by using Raman spectroscopy and large angle X-ray diffraction under ambient conditions. The positively charged sulfur atom in DMSO interacts with X⁻ and slightly positively charged methyl groups in the coordinating molecules also interact with X⁻. The X⁻---S, X⁻···C, and X⁻···O distances are determined as follows: Cl⁻---S: 416, Cl⁻···C: 363, Cl⁻···O: 543, Br⁻---S: 433, Br⁻···C: 372, Br⁻···O: 544, I⁻---S: 437, I⁻···C: 374 and I⁻···O: 520 pm. The coordination numbers of DMSO molecules around the anions are six, seven and eight for Cl⁻, Br⁻ and I⁻ ions, respectively, with the uncertainty of ±1. Rather large uncertainties in the measured solvation numbers suggest large fluctuations in the solvation structure of the anions.     

Improving of the adsorption capacity of halloysite nanotubes intercalated with dimethyl sulfoxide

Algerian halloysite intercalated with dimethyl sulfoxide (DMSO) was prepared. The starting (H) and resulting (H-DMSO) materials were characterized by X-ray powder diffraction, Fourier transformed infrared spectroscopy, thermal analysis, transmission electron microscopy, pore-size distribution analysis, and employed as crystal violet (CV⁺) adsorbents from aqueous solutions. Intercalation reaches a rate of 95% and increases the basal spacing to 11.2 Å. (CH₃)₂SO interacts with the inner surface hydroxyls of halloysite through new hydrogen bonds with the S=O groups. The release of DMSO occurs in two phases: a partial elimination at 195 °C and a second part due to the DMSO combustion at 277 °C. The TEM image of H-DMSO reveals halloysite nanotubes (HNTs) polydisperse in length and diameter. A heterogeneous distribution in the nanotube size was highlighted with pore diameters of 10–11, 20.6, 28.6, and 37.0 nm, in correlation with transmission electron microscopy. The Redlich–Peterson equation describes efficiently the CV⁺ adsorption onto the modified sample. H-DMSO adsorbs 93.6 against 50.9 mg g^?1 for the starting material. This improving of the adsorption capacity of DMSO-intercalated HNTs, was explained via the behavior of the intercalated DMSO molecules. Intercalation constitutes a key procedure for developing new nanocomposites, attractive in technological applications, such as effective adsorbents.     

On the solvation force of water-like fluid models with square-well attraction and site–site association in slit-like pores: density functional approach

The solvation force of the water-like fluid models with square-well attraction and site–site chemical association confined to slit-like pores has been explored. Theoretical procedure is based on the application of the density functional approach with mean-field approximation for the attractive interparticle interactions. The chemical association effects are treated by using the first-order thermodynamic perturbation theory of Wertheim. Trends of behaviour of the solvation force are put in correspondence with the distribution of molecules in the pores and with the average density of the adsorbate. Moreover, the distribution of non-bonded species on pore width is described. The influence of the width of the square-well and of the gas–solid attraction is discussed. A comparison of theoretical predictions with computer simulations results for water models in slit-like pores is performed.     

Temperature and pressure dependence of Raman active lattice mode frequencies of cubic C8H6(Br)2, evidence of a phase transition

The temperature dependence of the Raman active frequencies of the lattice modes of dibromocubane is measured below room temperature. The frequencies are linearly dependent on the temperature decreasing with increased temperature with a marked change in slope occurring at 200?K indicative of a structural phase transition. The pressure dependence of the frequencies measured at room temperature up to 24?KBar shows no evidence of a phase change. Density functional calculations of the structure and Raman frequencies of the internal modes of an isolated molecule of C₈H₆(Br)₂ indicate the molecule is slightly distorted from a cubic carbon structure.     

哌啶分子在两种不同银电极上吸附行为的实验和理论研究

分别在粗糙银电极和银纳米颗粒修饰银电极上得到了哌啶分子的表面增强拉曼（SERS）光谱。哌啶在银电极与银纳米颗粒修饰的银电极上的SERS谱有很大的区别,分析认为是由于哌啶在不同基底上的吸附方式不同所引起的,据此建立了哌啶吸附在银颗粒表面的两种模型,用DFT-B3PW91-lanl2dz方法计算了两种模型的拉曼频移,通过与实验结果比较说明了哌啶分子主要通过N原子的孤对电子竖直吸附在粗糙银电极表面,而在银纳米颗粒修饰的银电极上则以平行吸附方式为主。     

Experimental and theoretical investigation of the apomorphine Raman spectrum

Apomorphine (aporphine‐10,11‐diol, CA Registry Number 58004) is a non‐narcotic derivative of morphine discovered in 1869 by Mattheisen [1] and it is a well‐known potent short‐acting dopamine agonist at D1 and D2 dopamine receptors, typically used in the treatment of patients with advanced Parkinson's disease (PD). To identify the unknown vibrational spectrum of this compound, apomorphine bare salt and its commercial drug formulation (Apofin) were examined by means of Raman spectroscopy. In the Raman spectrum of apomorphine (both bare salt and commercial drug), two strong characteristic signals were found, which were assigned with the help of first‐principles calculations: the band at 1589 cm⁻¹ (assigned to the stretching mode of the B aromatic ring coupled with C H in‐plane bending) and the band at 1302 cm⁻¹ (assigned to O‐H in‐plane bending and CH₂ twisting and wagging vibrations). Copyright © 2009 John Wiley & Sons, Ltd.     

Surface-enhanced Raman spectroscopy of hexabenzobenzene,C24H12, an analogue of a graphene nanostructure

While large scale fabrication of graphene nanoribbons remains a challenge, there exist materials which can be fabricated in quantities such as hexabenzobenzene,HBZB, (C₂₄H₁₂) and which have a two-dimensional (2D) carbon structure similar to graphene nanostructures. Using a 632 nm laser, no Raman spectra could be obtained from the solid material because of a strong luminescence produced by the laser. However, surface-enhanced Raman spectroscopy enabled the measurement of some of the Raman active modes. The G and D modes, which are characteristic fingerprints of a 2D graphene structure, were observed at 1331 and 1600 cm^?1, respectively. Density functional theory at the B3LYP/6-31G^* level was used to calculate the minimum energy structure and the Raman active vibrational frequencies of HBZB. The calculated minimum energy structure was 2D having D_6h symmetry in agreement with the experimental structure in the liquid phase. The calculated frequencies were in good agreement with the measured values.     

皮秒激光瞬态受激喇曼散射的实验研究

本文采用对撞脉冲锁模Nd:YAG激光器输出10ps脉冲串,经KTP非线性晶体腔外倍频,泵浦喇曼介质为二甲亚砜(DMSO)液体.实验研究了不同透镜焦长、焦点位置及不同喇曼介质氏度对瞬态受激喇曼散射的影响,获得了能量转换效率分别为45.6%和10.5%的前、后向一阶斯托克斯-喇曼散射光,并对实验结果进行了讨论.     

First-principles studies of the vibrational properties of amorphous carbon nitrides

Raman spectra of amorphous carbon nitride films (a-C:N) resemble those of typical amorphous carbon (a-C), and no specific features in the spectra are shown due to N doping. The present work provides a correlation between the microstructure and vibrational properties of a-C:N films from first principles. The six periodic model structures of 64 atoms with various mass densities and nitrogen contents are generated by the liquid-quench method using Car-Parinello molecular dynamics. By using Raman coupling tensors calculated with the finite electric field method, Raman spectra are obtained. The calculated results show that the vibrations of C=N could directly contribute to the Raman spectrum. The similarity of the Raman line shapes of N-doped and N-free amorphous carbons is due to the overlapping of C=N and C=C vibration bands. In addition, the origin of characteristic Raman peaks is also given.     

Investigation of hydrogen bonding in neat dimethyl sulfoxide and binary mixture (dimethyl sulfoxide + water) by concentration-dependent Raman study and ab initio calculation

In this study,our vibrational spectroscopic analysis is made on hydrogen-bonding between dimethyl sulfoxide and water comprises both experimental Raman spectra and ab initio calculations on structures of various dimethyl sulfoxide/water clusters with increasing water content.The Raman peak position of the v(S=O) stretching mode of dimethyl sulfoxide serves as a probe for monitoring the degree of hydrogen-bonding between dimethyl sulfoxide and water.In addition,the two vibrational modes,namely,the CH 3 symmetric stretching mode and the CH 3 asymmetric stretching mode have been analysed under different concentrations.We relate the computational results to the experimental vibrational wavenumber trends that are observed in our concentration-dependent Raman study.The combination of experimental Raman data with ab initio calculation leads to a better knowledge of the nature of the hydrogen bonding and the structures of the hydrogen-bonded complexes studied.     

Vibrational spectroscopy of a compound with a CS7 ring

The product of the Asinger reaction between elemental sulfur, n‐butylamine and acetophenone is 8‐(n‐butylaminophenylmethyliden)‐1,2,3,4,5,6,7‐heptathiocane which contains a CS₇ ring. A combination of infrared, Raman and inelastic neutron scattering spectroscopies with periodic density functional theory calculations is used to provide a complete assignment of the vibrational spectra of this unusual species. The similarity between the Raman spectra of the compound and that of elemental sulfur is particularly striking. Copyright © 2009 John Wiley & Sons, Ltd.     

Theoretical investigation and computational evaluation of overtone and combination features in resonance Raman spectra of polyenes and carotenoids

We review the theory for overtones and combinations in resonant Raman spectroscopy introduced by Nafie, Stein and Peticolas in 1971 on the basis of time‐ordered diagrams, and we apply it to β‐carotene with the support of density functional theory calculations. Comparison with experimental results obtained by Tasumi's group in 1994 is provided. The theory here presented allows a prompt evaluation of resonant Raman intensities with presently available quantum chemistry tools. Copyright © 2014 John Wiley & Sons, Ltd.     

Chemiluminescence of curcumin and quenching effect of dimethyl sulfoxide on its peroxyoxalate system

The chemiluminescence behavior of the reaction between bis(2,4,6-trichlorophenyl)oxalate (TCPO) and hydrogen peroxide, in the presence of curcumin as fluorophore, has been investigated. Experimental factors such as TCPO, sodium salicylate (SS), hydrogen peroxide and curcumin concentration were optimized. The chemiluminescence signal showed a linear decay while dimethyl sulfoxide (DMSO) was added to the peroxyoxalate (PO-CL) system. The reaction resulted in a Stern-Volmer plot with a K_q value of 7.3×10⁴. The evaluated lower and upper detection limits of measurable concentrations of DMSO are 3.50×10⁻⁵ and 1.53×10⁻⁴ M, respectively. The PO-CL parameters were estimated by computer fitting of the experimental CL intensity to proper models.     

Raman studies on the effect of multiple-energy ion implantation on single-crystal hexagonal boron nitride

Single energy ion implantation of hexagonal boron nitride (h-BN) at various fluences and keV energies has shown that there is a change in the local symmetry of the crystal from hexagonal to the cubic (c-BN) symmetry. These conclusions have been primarily based on Raman scattering (RS) and Fourier transform infrared spectroscopy. Transmission electron microscopy (TEM) analyses have been a challenge because the sample preparation for cross-sectional study of both the polycrystalline substrates and single-crystal material used in the study presented problems that were difficult to circumvent. A multiple-energy implant with different fluence fractions has been used to create a uniform implanted layer in the material from the surface to the end of range of the implant in this study. We report on the initial RS studies on these samples.     

Phosphate group vibrational signatures of the osteoporosis drug alendronate

The infrared (IR) and Raman spectra of the osteoporosis drug alendronate in the monosodium trihydrate alendronate crystal were measured. In order to interpret them, density functional theory (DFT) calculations for the solvated alendronate molecule were performed following the structural features revealed by X‐ray data. A comparison between the DFT‐calculated IR and Raman of the converged species and the measured spectra unveils relevant phosphate group signatures in the 400–1400 cm⁻¹ wavenumber range, especially IR absorption bands at 1015, 1049, 1067, 1131, 1177, and 1235 cm⁻¹, which were related to CP and OP bond length stretching, and Raman lines at 449, 661, and 969 cm⁻¹, involving phosphate scissors and bond length vibrations. A comparison with experimental data of alendronate incorporated into hydroxyapatite (HAP) indicates that, for wavenumbers below 1500 cm⁻¹, the interaction of alendronate with HAP does not affect significantly the alendronate vibrational spectra, while for the 1600–3000 cm⁻¹ interval the interaction with HAP changes the normal mode wavenumbers by about −100 cm⁻¹. Copyright © 2014 John Wiley & Sons, Ltd.     

吩噻嗪表面增强拉曼光谱的密度泛函理论研究

吩噻嗪是含有N、S的杂环化合物,具有大的离域π键。用Gaussian 09程序,在B3LYP方法下,Ag原子使用LANL2DZ赝式基组,C、H、N、S等原子使用6-31++G(d,p)基组,优化并计算了吩噻嗪和吩噻嗪银配合物(PTH-Ag)的拉曼光谱,并利用GaussianView对PTH分子进行归属,为食品和产品中吩噻嗪残留的定性、定量测定提供理论依据。计算结果说明连接Ag原子越多,增强效果越明显。     

氟虫氰表面增强拉曼光谱的密度泛函理论研究（英文）

2017年8月初,荷兰发现大范围鸡蛋受杀虫剂氟虫腈污染。用拉曼光谱检测的方法对解决氟虫腈检测问题做了一定的探索。为了获得氟虫腈分子的分子结构振动信息,根据密度泛函理论中的B3LYP杂化泛函和6-311G++(d,p)基组,对氟虫腈分子进行了几何结构优化和频率计算,得到了该分子的稳定构型和全部振动模式,计算了氟虫腈分子稳定构型的拉曼散射光谱。利用HORIBA公司的T64000型光栅共聚焦显微拉曼光谱仪采集了FP的拉曼光谱并配合使用Ag/Cu纳米基底采集了表面增强拉曼光谱,较强峰出现在211,308,350,867,1323和1432 cm-1处,次强峰出现在254,407,443,463,511,607,646,712,800,1065和1639 cm-1处。结果表明,理论计算得到的振动频率与实验测量值在全部较强峰处和部分次强峰处吻合的较好。并对FP分子200~2000 cm-1区间内各频率谱线对应的振动模式进行了归属指认,6个较强峰依由小到大的次序分别指认为21H-22H蜷曲振动,10F-11F变形振动和21H-22H面外摇摆振动,15N-22H蜷曲振动,6C伸缩振动和21H面内弯曲振动,苯环呼吸振动和9C伸缩振动,7H-8H面内弯曲振动。发现表面增强拉曼光谱相对于拉曼光谱整体有微小的频移,两者整体吻合较好,表面增强拉曼光谱中211,867,1400和1432 cm-1处的峰得到了选择性增强,根据表面增强拉曼光谱的选择定则,解释为相关振动峰的原子与银衬底表面或许为接近垂直的状态,并可能与银表面吸附。下一步计划将氟虫腈混入鸡蛋中,对氟虫腈在鸡蛋中不同浓度情况下进行指认研究。研究结果可为氟虫腈的拉曼光谱分析提供理论依据,将促进食品和农产品中氟虫腈残留的快速检测和在线检测研究。将拉曼光谱作为对传统化学检测方法的补充。     

Ionic solvation and association in LiCl aqueous solution: a density functional theory,polarised continuum model and molecular dynamics investigation

In this work, the ionic solvation and association behaviours in the LiCl aqueous solution were investigated using density functional theory (DFT), a polarised continuum model and classical molecular dynamics simulations. DFT calculations of LiCl(H₂O)_1–6,8 clusters show that contact ion pair (CIP) and solvent-shared ion pair (SSIP) conformers of LiCl(H₂O)_n (n ≥ 4) clusters are generally energetic both in the gas phase and in the aqueous solution. Some SSIP conformers may be slightly more stable than their CIP isomers when at least eight water molecules are incorporated in the inner hydration shells of LiCl hydrates. The transformation between CIP and SSIP conformers is easy by overcoming a small energy barrier, which mainly results from the hydration shell reorganisation of Li⁺. Molecular dynamics simulations show that ion pairs or ion clusters can be found in the LiCl aqueous solution, and the probability of CIP conformers or ion clusters presented in the LiCl solution generally increases with rise in temperature. However, the presentation of ion pairs or ion clusters in the LiCl aqueous solution does not inevitably lead to the nucleation of LiCl crystallisation.     

Organic cyclic difluoramino‐nitramines: infrared and Raman spectroscopy of 3,3,7,7‐tetrakis(difluoramino)octahydro 1,5‐dinitro‐1,5‐diazocine (HNFX)

We present the first vibrational structure investigation of 3,3,7,7‐tetrakis(difluoramino)octahydro‐1,5‐dinitro‐ 1,5‐diazocine (HNFX)—and, more generally, of a member of the new class of gem‐bis(difluoramino)‐substituted heterocyclic nitramine energetic materials—using combined theoretical and experimental approaches. Optimized molecular structure and vibrational spectra of the Ci… symmetry conformer constituting the HNFX crystal were computed using density functional theory methods. Fourier transform infrared and Raman spectra of HNFX crystalline samples were also collected at ambient temperature and pressure. The average deviation of calculated structural parameters from X‐ray diffraction data is ∼1% at the B3LYP/6‐311 + + G(d,p) level of theory, suggesting the absence of significant molecular distortion induced by the crystal field. Very good agreement was found between simulated and measured spectra, allowing reliable assignment of the fundamental normal modes of vibration of the HNFX crystal. Detailed analysis of the normal modes of the C–(NF₂)₂ and N–NO₂ moieties was performed due to their critical importance in the initial steps of the molecular homolytic fragmentation process. Copyright © 2009 John Wiley & Sons, Ltd.     

Density functional and experimental studies on the FT‐IR and FT‐Raman spectra and structure of benzoic acid and 3,5‐dichloro salicylic acid

FT‐IR and FT‐Raman spectra of benzoic acid (BA) and 3,5‐dichloro salicylic acid (SA) have been recorded in the regions of 4000–400 and 4000–50 cm⁻¹ respectively. The spectra were interpreted with the aid of normal coordinate analysis following the full structure optimizations and force field calculations based on density functional theory (DFT) using standard B3LYP6‐31G** method and basis set combinations. The DFT force field transformed to natural internal coordinates was corrected by a well‐established set of scale factors that were found to be transferable to the title compounds. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. Copyright © 2008 John Wiley & Sons, Ltd.