Near‐infrared Raman spectroscopy for gastric precancer diagnosis

Raman spectroscopy is a molecular vibrational spectroscopic technique that is capable of optically probing the biomolecular changes associated with neoplastic transformation. The purpose of this study was to apply near‐infrared (NIR) Raman spectroscopy for differentiating dysplasia from normal gastric mucosa tissue. A total of 65 gastric mucosa tissues (44 normal and 21 dysplasia) were obtained from 35 patients who underwent endoscopy investigation or gastrectomy operation for this study. A rapid NIR Raman system was utilized for tissue Raman spectroscopic measurements at 785‐nm laser excitation. High‐quality Raman spectra in the range of 800–1800 cm⁻¹ can be acquired from gastric mucosa tissue within 5 s. Raman spectra showed significant differences between normal and dysplastic tissue, particularly in the spectral ranges of 850–1150, 1200–1500 and 1600–1750 cm⁻¹, which contained signals related to proteins, nucleic acids and lipids. The diagnostic decision algorithm based on the combination of Raman peak intensity ratios of I₈₇₅/I₁₄₅₀ and I₁₂₀₈/I₁₆₅₅ and the logistic regression analysis yielded a diagnostic sensitivity of 90.5% and specificity of 90.9% for identification of gastric dysplasia tissue. This work demonstrates that NIR Raman spectroscopy in conjunction with intensity ratio algorithms has the potential for the noninvasive diagnosis and detection of precancer in the stomach at the molecular level. Copyright © 2009 John Wiley & Sons, Ltd.     

Size‐dependent Raman and infrared studies of PbSe nanoparticles

Micro‐probe Raman and far‐infrared absorption spectroscopies were used to prove the existence of optical phonon modes of PbSe nanoparticles prepared by colloidal chemistry and preliminarily characterized by transmission electron microscopy. To the best of our knowledge, this is the first time that evidence of the surface phonon (SP) mode by Raman spectroscopy has been experimentally observed. The wavenumber of the SP mode is consistent with its prediction by a dielectric continuum model. While for different PbSe nanoparticle sizes the observed SP mode does not show any obvious change in its position, there is a clear shift by approximately 4 cm⁻¹ toward higher wavenumber in the appearance of the LO(Γ) in the Raman spectra from the 3 nm to the 7 nm PbSe nanoparticles. Far‐infrared measurements demonstrate the presence of the transverse optical TO(Γ) and of the coupled phonon modes. Copyright © 2008 John Wiley & Sons, Ltd.     

FT‐Raman,FT‐IR spectral and DFT studies on 6, 8‐dichloroflavone and 6, 8‐dibromoflavone

In this study, experimental and theoretical vibrational spectral results of the molecular structures of 6,8‐dichloroflavone (6,8‐dcf) and 6,8‐dibromoflavone (6,8‐dbf) are presented. The FT‐IR and FT‐Raman spectra of the compounds have been recorded together between 4000 and 400 cm⁻¹ and 3500–5 cm⁻¹ regions, respectively. The molecular geometry and vibrational wavenumbers of 6,8‐dcf and 6,8‐dbf in their ground state have been calculated by using DFT/B3LYP functional, with 6‐31 + + G(d,p) basis set used in calculations. All calculations were performed with Gaussian03 software. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Scale factors have been used in order to compare how the calculated and experimental data are in agreement. Theoretical infrared intensities are also reported. Copyright © 2009 John Wiley & Sons, Ltd.     

Crystal structure and phonon modes of ilmenite‐type NaBiO3 investigated by Raman and infrared spectroscopies

NaBiO₃ is an ilmenite‐type compound presenting a trigonal structure. In this work, we have performed optical spectroscopic investigations using Raman scattering and infrared reflectivity for this material. By using group‐theory calculations, it was possible to determine the number of optically active modes. Fitting procedures besides Kramers–Kronig (KK) procedures lead to a consistent collection of phonon modes. The Raman spectrum showed nine active first‐order modes, while the infrared one revealed eight polar phonons, in good agreement with the theoretical predictions. The results allowed us to confirm the R3 (#148) space group for this compound, and to establish a set of active phonons not yet reported in the literature. Copyright © 2009 John Wiley & Sons, Ltd.     

A joint FTIR,FT‐Raman and scaled quantum mechanical study of 1,3‐dibromo‐2,4,5,6‐tetra‐fluoro benzene (DTB) and 1,2,3,4,5‐pentafluoro benzene (PB)

The liquid phase FTIR and FT‐Raman spectra of 1,3‐dibromo‐2,4,5,6‐tetrafluoro benzene (DTB) and 1,2,3,4,5‐pentafluoro benzene (PB) were recorded in the regions 4000–400 cm⁻¹ and 4000–50 cm⁻¹, respectively. The spectra were interpreted with the aid of normal coordinate analysis following full structure opti1mization and force field calculations based on the density functional theory using the standard B3LYP/6‐31G* method and basis set combination. The scaled force field reproduced the experimental wavenumbers of the molecule for DTFB and PFB, respectively. The effects of halogen substituents on the structure and vibrational wavenumbers have been investigated. Assignments of fundamental modes were made based on the comparison between calculated and experimental results. Copyright © 2009 John Wiley & Sons, Ltd.     

Far‐infrared spectroscopy,the wavenumbers of metal–ligand vibrations and the characterisation of inorganic pigments

Extensive far‐infrared studies of inorganic materials and pigments in the early 1960s are highlighted and related to the many subsequent Raman studies of the same materials, studies which led to the formulation of Raman spectral libraries for use in conservation science. The need for complementary infrared/far‐infrared libraries is recognised. Copyright © 2010 John Wiley & Sons, Ltd.     

Bent polyynes: ring geometry studied by Raman and IR spectroscopy

Infrared (IR) and Raman spectroscopy have been used to examine the vibrational characteristics of a series of three macrocyclic tetraynes in comparison with an acyclic analog. By changing the length of the alkyl tether of the macrocycles, varying degrees of bending of the tetrayne moiety can be achieved, and the joint use of IR and Raman spectroscopies provides an avenue to probe the impact of bending on the sp‐chain. The spectroscopic data show a general trend toward decreasing activation of Raman bands in the IR spectra, and vice versa, as bending of the polyyne chain is decreased. Density functional theory calculations provide a detailed rationalization of the experimental observations. Copyright © 2011 John Wiley & Sons, Ltd.     

Visible,near‐infrared,and ultraviolet laser‐excited Raman spectroscopy of the monocytes/macrophages (U937) cells

Raman spectra of the monocytes were recorded with laser excitation at 532, 785, 830, and 244 nm. The measurements of the Raman spectra of monocytes excited with visible, near‐infrared (NIR), and ultraviolet (UV) lasers lad to the following conclusions. (1) The Raman peak pattern of the monocytes can be easily distinguished from those of HeLa and yeast cells; (2) Positions of the Raman peaks of the dried cell are in coincidence with those of the monocytes in a culture cell media. However, the relative intensities of the peaks are changed: the peak centered around 1045 cm⁻¹ is strongly intensified. (3) Raman spectra of the dead monocytes are similar to those of living cells with only one exception: the Raman peak centered around 1004 cm⁻¹ associated with breathing mode of phenylalanine is strongly intensified. The Raman spectra of monocytes excited with 244‐nm UV laser were measured on cells in a cell culture medium. A peak centered at 1485 cm⁻¹ dominates the UV Raman spectra of monocytes. The ratio I₁₅₇₄/I₁₆₁₃ for monocytes is found to be around 0.71. This number reflects the ratio between proteins and DNA content inside a cell and it is found to be twice as high as that of E. coli and 5 times as high as that of gram‐positive bacteria. Copyright © 2009 John Wiley & Sons, Ltd.     

Characterization of polycyclic aromatic hydrocarbons using Raman and surface‐enhanced Raman spectroscopy

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous atmospheric pollutants and food contaminants, which exhibit potent carcinogenicity, mutagenicity, and teratogenicity. Vibrational spectroscopy techniques, especially Raman spectroscopy and surface‐enhanced Raman spectroscopy (SERS), can be potentially used as an alternative technique to liquid and gas chromatography in PAH analysis. However, there is limited information on the intrinsic Raman and SERS fingerprints of PAHs. In this study, we have acquired the Raman and SERS spectra of seven PAH compounds and compared their experimental spectra with theoretical Raman spectra calculated by density function theory (DFT). The vibrational modes corresponding to the Raman peaks have also been assigned using DFT. Characteristic Raman and SERS peaks have been identified for five PAH compounds, and the limits of detection were estimated. Such information could be useful for developing SERS assays for simple and rapid PAH identification. Copyright © 2014 John Wiley & Sons, Ltd.     

Raman and infrared spectra of doped La8+xSr2−y(SiO4)6O2+δ compounds compared to the ab initio‐obtained spectroscopic characteristics of fully stoichiometric La8Sr2(SiO4)6O2

Vibrational spectroscopy data were used to gain insight into the possible locations of extra oxygen ions introduced into La_8+xSr_2−y(SiO₄)₆O_2+δ compounds to raise their ionic conductivity. Perturbations observed in the Raman and infrared spectra of these compounds with increasing δ were explained by using the ab initio calculation results for the fully stoichiometric (x = y = δ = 0) lattice. This allowed the inference that the extra oxygen ions are incorporated into La O tunnel‐like fragments inherent in the studied structures. Copyright © 2010 John Wiley & Sons, Ltd.     

Optical phonons in millerite (NiS) from single‐crystal polarized Raman spectroscopy

Although several fundamental physico‐chemical aspects of nickel sulfides have been studied in detail, particularly for millerite (nickel(II) monosulfide), the most common nickel sulfide mineral, no satisfactory investigation of optical vibrational modes has been reported previously. In this paper, we provide a definitive assignment of the optical phonons in millerite, investigated by polarized Raman spectroscopy on an oriented single crystal. The impact of the power of the incident laser beam on the spectra has also been investigated, revealing evidence for degradation in the quality of the spectra at sufficiently high laser power. Copyright © 2008 John Wiley & Sons, Ltd.     

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.     

Raman spectroscopy of 3‐(pent‐1‐enyl) methyl ether and selected deuterium‐labelled analogues

The Raman spectra of 3‐(pent‐1‐enyl) methyl ether (3‐methoxypent‐1‐ene) and four deuterium‐labelled analogues are reported and discussed. Correlations between specific structural features and the associated Raman bands are developed, with a view to enhancing the analytical application of Raman spectroscopy in investigating materials containing an alkenyl group. Particular attention is given to developing means of distinguishing the methyl group attached to the carbon skeleton from that of the methoxy group, to maximize the analytical utility of the signals associated with ν(sp² CH), ν(sp² CH₂) and ν(CC) stretching vibrations, and to interpreting in more detail certain δ(sp² CH) and δ(sp² CH₂) vibrations of the atoms of the double bond. These results establish a definitive spectroscopic protocol for differentiating a methoxy group from a methyl substituent attached directly to a carbon atom in unsaturated ethers. Copyright © 2007 John Wiley & Sons, Ltd.     

A‐band structural dynamics of thioanisole by resonance Raman spectroscopy

The structural dynamics of thioanisole in the S₂(ππ*) electronic state that has large oscillator strength was studied by using the resonance Raman spectroscopy. The vibrational assignments were done for thioanisole on the basis of the FT‐Raman and FT‐IR measurements, the density‐functional theory computations and the normal mode analysis. The A‐ and B‐band resonance Raman spectra were obtained in cyclohexane, methanol and acetonitrile, in which ten modes in A’ irreducible representations were observed. The structural dynamics were obtained according to the resonance Raman intensity pattern. The vibroinc‐coupling between the S₃(πσ*) electronic state that has no oscillator strength and the S₂(ππ*) electronic state were revealed. We discuss the correlation between our present structural dynamics and the previous S₂(ππ*)/S₃(πσ*) conical intersectional dynamics revealed by resonant‐enhanced two‐photon ionization and the photofragment excitation spectroscopic study. Copyright © 2012 John Wiley & Sons, Ltd.     

Raman spectroscopy of halogen‐containing carbonates

Raman spectroscopy complemented with infrared spectroscopy has been used to study a series of selected natural halogenated carbonates from different origins, including bastnasite, parisite and northupite. The position of CO₃²⁻ symmetric stretching vibration varies with the mineral composition. An additional band for northupite at 1107 cm⁻¹ is observed. Raman spectra of bastnasite, parisite and northupite show single bands at 1433, 1420 and 1554 cm⁻¹, respectively, assigned to the ν₃ (CO₃)²⁻ asymmetric stretching mode. The observation of additional Raman bands for the ν₃ modes for some halogenated carbonates is significant in that it shows distortion of the CaO₆ octahedron. No ν₂ Raman bending modes are observed for these minerals. The band is observed in the infrared spectra, and multiple ν₂ modes at 844 and 867 cm⁻¹ are observed for parisite. A single intense infrared band is found at 879 cm⁻¹ for northupite. Raman bands are observed forthe carbonate ν₄ in‐phase bending modes at 722 cm⁻¹ for bastnasite, 736 and 684 cm⁻¹ for parisite and 714 cm⁻¹ for northupite. Multiple bands are observed in the OH stretching region for selected bastansites and parisites, indicating the presence of water and OH units in the mineral structure. The presence of such bands brings into question the actual formula of these halogenated carbonate minerals. Copyright © 2007 John Wiley & Sons, Ltd.     

Raman,infrared, SERS and theoretical study of 3‐(1‐phenylpropan‐2‐ylamino) propanenitrile,fenproporex

Infrared, Raman and surface‐enhanced Raman scattering (SERS) spectra of 3‐(1‐phenylpropan‐2‐ylamino)propanenitrile (fenproporex) have been recorded. Density functional theory (DFT) with the B3LYP functional was used for optimizations of ground state geometries and simulation of Raman and SERS vibrational spectra of this molecule. Bands of the vibrational spectra were assigned in detail. The comparison of SERS spectra obtained by using colloidal silver and gold nanoparticles with the corresponding Raman spectrum reveals enhancement and shifts in bands, suggesting a possible partial charge‐transfer mechanism in the SERS effect. Information about the orientation of fenproporex on the nanometer‐sized metal structures is also obtained. Copyright © 2011 John Wiley & Sons, Ltd.     

Adsorption and reduction reactions of anthraquinone derivatives on gold electrodes studied with electrochemical surface‐enhanced Raman spectroscopy

Electrochemical surface‐enhanced Raman spectroscopy (EC‐SERS), combined with cyclic voltammetry, and the density functional theoretical (DFT) method were used to investigate self‐assembled monolayer (SAM) adsorption and reduction processes. Here, we choose the system of interest, being thiolacetyl‐terminated 2‐phenylene ethynylene‐substituted anthraquinone molecule (2‐AQ) on gold electrodes in buffered aqueous and aprotic solutions. In the buffered aqueous solution, the results of cyclic voltammetry and EC‐SERS measurements, as well as DFT calculations, indicate that the adsorbed molecules pass through a two‐electron two‐proton reduction reaction with cathodic polarization. In particular, the latter two methods confirmed the structural changes of SAMs during the process of redox reaction, 2‐AQ + 2e + 2H⁺ → 2‐AQH₂, where 2‐AQ and 2‐AQH₂ are the oxidized and reduced forms, respectively. In aprotic solutions (acetonitile), a stepwise reaction mechanism was proposed on the basis of the results of EC‐SERS and DFT calculations. The first reduction peak should be a half reaction process 2‐AQ + e → 2‐AQ⁻, where 2‐AQ⁻ is a single electron reduced form. Compared with that of 2‐AQ SAMs in the buffered aqueous solution, the results of EC‐SERS and DFT calculations in aprotic solution suggested that the solvent effect significantly influences the redox process of 2‐AQ in electrochemical interfaces. Copyright © 2012 John Wiley & Sons, Ltd.     

Dussertite BaFe3+3(AsO4)2(OH)5—a Raman spectroscopic study of a hydroxy‐arsenate mineral

The mineral dussertite, a hydroxy‐arsenate mineral with formula BaFe³⁺₃(AsO₄)₂(OH)₅, has been studied by Raman spectroscopy complemented with infrared spectroscopy. The spectra of three minerals from different origins were investigated and proved to be quite similar, although some minor differences were observed. In the Raman spectra of the Czech dussertite, four bands are observed in the 800–950 cm⁻¹ region. The bands are assigned as follows: the band at 902 cm⁻¹ is assigned to the (AsO₄)³⁻ν₃ antisymmetric stretching mode, the one at 870 cm⁻¹ to the (AsO₄)³⁻ν₁ symmetric stretching mode, and those at 859 and 825 cm⁻¹ to the As‐OM^{2 + /3+} stretching modes and/or hydroxyl bending modes. Raman bands at 372 and 409 cm⁻¹ are attributed to the ν₂ (AsO₄)³⁻ bending mode and the two bands at 429 and 474 cm⁻¹ are assigned to the ν₄ (AsO₄)³⁻ bending mode. An intense band at 3446 cm⁻¹ in the infrared spectrum and a complex set of bands centred upon 3453 cm⁻¹ in the Raman spectrum are attributed to the stretching vibrations of the hydrogen‐bonded (OH)⁻ units and/or water units in the mineral structure. The broad infrared band at 3223 cm⁻¹ is assigned to the vibrations of hydrogen‐bonded water molecules. Raman spectroscopy identified Raman bands attributable to (AsO₄)³⁻ and (AsO₃OH)²⁻ units. Copyright © 2010 John Wiley & Sons, Ltd.     

Single‐crystal Raman spectroscopy of natural leiteite (ZnAs2O4) and comparison with the synthesised mineral

The oriented single‐crystal Raman spectrum of leiteite has been obtained and the spectra related to the structure of the mineral. The intensities of the observed bands vary according to orientation, allowing them to be assigned to either A_g or B_g modes. A_g bands are generally the most intense in the CAAC spectrum, followed by ACCA, CBBC, and ABBA whereas B_g bands are generally the most intense in the CBAC followed by ABCA. The CAAC and ACCA spectra are identical, as are those obtained in the CBBC and ABBA orientations. Both cross‐polarised spectra are identical. Band assignments were made with respect to bridging and non‐bridging As O bonds. Copyright © 2010 John Wiley & Sons, Ltd.     

Single‐crystal Raman spectroscopy of brandholzite Mg[Sb(OH)6]2•6H2O and bottinoite Ni[Sb(OH)6]2• 6H2O and the polycrystalline Raman spectrum of mopungite Na[Sb(OH)6]

The single‐crystal Raman spectra of minerals brandholzite and bottinoite, formula M[Sb(OH)₆]₂•6H₂O, where M is Mg⁺² and Ni⁺², respectively, and the non‐aligned Raman spectrum of mopungite, formula Na[Sb(OH)₆], are presented for the first time. The mixed metal minerals comprise alternating layers of [Sb(OH)₆]⁻¹ octahedra and mixed [M(H₂O)₆]⁺²/[Sb(OH)₆]⁻¹ octahedra. Mopungite comprises hydrogen‐bonded layers of [Sb(OH)₆]⁻¹ octahedra linked within the layer by Na⁺ ions. The spectra of the three minerals were dominated by the Sb O symmetric stretch of the [Sb(OH)₆]⁻¹ octahedron, which occurs at approximately 620 cm⁻¹. The Raman spectrum of mopungite showed many similarities to spectra of the di‐octahedral minerals, supporting the view that the Sb octahedra give rise to most of the Raman bands observed, particularly below 1200 cm⁻¹. Assignments have been proposed on the basis of the spectral comparison between the minerals, prior literature and density functional theory (DFT) calculations of the vibrational spectra of the free [Sb(OH)₆]⁻¹ and [M(H₂O)₆]⁺² octahedra by a model chemistry of B3LYP/6‐31G(d) and lanl2dz for the Sb atom. The single‐crystal spectra showed good mode separation, allowing most of the bands to be assigned to the symmetry species A or E. Copyright © 2010 John Wiley & Sons, Ltd.