RAMAN SPECTRA OF SODIUM ALUMINATE SOLUTIONS WITH HIGH-CAUSTIC RATIO AND HIGH CONCENTRATION

The constitution of high-caustic ratio and highly concentrated sodium aluminate solutions has been investigated by Raman spectra method.By comparison with the Raman spectra of crystalline solids of Ca_3[Al(OH)_6]_2 and Ba_2[Al_2(OH)_(10)],it can be concluded that AI(OH)_6^(3-)ion and perhaps its polymers may be formed in these solutions.

A polyene chain of canthaxanthin investigated by temperature-dependent resonance Raman spectra and density functional theory (DFT) calculations

We report on a temperature-dependent resonance Raman spectral characterization of the polyene chain of canthax- anthin. It is observed that all vibrational intensities of the polyene chain are inversely proportional to temperature, which is analyzed by the resonance Raman effect and the coherent weakly damped electron/lattice vibrations. The increase in intensity of the CC overtone/combination relative to the fundamental with temperature decreasing is detected and discussed in terms of electron/phonon coupling and the activation energy Uop. Moreover, the polyene chain studies using the density functional theory B3LYP/6-31 G＊ level reveal a prominent peak at 1525 cm-1 consisting of two closely spaced modes that are both dominated by C=C stretching coordinates of the polyene chain.

Study on lattice vibrational properties and Raman spectra of Bi_2Te_3 based on density-functional perturbation theory

We present a variational density-functional perturbation theory （DFPT） to investigate the lattice dynamics and vibra- tional properties of single crystal bismuth telluride material. The phonon dispersion curves and phonon density of states （DOS） of the material were obtained. The phonon dispersions are divided into two fields by a phonon gap. In the lower field, atomic vibrations of both Bi and Te contribute to the DOS. In the higher field, most contributions come from Te atoms. The calculated Born effective charges and dielectric constants reveal a great anisotropy in the crystal. The largest Born effective charge generates a significant dynamic charge transferring along the c axis. By DFPT calculation, the greatest LO-TO splitting takes place in the infrared phonon modes and reaches 1.7 THz in the Brillouin zone center. The Raman spectra and peaks corresponding to respective atomic vibration modes were found to be in good agreement with the experimental data.

The pH Effect on Resonance Raman Spectra of Brilliant Yellow in Aqueous and CTAB Micella Solutions

Recently, we have developed an application of molecular spectrometric method to the exploration of the interracial properties of black soap films, using an azobenzene dye as a probe. In order to further study the problems of surface potential and microenvfronment, an effort should be made to clarify the pH controlled behavior of the structural change of azobenzene compounds in aqueous solution and on the surface of surfactant mlcella. Here, we examine the resonance Raman spectra of brilliant yellow(BY), an azobenzene derivative, in aqueous and cetyltrimethylammonium bromide(CTAB) micella

SURFACE-ENHANCED RAMAN SPECTRA OF p-AMINOBENZOIC ACID ADSORBED ON Ag2CO3 COLLOIDS

It was observed that the p-aminobenzoic acid(PABA)molecules adsorbed on A92CO3 colloids exhibited strong SERS effect,the enhancement factor is estimated at 10~7—10~8 The mechanism of SERS effect on PABA adsorbed on the colloids was discussed.

SURFACE ENHANCED RAMAN SPECTRA OF PHENYLMERCAPTOTETRAZOLE AND MERCAPTOBENZOTHIAZOLE ON SILVER

Normal Haman Spectra(NRS) of solid PMT (1-phenyl-5-mercaptotetrazole) and MBT (2-mercaptobenzothiazole) and their surface enhanced Raman spectra (SERS) adsorbed on the surface of the silver subcolloidal particles are reported and compared. It is supposed that PMT adsorbed on silver with both N and S atoms whereas MBT may be adsorbed on silver through S atom.

Size Effect on the Raman Spectra and Electronic Structure of the Glycine-alanine Oligopeptide Chains

A theoretical study on oligopeptide chains of glycine-alanine by density functional theory（DFT） is given in this paper. Raman spectra of the oligopeptide chains are examined. The geometric structures, frontier orbital, energy gap, atomic charge distribution, density of states and chemical activity of the side chain are studied at the B3LYP/6-31G（d） level. Results show that, with the number of residues increasing, vibrations of typical functional groups present Raman frequency shift, and the energy gap is gradually reduced. The HOMO and LUMO focus on the amino and carboxyl at the ends of oligopeptides. It is helpful for oligopeptides to self-assemble into chains. In addition, different residues（glycine or alanine） at the ends of chains result in the even-odd effect of orbital energy in the growth process. The size effects of physical and chemical properties only exist when the oligopeptides are shorter, and the phenomenon disappeared as the chain continues to grow.

Raman Spectra in Irradiated Graphene: Line Broadening, Effects of Aging and Annealing

The results of measurements of the Raman spectra in the same group of monolayer graphene samples, successively subjected to irradiation with different ions, prolonged aging, and annealing under different conditions, are considered. Changes in the position, width, and intensity of the Raman lines are analyzed in the study of the following problems: comparison of the results of irradiation with various ions, the influence of prolonged aging on the spectra of irradiated samples, the mechanism of broadening of Raman scattering lines caused by an increase in the density of radiation defects, the consequences of annealing of radiation damages in vacuum and in the atmosphere of the forming gas, the contribution of doping and lattice deformation to the shift of the position of the Raman lines after annealing. The results obtained made it possible to determine the level of stability of defects introduced by radiation, to reveal the possibility of restoring the damaged lattice using annealing. Since the results relate to graphene deposited on a widely used SiO2/Si substrate, they may be of interest when using ion irradiation to change the properties of graphene in appropriate devices.

Raman spectra of single cell from gastrointestinal cancer patients

AIM: To explore the difference between cancer cells and normal cells, we investigated the Raman spectra of singlecells from gastrointestinal cancer patients. METHODS: All samples were obtained from 30 diagnosed as gastrointestinal cancer patients. The flesh tumor specimen is located in the center of tumor tissue, while the normal ones were 5 cm away from the outside tumor section. The imprint was put under the microscope and a single cell was chosen for Raman measurement. All spectra were collected at confocal Raman micro-spectroscopy (British Renishaw) with NIR 780 nm laser.RESULTS: We measured the Raman spectra of several cells from gastrointestinal cancer patients. The result shows that there exists the strong line at 1 002/cm with less half-width assigned to the phenylalanine in several cells. The Raman lines of white cell were lower and less, while those of red cell were not only higher in intensity and more abundant, but also had a parti cular C-N breathing stretching band of pyrrole ring at 1 620-1 540/cm. The line at 1 084/cm assigned to phosphate backbone of DNA became obviously weaker in cancer cell. The Raman spectra of stomach cancer cells were similar to those of normal cells, but the Raman intensity of cancer cells was much lower than that of normal cells, and even some lines disappear. The lines of enteric cancer cells became weaker than spectra above and many lines disappeared, and the cancer cells in different position had different fluorescence intensity.CONCLUSION: The Raman spectra of several cells from cancer patients show that the structural changes of cancer cells happen and many bonds rupture so that the biological function of cells are lost. The results indicate that Raman spectra can offer the experiment basis for the cancer diagnosis and treatment.

IR and Raman Spectra Properties of Bi₂O₃-ZnO-B₂O₃-BaO Quaternary Glass System

Among new low-melting-point glasses, bismuth ate glass is deemed to have the most potential as an environmentally friendly replacement for polluting Pb-containing glasses. Current studies of boro-bismuthate glasses focus on the structural influence of the additional oxide in the context of low-melting-point electronic sealing applications. In this study, the structure of quaternary Bi2O3- ZnO-B2O3-BaO glasses was investigated spectroscopic ally, with Fourier-transform-infrared (FT-IR) and Raman spectra recorded for glasses with different main oxide contents. Signals in the FT-IR are mainly observed around 500 cm﹣1, 720 cm﹣1, 840 cm﹣1, 980 - 1080 cm﹣1, and 1200 - 1500 cm﹣1, while the Raman scattering peaks are located at 130 cm﹣1, 390 cm﹣1, 575 cm﹣1, 920 cm﹣1, and 1250 cm﹣1. The glasses are mainly structured around [BO3] units and the numbers of [BiO6] and [BiO3] units increase with the Bi2O3 content increasing. Concurrently, the FT-IR absorption peaks associated with [BO4] units shift to lower wave numbers, indicating a loosening of the glass structure. However, as the B2O3 content is increased, the numbers of [BO3] and [BO4] units increase, while those of [BiO3] and [BiO6] units decrease, highlighting a densification of the glass structure. ZnO acts as a network modifier in these glasses.

Quantum Chemical Vibrational Study, FTIR and FT-Raman Spectra of 1,3-Diphenyl Propenone

The Fourier Transform Infrared(FTIR)and Fourier transform Raman(FT-Raman)spectra of 1,3-Diphenyl Propenone were recorded in the regions 4000~400 and 4000~100 cm^-1,respectively,in the solid phase.Molecular electronic energy,geometrical structure,harmonic vibrational spectra was computed at the DFT/6-31G(d,p)and three parameter hybrid functional Lee-Yang-Parr/6-31G(d,p)levels of theory.The vibrational studies were interpreted in terms of potential energy distribution(PED).The results were compared with experimental values with the help of scaling procedures.Most of the modes have wave numbers in the expected range and are in good agreement with computed values and also the molecular properties of Mulliken population analysis have been calculated.Besides,thermodynamic properties were performed.

Raman Spectra and Crystallographic Properties of a New NLO Material,ZnCd(SCN)_4 Crystal

The crystallographic properties and R aman spectra of the title compound ZnCd(SCN) 4, which is a new nonlinear optica l crystal(NLO), are reported for the first time. This crystal is orthorhombic and its space group is I - 4 with unit cell parameters a =1.113 5(0.2) nm, c =0.437 60(1) nm. There are two formulas per unit cell. Raman spectra of zinc cadmium thiocyanatec (ZCTC) are given and the electron activities in the crystal are shown.

The Utilization of Low Frequency Raman Spectra of Gases for the Study of Molecules with Large Amplitude Vibration

The utilization of the Raman spectra of the low frequency bending mode for three quasi-linear molecules: disiloxane,(SiH3)2O;methylisocyanate,CH3NCO;and dimethylisocyanate,(CH3)2SiHNCO for observing the low frequency anharmonic bending vibration is demonstrated which is superior to the corresponding far infrared spectra.From the observed frequencies from the Raman spectra the potential function governing the heavy atom motion to linearity has been obtained from which the barrier has been determined.These experimental values are compared to the ab initio predicted values.Also low frequency Raman spectra of the ring puckering vibration of chlorocyclobutane,c-C4H7Cl,bromocyclobutane,c-C4H7Br,and aminocyclobutane,c-C4H7NH2,have been utilized to obtain the potential function governing the ring inversion for these molecules.The determined barriers to planarity are compared to those obtained from MP2(full) ab initio and density functional theory B3LYP calculations by utilizing a variety of basis sets.For all of these studies it is shown that the Raman spectra are superior to the infrared spectra for determining the frequencies of the excited state transitions.

Research of Tb∶Mo∶PbWO_4 Crystal Structure by Raman Spectra

The structure of Tb∶Mo∶PbWO4 crystals was investigated by Raman spectra and the results showed that the spectra were varied differently by doping dopants in different ranges of shift. Rotation-vibration, curving-vibration and non-symmetrical stretching-vibration had been investigated on the spectra. Rotation-vibration intensity of [WO4]2-group is weakened and curving-vibration intensity is undergirded; low Mo6+ doping enhances the intensity of non-symmetrical stretching-vibration, with the concentration of Mo6+ increasing, the intensity is weakened. So it could be inferred that Tb3+ ion replaced the vacancy of Pb, when achieving at a certain concentration, Tb3+ ion would substitute for the lattice of Pb2+, Mo6+ ion would substitute for W lattice and generate [MoO4]2-new group, these are the main reason for the properties changing. Furthermore it could suggest that the impurity ions doped in tetrahedral positions, strongly affect the electron-phonon coupling in [WO4]2-, which makes the intensities of the vibration changed regularly.

Evolution of molecular structure of TATB under shock loading from transient Raman spectroscopic technique

By combination of the transient Raman spectroscopic measurement and the density functional theoretical calculations,the structural evolution and stability of TATB under shock compression was investigated.Due to the improvement in synchronization control between two-stage light gas gun and the transient Raman spectra acquisition,as well as the sample preparation,the Raman peak of the N-O mode of TATB was firstly observed under shock pressure up to 13.6 GPa,noticeably higher than the upper limit of 8.5 GPa reported in available literatures.By taking into account of the continuous shift of the main peak and other observed Raman peaks,we did not distinguish any structural transition or any new species.Moreover,both the present Raman spectra and the time-resolved radiation of TATB during shock loading showed that TATB exhibits higher chemical stability than previous declaration.To reveal the detailed structural response and evolution of TATB under compression,the density functional theoretical calculations were conducted,and it was found that the pressure make N-O bond lengths shorter,nitro bond angles larger,and intermolecular and intra-molecular hydrogen bond interactions enhanced.The observed red shift of Raman peak was ascribed to the abnormal enhancement of H-bound effect on the scissor vibration mode of the nitro group.

Relaxor behavior and Raman spectra of CuO-doped Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)ferroelectric ceramics

In this work,Raman spectra and dielectricity-temperature dependence measurements were used to investigate the B-site order degree in CuO-doped Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)ferroelectric ceramics.The measurement results indicated a typical relaxor characteristic for all samples.With the increasing of CuO doping content,the B-site order degree increased first and then decreased.However,the frequency dispersion and the relaxation degree decreased first and then increased while the CuO addition content was increasing,which was thought to be strongly correlated with the variations of the B-site order.The opposite variation tendency of the B-site order degree and the relaxation degree revealed that the phase transition dispersity is closely related to the order-disorder behaviors.

Microstructure and Raman spectra of Ag-MgF_2 cermet films

Ag-MgF2 cermet films with different Ag fractions were prepared by vacuum evaporation. The micfostruc-ture of the films was examined by Raman scattering technique. The surface-enhanced Raman spectrum for MgF2 molecules in the cermet film strongly suggests the existence of Ag nanoparticles dispersed in MgFa matrix. The intensities of the Raman spectra of Ag-MgF2 cermet films increase with Ag fraction. The enhancement of Raman scattering disappears when Ag content reaches wt.20%. The analyses with the transmission electron microscopy showed that Ag-MgF2 cermet films are mainly composed of amorphous MgF2 matrix with embedded faced-center-cubic Ag nanoparticles. It suggests that the percolation threshold should be around wt.20% of Ag content.

Thermal Stability and Raman Scattering Spectra of Tellurite Glasses for Broadband Fiber Raman Amplifiers

The glass transition temperature （T）, crystallization onset temperature （T） and Raman scattering spectra of new tellurite glasses were studied as the function of glass composition. With the introduction of other metal oxides such as Nb2O5, BaO and WO3, T temperature increases, the intensity of exothermal peaks decreases, and thermal stability of tellurite glass improves. It was found that more TeO3 units transformed into TeO4 units and non-bridging oxygen atoms decreased with the incorporating other metal oxides in glassy network, when the content of TeO2 was fixed. Appearance of peak at 920 cm^-1 broadens the Raman bandwidth of tellurite glasses, which is very useful realize high efficient broadband fiber Raman amplifiers.

Manifestation of magnetoelastic interactions in Raman spectra of Ho_(x)Nd_(1-x)Fe_(3)(BO_(3))_(4) crystals

Raman spectra of Ho_(1-x)Nd_(x)Fe(BO_(3))4(x=1,0.75,0.5,0.25)have been studied in temperature range 10-400 K.Two compositions(x=1,x=0.75)demonstrate structural phase transition with soft mode restoration.The addition of Nd atoms increases interatomic spacing and decreases the temperature of structural phase transition.The solid solutions(x=0.75,0.5,0.25)demonstrate the emergence of the peaks corresponding to magnetoelastic interaction below Neel temperature.The order parameter of the magnetic phase transition has been determined.The equal concentrations of holmium and neodymium atoms prevent magnon soft modes condensation caused by exchange interactions in Fe-O-Fe chains are observed.Calculations confirm the data obtained in the experiment.

RAMAN SPECTRAL STUDY ON ISOPOLYTUNGSTATES IN AQUEOUS SOLUTION

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