In-situ Raman observation on crack tips of Vickers indent in PLZT ceramics

Vickers indentation was introduced into the originally in-plane and out-of-plane poled PLZT ceramics.The Raman spectra were in-situ recorded at selected crack tips before and after the indentations,as well as after the applications of external electric field.The results show that the changes in Raman intensities of optical modes could be sensitively related to 90° domain switching around the crack tips which are strongly dependent on the directions of original polarization and geometric locations.When the direction of electric field was perpendicular to the direction of original polarization,the 90° domain switching at crack tips of the Vickers indentation on the originally in-plane poled PLZT ceramics caused most significant change in the Raman intensity,which inhibited the crack growth.However,when the direction of electric field was parallel to the direction of original polarization,the growth of crack tips became predominantly without the 90° domain switching,which led to the crack growth.

盐湖卤水中硼酸盐化学形态及Raman光谱定量分析

我国青藏盐湖以富含硼锂而著称,卤水中硼化学赋存状态随湖水化学类型的不同而发生变化,其中以硫酸盐型盐湖卤水中硼酸盐的存在形式变化最为复杂,卤水蒸发过程一般不以固体盐形式结晶析出,而是以多硼物种形式富集于氯化镁饱和老卤中,表现出严重的过饱和性,对后续锂盐和镁盐的分离提取影响较大。开展盐湖卤水体系中硼酸盐化学形态、分布规律及离子间作用机制等溶液化学研究对盐湖资源高效开发具有重要的意义。相比常规拉曼光谱技术,拉曼积分球基于拉曼散射原理可极大地提高激发光的使用效率和拉曼散射信号,对硼酸盐溶液结构检测具有拉曼响应信号强、检出限低、信噪比高等优点,为盐卤复杂体系硼酸盐化学形态的定量分析奠定了基础。利用拉曼积分球开展了盐湖卤水硼酸盐化学形态研究,阐述了卤水蒸发过程多硼酸根离子的变化规律;同时借助响应曲面法进行实验设计与优化,建立了共存盐类干扰回归模型用于盐湖卤水中单硼物种B(OH)_(3)的准确测定。结果表明,盐湖卤水浓缩过程中硼不断聚合生成多聚度硼酸根离子如B_(3)O_(3)(OH)_(4)^(-)和B_(6)O_(7)(OH)_(7)^(2-)等,硼的化学形态变化规律与碱土金属如MgCl_(2)-MgO-2B_(2)O_(3)-H_(2)O体系中硼物种变化一致,但与碱金属溶液体系物种变化差别较大。回归模型对卤水中正硼酸B(OH)_(3)定量分析的相对误差小于5%,准确度较高;阐明了蒸发浓缩过程中B(OH)_(3)物种分布的变化规律,从定量视角初步阐述了卤水富集过程硼酸根离子间的聚合作用关系,可为后续开展盐卤体系多硼物种分布及作用机制研究提供新思路、新方法。

Raman Spectra of Liquid Nitromethane under Singly Shocked Conditions

Raman spectra of liquid nitromethane were measured in single-shock experiments using transient Raman scattering system with high sensitivity. The measurement system was combined with a two-stage light gas gun to interrogate the vibrational mode-dependent behaviors of shock-compressed nitromethane molecules. Up to 12 GPa, all Raman peaks were able to be clearly detected, and showed the shock-induced shifting and broadening, but no signs of chemical changes occurred in the sample. Thus, it is concluded that chemical reactions could not be initiated in singly-shocked nitromethane below 12 GPa.

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.

RAMAN SPECTRAL STUDY ON ISOPOLYTUNGSTATES IN AQUEOUS SOLUTION

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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.

EFFECT OF SOLVENT ON SURFACE ENHANCED RAMAN SCATTERING SPECTRA OF COLLOIDAL SILVER

The effect of solvent on surface enhanced Raman scattering [SERS) of colloidal silver has been studied. Experiments show that the intensity of SERS is related to the polarity and molecular constitution of the solvent. The influence of solvent is due to the change of the adsorption quantity and adsorption intensity.

In-situ electrochemical surface-enhanced Raman spectroscopy in metal/polyelectrolyte interfaces

Polyelectrolyte becomes more and more popular in electrocatalysis.The understanding of electrode/polyelectrolyte interfaces at the molecular level is important for guiding further the polyelectrolyte-based electrocatalysis.Herein,we demonstrate an in-situ surface-enhanced Raman spectroscopic method by using a three-electrode spectroelectrochemical cell towards characterizing the electrode/polyelectrolyte interfaces.The Ag/AgCl and Ag/Ag_(2)O electrodes are used as the reference electrode in the acidic and the alkaline systems,respectively.The working electrode is made of a transparent carbon thin film which loads the electrocatalysts.The applications of this method are demonstrated through the in-situ characterizations of the p-methylthiophenol adsorbed on the Au and Pt and the electrochemical oxidation of Au on polyelectrolyte membranes.The potential-dependent spectral features of these two systems show that this method is a powerful tool for investigating the electrode/polyelectrolyte interfaces in electrocatalysis.

Integration of a fused silica capillary and in-situ Raman spectroscopy for investigating CO_(2) solubility in n-dodecane at near-critical and supercritical conditions of CO_(2)

To determine the solubility of CO_(2)in n-dodecane at T=303.15-353.15 K,P≤11.00 MPa,an integrated fused silica capillary and in-situ Raman spectroscopy system was built.The Raman peak intensity ratio(I_(CO_(2))/IC-H)between the upper band of CO_(2)Fermi diad(I_(CO_(2)))and the C-H stretching band of n-dodecane(IC-H)was employed to determine the solubility of CO_(2)in n-dodecane based on the calibrated correlation equation between the known CO_(2)molality in n-dodecane and the I_(CO_(2))/IC-Hratio with R^(2)=0.9998.The results indicated that the solubility of CO_(2)decreased with increasing temperature and increased with increasing pressure.The maximum CO_(2)molality(30.7314 mol/kg)was obtained at 303.15 K and7.00 MPa.Finally,a solubility prediction model(lnS=(P-A)/B)based on the relationship with temperature(T in K)and pressure(P in MPa)was developed,where S is CO_(2)molality,A=-8×10^(-6)T^(2)+0.0354T-8.1605,and B=0.0405T-10.756.The results indicated that the solubilities of CO_(2)derived from this model were in good agreement with the experimental data.

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.

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.

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.

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

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 Raman Spectra of the Antibacterial Peptide β-Component of Silkworm · Bombyx Mori · Pupae in Aqueous Solution

he Raman spectra of the antibacterial peptide βcomponent of silkworm· Bombyx Mori· pupae in aqueous solution have been studied. The results show that its mainchain consists of lots of αhelicals and only a few βsheets and βturns. This suggests that the antibacterial peptide βcomponent may be the glycopeptide.

A New Method for In-Situ Measurement of Internal Solitary Waves Based on the Stimulated Raman Scattering in Optical Fibers

In-situ measurement of internal solitary waves(ISWs)is complicated in the ocean due to their randomness.At present,the ISWs are mainly detected by the chain structure of conductivity-temperature-depth systems(CTDs)or temperature sensors.The high cost limits the spatial resolution,which ultimately affects the measuring accuracy of the ISW amplitude.In this paper,we developed an experimental measurement system for detecting ISWs based on the stimulated Raman scattering in distributed optical fibers.This system has the advantages of high precision,low cost,and easy operation.The experimental results show that the system is consistent with CTDs in the measurement of vertical ocean temperature variation.The spatial resolution of the system can reach 1.0 m and the measuring accuracy of temperature is 0.2℃.We successfully detected 3 ISWs by the system in the South China Sea and two optical remote sensing images collected on May 18,2021,the same day of two detected ISWs,verify the occurrence of the measured ISWs.We used the image pairs method to calculate the phase velocity of ISW and the result is 1.71 ms^(-1).By extracting the distances between wave packets,it can be found that the semi-diurnal tide generates the detected ISWs.The impact of the tidal current velocity on the ISW in amplitude is undeniable.Undoubtedly,the system has a great application prospect for detecting ISWs and other dynamic phenomena in the ocean.

Ab Initio Calculation of Structure and Raman and Infrared Spectra of Trifluoromethylthiosulphenyl Chloride

The molecular model of Trifluoromethylthiosulphenyl Chloride,CF_(3)SSCl,was presented.Ab initio method was used to calculate the structure and Raman and Infrared spectra.The results show that CF_(3)SSCl possess stereoscopic structure of C_(1)symmetry with a torsional angle of 94.2°.The potential energy distribution and isotope replacement methods were applied to determine the vibrational assignment.The vibrational frequencies and corresponding modes of the molecule were obtained.The calculated vibrational frequencies are in good agreement with experiments.

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.

Raman and infrared spectra of complex low energy tetrahedral carbon allotropes from first-principles calculations

Up to now,at least 806 carbon allotropes have been proposed theoretically.Three interesting carbon allotropes(named Pbam-32,P6/mmm,and I43d)were recently uncovered based on a random sampling strategy combined with space group and graph theory.The calculation results show that they are superhard and remarkably stable compared with previously proposed metastable phases.This indicates that they are likely to be synthesized in experiment.We use the factor group analysis method to analyze theirΓ-point vibrational modes.Owing to their large number of atoms in primitive unit cells(32 atoms in Pbam-32,36 atoms in P6/mmm,and 94 atoms in I43d),they have many Raman-and infrared-active modes.There are 48 Raman-active modes and 37 infrared-active modes in Pbam-32,24 Raman-active modes and 14 infrared-active modes in P6/mmm,and 34 Raman-active modes and 35 Raman-and infrared-active modes in I43d.Their calculated Raman spectra can be divided into middle frequency range from 600 cm-1 to 1150 cm-1 and high frequency range above 1150 cm-1.Their largest infrared intensities are 0.82,0.77,and 0.70(D/Å)2/amu for Pbam,P6/mmm,and I43d,respectively.Our calculated results provide an insight into the lattice vibrational spectra of these sp3 carbon allotropes and suggest that the middle frequency Raman shift and infrared spectrum may play a key role in identifying newly proposed carbon allotropes.

Generalized Energy-Based Fragmentation Approach for Accurate Binding Energies and Raman Spectra of Methane Hydrate Clusters

Methane hydrates(MHs)play important roles in the fields of chemistry,energy,environmental sciences,etc.In this work,we employ the generalized energy-based fragmentation(GEBF)approach to compute the binding energies and Raman spectra of various MH clusters.For the GEBF binding energies of various MH clusters,we first evaluated the various functionals of density functional theory(DFT),and compared them with the results of explicitly correlated combined coupled-cluster singles and doubles with noniterative triples corrections[CCSD(T)(F12^(*))]method.Our results show that the two best functionals are B3PW91-D3 and B97D,with mean absolute errors of only 0.27 and 0.47 kcal/mol,respectively.Then we employed GEBF-B3PW91-D3 to obtain the structures and Raman spectra of MH clusters with mono-and double-cages.Our results show that the B3PW91-D3 functional can well reproduce the experimental C-H stretching Raman spectra of methane in MH crystals,with errors less than 3 cm^(-1).As the size of the water cages increased,the C-H stretching Raman spectra exhibited a redshift,which is also in agreement with the experimental“loose cage-tight cage”model.In addition,the Raman spectra are only slightly affected by the neighboring environment(cages)of methane.The blueshifts of C-H stretching frequencies are no larger than 3 cm^(-1) for CH_(4) from monocages to doublecages.The Raman spectra of the MH clusters could be combined with the experimental Raman spectra to investigate the structures of methane hydrates in the ocean bottom or in the interior of interstellar icy bodies.Based on the B3PW91-D3 or B97D functional and machine learning models,molecular dynamics simulations could be applied to the nucleation and growth mechanisms,and the phase transitions of methane hydrates.