The initial stages of Li_(2)O_(2) formation during oxygen reduction reaction in Li-O_(2) batteries:The significance of Li_(2)O_(2) in charge-transfer reactions within devices

Lithium-oxygen batteries are a promising technology because they can greatly surpass the energy density of lithium-ion batteries.However,this theoretical characteristic has not yet been converted into a real device with high cyclability.Problems with air contamination,metallic lithium reactivity,and complex discharge and charge reactions are the main issues for this technology.A fast and reversible oxygen reduction reaction(ORR)is crucial for good performance of secondary batteries',but the partial knowledge of its mechanisms,especially when devices are concerned,hinders further development.From this perspective,the present work uses operando Raman experiments and electrochemical impedance spectroscopy(EIS)to assess the first stages of the discharge processes in porous carbon electrodes,following their changes cycle by cycle at initial operation.A growth kinetic formation of the discharge product signal(Li_(2)O_(2))was observed with operando Raman,indicating a first-order reaction and enabling an analysis by a microkinetic model.The solution mechanism in the evaluated system was ascribed for an equivalent circuit with three time constants.While the time constant for the anode interface reveals to remain relatively constant after the first discharge,its surface seemed to be more non-uniform.The model indicated that the reaction occurs at the Li_(2)O_(2) surface,decreasing the associated resistance during the initial discharge phase.Furthermore,the growth of Li_(2)O_(2) forms a hetero-phase between Li_(2)O_(2)/electrolyte,while creating a more compact and homogeneous on the Li_(2)O_(2)/cathode surface.The methodology here described thus offers a way of directly probing changes in surface chemistry evolution during cycling from a device through EIS analysis.

CO_2 Density-Raman Shift Relation Derived from Synthetic Inclusions in Fused Silica Capillaries and Its Application

The densities of CO2 inclusions in minerals are commonly used to determine the crystallizing conditions of the host minerals. However, conventional microthermometry is difficult to apply for inclusions of small size （〈 5-10 μm） or low density. Raman analysis is an alternative method for determining CO2 density, provided that the CO2 density-Raman shift relation is known. This study aims to establish this CO2 density-Raman shift relation by using CO2 inclusions synthesized in fused silica capillaries. By using this newly-developed synthetic technique, we formed pure CO2 inclusions, and their densities were determined by microthermometry. The Raman analysis showed that the relation between CO2 density （D in g/cm^3） and the separations （△ in cm^-1） between the two main bands （i.e. Fermi diad bands） in CO2 Raman spectra can be represented by a cubic equation： D （g/cm^3）=0.74203（-0.019^3＋5.90332△^2-610.79472△＋21050.30165）-3.54278 （r^2=0.99920）. Our calculated D value for a given A is between those obtained from two previously-reported equations, which were derived from different experimental methods. An example was given in this study to demonstrate that the densities of natural CO2 inclusions that could not be derived from microthermometry could be determined by using our method.

3D Confocal Raman Imaging of Oil-Rich Emulsion from Enzyme-Assisted Aqueous Extraction of Extruded Soybean Powder

The understanding of the structure morphology of oil-rich emulsion from enzyme-assisted extraction processing(EAEP)was a critical step to break the oil-rich emulsion structure in order to recover oil.Albeit EAEP method has been applied as an alternative way to conventional solvent extraction method,the structure morphology of oil-rich emulsion was still unclear.The current study aimed to investigate the structure morphology of oil-rich emulsion from EAEP using 3 D confocal Raman imaging technique.With increasing the enzymatic hydrolysis duration from 1 to 3 h,the stability of oil-rich emulsion was decreased as visualized in the 3 D confocal Raman images that the protein and oil were mixed together.The subsequent Raman spectrum analysis further revealed that the decreased stability of oil-rich emulsion was due to the protein aggregations via SS bonds or protein-lipid interactions.The conformational transfer in protein indicated the formation of a compact structure.

High-precision analysis of carbon isotopic composition for individual CO_(2)inclusions via Raman spectroscopy to reveal the multiple-stages evolution of CO_(2)-bearing fluids and melts

The carbon isotopic composition of CO_(2)inclusions trapped in minerals reflects the origin and evolution of CO_(2)-bearing fluids and melts,and records the multiple-stages carbon geodynamic cycle,as CO_(2)took part in various geological processes widely.However,the practical method for determination isotope composition of individual CO_(2)inclusion is still lacking.Developing a microanalytical technique with spatial resolution in micrometers to precisely determinate theδ^(13)C value of individual CO_(2)inclusion,will make it possible to analyze a tiny portion of a zoning mineral crystal,distinguish the differences in micro-scale,and possible to find many useful information that could not be obtained with the bulk extraction and analysis techniques.In this study,we systematically collected Raman spectra of CO_(2)standards with different d13C values(34.9‰to 3.58‰)at 32.0℃and from 7.0 MPa to 120.0 MPa,and developed a new procedure to precisely determinate theδ^(13)C value of individual CO_(2)inclusion.We investigated the relationship among the Raman peak intensity ratio,d13C value,and CO_(2)density,and established a calibration model with high accuracy(0.5‰1.5‰),sufficient for geological application to distinguish different source of CO_(2)with varyingδ^(13)CO_(2).As a demonstration,we measured theδ^(13)C values and the density of CO_(2)inclusions in the growth zones of alkali basalt-hosted corundum megacrysts from Changle,Shandong Province.We found the significant differences of density and d13C between the CO_(2)inclusions in the core of corundum and those inclusions in the outer growth zones,the d13C value decreases from core to rim with decreasing density:δ^(13)C values are from7.5‰to9.2‰for the inclusions in the core,indicating the corundum core was crystallized from mantle-derived magmas;from13.5‰to18.5‰for CO_(2)inclusions in zone 1 and from16.5‰to–22.0‰for inclusions in zone 2,indicating the outer zones of corundum grew in a lowδ^(13)C value environment,resulted from an infilling of low d13C value fluid and/or degassing of the ascending basaltic magma.

Stable and unique graphitic Raman internal standard nanocapsules for surface-enhanced Raman spectroscopy quantitative analysis

Graphitic nanomaterials have unique, strong, and stable Raman vibrations that have been widely applied in chemistry and biomedicine. However, utilizing them as internal standards （ISs） to improve the accuracy of surface-enhanced Raman spectroscopy （SERS） analysis has not been attempted. Herein, we report the design of a unique IS nanostructure consisting of a large number of gold nanoparticles （AuNPs） decorated on multilayered graphitic magnetic nanocapsules （AGNs） to quantify the analyte and eliminate the problems associated with traditional ISs. The AGNs demonstrated a unique Raman band from the graphitic component, which was localized in the Raman silent region of the biomolecules, making them an ideal IS for quantitative Raman analysis without any background interference. The IS signal from the AGNs also indicated superior stability, even under harsh conditions. With the enhancement of the decorated AuNPs, the AGN nanostructures greatly improved the quantitative accuracy of SERS, in particular the exclusion of quantitative errors resulting from collection loss and non-uniform distribution of the analytes. The AGNs were further utilized for cell staining and Raman imaging, and they showed great promise for applications in biomedicine.

Quantitative evaluation of geological fluid evolution and accumulated mechanism:in case of tight sandstone gas field in central Sichuan Basin

Tight gas exploration plays an important part in China’s unconventional energy strategy.The tight gas reservoirs in the Jurassic Shaximiao Formation in the Qiulin and Jinhua Gas Fields of central Sichuan Basin are characterized by shallow burial depths and large reserves.The evolution of the fluid phases is a key element in understanding the accumulation of hydrocarbons in tight gas reservoirs.This study investigates the fluid accumulation mechanisms and the indicators of reservoir properties preservation and degradation in a tight gas reservoir.Based on petrographic observations and micro-Raman spectroscopy,pure CH4 inclusions,pure CO2 inclusions,hybrid CH4–CO2 gas inclusions,and N2-rich gas inclusions were studied in quartz grains.The pressure–volume–temperature–composition properties(PVT-x)of the CH4 and CO2 bearing inclusions were determined using quantitative Raman analysis and thermodynamic models,while the density of pure CO2 inclusions was calculated based on the separation of Fermi diad.Two stages of CO2 fluid accumulation were observed:primary CO2 inclusions,characterized by higher densities(0.874–1.020 g/cm3)and higher homogenization temperatures(>210°C)and secondary CO2 inclusions,characterized by lower densities(0.514–0.715 g/cm3)and lower homogenization temperatures:~180–200°C).CO2 inclusions with abnormally high homogenization temperatures are thought to be the result of deep hydrothermal fluid activity.The pore fluid pressure(44.0–58.5 MPa)calculated from the Raman shift of C–H symmetric stretching(v1)band of methane inclusions is key to understanding the development of overpressure.PT entrapment conditions and simulation of burial history can be used to constrain the timing of paleo-fluid emplacement.Methane accumulated in the late Cretaceous(~75–65 Ma),close to the maximum burial depth during the early stages of the Himalayan tectonic event while maximum overpressure occurred at~70 Ma,just before uplift.Later,hydrocarbon gas migrated through the faults and gradually displaced the early emplaced CO2 in the reservoirs accompanied by a continuous decrease in overpressure during and after the Himalayan event,which has led to a decrease in the reservoir sealing capabilities.The continuous release of overpressure to present-day conditions indicates that the tectonic movement after the Himalayan period has led to a decline in reservoir conditions and sealing properties.

Design and analysis of Wedge-enhanced Raman spectroscopy substrate

Here,a novel Au Wedge-enhanced Raman spectroscopy(WERS)substrate is proposed.The electric field enhancement factor and the effective mode field radius with varying geometry parameters are investigated.The proper excitation wavelength 633 nm is obtained.The practical application of WERS substrate is discussed.The Au WERS not only can provide a continuous extremely highly localized electric field as surface-enhanced Raman scattering(SERS)hotspots,but also can offer 10 orders of magnitude of SERS enhancement factor.The corresponding results reveal that WERS substrate will be widely applied in optics,biology,chemistry and other fields.

Detection of breast cancer based on novel porous silicon Bragg reflector surface-enhanced Raman spectroscopy-active structure

In this Letter, the surface-enhanced Raman scattering(SERS) signal of early breast cancer(BRC) patient serum is obtained by a composite silver nanoparticles(Ag NPs) PSi Bragg reflector SERS substrate. Based on these advantages, the serum SERS signals of 30 normal people and 30 early BRC patients were detected by this substrate. After a baseline correction of the experimental data, principal component analysis and linear discriminant analysis were used to complete the data processing. The results showed that the diagnostic accuracy, specificity,and sensitivity of the composite Ag NPs PSi Bragg reflector SERS substrate were 95%, 96.7%, and 93.3%, respectively. The results of this exploratory study prove that the detection of early BRC serum based on a composite Ag NPs PSi Bragg reflector SERS substrate is with a stable strong SERS signal, and an unmarked and noninvasive BRC diagnosis technology. In the future, this technology can serve as a noninvasive clinical tool to detect cancer diseases and have a considerable impact on clinical medical detection.

Study of the structural and electrical behavior of Bi(Mg,Ti)O_(3)modified(Ba,Ca)TiO_(3)ceramics

The ability of BaTiO_(3)to form solid solutions with different dopants(both iso-and aliovalent)makes it versatile for various applications.In the present study,(Ba,Ca)TiO_(3)(BCT)is modified with Bi(MgTi)O_(3)(BMT)in search for new lead-free ferroelectric material and improve their properties.For this purpose,BCT acts as a main base material and BMT acts as a modifier to fabricate a multifunctional material.In this study,we report the structural and electrical properties of lead free piezo-ceramics(1-x)(Ba_(0.8)Ca_(0.2))TiO_(3–x)Bi(Mg_(0.5)Ti_(0.5))O_(3)with x=0.2,0.4,0.5 prepared by solid-state sintering technique.Single perovskite phase with tetragonal structure is obtained for all the compositions,which is reconfirmed by the Raman Spectroscopic study.Dielectric study confirm the temperature stable behavior of the dielectric permittivity values above 300℃.The dielectric constant value decreases with increase in BMT doping content.Impedance Spectroscopic study confirms non-Debye type dielectric relaxation in the specimen.The Nyquist plot and conductivity studies show the negative temperature coefficient of resistance behavior(NTCR)of the samples.

Synthesis,structural study,thermal,optical properties and characterization of the new compound[C6H7N2O2]3TeCl5·2Cl

The new organic-inorganic compound, [C_6H_7N_2O_2]_3TeCl_5·2Cl was synthesized and its structure was determined at room temperature in the triclinic system （P^-1） with the following parameters： a = 10.5330（11） ？, b = 10.6663（11） ？, c = 15.9751（16）？, α = 82.090（2）°, β = 71.193（2）°, γ = 68.284（2）°and Z = 2. The final cycle of refinement led to R = 0.057 and Rw = 0.149. The crystal structure was stabilized by an extensive network of N--H···Cl and non-classical C--H···Cl hydrogen bonds between the cation and the anionic group. Several thermal analysis techniques such as thermogravimetric analysis, differential scanning calorimetric analysis and evolved gas analysis were used. We used isoconversional kinetics methods to determine the kinetics parameters. We observe that the decomposition of [C_6H_7N_2O_2]_3TeCl_5·2Cl entails the formation hydrochloric acid of nitroaniline as volatiles. The infrared spectra were recorded in the4000–400 cm^（-1）frequency region. The Raman spectra were recorded in the external region of the anionic sublattice vibration 50–1500 cm^（-1）. The optical band gap was calculated from the UV-Vis absorbance spectra using classical Tauc relation which was found to be 3.12 and 3.67 eV.

Spectroscopic studies of gel-grown lanthanum malonate crystals

Lanthanum malonate crystals were grown by single tube ionic diffusion through silica gel. The crystallinity of the grown crystals was analyzed by powder X-ray diffraction studies. Fourier transform infrared spectroscopy （FTIR） and fourier transform （FT） Raman studies confirmed the presence of functional groups in the title compound. The optical band gap energy of the material was extracted from diffuse reflectance spectrum.