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Raman scattering of impact diamonds
摘要： We report the results of a study of the polycrystalline powder of the diamond-lonsdaleite from the Popigai crater (Siberia) using UV micro-Raman spectroscopy and high-resolution synchrotron X-ray diffraction. By subtracting two experimental Raman spectra of diamond-lonsdaleite samples with close amounts of diamond and lonsdaleite, we were able to identify the polytypic composition of impact diamonds in contrast to the method of X-ray diffraction. We have managed to get for the first time the spectrum of "pure" lonsdaleite. Its deconvolution has allowed us to identify all the three Raman - active vibrational modes E2g, A1g, and E1g whose positions agree well with the results of ab initio calculations.
关键词： Raman scattering,polytypic composition,impact diamonds,synchrotron X-ray diffraction,lonsdaleite,UV micro-Raman spectroscopy
更新于2025-09-10 09:29:36
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Investigation of structural, optical and electrical properties of transition metal oxide semiconductor CdO ZnO nanocomposite and its effective role in the removal of water contaminants
摘要： In this technological era as the usage and development of technology is on the rise we encounter serious repercussions of pollutions in both drinking and daily usage of water. Nanocomposite of Cadmium Oxide and Zinc Oxide (CdO-ZnO) has the property of alienating the pollutants from the water. A conventional hydrothermal method was adapted for the preparation of nanocomposite of CdO-ZnO from their respective metal acetate dihydrates and NaOH. Structural and morphological analysis by electron beam diffraction technique reveals the formation of unique nanorod with spherical morphology of the synthesized particle. Williamson-Hall method was used to find the crystallite size and the lattice strain. Fourier transforms infrared (FTIR) spectroscopy further confirmed the stretching and vibration of chemical bonds of the materials. The study of electronic transitions within the material was portrayed with UV-Vis absorption spectrum and the obtained energy gap is 3.99 eV. A thorough investigation of temperature dependent electrical properties of CdO-ZnO nanocomposite was carried out in the frequency range from 50 Hz to 5 MHz. Studies revealed that the composite material is responsible for higher photocatalytic performance under the irradiation of UV photon. The high photocatalytic activity was originated from superoxide O2? radicals due to the efficient trapping of photogenerated electrons in CdO by ZnO.
关键词： Zinc Oxide,Williamson-Hall method,Photocatalytic Activity,Cadmium Oxide,Electron Beam Diffraction
更新于2025-09-10 09:29:36
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Crystal growth, Hirshfeld surface analysis, DFT study and third order NLO studies of Thiourea 4 dimethyl aminobenzaldehyde
摘要： In this work we investigate the crystal growth and the characterization of Thiourea 4 dimethyl aminobenzaldehyde (TDA) crystal. The Molecular geometry shows good agreement with Experimental and Theoretical (HF and DFT) bond lengths and bond angles. From X-ray diffraction studies it shows that the structure belongs to monoclinic structure and experimental, refinement data also discussed. Hirshfeld surface analysis used to clarify the intermolecular interactions in a visual manner. Vibrational assignments of TDA crystal is discussed by FT-IR and FT-Raman spectroscopic studies. The assignments are compared with Density Functional Theory calculation and it shows good agreement with experimental data. The Frontier molecular orbital energy gap is found by TD-DFT method with HOMO-LUMO calculation. The Third order NLO studies for TDA organic crystal is done by Z-scan technique and Optical parameters like Non linear and Linear refractive index are calculated.
关键词： Z-scan Technique,DFT,Hirshfeld surface analysis,X-Ray diffraction,Molecular Geometry.
更新于2025-09-10 09:29:36
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Scattering of a Plane Electromagnetic Wave by a Multilayer Spherical Lens
摘要： We propose an analytical solution of the problem of diffraction of a plane electromagnetic wave by a multilayer dielectric (including plasmon) sphere. The solution is obtained using the method of separation of variables. New efficient recurrence relationships are obtained for calculations of the fields in layers, as well as formulas for the fields in the near and far diffraction zones. The novelty of the proposed solution is connected with the way of representing its radial part in the form of normalized functions. It is shown that as the number of the lens layers, which approximate the smooth profile of dielectric permittivity, grows, the electric field at the focusing point increases and reaches the maximum value. This allows one to determine the minimum required number of layers in practical problems. Resonance properties of metal-dielectric nanoparticles are studied in the optical band.
关键词： diffraction,multilayer dielectric sphere,plane electromagnetic wave,separation of variables,optical band,metal-dielectric nanoparticles,resonance properties,recurrence relationships,focusing point
更新于2025-09-10 09:29:36
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Site-sensitive X-ray photoelectron spectroscopy of Fe <sub/>3</sub> O <sub/>4</sub> by photoelectron diffraction
摘要： Fe 2p core-level photoelectron spectra of magnetite were measured using soft X-ray and hard X-ray, and its emission angle dependence was investigated. The photoelectron diffraction pattern from different atomic sites differs because the atomic arrangement surrounding each site is different. By selecting the forward-focusing-peak (FFP) directions characteristic to each atomic site and measuring the kinetic energy dependence of the FFP intensities at the Fe 2p core-level range, we succeed in detecting the variation of the peak intensity of Fe 2p core-level spectra at different emission directions. This result, consistent with recent results, suggests that the lower-binding-energy peak of the Fe 2p core-level spectrum may be assigned as the B site component.
关键词： photoelectron diffraction,magnetic materials,mixed valence
更新于2025-09-10 09:29:36
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Determination of Sulfite in Botanical Medicine Using Headspace Thin-Film Microextraction and Surface Enhanced Raman Spectrometry
摘要： A facile method using headspace thin-film microextraction (HS-TFME) coupled with surface enhanced Raman spectrometry (SERS) has been developed for the determination of sulfite in traditional Chinese herbal medicine. The extraction substrate was synthesized by depositing urchin-like ZnO micron particles on glass sheets using chemical liquid phase deposition. Under the optimal conditions, the intensity of the SERS signal at 630–640 cm?1 provided a good linear relationship with the concentration of sulfite from 25 to 400 mg/kg, and the linear correlation coefficient (R) was 0.996 with a detection limit of 6 mg/kg. The method was employed for the determination of sulfite in herbal medicines, and the results were confirmed by a traditional distillation-titration method. Therefore, this developed HS-TFME-SERS method may play an important role in the rapid, simple, and selective determination of sulfite residues in Chinese herbal medicine and become a potentially universal method for this analyte in various solid samples.
关键词： Headspace thin-film microextraction (HS-TFME),scanning electron microscopy (SEM),X-ray diffraction (XRD),surface enhanced Raman spectrometry (SERS),transmission electron microscopy (TEM)
更新于2025-09-10 09:29:36
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Spectroscopic properties and martensitic phase transition of Y4Al2O9:Ce single crystals under high pressure
摘要： High pressure studies of monoclinic yttrium aluminum oxide single crystals (Y4Al2O9 -YAM) doped with Ce3+ ions grown by micro-pulling-down method are reported. The results of absorption measurements in the mid-infrared prove the existence of four different sites in which Ce3+ ions substitute Y ions, in accordance with the crystallographic structure of YAM. The lowest 5d level of Ce3+ is located very close to the bottom of the conduction band for two of four Ce3+ related centers at ambient pressure, which results in strong temperature quenching of their luminescence. Two other Ce3+ centers do not emit at ambient pressure since their 5d levels are resonant with the conduction band. Application of high pressure above 11 GPa restores their luminescence. Consequences of such energy structure of various Ce3+ sites in YAM for the Dorenbos theory are discussed. The bandgap energy of YAM is found to be 5.93 eV, which is the smallest out of the three yttrium aluminum oxides. High-pressure synchrotron angle dispersive x-ray diffraction and Raman scattering measurements identify a phase transition occurring at pressures between 8 and 11 GPa, which has martensitic character. The second phase transition to another structure (likely with hexagonal symmetry) occurs at a pressure around 16 GPa.
关键词： high pressure,phase transition,X-ray diffraction,luminescence,single crystal
更新于2025-09-10 09:29:36
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Effect of hydrogen concentration on graphene synthesis using microwave-driven plasma-mediated methane cracking
摘要： Gas phase graphene forms as an aerosol in a microwave plasma among other carbon forms. Consisting of 2-6 sheets per stack with dimensions between 100 – 500 nm, it is referred to as nanographene (NG). Surprisingly, increasing H/C ratio in the feedstock increases the relative graphitic content of the product. Dependence of the different carbon forms upon H/C ratio of the gas feed mixture is shown across multiple analytical characterizations. Attributes of (a) phase quality (pristine nature of NG) and (b) phase quantity (how much NG forms relative to other carbon sp2 phases) are addressed. Phase identification of the forms is performed via transmission electron microscopy with quantification by thermogravimetric analysis, assessing their respective oxidative reactivity benchmarked to commercially available similar carbon products applied as standards. X-ray diffraction differentiates these forms based on varied extent of graphitic structure. Electron energy loss spectroscopy assesses graphitic content by the ratio of sp2/sp3 bonding. Raman spectroscopy supports the observed shift in relative proportions of the carbon forms towards preferential graphitic content with increasing H/C. Selected area diffraction illustrates this for NG. Fringe analyses of nanostructure quantifies this shift for carbon particles. Infra-red spectroscopy reveals complementary C-H bonding as a measure of graphitic quality.
关键词： electron energy loss spectroscopy,thermogravimetric analysis,hydrogen concentration,methane cracking,graphene synthesis,X-ray diffraction,nanographene,microwave-driven plasma,Raman spectroscopy,infra-red spectroscopy
更新于2025-09-10 09:29:36
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The Origin of the π-π Spacing Change upon Doping of Semiconducting Polymers
摘要： While there is agreement about the local structural order of semiconducting polymers such as poly(3-hexylthiophene) (P3HT), there is still debate over the impact of molecular doping. One prevalent interpretation is that dopant molecules intercalate in the π-π stacking of crystallites; however, this idea has recently been challenged. We present here electron diffraction measurements of P3HT doped with the two dopants 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) and molybdenum tris[1-(methoxycarbonyl)-2-(trifluoromethyl)-ethane-1,2-dithiolene] (Mo(tfd-CO2Me)3), which have considerably different sizes and shapes, processed by different doping techniques. We observe a reduction in the π-π spacing of P3HT upon doping with both dopant molecules and doping techniques. These data are not consistent with both of the dopants intercalating in the π-π stacks and an alternative explanation is, therefore, required to explain these results. Density functional theory calculations for P3HT model oligomers suggest that the polaron delocalizes between adjacent chains and thus leads to attractive forces that reduce the π-π spacing, without the physical presence of any dopant molecules. Our study emphasizes that not only geometric effects induced by dopant molecules lead to the observed reduction of π-π spacing, but the charging itself.
关键词： semiconducting polymers,electron diffraction,π-π spacing,F4TCNQ,Mo(tfd-CO2Me)3,density functional theory,molecular doping,P3HT
更新于2025-09-10 09:29:36
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Effect of Heat Treatment on The Crystal Structur, Electrical Conductivity and Surface of Ba <sub/>1.5</sub> Sr <sub/>0.5</sub> Fe <sub/>2</sub> O <sub/>5</sub> Composite
摘要： The Composite of Ba1,5Sr0,5Fe2O5 has been synthesized by using powder metallurgy technique. The Ba1.5Sr0.5Fe2O5 were prepared from BaCO3, SrCO3 and Fe2O3 raw materials with a specific weight ratio. The three materials were synthesized by powder metallurgy under heat treatment at 800 °C, 900 °C, and 1000 °C for 5 hours. All the three samples were characterized by using X-ray Diffraction (XRD) to determine the crystal structure and crystal size, LCR meter to determine the conductivity, and Scanning Electron Microscope (SEM) to observe the morphological of the composites. The phase analysis result showed that the composite consists of several minor phases such as BaO2, SrO2, and Fe2O3. The Crystal size of composite Ba1.5Sr0.5Fe2O5 decreased while increases the strain of crystal with increasing of sintering temperature. The crystal size of the Ba1.5Sr0.5Fe2O5 composite is 3.55 nm to 7.23 nm and value of strain is 8.47% until 3.90%. Based on the conductivity measurement, it was obtained that the conductivity of the Ba1.5Sr0.5Fe2O5 composite decreased with increasing sintering temperature. It was also noticed that the conductivity increased with increasing of frequency. The conductivity ranged from 6.619?10-7 S/cm to 65.659?10-7 S/cm. The energy dispersive spectroscopy (EDS) analysis showed that several dominant elements were a good agreement with the phase analysis.
关键词： surface,Ba1.5Sr0.5Fe2O5,conductivity,Composite,X-ray diffraction
更新于2025-09-10 09:29:36