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The influence of nitrogen doping on the electronic structure of the valence and conduction band in TiO <sub/>2</sub>
摘要： X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) provide a unique opportunity to probe both the highest occupied and the lowest unoccupied states in matter with bulk sensitivity. In this work, a combination of valence-to-core XES and pre-edge XAS techniques are used to determine changes induced in the electronic structure of titanium dioxide doped with nitrogen atoms. Based on the experimental data it is shown that N-doping leads to incorporation of the p-states on the occupied electronic site. For the conduction band, a decrease in population of the lowest unoccupied d-localized orbitals with respect to the d-delocalized orbitals is observed. As confirmed by theoretical calculations, the N p-states in TiO2 structure are characterized by higher binding energy than the O p-states which gives a smaller value of the band-gap energy for the doped material.
关键词： TiO2 doping,X-ray absorption spectroscopy,electronic structure analysis,X-ray emission spectroscopy
更新于2025-09-23 15:23:52
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Multi-field dependence responses and their micro-structure analysis in YBa <sub/>2</sub> Cu <sub/>3</sub> O <sub/>7a??x</sub> -based second-generation coated conductors with different protective layers by Nd-laser irradiations
摘要： High-temperature superconductors (HTS) are materials that hold great promise for future particle-accelerator plants. YBa2Cu3O7-x-based (YBCO) second-generation coated conductor coils can produce the intense field needed for ion confinement. Such coils can act as a radiation resistance magnet when exposed to radiation, and therefore, it is essential to better understand irradiation responses and defect creation in YBCO superconductors. The influence of laser or ion irradiation on the electrical characteristics of HTS has been studied previously; however, most results remain ambiguous and inconsistent. Degradation of or incremental changes in the critical current of the HTS tap are currently only observed and explained via irradiation dose. The relation between irradiation defects and macro-multi-field responses has yet to be established for YBCO tapes, for magnet design and operation. In this study, YBCO (2 G HTS) taps with Ag, Cu–Ag, and Cu protective cap layers were selected as targets of Nd-laser irradiation, at varying power. Irradiation defects were formed in YBCO taps, and irradiation dose was monitored as a function of superconducting properties and mechanical behaviors. The critical current and its N-values eventually degrade under intense Nd-laser irradiation, and the mechanical behavior of YBCO tapes shows nonlinear features after irradiation. Scanning electron microscopy and x-ray energy-dispersive spectrometry were applied to investigate the micro-defect changes that occurred in the taps after each Nd-laser irradiation dose. Micro-structural observations showed that the protective layers were critical for radiation resistance in YBCO taps. Furthermore, the macro-stress dependence of the critical current field was measured before and after Nd-laser irradiation to establish the relationship with micro-defect morphology by Nd-laser irradiation.
关键词： micro-structure analysis,YBa2Cu3O7-x,critical current,High-temperature superconductors,Nd-laser irradiation
更新于2025-09-23 15:19:57
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Solvent-controlled assembly of two Zn(II) coordination polymers constructed from 1,3,5-tris(1-imidazolyl)benzene and 2,5-dichloroterephthalic acid with fluorescent recognition of carcinogenic dye in chloroform
摘要： Two Zn(II) coordination polymers, [Zn2(tib)2(BDC-Cl2)(HBDC-Cl2)2](cid:1)2H2O (1) and [Zn(tib)(BDC-Cl2)](cid:1)H2O (2), were synthesized by reaction of 1,3,5-tris(1-imidazolyl)benzene (tib) and 2,5-dichloroterephthalic acid (H2BDC-Cl2) with Zn2t under solvothermal conditions. The results of X-ray single-crystal analysis show that 1 possesses a 1-D chain structure, while 2 exhibits a 2-D layer structure with {44(cid:1)62} topology. Both display a 3-D supramolecular framework through hydrogen bonding interactions. Experimental results indicated that the ratio of solvent may regulate the structural formation of the polymers. 1 and 2 were further characterized by powder X-ray diffraction (PXRD), IR spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Notably, 1 and 2 possess the ability to identify chloroform by emitting specific fluorescence spectra. Both can detect carcinogens in dyes by the modified fluorescent signal of the compound in chloroform.
关键词： crystal structure analysis,mixed-ligand strategy,carcinogen identification,Zinc(II)-coordination polymers,fluorescent recognition
更新于2025-09-23 15:19:57
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Determination of pH Dependent Structures of Thymol Blue Revealed by Cooperative Analytical Method of Quantum Chemistry and Multivariate Analysis of Electronic Absorption Spectra
摘要： The pH dependent structure of thymol blue (TB) in solution, a long-standing controversial issue, has been determined by quantum chemistry with an aid of multivariate analysis of electronic absorption spectra. It has been revealed that the TB structure varies from the neutral biprotonated form with open-sulton ring showing red to the monovalent anion of the pure quinoid form showing yellow and then to the quinoid-phenolate form showing blue on raising the pH for a solution.
关键词： Molecular structure analysis,Chemometrics,Acid-base indicator
更新于2025-09-16 10:30:52
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Chemical Structure of EVA Films Obtained by Pulsed Electron Beam and Pulse Laser Ablation
摘要： Poly(ethylene-co-vinyl acetate) (EVA) films were deposited for the first time using physical methods. The chemical structure of the films obtained using two techniques, pulsed electron beam deposition (PED) and pulsed laser deposition (PLD), was studied by attenuated total reflection Fourier infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Whilst significant molecular degradation of the EVA films was observed for the PLD method, the original macromolecular structure was only partially degraded when the PED technique was used, emphasizing the superiority of the PED method over PLD for structurally complex polymers such as EVA. Optical and scanning electron microscopic observations revealed compact and smooth EVA films deposited by pulsed electron beam ablation as opposed to heterogeneous films with many different sized particulates obtained by PLD.
关键词： chemical structure analysis,poly(ethylene-co-vinyl acetate),pulsed laser deposition,pulsed electron beam deposition
更新于2025-09-11 14:15:04
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Tuning of structural and optical properties of 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine thin films as a promising photovoltaic absorber material
摘要： Thin films of 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (H2TPyP) dye have been prepared using thermal evaporation technique. The crystal structure has been studied using the field emission scanning electron microscopy and X-ray diffraction pattern. The structure investigation of H2TPyP exhibited a polycrystalline nature in the form of powder while the thin films revealed a nanocrystalline structure. The optical features of H2TPyP thin films have been examined using spectroscopic measurements of the absorbance, the transmittance, and the reflectance of those films within spectral range of 200–2500 nm. From such measurements, the optical constants, the dispersion parameters, and the related optical variables were calculated and interpreted. The absorbance spectra of the films revealed the four quasi-electronic states named Q-bands and more intense Soret (B) band located at UV–visible spectral region. In addition to other weaker bands labeled M, N, and L observed at UV spectrum. The electronic inter-band transition for the H2TPyP thin films revealed an indirect allowed transition with the onset optical band gap Eg of 1.78 eV. Urbach tail energy EU was observed beyond the Eg and was found to be 0.36 eV. Furthermore, the energy loss functions, dielectric constants and optical conductivities were also studied.
关键词： Thin films,Structure analysis,Optical properties,Energy loss functions,Porphyrins
更新于2025-09-11 14:15:04
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Effect of Qamma Irradiation on Optoelectronic Properties of Two Barrier Structures of Nano Crystalline Silicon Solar Cells
摘要： The possibilities of applying the technology of plasma-chemical deposition of films of a-Si1-xGex: H (x=0 ÷ 1), undoped and doped with PH3 and B2H6, for use in a pin-structure solar cells. The optical, electrical and photoelectric properties, as determined by the amount of hydrogen of the film. We found that the property of the film strongly depends on the composition and level of hydrogenation. The number of hydrogen atoms in the films was varied by changing the composition of the gas mixture and measured the infrared absorption films a-Si:H and a-Ge:H.
关键词： Coefficient of carrier collection,Method double-barrier structure analysis,Silicon thin films,Photocurrent photogeneration
更新于2025-09-11 14:15:04
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Time-resolved structure analysis of piezoelectric crystals by X-ray diffraction under alternating electric field
摘要： Rare-earth substitution effects on atomic motions in resonantly vibrating piezoelectric oscillators of langasite-type crystals, namely, La3Ga5SiO14 (LGS) and Nd3Ga5SiO14 (NGS), are revealed by time-resolved X-ray crystal structure analysis under alternating electric fields. Deformations of Ga–O–Ga and Ga–O–Ga/Si bond angles accompanying deformations of RE–O (RE: La or Nd) bond lengths found in LGS are suppressed in NGS. Alternatively, rigid GaO6 octahedra are deformed in NGS. The decreases in RE–O bond lengths and Ga–O–Ga and Ga–O–Ga/Si bond angles caused by the substitution of La by Nd would make the bond lengths and angles more difficult to deform under electric fields; hence, the piezoelectric constants of NGS are smaller than those of LGS.
关键词： rare-earth substitution,piezoelectric crystals,alternating electric field,X-ray diffraction,time-resolved structure analysis
更新于2025-09-09 09:28:46