查看更多>>摘要：? 2022 Elsevier B.V.In this work, the Er3+, Yb3+co-doped Gd2O3 phosphors have been prepared through a facile hydrothermal method. The optimum doping concentration of the Er3+, Yb3+ co-doped Gd2O3 phosphors are studied in detail. By studying the samples calcined at different temperatures, the process of grain forming self-assembled structure was revealed. The up-conversion luminescence intensity of the phosphors can be regulated by the ratio of NH4F and lanthanoid nitrate (F-/Ln3+) in the synthesis process. The enhancement of red and green emission intensities can reach 8.0 times, 6.7 times respectively than the sample with F-/Ln3+ = 0.5. In addition, the florescence intensity ratio based on thermally coupled energy levels by the Stark sublevels is also investigated. The maximal absolute sensitivity of optical temperature sensing reaches 1.27% K?1 at 574 K, which is 1.51 times higher than that based on traditional thermally coupled energy levels by Stark levels. Therefore, the results show that this is a useful method to improve the absolute sensitivity of optical temperature sensing and the Er3+, Yb3+ co-doped Gd2O3 phosphors have application potential in high sensitivity optical temperature sensing.
查看更多>>摘要：? 2022 Elsevier B.V.Two-dimensional (2D) In2Se3 with excellent optical and electrical properties has great application potential for flexible devices, photodetectors, and phase change memories. Here, we report the successes of growing In2Se3 nanosheets on SiO2/Si substrates by chemical vapor deposition (CVD) and fabricating broadband photodetector based on In2Se3. The Raman spectroscopy and transmission electron microscopy studies indicate that our 2D In2Se3 is in γ-phase. Our 2D γ-In2Se3 photodetector shows a broadband response range from near ultraviolet (350 nm) to infrared (1000 nm). The stable broadband response provides opportunities for the application of 2D γ-In2Se3-based devices and also a reference for the preparation and application of other 2D materials.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, the photocatalytic activity of the Cu-Rh/TiO2 system in the ultraviolet and visible regions was studied. A rough TiO2 layer was formed on a metal grid by electrophoretic deposition. The Cu-Rh nanoalloy on the surface of the TiO2 layer was obtained by the method of sequential vacuum-thermal evaporation of components followed by heat treatment of the condensate. This approach makes it possible to form Cu-Rh nanostructures of a given composition in a wide concentration range. According to the phase equilibrium diagram of the Cu-Rh system for temperatures below 1150 °C, separation two solid solutions should be observed: rich in Cu and rich in Rh. However, a detailed study of the structure by high-resolution transmission electron microscopy analysis characterizes the obtained nanoislands as a single-phase solid solution, the lattice parameter of which changes linearly in accordance with Vegard's law. The resulting photocatalytic system, which is an array of Cu-Rh nanoislands with a ratio of 25/75, 50/50, 75/25 at% on a TiO2 layer, was used for CO2 photoreduction. It has been demonstrated that TiO2 modified with Cu-Rh nanoislands has a higher photocatalytic activity in the ultraviolet region as compared to pure TiO2. At the same time, it retains it to a much greater extent in the visible range, in contrast to pure TiO2.
查看更多>>摘要：? 2022 Elsevier B.V.Undoped and Tb3+-doped (0.5–10 mol%) gallium tungsten-phosphate glasses, in the new compositional system NaPO3-Ga2O3-Na2WO4, were prepared and characterized by UV–visible absorption, photoluminescence excitation and emission, excited state decay measurements and X-ray excited radioluminescence measurements. A detailed study of ion-ion energy transfer, based on the analysis of decay curves by the Inokuti-Hirayama model, indicated that the energy transfer process affecting the emitting level 5D3 of Tb3+ is related to dipole–dipole interaction. Additionally, a theoretical model was successfully employed to establish a correlation between the emission color variation due to changes in the green to blue emission ratio (IG/IB). The emission spectra of the undoped and Tb3+-doped glasses were measured under UV and X-ray excitation. From the viewpoint of UV-sensing, samples doped with up to 7.0 mol% Tb3+ do not present visible emission quenching, whereas X-ray sensing is not prone to quenching at all up to 10 mol% Tb3+ doping. These characteristics, associated to a relatively high density, highlight the potential of these glasses as X-ray scintillators.
查看更多>>摘要：? 2022 Elsevier B.V.The relationship between plastic deformation and hydrogen transport behaviour in the quenching and partitioning (Q&P) steel is studied. The evolution of microstructure after different levels of plastic deformation is characterized using the electron backscatter diffraction (EBSD) and X-ray diffraction technique. Also, the hydrogen diffusion and trapping of the plastically deformed Q&P steel are investigated using the hydrogen permeation electrochemical method and thermal desorption spectroscopy (TDS) on pre-strained specimens up to 14% engineering strain. The major findings through the experimental approach can be summarized as follows: (1) retained austenite fraction in Q&P steel decreased after plastic deformation; (2) the geometrically necessary dislocation (GND) density measured by KAM analysis increased; (3) hydrogen diffusivity decreased, while solubility increased as the plastic deformation increased. The increase in hydrogen trapping in the Q&P steel with plastic deformation can be attributed to the enhanced hydrogen trapping environment by increased dislocation density in ferrite and martensite transformed from metastable austenitic phase. The TDS analysis could support the hydrogen-trapping characteristics of Q&P steel, in which two major peaks were measured in different temperature ranges. Moreover, the EBSD observation and scanning transmission electron microscope (STEM) using transmission Kikuchi diffraction (TKD) analysis provided good correlation with the result of TDS analysis.
查看更多>>摘要：? 2022 Elsevier B.V.A fundamental understanding of dynamism of charge-transfer characteristic at different phase and pH combination play an significant role for the development of highly efficient light harvesting photocatalyst. Herein, we describe the phase modulation at different pH and its relationship with the photocatalytic activities is emphasized. The pH of the precursor solution allows to control phase and size of TiO2 nanoparticles at constant temperature. The phase modulation at different pH proceeds through hydrolysis and polycondensation based on partial charge model. Rutile phase were formed at pH 3 of precursor solution. Anatase phase were formed at pH 9 while the mixed phase Anatase/Rutile formed at pH 5. A complementary role of phases on the catalytic activity of TiO2 under UV and visible irradiance was established using pseudo first order kinetics. This study was supported by XRD, HR-TEM, UV-DRS, XPS and FTIR analysis. This result gives a new strategy for controlled phase transition offset and size of TiO2 nanoparticles by manipulating pH.
查看更多>>摘要：? 2022 Elsevier B.V.The resonant inelastic X-ray scattering (RIXS) is a powerful tool as a probe for the local electronic and magnetic structures and provides detailed knowledge on the 3d open shell valence state in solids and molecules. In this work, the electronic structure, charge transfer (CT), and d-d excitation studies in perovskite manganite: LaSr2Mn2O7 and La1.2(Ba, Ca)1.8Mn2O7 single crystals have been explored using X-ray absorption spectra (XAS) and RIXS. The incident photon energy was tuned in the vicinity of Mn L3,2 absorption edges (639.2, 650.2, and 660 eV) to induce the RIXS matrix. The various electronic structural parameters were estimated using the charge transfer multiplet (CTM) approach implemented in Cowan. It is observed that manganese ions are present in the predominant Mn3+/Mn4+ ground configurations. The TEY-XAS spectra showed a similarity in the surface electronic structure of both samples. However, the pre-edge shoulder, at XAS Mn L3 edge of La1.2(Ba, Ca)1.8Mn2O7 single crystal, is indicative of enhanced Mn3+ valence state and increase the Mn3+/Mn4+ concentration ratio. The ground and excited states of Mn3+ (3d4) in octahedral (Oh) local symmetry are 2T1 (1D) and 2E(2D) respectively. The ground state of trivalent Mn3+ (5D) exists with a high spin (HS) active state (|t2 g3 eg1>). We find that the separation between t2 g and eg states and the d–d excitation is primarily influenced by CF with a weak involvement of CT.
查看更多>>摘要：? 2022 Elsevier B.V.Photocatalytic water splitting for H2 generation is considered most effective for the comprehensive utilization of solar energy. H2 produced by utilizing the ZnO-ZnS heterostructure still faces serious challenges because of its fast combination of photogenerated carriers and non-negligible photo-corrosion. In this study, we devise an original synthesis strategy for the Rh-ZnO/rGO/ZnS heterostructure via Rh-induced micro-cell growth and the dynamic ion-exchange process. Given the in-situ formation of the interfaces between the heterostructure and Rh atoms, the as-prepared heterostructure based on the solid-state Z-scheme demonstrates rapid carrier migration, low overpotential, and reduced photo-excited charge carrier combination due to the synergetic effect, which presents excellent performance in solar-driven H2 generation. The stable Schottky junctions between Rh and the ZnO-ZnS heterostructure further facilitate the catalytic performance. Therefore, this work provides a promising viewpoint on the Z-scheme heterostructure for photocatalytic water splitting.
查看更多>>摘要：? 2022 Elsevier B.V.Li-rich layered cathode materials based on Li1.2Mn0.54Ni0.13Co0.13O2(LMNCO) have received increasing attention due to their high capacity densities. Nevertheless, these materials are still limited by their unsatisfactory cycle performances. In this work, the sol-gel method was used to construct heterostructured LiCo0.99Al0.01O2-Li1.2Mn0.54Ni0.13Co0.13O2 (LCAO-LMNCO) cathode material to overcome the capacity fading of LMNCO and charging voltage limitation of LiCo0.99Al0.01O2 (LCAO). The as-obtained heterostructured LCAO-LMNCO cathode material showed 273.90 mAh/g capacity at charge-discharge voltages of 2.0–4.6 V. The capacity retention was 72.10% after 100 cycles at 1 C, superior to LCAO or LMNCO.
查看更多>>摘要：? 2022 Elsevier B.V.Li4Ti5O12 (LTO) is the most promising anode material for lithium-ion batteries owing to its excellent cycle stability and safety. However, the electrochemical performance of LTO at high rates is limited by its low conductivity. Generally, LTO preparation requires organic titanium sources, which are expensive. In this study, inexpensive H2TiO3 was used as the titanium source, LiOH?H2O served as the lithium source, and NH3?H2O was added to control the pH of the solution. Simple one-step liquid-phase deposition and calcination were performed for obtaining in situ self-assembled LTO submicron spheres with stable morphology and excellent electrochemical performance. According to electrochemical performance tests, the sample calcined with 4 mL of 25% NH3?H2O at 700 °C (LTO-4–700) exhibited the best performance. Its discharge capacity remained at 176.4 mAh g?1 over 100 cycles at 87.5 mA g?1 and retained at 136.7 mAh g?1 over 500 cycles at 875 mA g?1, and its specific capacity was 105.6 mAh g?1 over 1000 cycles, even at a current of 1750 mA g?1 with a retention rate of 96.7%. Furthermore, LTO-4–700 exhibited excellent rate performance at 3500 mA g?1 compared to other samples. Cyclic voltammetry and electrochemical impedance spectroscopy confirmed that submicron spherical LTO-4–700 had a high Li+ migration rate and low electrochemical impedance.
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