Dalai Jin

Preparation and the luminescent properties of Tb3 + -doped Gd2O3 fluorescent nanofibers via electrospinning

Tb(3+)-doped Gd(2)O(3) (Gd(2)O(3):Tb(3+)) nanofibers were prepared via a simple electrospinning technique using poly(ethylene oxide) (PEO) and rare-earth acetate tetrahydrates (Ln(CH(3)COO)(3)·4H(2)O (Ln = Gd, Tb)) as precursors. The obtained nanofibers have an average diameter of about 80 nm and are composed of pure cubic Gd(2)O(3) phase. A possible formation mechanism for the nanofibers is proposed on the basis of the experimental results, which reveals that PEO acts as the structure directing template during the whole electrospinning and subsequent calcination process. The luminescent properties of the nanofibers were investigated in detail. The nanofibers exhibit a favorable fluorescent property symbolized by the characteristic green emission (545 nm) resulting from the 5D4-->7F5 transition of Tb(3+). Concentration quenching occurs when the Tb(3+) concentration is 3 at.%, indicating that the Gd(2)O(3):Tb(3+) nanofibers have an optimum luminescent intensity under such a doping concentration.

Hydrothermal synthesis of SnO nanoflakes as anode materials for lithium-ion batteries

SnO nanoflakes were successfully prepared by a simple hydrothermal process, with the use of hydrazine hydrate as the mineralizer and polyethylene glycol (PEG) or citric acid as an additive. Hydrazine hydrate serves as both a mineralizer and a protective agent against the oxidation of the SnO products at the hydrothermal stage. X-ray diffraction, field-emission scanning electron microscopy (FESEM), and transmission electron microscopy were employed to characterize the products. FESEM images reveal that the thickness of the SnO nanoflakes prepared by the hydrothermal process with the use of PEG as an additive is around 15 nm. The first reversible specific capacity of the SnO nanoflakes reaches 856 mA h/g, which is near the theoretical value (876 mA h/g). Hydrazine hydrate, the hydrothermal temperature, and the surfactant/complexing agent are three key factors for the hydrothermal synthesis of the SnO nanoflakes by the process presented here.

Preparation of ZnO particle with novel nut-like morphology by ultrasonic pretreatment and its luminescence property

Novel nut-like zinc oxide crystal has been prepared by a low temperature hydrothermal method with the presence of Cu(2+) ion. It seemed that the ultrasonic pretreatment was the key factor during the preparation process. SEM observations revealed that the as-prepared ZnO crystal exhibited nut shape showing well-defined crystallographic facets. The cross-section of the ZnO crystal was hexagonal of about 800 nm-1 microm in diameter, and the aspect ratio was a little smaller than 1:1. The room temperature photoluminescence behavior of the nut-like zinc oxide crystal was much stronger than the reference samples.

CONTROLLED SYNTHESIS OF CU2O MICRO-CRYSTALS WITH VARIOUS MORPHOLOGIES BY ADJUSTING SOLUTION CONDITIONS

Micro-crystals of cuprous oxide with different morphologies were prepared by a hydrothermal process with copper sulfate and sodium lactate as precursors. Morphology of cuprous oxide was simply controlled by adjusting solution pH values or addition of different amounts of organic solvent. Structural properties of all the samples were characterized by X-ray diffraction and scanning electron microscopy. The growth mechanism of cuprous oxide micro-crystal under different conditions was discussed. Results show that morphologies of cuprous oxide micro-crystals alter from branched structure to octahedron structure and cube structure with growth conditions.

Optimization of the Photoluminescence Properties of Electrodeposited Y2O3 : Eu3 + Thin-Film Phosphors

In this work, electrodeposition is proved to be a promising method to prepare Y 2 O 3 :Eu 3+ thin-film phosphors. The photoluminescence (PL) property of the Y 2 O 3 :Eu 3+ thin-film phosphor strongly depends on different factors such as the crystal structure of host materials, annealing temperature, and doping concentration of Eu 3+ . The best PL performance of the Y 2 O 3 :Eu 3+ thin-film phosphor is achieved for a sample annealed at 600°C with a Eu 3+ doping concentration of 1.85 atom %.

A facile template-free preparation of porous manganese oxides by thermal decomposition method

Porous Manganese oxides with large surface area were prepared by a facile template-free method. Highly crystallized MnCO3 precursors with micron size in high dispersivity were prepared in water first. Thermal treatment was carried out with the obtained composite at different temperatures to produce porous manganese oxides. Thermogravimetry and differential thermal analysis (TG-DTA), X-ray powder diffraction (XRD), Scanning electron microscopy (SEM) and N2 adsorption-desorption measurements were applied to characterize the porous manganese oxides. Amorphous MnO2 obtained at 400°C shows a mesoporous structure and has a large specific surface area of 135.1 m2/g. Well crystallized α-Mn2O3 crystal with surface area of 18.51 m2/g macroporous framework was obtained at 600°C.

Study on the Photoluminescence Properties of Electrodeposited Y2O3 : Tb3 + Thin-Film Phosphor

In this work, photoluminescence properties of Y 2 O 3 :Tb 3+ thin-film phosphors were studied in detail. Y 2 O 3 :Tb 3+ thin-film phosphors were prepared by a two-step process: electrodeposition followed by an annealing process. Photoluminescence properties of the Y 2 O 3 :Tb 3+ thin-film phosphors strongly depend on the atomic content of Tb 3+ . The strongest photoluminescence emission was achieved with the atomic content of Tb 3+ of 5.02 atom %. The photoluminescence decay behavior of the Y 2 O 3 :Tb 3+ thin-film phosphors was also studied to understand the concentration quenching behavior. Based on the results and calculations, the concentration quenching of Tb 3+ was caused by the dipole―dipole interaction between Tb 3+ ions.

Influence of microstructure on the luminescence properties of YVO4:Eu3+ nanoparticles

YVO4:Eu3+ nanoparticles were synthesized by hydrothermal method at different conditions. The microstructures and photoluminescence (PL) properties of the as-prepared YVO4:Eu3+ nanoparticles were investigated by X-ray powder diffraction, field emission scanning electron microscopy and PL spectroscopy. The detailed relationship between the microstructures and luminescence properties was investigated. It has been found that the crystallinity, the grain size and the duty factor of Eu3+ play important roles in influencing the luminescence properties.

Synthesis and electrochemical properties of hierarchically porous Fe2O3

Porous Fe2O3 with hierarchical structure was obtained by a two-step template-free synthesis route. Brick-shaped ironic oxalate precursor in micrometer size was first synthesized by a hydrothermal process using (NH4)2SO4 · FeSO4 · 6H2O and K2C2O4 · H2O as raw materials. Then porous iron oxide with well retained brick-shape was obtained by a decomposition process under precisely controlled annealing condition. Morphology and structure of the as-prepared products were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), thermo-gravimetric/differential thermal (TG-DTA) and N2 adsorption-desorption measurements. The electrochemical properties were performed by galvanostatic cell cycling. It revealed that the pore structure can be tailored by the annealing condition and the crystallinity can be tuned by the solvent system. Product with porous structure and low crystallinity exhibited storage capacity of 634 mA h g−1 during the first cycle and efficiency of over 90% after 20 cycles.

Study on the oxygen exchange capacities of Ce2Sn2O7 pyrochlore

Ce2Sn2O7 pyrochlore was synthesized by a hydrothermal method. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the composition and valence state of the sample. The oxygen exchange property of the Ce2Sn2O7 phase was measured by an oxidation reaction in sealed air atmosphere and a followed reduction reaction in 5% H2-95% N2 atmosphere. Gas chromatography (GC) was used to analyze the oxygen change in the reaction. The results show that Ce2Sn2O7 sample has excellent oxygen absorption capacity at 250°C as Ce3+ ions are oxidized to Ce4+ ions. The oxidized sample can be reduced by 5% H2-95% N2. The refreshed sample remains the capacity of oxygen absorption, while the oxygen exchange capacity degrades with the reduction times.