Xiaojing Yu

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 %.

Hydrothermal synthesis and photoluminescence behavior of Eu-doped GdVO4

Eu3+ doped GdVO4 was successfully prepared by a simple hydrothermal method. It was characterized by x-ray diffraction and scanning electron microscopy, which revealed that the GdVO4:Eu3+ was tetragonal (zircon-type structure). Photoluminescence spectra revealed that there was efficient energy transfer from the GdVO4 host to the Eu3+, and the GdVO4:Eu3+ crystal exhibited a strong red emission peaked at 616 nm due to the Eu3+5D0-7F2 transition. The hydrothermal route is proposed for synthesizing a red luminescent GdVO4:Eu3+ phosphor as an economical technique.

Synthesis of ZnO rods by a simple chemical solution deposition method

ZnO short rods with large yield have been synthesized by a simple chemical solution deposition method at a low temperature of 80°C. Polymethyl methacrylate was used as the structure-directing agent in the formation of the rod-like ZnO crystals. X-ray powder diffraction and field emission scanning electron microscopy were used to characterize the obtained product. The results showed that the as-prepared ZnO crystals were rod-like, which have fairly uniform diameter of around 0.5 ∼ 2 μm and length of 4 ∼ 6 μm. A possible formation mechanism of the ZnO rods has been considered.

Novel petal-like ZnO crystal synthesized by organic solution method

ZnO crystals with different morphologies have been synthesized by an organic solution method using Zn(CH3COO)2 · 2H2O and polyvinylpyrrolidone as precursors. X-ray powder diffraction, field emission scanning electron microscopy and transition electron microscopy were used to characterize the obtained samples. The results showed that novel petal-like ZnO particles could be obtained when the molar ratio of Zn2+/C = O was 1 : 4. The particle had uniform diameter in 200–300 nm and with good dispersibility. Otherwise, octahedron shaped particles with sub-crystalline were achieved when the molar ratio of Zn2+ to the carbonyl group of polyvinylpyrrolidone was 1 : 2 or 1 : 8.

Study of the effect of Li+ concentration on the photoluminescence properties of Y2O3:Eu3+ phosphors

Y2O3:Eu3+ phosphors were prepared by hydrothermal method. Effect of the doping concentration of Eu3+ on the photoluminescence properties of Y2O3:Eu3+ phosphor was studied in details. It was found that the strongest emission intensity is achieved as atomic ratio of Y3+ to Eu3+ is 8. As concentration of Eu3+ exceeds the critical concentration, the emission intensity decreases dramatically due to the concentration quenching of Eu3+. Also, the effect of Li+ on the photoluminescence performance of the Y2O3:Eu3+ phosphor is studied in this work. According to the results, the doping of Li+ may greatly improve the PL performance of the Y2O3:Eu3+ phosphors due to the flux effect and improved crystallinity caused by the doping of Li+.

Synthesis of BaCO3 with different morphologies using amphiphilic PS-PAA copolymer as medium

Barium carbonate (BaCO3) with multiple morphologies were synthesized using BaCl2 and Na2CO3 in the presence of a copolymer of poly(styrene) (PS) and poly(acrylic acid) (PAA), an amphiphilic copolymer, by a simple solvent reaction route. X-ray powder diffraction and field emission scanning electron microscopy were used to characterize the obtained products. The mole ratio of the PS/PAA was found to play an important role in determining the morphologies of the final products.