Papers by Author: Mei Zhang

Abstract: In this work, the effects of Ag nanoparticles or Ag-PVP nanocomposites on the fluorescence properties of rhodamine B and fluorescein were investigated. The fluorescence intensities of the dyes could be largely enhanced by Ag nanoparticles with various concentrations. Moreover, the intensities were further increased by Ag-PVP nanocomposites. The results show that the maximum enhancement ratio of 36.5 fold is achieved for rhodamine B in the presence of 2% Ag-PVP nanocomposites, as well as 4.37 fold for fluorescein with 5% Ag-PVP nanocomposites. The enhancement is believed to mainly be originated from the increased excitation rate of the dyes due to the local electromagnetic field which is improved by the interaction of light with Ag nanoparticles. The further fluorescence enhancement of the dyes by Ag-PVP nanocomposites is attributed to the effective separation of Ag nanoparticles from the dyes by PVP molecules. Additionally, the difference in the enhancement ratio of two dyes was also discussed. The lower quantum yield of the dye, as well as higher overlapped degree between Ag nanoparticles and the absorption of dye result in the larger enhancement ratio. The research could be meaningful for improving the sensitivity of rapidly medical or biological assays.

Abstract: A series of Ba1.91-xSrxSiO4:Eu2+, Dy3+phosphors were synthesized by the high-temperature solid-state reaction. The structure of powder samples were characterized by X-ray powder diffraction. The photoluminescence emission and excitation spectra are also studied. It can be proved the formation of the solid solution of Ba1.91-xSrxSiO4:Eu2+, Dy3+ compounds, and the phosphors can be efficiently excited by UV-visible light from 300 to 480 nm. The as-synthesized Ba1.91-xSrxSiO4:Eu2+, Dy3+ phosphors are promising candidates applicable to near-UV and blue LEDs for solid-state lighting.

Abstract: Silver nanowires with lenghths of several hundred micrometers and diameters of 90~150 nm were prepared by glucose and Fe3+ in the presence of poly (vinyl pyrrolidone). The results show that the concentration of poly (vinyl pyrrolidone), Fe3+ and AgNO3 are the vital factors to determine the shape of the final products. The growth kinetics of the as-synthesized silver nanowires with high aspect ratios are also discussed in this work. This silver nanowires are expected to form the network used for excellent conductors or electrodes.

Abstract: We demonstrated the fabrication of the flower-like silver nanoplate micro-assemblies in high yields by a facile hydrothermal method. This novel nanostructure was synthesized in the presence of poly (vinyl pyrrolidone) (PVP) and ascorbic acid (AsA) at 150 °C for 10 h. The microassemblies with average size of 1~2 μm are consisted of several uniform nanoplates and show face centered cubic structure. The effects of the concentration of reactants, molar ratio of silver nitrate to ascorbic acid on the formation of the flower-like silver micro-assemblies were also presented.