Preparation And Properties Of Tungstate And Silicate Nano Fluorescent Material

Yb³⁺,Er³⁺ co-doped MWO₄(M=Cd,Zn,Ba) nanocrystals and core-shell particles of SiO₂@Zn₂SiO₄:Mn were prepared via a hydrothermal and sol-gel method.The characterization of the materials was performed using Transmission electron microscopy(TEM),X-ray diffraction (XRD),energy-dispersive X-ray spectroscope(EDS) and Fluorescence spectrophotometer.The doping ion,concentration and temperature on their morphology,structure and fluorescence properties were investigated,the possible mechanism were also proposed,the luminescence mechanism was discussed.In the first part of the thesis,the basic knowledge of species and characteristic of the nano materials was introduced;the mechanism of up-conversion fluorescence,preparation method,host material and the application were reviewed emphatically.In the second part of this dissertation,CdWO₄,ZnWO₄ nanorod,BaWO₄ spindle have been synthesized via hydrothermal method.We can observed that doping had an effect on the morphology of CdWO₄,the doping concentrations has an effect on the phase purity of ZnWO₄.From the experiment we can know that CdWO₄:Yb³⁺,Er³⁺ emit green up-conversion fluorescence at 150℃. ZnWO₄:Yb³⁺,Er³⁺ need annealing at 700℃,but CdWO₄:Yb³⁺,Er³⁺ need annealing at 900℃.And the up-conversion mechanism of Yb³⁺,Er³⁺ co-doped tungstate was discussed.In the third parts,using sol-gel process,citric acid and polyethylene glycol as crosslinker prepared SiO₂@Zn₂SiO₄:Mn core-shell structure of fluorescent nanoparticles.The nanoparticles were characterized by XRD and TEM measurement,the result show that the existence of Zn₂SiO₄:Mn layer on the surfaces of silica particles.The green fluorescence was observed under uv excitation.