The Influence Of Precursor Ph And Sample Excitation Of The Fluorescence Properties Of Fluoride Nanocrystals

Rare earth (RE) doped nano materials played an important role in the research of luminescence materials. It possesses the good spectroscopy properties of rare earth ions and the excellent quality of nano materials. Therefore, in current research, it is the main rhythm to research the effects of influential factors on luminous properties of rare earth doped nano materials to improve the luminous efficiency. In this dissertation, Eu3+ doped LaF3 nanoparticles and Tm3+ (Yb3+) doped LaF3 or LaOF nanocrystals are prepared by hydrothermal method; the photoluminescent properties of the samples are studied by laser spectroscopy method. The influences of PH values of precursor complexe solution, excitation method, doping behavior, doping concentration and doping matrix on the fluorescence properties are also discussed. There are two parts in this dissertation. In the first part, it introduces that Eu3+: LaF3 nanoparticles were prepared by hydrothermal method with different PH values of precursor complexe solution.The influences of PH values on the Eu3+ fluorescence properties were studied. In the second part, the luminescence properties of Tm3+: Yb3+ doped fluoride was investigated under the excitation with 980 nm and 800 nm. The influence of doping behavioran and doping concentration on the luminescence properties is investigated. The up-conversion luminescence of the Tm3+: Yb3+ doped lanthanide fluoride (LaF3) and fluorine oxide nanoparticles was also studied to discuss the influence of host on the fluorescence intensity.Part one:Europium doped lanthanide fluoride (LaF3) nanoparticles were prepared through a hydrothermal method with different PH values of precursor complexe solution. The influence of PH value on the lumine-scence properties is investigated. It was found that the local symmetry of doped ions reduced with the increase of PH value, leading to the increase of the inversion symmetry ratio. The fluorescence quenching was observed for small nanoparticles, which was attributed to the large amount of OH groups absorbed to the surface of the nanoparticles.Part two:Tm3+ and Tm3+: Yb3+ doped lanthanide fluoride (LaF3) and fluorine oxide nanoparticles were prepared through a hydrothermal method and hydrothermal-sintering. Excited with 980nm and 800nm pulsed laser, the fluorescence of the Tm3+ were observed. The upconversion mechanism of the Tm3+ dopant and Tm3+: Yb3+ co-dopant in lanthanide fluoride (LaF3) and fluorine oxide systems were analyzed under the different excitated light. The influence of Tm3+ and Yb3+ concentration on the luminescence properties is investigated. It was found that The fluorescence increasing was observed with the increase of the Tm3+ concentration when the Yb3+ concentration is fixed. Conversely, the same result was received. A good enhancement of the fluorescence intensity was observed in the LaOF host. Base on theoretical analysis, the change of local crystal field was considered to be the main reason.