Enhancing up conversion luminescence effect of β-NaYF_4: Yb~(3+) and Tm~(3+) by Li~+ ion doped approach

摘要

Up-conversion (UC) is a photoluminescence process which converts few low energy photons to a higher energy photon. This process has more potential usages in many different fields like bioimaging, solar spectrum tuning, and security encoding. Nowadays, researches about UC mostly focusing on biomedical signory and synthesis of nanoparticles. The synthesis of NaYF_4 nanoparticles executed under series of pH value condition results in different morphology and photoluminescence effect. Samples in low pH value created better consequent and quality than the specimen which had higher pH value. In addition, we observed NaYF_4 samples of doping Li~+, realizing that the action of distorting in the local symmetry around rare-earth ions is caused by Li~+ doping. The NaYF_4 microparticles which doped higher concentration of Li~+ has strong fluorescence properties and intensities compared with their corresponding group of Li~+-free, the blue emission 479 nm luminescence intensities and 454 nm luminescence intensities in NaYF_4:Yb~(3+), Tm~(3+) microparticles doped 20 mol% Li~+ are enhanced 3 and 8 times, separately. And violet emission luminescence intensities around 345 and 360 nm are about 10 and 7 times, respectively. The result indicated that the improved UC luminescence of NaYF_4:Yb~(3+). Tm~(3+) microparticles with Li~+ doping have potentially applications.