The Study Of Synthesis And Luminescence Properties Of Alkaline Rare Earth Fluoride Nanocrystals

Lanthanide （Ln） doped UC nanocrystals are widely used in laser, color display,biological molecules detection, cell imaging, solar cells, NMR developer andscintillator various specific field due to their multiple characteristics such as narrowluminescence band, high color purity, sharp optical absorptivity, low phonon energyand high conversion efficiency. Especially, potential application in biomedicine hasmade these nanocrystals attract much attention in recent years. Owing to the uniqueUC property, converting low energy irradiation to high energy emissions, thelanthanide doped UC nanocrystals have many unique advantages in biomedicalimaging, including deep penetration owing to the excitation of NIR light, lowradiation damage, and weak auto-fluorescence, compared with the conventionalfluorescent nanomaterials such as organic dyes and quantum dots. It is well knownthat the properties of nanocrystals depend highly on their phase, size, and shape.However, there are many factors affecting crystal growth, mainly including reactiontime, temperature, PH of reaction environment and ratio concentration of reactionprecursor. In order to explore the evolution law of phase, size, and shape ofnanocrystals and the influence of phase, size, and shape on UC luminescence property,Ba_xYb_1-xF_3-xnanocrystals are synthesized and studied systematically the evolution lawof phase, size, shape and luminescence property of nanocrystals. The maincontentsare listed as follows:1. Monodisperse Ba_xYb_1-xF_3-x:1%Er NCs with different proportion of thereaction precursor Ba²⁺and Yb³⁺are synthesized by a solvothermal method. Whenother experiment parameters are constant, the evolution laws of phase, size and shapeof as-synthetized nanocrystals are studied by varying ratio of reaction precursor Ba²⁺and Yb³⁺. The influence of Yb³⁺concentration, phase, size and shape etc. onupconversion emission property of Ba_xYb_1-xF_3-xnanocrystals is studied by dopingEr³⁺.2. Monodisperse Ba_xYb_1-xF_3-xNCs with fixed proportion of the reactionprecursor Ba²⁺and Yb³⁺(Ba²⁺:Yb³⁺=0.2:0.8) are synthesized by a solvothermalmethod. Formation mechanism of nanocrystals is studied and shape and size ofBa_xYb_1-xF_3-xnanocrystals is controlled effectively by varying experiment parameterssuch as the reaction time, PH value of the reaction environment and F-concentration.Finally, upconversion luminescence property and luminescence mechanism of nanocrystals are also discussed by doping different Ln³⁺ions such as Er³⁺, Ho³⁺andTm³⁺, and the multi-color upconversion luminescence is achieved.3. Monodisperse Ba_xYb_1-xF_3-xNCs with fixed proportion of the reactionprecursor Ba²⁺and Yb³⁺(Ba²⁺:Yb³⁺=0.7:0.3) are synthesized by a solvothermalmethod. The evolution laws of size and shape of Ba_xYb_1-xF_3-xnanocrystals are studiedby varying other experiment parameters such as the reaction time, PH value of thereaction environment and F-concentration. The upconversion emission colorsincluding red, green, blue and white are achieved through doping different Ln³⁺ionssuch as Er³⁺, Ho³⁺and Tm³⁺. In addition, upconversion mechanism of variousluminescence is studied by energy level transition.