Synthesis And Luminescence Properties Of Several Alkaline Rare Earth Fluoride Ultrasmall Nanocrystals

Rare earth （RE） fluorides including REF₃and A_xRE_yF_z（A=Li, Na, K, Ca, Sr, Ba）,compared with RE oxides, are of low phonon energy (<400cm^-1) and nicephotochemistry stability, so they are considered as the best matrix materials. Atpresent, a cutting-edge research of the RE fluoride nanocrystals is to constructfluorescent bioprobes for fluorescent bioimaging. Relative to semiconductor quantumdots and organic dyes and fluorescent labels, RE fluoride upconversion nanocrystalspresent great advantages due to low damage to biological tissue, lack of backgroundfluorescence, high signal to noise ratio and deep penetration in biological tissues. Inthis master’s thesis, we had studied controllable synthesis of several RE fluoridenanocrystals of which morphology, crystalline size and phase, upconversionproperties can be tuned by varying reaction parameters and lanthanide doping. Theresearch of these nanocrystals can supply theoretical foundation for their applicationsin biolabels. The major contents of this thesis are following:（1） High-quality near-monodisperse Sr₂LaF₇ultrasmall nanocrystals with the sizeof5nm were synthesized via solvothermal method. The crystalline size andupconversion properties can be tuned by varying the reaction parameters. The dosageof NaOH can change the crystalline phase of products and Yb³⁺doping can promotethe synthesis of pure face-centered cubic Sr₂LaF₇nanocrystals of which emissionproperties can be tailored by Yb³⁺/Tm³⁺, Yb³⁺/Er³⁺or Yb³⁺/Tm³⁺/Er³⁺doping.（2） High-qualigy monodisperse SrYbF₅and SrErF₅ultrasmall nanocrystals withface-centered cubic structure were synthesized via solvothermal method. SrYbF₅nanocrystals with the size of10nm can realize intense infrared to infraredupconversion emission by Tm³⁺-doping.（3） High-quality monodisperse Ba₂LaF₇ultrasmall nanocrystals were synthesizedvia solvothermal method. The effects of Er³⁺, Ho3+, Tm³⁺and Yb³⁺doping on theupconversion properties had been systematically discussed, and it has been provedthat Ba₂LaF₇nanocrystals are the host materials with superior performance of anoptical upconversion.