Synthesis features of Li<i>R</i>F₄ (<i>R</i> = Er–Lu) nanoparticles by the high-temperature co-precipitation method and their photoluminescent properties

Abstract

Nanoparticles of LiRF4 (R = Y, Yb, Lu), activated with Yb3+/Er3+ and Yb3+/Tm3+ ions, were obtained by the high-temperature co-precipitation method. The influence of the precursor molar ratio and the cationic composition of matrices on their dimensionality and morphology was studied. A method for the heterogeneous crystallization of these compounds using LiYF4 nanoseeds was optimized, which opens up opportunities for controlled synthesis of LiRF4 nanoparticles with controllable characteristics. Among the studied objects, LiYF4@LiYbF4:Tm3+@LiYF4 nanoparticles demonstrate the most intense anti-Stokes photoluminescence in the UV (λ = 362 nm) and blue (λ = 450 nm) ranges, exceeding similar indicators for β-NaYF4:Yb3+/Tm3+@NaYF4 particles. LiYF4@LiLuF4:Yb3+/Er3+@LiYF4 nanoparticles are the most efficient converters of IR radiation in the λ = 1530 nm range among the investigated isostructural matrices and exhibit similar spectral-luminescent properties to the β-NaYF4:Yb3+/Er3+@NaYF4 compound with an equivalent degree of codoping. The obtained results allow considering LiYF4@LiYbF4:Tm3+@LiYF4 and LiYF4@LiLuF4:Yb3+/Er3+@LiYF4 nanoparticles as a real alternative to the most widely used phosphors based on the hexagonal matrix β-NaYF4 for photonics and biotechnology applications.