Simple Postsynthesis Thermal Treatment toward High Luminescence Performance of Rare Earth Vanadate Nanoparticles

Simple heat treatment of rare earth vanadatenanoparticlespromotes crystalline enhancement through intraparticle reconstruction,enabling high-performance luminescent systems. Optical applications of colloidal oxide nanoparticlesare oftenlimited by low luminescence efficiencies caused by poor crystallinityand surface quenching. Bulk oxides prepared via conventional high-temperatureannealing offer intense luminescence but commonly fail to yield stablecolloidal dispersions. Coupling the best of these two situations toafford highly crystalline, dispersible nanoparticles with luminescenceperformance exceeding that of bulk solids is still challenging, thusrequiring new, safe, scalable, and reproducible methodologies. Herein,we report a silicate-coating strategy followed by aggregate eliminationto recover stable colloids of 40-150 nm single crystallinerare earth vanadates after unprotected annealing (800-1000 & DEG;C). Eu3+-doped nanoparticles showed enhanced photostabilityand & SIM;50% emission quantum yields in water (& lambda;(exc) = 280 nm), while Dy3+-, Tm3+-, and Yb3+/Er3+-doped vanadates provided remarkably intensemulticolor emissions via downshift or upconversion luminescence. Wecorrelated the spectroscopic properties of pristine and annealed solidsto microstructural characteristics to explain the superior emissionfeatures, opening new perspectives for sensing applications.