Photoluminescence of colloidal YVO4:Eu/SiO2 core/shell nanocrystals

YVO4:Eu, and YVO4:Eu/SiO2 nanocrystals (NCs) were prepared by hydrothermal method with citrate as capping ligands. Their morphologies, structures, components, and photoluminescence properties were investigated and presented in this paper. A remarkable fluorescence enhancement up to 2.17 times was observed in colloidal YVO4:Eu/SiO2 NCs, compared to that of colloidal YVO4:Eu NCs. This is mainly attributed to the formation of the outer protecting layers of biocompatible SiO2 shells; which shield the Eu3+ ions effectively from water and thus reduces the deleterious effects of water on the luminescence. Meanwhile, on the basis of laser selective excitation, two kinds of luminescent centers were confirmed in the NCs, namely, inner Eu3+ ions and surface Eu3+ ions. The surface modifications for YVO4:Eu NCs effectively reduced the surface defects and accordingly enhanced the luminescence. The core/shell NCs exhibited long fluorescence lifetime and high photostability under ultraviolet radiation.