Other methods such as microwave irradiation, microemulsion have also been adopted in the preparation of colloidal YVO 4:Eu NCs. obtained different rare-earth ions doped colloidal YVO 4 NCs with the size range from 10 to 30 nm via hydrothermal method. achieved transparent aqueous dispersions of 10 nm sized YVO 4:Eu NCs based on the aqueous precipitation reaction by the addition of a citrate ligand. Recently, considerable efforts have been devoted to develop the different synthesis methods for preparation of luminescent colloidal YVO 4:Eu NCs. The Eu 3+-activated Yttrium orthovanadate (YVO 4), a well-known rare-earth (RE) doped inorganic luminescent materials, has been used as an important commercial red phosphor owing to its high luminescence efficiency on electron-beam excitation since 1964. The core/shell NCs exhibited long fluorescence lifetime and high photostability under ultraviolet radiation. The surface modifications for YVO 4:Eu NCs effectively reduced the surface defects and accordingly enhanced the luminescence. Meanwhile, on the basis of laser selective excitation, two kinds of luminescent centers were confirmed in the NCs, namely, inner Eu 3+ ions and surface Eu 3+ ions. This is mainly attributed to the formation of the outer protecting layers of biocompatible SiO 2 shells which shield the Eu 3+ ions effectively from water and thus reduces the deleterious effects of water on the luminescence. A remarkable fluorescence enhancement up to 2.17 times was observed in colloidal YVO 4:Eu/SiO 2 NCs, compared to that of colloidal YVO 4:Eu NCs. Their morphologies, structures, components, and photoluminescence properties were investigated and presented in this paper. YVO 4:Eu, and YVO 4:Eu/SiO 2 nanocrystals (NCs) were prepared by hydrothermal method with citrate as capping ligands.
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