![]() Crystallized as small discs, 'the products', with an average diameter around 10 nm, showed an increase in the concentration of Tb(3+) ions from surface to the core of nanocrystals. High resolution transmission electron microscopy in connection with energy-dispersive X-ray spectroscopy showed a complex structure of the formed nanocrystals. X-ray diffraction patterns confirmed the trigonal crystal structure of nanocrystals. Spectroscopic studies showed that the differences between these two groups of products resulted from the presence of the SiO2 shell. The properties of and nanocrystals, formed in this way, were investigated. The surface of these core/shell nanocrystals was additionally modified by silica. Their complex structure was formed spontaneously during the synthesis. Terbium fluoride nanocrystals, covered by a shell, composed of cerium fluoride were synthesized by a co-precipitation method. The core/shell NCs exhibited long fluorescence lifetime and high photostability under ultraviolet radiation. The surface modifications for YVO4: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 Eu3+ ions and surface Eu3+ ions. ![]() 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. 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. Their morphologies, structures, components, and photoluminescence properties were investigated and presented in this paper. YVO4:Eu, and YVO4:Eu/SiO2 nanocrystals (NCs) were prepared by hydrothermal method with citrate as capping ligands. ![]()
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