Comparative Structural, Optical and Luminescent Studies of Aqueous Soluble LaF3:Eu@LaF3@SiO2 Nanoparticles

摘要

LaF3:Eu3+ (core) and LaF3:Eu3+@LaF3 (core/shell) nanoparticles (NPs) have been successfully prepared by a polyol process at low temperature. The crystal structure, phase purity, morphological, thermal, optical, and photoluminescence (PL) properties were systematically investigated using the X-ray powder diffraction pattern, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), ultraviolet-visible absorption spectra and photoluminescence spectroscopy. Distinct surface effects on the structural, optical and luminescent properties of water-soluble core NPs were demonstrated. TEM image indicated the effective encapsulation of silica shell over the core/shell NPs; which was further confirmed by Fourier transform infrared analysis. The surface encapsulated inert LaF3 and amorphous silica layers surrounding the core NPs enlarged the particle size, resulting in a decreased band gap energy because of the quantum confinement effect. The luminescence properties of core NPs were greatly affected after shell formation, owing to nonradiative centers present on their surface. The growth of inert LaF3 and silica layers not only increased the size of the NPs but also significantly enhanced the photoluminescence properties.