Photoluminescence properties of core-shell SiO$_2$/Lu$_2$O$_3$ : Eu monodisperse heteronanoparticles

Core-shell monodisperse heteroparticles of the composition SiO$_2$/Lu$_{1.86}$Eu$_{0.14}$O$_3$ have been synthesized using the developed technique for preparing spherical colloidal silicon dioxide particles with the size dispersion in the range 2.0–2.5% and the procedure for producing nanocoatings on the surface of spheres by codeposition. The structure of heteroparticles has been investigated, their excitation and photoluminescence spectra have been analyzed, and the lifetime of the $^5D_0$ excited state of Eu$^{3+}$ ions has been examined. It has been revealed that the luminescence decay time for heteroparticles increases by a factor of approximately two compared to that for a powdered luminophor Lu$_2$O$_3$: Eu (7 at%) prepared and treated under the same temperature conditions as the SiO$_2$/Lu$_2$O$_3$: Eu (7 at%) heteroparticles. This effect has been attributed to the change in the effective refractive index and the local density of photon states in luminophor nanolayers of heteroparticles.