Synthesis, structural, and photoluminescence studies of LaF3:Pr, LaF3:Pr@LaF3, and LaF3:Pr@LaF3@SiO2 nanophosphors

LaF3: Pr (core) and LaF3:Pr@LaF3 (core/shell) nanophosphors (NPs) were successfully synthesized by a facile polyol-based co-precipitation process and their surface was modified with silica using sol-gel route. Powder X-ray diffraction pattern revealed a well crystalline hexagonal structure. The TEM images revealed a successful silica surface coating on the surface of core/shell NPs, which was further confirmed by EDX and FTIR analysis. These core and core/shell/SiO2 NPs show good solubility in aqueous and non-aqueous solvent. Optical band gap energy decreased after surface coating as growth of surface shell enhanced the crystallinity of the material. The excitation and emission spectra were measured to investigate the successful doping of luminescent praseodymium in the core matrix. The emission and excitation transitions were greatly enhanced after inert layer coating causing light scattering effect, which reduced the nonradioactive transition rate surrounding the core NPs. It was found that silica surface modification thus improved the solubility and colloidal stability in aqueous and non-aqueous solvent.