Mesoporous luminescent GdF₃:Tb@LaF₃@SiO₂ nanorods: comparative structural and optoelectronic studies

Terbium doped gadolinium fluoride (GdF₃:Tb) nanorods (core-NRs) subsequently covered by inert LaF₃ and silica shells to form the GdF₃:Tb@LaF₃@SiO₂ core–shell–SiO₂-NRs type structure was synthesized by polyol based co-precipitation and sol–gel process. X-ray diffraction pattern confirmed the crystal structure and grain size of the materials. FETEM, EDX and FTIR spectral studies show the successful amorphous silica surface coating surrounding the core–shell NRs. The reduction in energy band gap from core to core–shell–SiO₂-NRs could be due to increase the crystalline size of the material. In comparison with core-NRs, the excitation and emission efficiency of core–shell-NRs were remarkably increased. This obvious feature is mainly attributed to the formation of the inert LaF₃ layer, which effectively protected Tb³⁺ ion from the surrounding environment. Spectroscopic studies clearly revealed the difference between these three type products. Silica surface modified core–shell–SiO₂-NRs exhibited good dispersibility along with excellent colloidal stability in aqueous and non-aqueous solvents which is the novel character of the highly photostable luminescent nanomaterials. This novel approach of core-NRs coated with passive LaF₃ and silica shell has potential applications in photonic based bio-medical sciences.