Influence of Eu³⁺ on the Structure and Photophysical Properties in (Y,Gd)F₃ Nanophosphors

The scientific community has shown a growing interest in relating to the lanthanide based luminescent materials and it has made an effort to develop them. Among these several luminescent materials, we have proposed to developed (Y,Gd)F₃ nanophosphors doped with distinct of Eu³⁺ concentrations using modified hydrothermal process. The effect of co-doping of rare earth activators to the host lattice structure and morphology are investigated using different analytical techniques. The diffuse reflectance spectra reveal a tuning of optical band gap due to substitutions. From the extensive XPS analysis, Gd and Eu are found to be in a stable ionic state of +3 which is replacing Y³⁺ in YF₃ host. Photoluminescence emission spectra of the nanophosphors are excited by near ultraviolet (UV, 393 nm) excitation. From photoluminescence study, the intensity variation is observed for emission peak at 591 nm and fluorescence quenching occurs at higher doping level. This effect subsequently explained on the frame work of local symmetry and nonradiative transfer among multipole-multipole interaction. At 393 nm excitation Eu³⁺ (2, 3, 5, 7, 10 at %) doped (Y, Gd) F₃ show CIE chromaticity coordinates shifted to red regions with increase in Eu doping levels. Because of the longer decay time these phosphors can be used for bio-labeling and other similar applications.