Impregnation of Ce³⁺ in YPO₄ Lattice for Enhanced Green Emission for Biomedical Applications

Green light-emitting YPO4:Tb3+ and YPO4:Tb3+: Ce3+ nanoparticles were synthesised at low temperatures using the polyol method. The phase purity, micromorphology and luminescence characteristics were studied using Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier Transfer Infrared absorption spectroscopy (FT-IR) and Photoluminescence spectroscopy (PL). Combined XRD and TEM analysis showed that the YPO4 nanoparticles crystallised into a single phase of tetragonal (I41/amd) structure. For all samples, the emission intensity at λem=543 nm assigned to 5D4→7F5 is more prominent than 5D4→7F6 with a maximum at λem=488 nm, and the asymmetric ratio was calculated and analysed. The asymmetric ratio is strongly correlated with the symmetry around the local environment of Tb3+ ions. A significant increase in the asymmetric ratio is observed with an increase in annealing temperature. The energy transfer from Ce3+ ions to Tb3+ ions was tested by studying the photoluminescence properties of YPO4:Tb3+ and YPO4:Tb3+: Ce3+ nanoparticles and how it results in the improvement of the luminescence intensity. The Ce3+5d−4f and Tb3+5D4→7FJ (J = 6 − 3) transitions were observed.