Tb3+-doped lanthanide phosphate nanoparticles: crystal structure, optical and luminescent properties

Tb3+-ion-doped metal phosphates (YPO4, LaPO4, CePO4 and GdPO4) nanoparticles (NPs) were synthesized by a urea-supported thermal decomposition method. A comparative analysis was presented to inspect the influence of the host lattice on crystal structure, optical and luminescent properties of the doped Tb3+ ion. X-ray diffraction (XRD) results show the rhabdophane-type hexagonal phase of all lanthanide phosphate (LnPO(4)) NPs with an average particles size 12.8, 14.9, 18 and 19.5 nm for the YPO4:Tb, LaPO4:Ce/Tb, CePO4:Tb and GdPO4:Tb NPs, respectively. Fourier transforms infrared (FTIR) spectra illustrated the characteristics of crystal and surface build phosphate (PO43-) ion and hydroxyl (OH) vibrational modes, respectively. Absorption spectra were measured to determine the aqueous dispersibility, colloidal stability and charge transfer absorption transitions of the host and guest ions. The absorption edge and bandgap energies were greatly affected in Ce3+-ion-containing NPs because of the high absorbance in the visible region. Upon irradiation of all samples from the similar ultraviolet range 368 nm, the emission efficiency of the D-5(4)-> F-7(5) of the YPO4:Tb NPs was the least, whereas LaPO4:Ce/Tb NPs exhibited the largest emission and excitation efficiency, because of the proficient energy transfer amid the co-doped absorber Ce3+ and emitter Tb3+ ions. These observed findings are highly beneficial in the development of the most efficient photonic-based material for their multipurpose uses.