BiPO4:Ln3+ (Ln = Eu, Tb, Eu/Tb) nanorods: Room-temperature synthesis, reaction mechanism, and color-tunable emission

Ln3+ (LnEu, Tb, Eu/Tb) doping hexagonal BiPO4 nanorods were synthesized by a room-temperature co-precipitation method using ethylene glycol as solvent. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy (IR), thermal gravimetric (TG), and photoluminescence spectroscopy (PL) were utilized to investigate the structure, morphology, surface chemistry, and fluorescence performance of the obtained phosphors, respectively. The results showed that hexagonal phase of BiPO4 formed at room temperature, which consisted almost entirely of nanorods with an average diameter of 70 nm and an average length of 292 nm. The chemical reactions mechanism was well elucidated. Under short-wavelength UV light excitation, the as-obtained BiPO4:Eu3+ and BiPO4:Tb3+ samples exhibited strong orange-red and green emissions, respectively. Moreover, the photoluminescence color could be tuned from red, orange, yellow, and green-yellow, to green by simply adjusting the relative doping concentrations of Tb3+ and Eu3+ ions. The room-temperature synthesis reported in the present study could be extended to prepare other rare-earth doped inorganic luminescent materials.