Synthesis and up-conversion photoluminescence properties of uniform monodisperse YbPO4:Ln3+ (Ln3+ = Er3+, Tm3+, Ho3+) hollow microspheres

Uniform monodisperse YbPO4 hollow microspheres have been successfully synthesized via the combination of a facile homogeneous precipitation approach, an ion-exchange process, and a calcination process for the first time. The crystal structure, morphology, and luminescence properties of the as-obtained samples have been characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and up-conversion (UC) luminescence spectroscopy. It is noted that the polystyrene (PS) microspheres essentially determine the shape and structure of the final products. Furthermore, the UC luminescence properties as well as the emission mechanisms of the YbPO4:Ln(3+) (Ln(3+) = Er3+, Tm3+, Ho3+) hollow microspheres were systematically investigated, which show green (Er3+, S-4(3/2), H-2(11/2)-I-4(15/2)), blue (Tm3+, (1)G(4)-H-3(6)) and red (Ho3+, F-5(5)-I-5(8)) luminescence under 980 nm NIR excitation, which provides potential applications in bioanalysis, optoelectronic and nanoscale devices, future color displays and light-emitting devices, and so on.