Hydrothermal synthesis of monodispersed CePO₄:Tb³⁺ porous microspheres and their redox-responsive luminescence

Monodispersed CePO₄:Tb³⁺ microspheres, which were formed by aggregation of primary nanoparticles, were synthesized by a hydrothermal reaction method assisted with ethylenediaminetetraacetic acid. The microspheres were found to have a hierarchically porous structure as well as a high specific surface area according to structural and chemical analyses. The microspheres exhibited green photoluminescence (PL) due to 4f–4f electronic transitions of Tb³⁺ ions doped in the CePO₄ crystal upon irradiation with ultraviolet light. The microspheres were then treated with an oxidant (potassium permanganate) and a reductant (l(+)-ascorbic acid) in aqueous solutions at room temperature to examine their effect on the PL property. The PL intensity of the microspheres was once decreased by the oxidation and then increased by the reduction. Such the change in the PL intensity was also shown to be quantitative against the concentration of the oxidant and the reductant. Thus the monodispersed CePO₄:Tb³⁺ porous microspheres were demonstrated to be a facile luminescence-sensing material.