Urea-assisted synthesis of AlPO₄:Ce,Tb nanorods as a redox luminescence switch

AlPO₄:Ce,Tb nanorods were synthesized by a facile hydrothermal method. The morphology of rod-like AlPO₄ was tuned by varying urea concentrations, AlPO₄ gradually changed from nanosheets to nanorods, and urea provided hydroxyl anion (OH⁻) in the aqueous solution to prepare the dispersed nanorods under the hydrothermal conditions. The emission intensity of nanorods increased significantly compared to that of nanosheets. AlPO₄:Ce,Tb nanorods provided a novel redox luminescence switch on the basis of the reversible switching of the Ce³⁺/Ce⁴⁺ redox couple. The luminescence is quenched (off) when the system is in the oxidized form while it is restored (on) in the reduced form. The mechanism of the energy transfer and electronic transition between Ce³⁺ and Tb³⁺ in the AlPO₄ nanorods was also discussed. This switch has biocompatibility and low toxicity, and may have a potential application in biomedical diagnostics and analysis.