Smart YPO₄:Er–Yb Nanophosphor for Optical Heating, Hyperthermia, Security Ink, Cancer Endoradiotherapy, and Uranyl Recovery

A YPO4:Er3+–Yb3+ nanophosphor has been synthesized by a facile coprecipitation method. The photon upconversion has been carried out at 980 nm continuous-wave laser diode excitation. Optical heating performance has been shown via the fluorescence intensity ratio (FIR) technique employed on two thermally coupled emitting levels: 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2. The calculated temperature gain (from ∼28 to 375 °C) under various pump powers is used in the hyperthermia-based medical treatment. The dispersion capability of the synthesized nanoparticles in the liquid reveals their usefulness in the development of security ink. For the first time, it is demonstrated that Er3+/Yb3+ ion codoped YPO4 could be used in the detection of uranyl ions up to a few ppm using the downconversion method. The beta (β) emission study shows its fruitfulness as a radioactive tracer as well as therapy for arthritis treatment. The nanomaterial was radiolabeled with β– emitting radionuclides 90Y [T1/2 = 64.1 h; Eβ(max) = 2.28 MeV] and 177Lu [T1/2 = 6.65 d; Eβ(max) = 497 keV; Eγ = 208 keV (11.0%), 113 keV (6.4%)], and the radiolabeled formulation could be potentially used for delivery of an ionizing radiation dose to a malignant lesion site. Moreover, the hybrid (YPO4:Er3+–Yb3+@Fe3O4) formation with Fe3O4 has also been employed for potential applications in the therapy through hyperthermia heating as well as imaging. This study has shown the potential applications of phosphor in light conversion, optical heating, hyperthermia, security ink, uranyl ion detection, and radioactive labeling.