808 nm Light-Triggered Thermometer–Heater Upconverting Platform Based on Nd³⁺-Sensitized Yolk–Shell GdOF@SiO₂

The realization of real-time and accurate temperature reading at subcutaneous level during the photothermal therapy (PTT) could maximally avoid the collateral damages induced by overheating effects, which remains a formidable challenge for biomedical applications. Herein, 808 nm light-driven yolk–shell GdOF:Nd 3+ /Yb 3+ /Er 3+ @SiO 2 microcapsules were developed with thermal-sensing and heating bifunctions. Under 808 nm excitation, sensitive thermometry was implemented by monitoring thermoresponsive emission from 2 H 11/2 / 4 S 3/2 levels of Er 3+; meanwhile, the addition of Nd 3+ with rich metastable intermediate levels and the yolk–shell configuration with large specific surface area triggered efficient light-to-heat conversion via enhanced nonradiative channels. The potentiality of dual-functional samples for controlled subcutaneous photothermal treatment was validated through ex vivo experiments, and the antibacterial activity against Escherichia coli was also elaborately evaluated. Results open a general avenue for designing and developing upconverting platforms with sensitive thermal-sensing and efficient heating bifunctions, which makes a significant step toward the achievement of real-time controlled PTT.