A highly precise temperature-feedback photothermal therapy platform in deep tissue is proposed based on all-fiber fluorescence intensity ratio (FIR) thermometry, which provides a promising route to realize real-time temperature monitoring in the minimally invasive treatment of tumors. Highly disordered double perovskite Li2Zn2Mo3O12 (LZMO) phosphors doped with rare earth ions were prepared and intense green upconversion emissions were observed with an ultra-low excitation power. The thermal enhancement of the upconversion luminescence was achieved up to 423 K, which is very beneficial to achieve a good signal-to-noise performance during the temperature-rise period. Superior temperature sensing performance was demonstrated with the maximum absolute sensitivity of 89.9 × 10-4 at 423 K. The strong upconversion emissions and high temperature sensitivity result in a small temperature error (±0.4 K). The integrated bifunctional needle could simultaneously realize temperature measurement and laser heating, which was exhibited in the denaturation of egg white and laser ablation of the porcine liver in vitro.
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