A Eu/Gd-mixed metal-organic framework for ultrasensitive physiological temperature sensing

A series of Eu/Gd-mixed metal-organic frameworks Eu_xGd_1-xNDC (x = 0.0005, 0.001, 0.003, 0.01; H₂NDC = 1,4-naphthalene dicarboxylic acid) utilizing back energy transfer have been developed for physiological temperature sensing. The suitable high triplet level of H₂NDC allows an efficient back energy transfer from Eu³⁺ ions to ligands. The back energy transfer efficiency is further enhanced by the Eu³⁺/Gd³⁺-mixed strategy. As a consequence, the emission of Eu³⁺ dramatically weakens when temperature arises. The resultant Eu_0.0005Gd_0.9995NDC exhibits exceptional stability and good biocompatibility, and can detect physiological temperature in single-emission, dual-emission, and colorimetric models with ultra-high sensitivity.