Carbon dot-based nanocomposite: Long-lived thermally activated delayed fluorescence for lifetime thermal sensing

Temperature sensors with unique temperature-dependent luminescent properties have a great advantage to be used as noncontact luminescence thermometers especially in biological applications . To date, most of the photoluminescent materials for temperature sensing are based on the temperature-dependent luminescent intensity or short-lived emission lifetime, which suffer from the interference from excitation power, sample concentration, or background fluorescence. Herein, we report a carbon dot (CD)-based nanocomposite showing distinct long-lived thermally activated delayed fluorescence (TADF) property with the lifetime of 30.85 ms at room temperature and under an air atmosphere. Notably, the TADF emission presents variable long-lived lifetimes under different temperatures, which demonstrates its promising application in lifetime thermal sensing. The interaction between the functional groups of CD and SiO 2 matrix by forming Si–O–C bonds plays a key role for the synthesis process, which further improves the confinement of vibrations and rotation and harvests the triplet state efficiently. This work introduces a new perspective to prepare nanothermometers, which opens up the potential application of CD-based materials with long-lived TADF emission in highly sensitive temperature sensing with their convenience and high efficiency.