Multifunctional Thermally Activated Delayed Fluorescence Carbon Dots for Temperature‐Responsive Sensor, Information Encryption, and Organelle Imaging

Thermally activated delay fluorescence (TADF) has great potential for information encryption, temperature detection, and bioimaging due to its long‐lived luminescence, temperature‐sensitive and high signal‐to‐noise ratio. However, it is still a challenge to establish TADF in aqueous environments. In this study, the composite with TADF (M‐FNCDs) is prepared using fluorine‐nitrogen co‐doped carbon dots (FNCDs) and melamine. It is worth mentioning that the M‐FNCDs show stable TADF under long‐wavelength excitation (470 nm) in aqueous environments. Moreover, the M‐FNCDs has distinctive temperature‐responsive properties and exhibit good linear relationships in the temperature range of 77–370 K. Simultaneously, M‐FNCDs suspension as the ink is utilized to realize information encryption/decryption due to their afterglow cannot be quenched in an aqueous solution. More importantly, M‐FNCDs with biocompatibility can target the mitochondria and lysosomes of living cells, and for the first time achieve the high signal‐to‐noise ratio and low background signal afterglow imaging of organelles. This work proposes a new strategy to prepare the stable TADF in aqueous solutions under long‐wavelength excitation and extend the TADF material potential applications in the future.