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. The M-FNCDs with stable TADF in the aqueous solution are successfully prepared and they show good biocompatibility, strong organelle targeting and sensitive temperature-responsive properties. Based on the above properties, M-FNCDs are used in the fields of temperature sensors, information encryption and organelle afterglow imaging. image