Multifunctional Carbon Dots for Trace Water Detection, White LEDs, and Bioimaging

Abstract Highly fluorescent, ultrafine CDs were synthesized by a simple one‐pot solvothermal method. The as‐prepared CDs exhibited unique yellow emission and intrinsic fluorescence characteristics independent of excitation wavelengths. We revealed a distinct fluorescence quenching mechanism in the CDs, where the reversible alternation between aggregation and dispersion states can mediate the fluorescence turn‐on and turn‐off response. Therefore, the CDs can be used as a fluorescence nanoswitch for the highly sensitive quantitative detection of trace water in organic solvents. We also demonstrated the applications of the CDs as a stable yellow phosphor and biological probe for white LEDs and biomembrane imaging. Our results suggest that the low‐cost fluorescent material has great promise for practice applications in sensing, bioimaging, and optoelectronic device.