Fluorescent Lignin Carbon Dots for Reversible Responses to High-Valence Metal Ions and Its Bioapplications

A sensitive and reversible sensing platform based on fluorescent carbon dots (CDs) allowing capture and detection of metal ions is of significance for developing diagnostic probes and in-situ environmental-monitoring. Here, a simple and effective method for converting biomass lignin into fluorescent CDs is developed. The obtained CDs, with stable fluorescence and excellent water solubility, are fabricated as unique model biosensors to access the metal-induced quenching mechanism. It is demonstrated that selective fluorescence quenching behaviors of lignin CDs are firstly found related to the valence-state of metal ions. Moreover, a reversible control of CDs fluorescence is realized by introducing reducing agents. This novel biosensor and the approach to quenching mechanism may evoke new insight in designing ions-sensor and monitoring biologic redox signal.