An “on-off-on” fluorescent nanoprobe for recognition of Cu2+ and GSH based on nitrogen co-doped carbon quantum dots and its logic gate operation

A novel nitrogen co-doped carbon dots (NCDs) were synthesized as a fluorescent “on-off-on” switch for highly sensitive and selective sensing of Cu2+ and glutathione (GSH) by a straightforward pyrolysis route. The as-prepared NCDs exhibited not only highly optical stability but also superior biocompatibility and biolabeling potentials. The “on-off” process was realized by the introduction of Cu2+ on luminescent NCDs, which formed the complex of NCDs-Cu2+ and quenched the fluorescence of NCDs efficiently, and recovered (“off-on”) upon addition of GSH owing to the competitive binding of GSH and Cu2+ that leads Cu2+ to escape from the surface of NCDs. The probe demonstrated high sensitivity and selectivity toward Cu2+ and GSH over other analytes with a low detection limit of 3.62 ×10-4 μM and 6.32×10-4 μM, respectively. Concurrently, an “AND” logic gate has been constructed based on the as-fabricated NCDs. Thanks to the highly intense emission of NCDs, the gradual quenching and restoration of their fluorescence with the addition of Cu2+ and further GSH could also be observed with the naked eye. More importantly, the probe was also extended to cellular imaging. The probe demonstrates high selectivity, repeatability, stability, which offers a promising platform for environmental and biological sensing applications. (Scheme 1.)