pH-dependent photoluminescence “switch-on” nanosensor composed of silver nanoparticles and nitrogen and sulphur co-doped carbon dots for discriminative detection of biothiols
Very close structure and property similarities among biothiols such as glutathione (GSH), cysteine (Cys), and homocysteine (Hcy), present a major challenge to achieve their discrimination detection. In this contribution, a nanomaterial surface energy transfer (NSET) system was established to discriminate GSH from Cys and Hcy with photoluminescence (PL) “switch-on” response. The nanosensor was constructed by nitrogen and sulphur co-doped carbon dots (N, S-CDs) and silver nanoparticles (AgNPs) through assembling an energy transfer-based quenching system, featuring pH-promoted distinct PL “switch-on” response. Under neutral conditions, only Cys and Hcy can encapsulate AgNPs, leaving little chance for the N, S-CDs binding on the surface of AgNPs, which can lead to the PL signal recovery and the total quantity of the Cys and Hcy can be determined. However, at pH 3.0 all the three kinds of biothiols can lead to the PL signal recovery and the total quantity of GSH, Cys, Hcy can be determined, due to the slopes and intercepts of their calibration curve being similar. Thus, the concentration of GSH could be further calculated and the strategy was successfully applied for the detection of GSH in human serum, demonstrating its potential in bioanalysis and being significant to address biological and medicinal requirements.