A novel “off-on-off” fluorescent-nanoprobe based on B, N co-doped carbon dots and MnO2 nanosheets for sensitive detection of GSH and Ag+

In this study, a new “off-on-off” fluorescence strategy for detecting glutathione (GSH) and silver ions (Ag+) is presented. The constructed nanoprobe is composed of B, N co-doped carbon dots (B, N-CDs) and manganese dioxide nanosheets (MnO2 nanosheets), where MnO2 nanosheets serve as a kind of efficient fluorescence quencher. The sensing mechanism of the system is based on the inner filter effect (IFE) and destruction-protection strategy. The assay strategy includes three processes: fluorescence quenching of B, N-CDs by MnO2 nanosheets, the deconstruction of MnO2 nanosheets by GSH, the combination between GSH and Ag+. The MnO2 nanosheets are reduced to Mn2+ because of the addition of GSH and restoring the fluorescence intensity of the system, while the formation of the complex between GSH and Ag+ inhibit the reduction of MnO2 nanosheets on account of the addition of Ag+, leading to the decrease in fluorescence of the probe. This strategy allows the quantitative detection of GSH and Ag+ with detection limit of 0.32 μmol·L−1 and 0.24 μmol·L−1, respectively. Moreover, this approach displays good sensitivity, selectivity and broad linear range, which could be broadly applicable for practical applications.