Nitrogen and bromine co-doped carbon dots with red fluorescence for sensing of Ag+ and visual monitoring of glutathione in cells

Carbon dots (CDs) with red fluorescence emission have excellent advantages in cell imaging. Herein, novel nitrogen and bromine doped CDs (N,Br-CDs) were prepared with 4-bromo-1,2-phenylenediamine as precursor. The N, Br-CDs present the optimal emission wavelength at 582 nm (λex = 510 nm) at pH 7.0 and 648 nm (λex = 580 nm) at pH 3.0 ∼ 5.0, respectively. The fluorescence intensity of N,Br-CDs at 648 nm versus Ag+ concentration shows a good relationship from 0 to 60 μM with the limit of detection (LOD) of 0.14 μM. Furthermore, the fluorescence of N,Br-CDs/Ag+ is efficiently restored via the combination of glutathione (GSH) and Ag+ and linearly changes with GSH concentration from 0 ∼ 6.0 μM with LOD of 49 nM. This method has been successfully employed to monitor intracellular Ag+ and GSH with fluorescence imaging. The results suggest that the N,Br-CDs has application potential in the sensing of Ag+ and visual monitoring of GSH in cells.