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 (λ = 510 nm) at pH 7.0 and 648 nm (λ = 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.