“ON–OFF–ON” fluorescent probes based on nitrogen-doped carbon dots for hypochlorite and bisulfite detection in living cells

Abstract

Although hypochlorite (ClO⁻) and bisulfite (HSO₃⁻) play important roles in the biological immune system and the aging process of living organisms, they are also classified as a third type of carcinogens. Hence, a convenient and efficient method to monitor ClO⁻ and HSO₃⁻ in ecological environments is highly desired. In this article, an “ON–OFF–ON” fluorescent probe based on nitrogen-doped carbon dots (N-CDs) for the detection of ClO⁻ and HSO₃⁻ has been demonstrated successfully. Because of the destruction of the surface passivation layer, the fluorescence of the N-CDs was quenched by ClO⁻. Furthermore, the quenched fluorescence of the N-CDs was restored efficiently through the increase in conjugation from the attached sulfo groups, indicating the feasibility of ClO⁻ and HSO₃⁻ detection. This fluorescent probe exhibited excellent sensitivity and selectivity to ClO⁻ and HSO₃⁻ detection with the limits of detection (LODs) of 3.4 μM and 0.27 μM in aqueous solution, respectively. In addition, the as-prepared N-CDs were successfully applied to detect both ClO⁻ and HSO₃⁻ in living cells due to their low toxicity and fast response speed.