One-pot hydrothermal synthesis of dual-emission fluorescent carbon dots for hypochlorous acid detection

In this work, we developed a dual-emission fluorescent carbon dots (CDs) using sodium citrate (SC), triethylenetetramine (TETA) and rose bengal (RB) as raw materials. Under the hydrothermal treatment , the carboxyl group in SC can crosslink with the amino group in TETA to form polymer-like intermediate by amide bond network. The RB molecule, a fluorescein derivative, lost halogen atoms under hydrothermal conditions and integrated with the skeleton structure of the network intermediate. Further dehydration and carbonization resulted in the dual-emission fluorescent CDs. Excited by ultraviolet (UV) light, the CDs exhibited blue and green luminescence centered at 440 nm and 525 nm, respectively. Due to the emission centers of these two colors showed different sensitivity to hypochlorous acid (HClO), we have designed a fluorescence assay to achieve quantitative detection of HClO. Upon addition of different concentrations of HClO to CDs solution in phosphate buffer (pH = 6), the blue emission decreased gradually while the green emission showed only a minimal decrease. By calculating the emission intensity ratio, a good linear relationship was achieved in the range of 0–17 μM, and the limit of detection was as low as 0.75 μM. The results reported here demonstrated a promising way to design organic dye modified CDs for sensing applications.