Green fluorescent carbon quantum dots as a label-free probe for rapid and sensitive detection of hematin

Hematin is an oxidized form of heme, and the abnormal levels of hematin in the human body can lead to various inflammatory lesions. Hence, there is still a need to establish a rapid, sensitive and efficient method for hematin detection. Herein, the green fluorescent carbon quantum dots (CQDs) are synthesized by using L-cysteine and hydrogen peroxide as precursors. The synthesized CQDs exhibit some fascinating characters including excellent water solubility, high fluorescence quantum yield, and good stability in a broad pH range of 7.0–11.0 and high ionic strength solution. Excitingly, the fluorescence of CQDs can be rapidly and selectively quenched by hematin via the inner filter effect. Moreover, the detection of hematin by the CQDs fluorescent probe shows a good linearity in the concentration range of 0.5–30 μM with a minimum detection limit of 0.1 μM. Finally, the proposed approach is successfully applied to detect hematin in human blood samples.