Pyrrolic nitrogen dominated the carbon dot mimic oxidase activity

Carbon dots (CDs) with enzyme-like activities play crucial roles in nanobiotechnology. However, it is difficult to establish a relationship between their structure and biocatalytic properties. In this work, a series of nitrogen-doped carbon dots (TA-NCDs) were synthesized by a hydrothermal method. Their oxidase-like activity could be triggered by visible light irradiation (420 nm≤λ ≤ 700 nm). As a nanozyme, TA-NCDs show the value of maximum reaction rates (Vmax) is 121.95 × 10−8 M/s and the Michaelis–Menten constants (Km) is 0.61 mM. In situ transient photovoltage (TPV) tests prove that the pyrrolic nitrogen in TA-NCDs is the catalytic active sites and substrate binding sites. Under visible light irradiation, TA-NCDs, with oxidase-like activity, increased the cellular ROS level significantly, leading to their visible light induced bioactivity to kill nearly 60% of HeLa cells.