Redox cycling of iron by carbon dot enhanced chemiluminescence: mechanism of electron–hole induction in carbon dot

The chemiluminescence (CL) of the Fenton system with nitrogen doped carbon dots (N-CDs) was significantly enhanced. The introduction of N-CDs improved the utilization of H2O2 and drastically enhanced the generation of ˙OH, which resulted in enhanced CL emission of the Fenton system through energy and electron transfer processes. The oxidation of N-CDs by ˙OH led to rapid incorporation of oxygen into N-CDs. The mechanism relied on the production of •OH radicals through the Fenton reaction and clearly indicated the important role of peroxide-induced redox cycling of Fe2+ ⇔ Fe3+ in the presence of N-CDs. The CL intensity of the system containing Fe2+ was higher than that containing Fe3+ because the rate of the Fe3+ reaction was much slower than that of the Fe2+ reaction. The CL signal remained constant after some time due to redox cycling, which established equilibrium, irrespective of the form of iron. This study provides a feasible approach to greatly enhance the weak CL of the Fenton system with the introduction of environmentally friendly N-CDs, and initiates an inspiring research in the domain of catalysis, CL and the mechanism of the Fenton system, which will be helpful in various applied research areas.