Chemiluminescence (CL) of Fenton system was significantly enhanced by nitrogen doped carbon dots (N-CDs) and investigated in detail. The introduction of N-CDs into the Fenton system obviously improved the H2O2 utilization efficiency and drastically enhanced the generation of •OH which resulted in enhanced CL emission from Fenton system. Detailed studies show that the enhanced CL was due to excited N-CDs which was produced through energy and electron transfer processes. Indeed, oxidation by H2O2 led to rapid incorporation of oxygen to N-CDs. This mechanism would rely on production of •OH radicals through Fenton reaction. The results clearly indicated the important role of peroxide-induced redox cycling of Fe2+/Fe3+ in presence of N-CDs. This is interpreted to be due to peroxide-induced autoxidation of Fe2+ which will cause back-reaction of the produced Fe3+ to Fe2+ and vice versa. The CL intensity of system containing Fe2+ was higher than Fe3+ because the rate of Fe3+ reaction was much slower than Fe2+ reaction. The CL signal remained constant after sometime due to redox cycling to establish equilibrium, irrespective to any form of iron.

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