Iron Single-Atom Catalyst-Enabled Peroxydisulfate Activation Enhances Cathodic Electrochemiluminescence of Tris(bipyridine)ruthenium(II)

The tris(bipyridine)ruthenium(II) (Ru(bpy)32+)–tripropylamine anodic electrochemiluminescence (ECL) system has been widely applied in commercial bioanalysis. However, the presence of amine compounds in the biological environment results in unavoidable anodic interference signals, which hinder further extensive use of the system. In contrast, the cathodic Ru(bpy)32+ ECL system can overcome these limitations. The Ru(bpy)32+/peroxydisulfate (S2O82–, PDS) ECL system has been extensively employed due to its ability to produce a sulfate radical anion (SO4•–) with strong oxidation ability, which enhances the ECL signal. However, the symmetrical molecular structure of PDS makes it challenging to be activated and causes low luminescence efficiency. To address this issue, we propose an efficient Ru(bpy)32+-based ternary ECL system that uses the iron–nitrogen–carbon single-atom catalyst (Fe–N–C SAC) as an advanced accelerator. Fe–N–C SAC can efficiently activate PDS into reactive oxygen species at a lower voltage, which significantly boosts the cathodic ECL emission of Ru(bpy)32+. Benefiting from the outstanding catalytic activity of Fe–N–C SAC, we successfully established an ECL biosensor that detects alkaline phosphatase activity with high sensitivity, demonstrating the feasibility of practical application.