Co-reactant-on-Demand ECL: Electrogenerated Chemiluminescence by the in Situ Production of S₂O₈²– at Boron-Doped Diamond Electrodes

A novel co-reactant-free electrogenerated chemiluminescence (ECL) system is developed where Ru(bpy) 3 2+ emission is obtained on boron-doped diamond (BDD) electrodes. The method exploits the unique ability of BDD to operate at very high oxidation potential in aqueous solutions and to promote the conversion of inert SO 4 2– into the reactive co-reactant S 2 O 8 2– . This novel procedure is rather straightforward, not requiring any particular electrode geometry, and since the co-reactant is only generated in situ, the interference with biological samples is minimized. The underlying mechanism is similar to that of the Ru(bpy) 3 2+ /S 2 O 8 2– system; however, the intensity of the emitted signal increases linearly with [SO 4 2– ] up to ∼0.6 M, with possible implications for analytical uses of the proposed procedure.