Novel cathodic electrochemiluminescence of tris(bipyridine) ruthenium(II) on a gold electrode in acidic solution

The novel phenomenon of cathodic electrochemiluminescence on a gold electrode in tris(bipyridine) ruthenium(II) (Ru(bpy)32+) solution is described for the first time. A cathodic electrochemiluminescence (ECL) was found to mainly occur at 0.4–0.8 V with continuous potential scanning from 0.2–1.4 V and the ECL peak was observed around 0.68 V, which was quite different from generally reported Ru(bpy)32+ ECL. Our group speculated that Ru(bpy)32+ possibly reacts with the gold electrode in the acidic phosphate buffer solution (PBS) to generate luminescence. The possible ECL mechanism was discussed according to the presented results. Moreover, it is revealed that the Au as co-reactant in the Ru-system contributed dominantly to the whole ECL . Therefore, the reaction between Ru(bpy)32+ and the newly formed Au implied that the inert metal Au could become a promising material for ECL investigations.