Cathodic electrochemiluminescence and reversible electrochemistry of [Ru(bpy)3](2+/1+) in aqueous solutions on tricresyl phosphate-based carbon paste electrode with extremely high hydrogen evolution potential.

Many cathodic electrochemiluminescence (ECL) systems require very negative potentials; it is difficult to achieve stable cathodic ECL in aqueous solutions because of hydrogen evolution and instability of intermediates. In this study, tricresyl phosphate-based carbon paste electrode (CPE) was used to achieve cathodic ECL. It exhibits no obvious hydrogen evolution even at a potential up to -1.6 V and dramatically stabilizes electrogenerated [Ru(bpy)3](+). Therefore, a reversible wave of [Ru(bpy)3](2+/1+) in aqueous solutions at carbon electrode has been observed for the first time, and cathodic ECL of [Ru(bpy)3](2+)/S2O8(2-) has been achieved. Under the optimum conditions, the plots of the ECL versus the concentration of S2O8(2-) are linear in the range of 10(-6) to 10(-2) M with the detection limit of 3.98 × 10(-7) M. Common anions have no effect on the ECL intensity of the [Ru(bpy)3](2+)/S2O8(2-) system. Since CPEs have been widely used, CPEs with high hydrogen evolution potential are versatile platforms for electrochemical study and cathodic ECL study.