Electrogenerated chemiluminescence (ECL) 79.

Hydrogen peroxide (H2O2) can be used as a coreactant to generate reductive-oxidation ECL of Tris(2,2′-bipyridine)ruthenium(II), Ru(bpy)32+ (bpy = 2,2′-bipyridine), in pH 7.5 phosphate buffer solution (PBS). Although Ru(bpy)3+ is adsorbed and precipitated on the electrode upon reduction of Ru(bpy)32+ in aqueous solutions, ECL can still be generated and scanning electrochemical microscopy (SECM) experiments verified the presence of some dissolved Ru(bpy)3+ in the solution. When H2O2 is electrochemically reduced, it produces hydroxyl radical (OH). ECL is generated by an energetic electron transfer (ET) reaction between Ru(bpy)3+ and OH. The ECL intensity depends on both the Ru(bpy)32+ and H2O2 concentrations. However, a relatively high concentration of H2O2 (>1 mM H2O2 with 0.1 mM Ru(bpy)32+) quenches ECL significantly. H2O2 also quenches the photoluminescence of Ru(bpy)32+ with a quenching rate constant of 5.7 × 106 M−1 s−1.