Electrogenerated chemiluminescence (ECL) 79. Reductive-oxidation ECL of tris(2,2'-bipyridine)ruthenium(II) using hydrogen peroxide as a coreactant in pH 7.5 phosphate buffer solution

Hydrogen peroxide (H2O3) can be used as a coreactant to generate reductive-oxidation ECL of Tris(2,2'-bipyridine)ruthenium(II), Ru(bpy)(3)(2+) (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)3 2, 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 H2O3 is electrochemically reduced, it produces hydroxyl radical ((OH)-O-center dot). ECL is generated by an energetic electron transfer (ET) reaction between Ru(bpy)(3)(+) and (OH)-O-center dot. The ECL intensity depends on both the Ru(bpy)(3)(2+) and H2O, concentrations. However, a relatively high concentration of H2O3 (> 1 mM H2O2 with 0.1 mM Ru(bpy)(3)(2+)) quenches ECL significantly. H2O2 also quenches the photoluminescence of Ru(bpy)3 21 with a quenching rate constant of 5.7 x 10(6)M(-1) S-1. (c) 2004 Elsevier B.V. All rights reserved.