The effects of nonionic surfactants on the tris(2,2 '-bipyridyl)ruthenium(II) - Tripropylamine electrochemiluminescence system

The,electrochemistry and electrogenerated chemiluminescence (ECL) of Ru(bpy )(3)(2+) (bpy =2,2'-bipyridyl) were studied in the presence of the nonionic surfactants Triton X-100, Thesit, and Nonidet P40. The anodic oxidation of Ru(bpy)(3)(2+) produces ECL in the presence of tri-n-propylamine in both a queous and surfactant solutions. Increases in both ECL efficiency (greater than or equal to8-fold) and duration of the ECL Signal were observed in sur factant media. A shift to lower energies of the Ru(bpy)(3)(2+) ECL emission by similar to8 nm was also observed. The one-electron oxidation Of RU(bpy) (3)(2+) to Ru(bpy)(3)(2+) occurs at +1.03 Vvs Ag/AgCl in aqueous buffered ( 0.2 M potassium phosphate) solution as found by square wave voltammetry, Th is potential did not shift in surfactant systems, indicating that the redsh ifts: in ECL emission are due to stabilization of ligand pi* orbitals in th e metal-to-ligand charge-transfer excited state. These results are consiste nt with hydrophobic interactions: :between Ru(bpy)(3)(2+) and the nonionic surfactants.