Thesis Title

The Effects of Nonionic Surfactants on the Tris(2,2'-Bipyridl) Ruthenium(Ii)-Tripropylamine Electrochemiluminescence System

Date of Graduation

Spring 2000

Degree

Master of Science in Chemistry

Department

Chemistery

Committee Chair

Mark Richter

Subject Categories

Chemistry

Abstract

When oxidized in the presence of tri-n-propylamine (TPA), the molecule Ru(bpy)₃²⁺ (bpy= 2,2'-bipyridyl) undergoes reactions to produce electrochemiluminescence (ECL). In this investigation, the effects of the nonionic surfactants Nonidet P40®, Thesit®, and Triton X-100® were studied. ECL occurs in the Ru(bpy)₃²⁺/TPA system in aqueous solutions with and without surfactants present. An increase in ECL signal (>_8-fold) and duration of the signal (from two seconds to five seconds) occurred in the presence of surfactants. It was also found that the ECL spectra undergo red shifts in the presence of all three nonionic surfactants. The oxidation of Ru(bpy)₃²⁺ occurs at +1.03 V vs. Ag/AgC1 in aqueous buffered (0.2M potassium phosphate) solution as found by square wave voltammetry. This oxidation potential does not change when nonionic surfactants are added to the solution, which suggested that the red shifts in the ECL spectra are caused by a stabilization of the ligand π* orbitals in the metal-to-ligand charge transfer (MLCT) excited state. These results are consistent with the hydrophobic interactions between Ru(bpy)₃²⁺ and the nonionic surfactants. There was no observable change in the fluorescence of Ru(bpy)₃²⁺ in the presence of nonionic surfactants.

Copyright

© Michael Scott Workman

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