EQCM study of the ECL quenching of the tris(2,2 '-bipyridyl)ruthenium(II)/tris-n-propylamine system at a Au electrode in the presence of chloride ions

Shijun Wang, University of Southern Mississippi
Wujian Miao, University of Southern Mississippi


Significant effect of chloride ions on the electrogenerated chemiluminescence (ECL) behavior of the ruthenium(II)tris(2,2'-bipyridine) (Ru(bPY)(3)(2+))/tri-n-propylamine (TPrA) system at a Au electrode was reported. At low concentrations (e.g., vertical bar Cl(-)vertical bar < 5 mM), the ECL was enhanced; at relatively high concentrations, however, the ECL intensity decreased with the increase of the vertical bar Cl(-1)vertical bar. At vertical bar Cl(-)vertical bar = 90mM, similar to 50% and 100% ECL inhibition was observed for the first and the second ECL wave, respectively. The electrogenerated gold-chloride complexes (AuCl(2)(-) and AuCl(4)(-)) Which were verified using an electrochemical quartz-crystal microbalance (EQCM) method were found to be responsible for the ECL inhibition. This study suggests that care must be taken when a Au working electrode is used for ECL studies in chloride-containing buffer solutions (widely used in DNA probes) and/or with the commonly used chloride-containing reference electrodes since in these cases the ECL behavior may significantly disagree with that obtained using other electrodes and reaction media. (c) 2008 Elsevier Ltd. All rights reserved.