| Abstract
| - The electrogenerated chemiluminescence (ECL) of Ru(bpy)32+ and tripropylamine, tributylamine, triethylamine,trimethylamine, or sodium oxalate encapsulated withinsol−gel-derived silica monoliths have been investigatedusing an immobilized ultramicroelectrode assembly. Themajor purpose of this study was to investigate the role ofthe reductant on the magnitude and stability of the ECLin this solid host matrix. For gel-entrapped Ru(bpy)32+/tertiary amines, the shape and intensity of the ECL−potential curves were highly dependent on scan rate. At10 mV/s, the ECL intensity was ca. 6-fold higher relativeto that observed at 500 mV/s. When the ECL acquired atlow scan rates was normalized by that obtained in solutionunder similar conditions, a value of 0.03−0.06 wasobtained. In direct contrast, the ECL of the Ru(bpy)32+-oxalate system showed little dependence on scan rate, andthe ECL was ca. 65−75% of that measured in solution.These differences can be attributed to differences inrotational and translational mobility between the reductants (amines vs oxalate) trapped in this porous solid host.For both systems, the ECL was found to be stable uponcontinuous oxidation or upon drying the gels in a high-humidity environment for over 10 days.
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