Solid-state electrogenerated chemiluminescence from gel-entrapped ruthenium(II) tris(bipyridine) and tripropylamine

A navel approach for the electrogeneration of stable light emission in a solid host; structure under room conditions is. described. In this work, the chemiluminescent precursors, ruthenium(II) tris(bipyridine) (Ru(bpy)(3)(2+)) and tripropylamine (TPA), were trapped in a porous silicate host matrix along with an electrode assembly. When the electrode potential was scanned or stepped to a potential sufficient to oxidize gel-entrapped TPA and RU(bpy)(3)(2+), electrochemiluminescence (ECL) was observed. The solid-state ECL spectrum was identical to the fluorescence spectrum of gel-entrapped Ru(bpy)(3)(2+). The intensity of the emission depends on the amount of TPA and RU(bpy)(3)(2+) in the gel as well as the size of the electrode. When an ultramicroelectrode (microband or microdisk) was used to generate the ECL, the resultant emission was found to be remarkably stable. Little drop in intensity was observed upon continuous application of ca. 1.2 V for 2-12 h. In direct contrast, the ECL dropped significantly at a large electrode (e.g., r = 1.1 mm) in a relatively short period of time. The improved stability of the ECL at ultramicroelectrodes can be attributed not only to their small size, which results in a decreased consumption of TPA, but also to the steady-state flux of reagents to the electrode surface.