Electrogenerated Chemiluminescence of Tris(2,2‘-bipyridyl)ruthenium(II) Ion-Exchanged in Nafion−Silica Composite Films

Abstract

The voltammetry and electrogenerated chemiluminescence (ECL) of tris(2,2‘-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) ion-exchanged in Nafion and Nafion−silica composite materials have been investigated. The major goal of this work was to investigate and develop new materials and immobilization approaches for the fabrication of ECL-based sensors with improved reactivity and long-term stability. Nafion−silica composite materials with varying contents of Nafion (53−100 wt % relative to silica) were prepared via the two-step acid/base hydrolysis and condensation of tetramethoxysilane. The Nafion doped sols were spin cast on glassy carbon electrodes, dried, and then ion-exchanged with Ru(bpy)₃²⁺. The shapes of the cyclic voltammetric curves and the amount of Ru(bpy)₃²⁺ exchanged into the films strongly depends on the amount of Nafion incorporated into the hybrid sol. Nafion−silica films with a low content of Nafion ion-exchanged less Ru(bpy)₃²⁺ and exhibited tail-shaped voltammetry at 100 mV/s. The ECL of immobilized Ru(bpy)₃²⁺ in the presence of either tripropylamine or sodium oxalate in pH 5 acetate buffer was also strongly dependent on the amount of Nafion introduced into the composite with greater ECL observed for the Nafion−silica films relative to pure Nafion.