Electrochemiluminescence from tris(2,2′-bipyridyl)ruthenium(II)-graphene-Nafion modified electrode

An electrochemiluminescence (ECL) sensor based on Ru(bpy)₃²⁺-graphene-Nafion composite film was developed. The graphene sheet was produced by chemical conversion of graphite, and was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and Raman spectroscopy. The introduction of conductive graphene into Nafion not only greatly facilitates the electron transfer of Ru(bpy)₃²⁺, but also dramatically improves the long-term stability of the sensor by inhibiting the migration of Ru(bpy)₃²⁺ into the electrochemically inactive hydrophobic region of Nafion. The ECL sensor gives a good linear range over 1 × 10⁻⁷ to 1 × 10⁻⁴ M with a detection limit of 50 nM towards the determination of tripropylamine (TPA), comparable to that obtained by Nafion-CNT. The ECL sensor keeps over 80% and 85% activity towards 0.1 mM TPA after being stored in air and in 0.1 M pH 7.5 phosphate buffer solution (PBS) for a month, respectively. The long-term stability of the modified electrode is better than electrodes modified with Nafion, Nafion-silica, Nafion-titania, or sol-gel films containing Ru(bpy)₃²⁺. Furthermore, the ECL sensor was successfully applied to the selective and sensitive determination of oxalate in urine samples.