Nafion - Tris(2-2'-bipyridyl)ruthenium(II) ultrathin Langmuir - Schaefer films: Redox catalysis and electrochemiluminescent properties

A simple procedure to incorporate tris(2-2'-bipyridyl)ruthenium(II), [Ru(bPY)(3)](2+), into Nafion Langmuir-Schaefer (LS) films is described. Nafion LS films (tens of nanometers thick) were formed on quartz glass and indium tin oxide (ITO) directly from Nafion-[Ru(bPY)(3)](2+) Langmuir films assembled at the water-air interface. This procedure allowed the direct incorporation of [Ru(bPY)(3)](2+) into Nafion films without the need for subsequent loading. UV-vis spectroscopy confirmed the successful incorporation of [Ru(bPY)(3)](2+) within the LS films and showed that the amount of [Ru(bPY)(3)](2+) immobilized in this way scaled with film thickness. Voltammetric studies on ITO-modified electrodes confirmed the successful incorporation of [Ru(bPY)(3)](2+) and demonstrated that [Ru(bPY)(3)](2+) was retained within the ultrathin films over a long time scale. These electrodes were tested for the electrocatalytic reduction of tripropylamine. Significant catalysis was observed due to the rapid turnover of [Ru(bPY)(3)](2+/3+) between the electrode surface and outer boundary of the film, as a direct consequence of the ultrathin film dimensions. Concomitant electrochemiluminescence (ECL) was demonstrated highlighting the potential of this material for sensing applications.