Electrochemiluminescence of Ru(bpy)(3)(2+) loaded in Nafion Langmuir-Blodgett films: Role of the interfacial ultrathin film

Electrochemiluminescence (ECL) of Ru(bpy)2 3+ immobilized at Nafion modified electrodes prepared by the Langmuir–Blodgett (LB) technique is studied in the presence of tri-n-propylamine (TPrA). A significant dependence of electrochemical and luminescence signals on the number of Nafion-LB layers is evidenced. The study of the dependence of light emission as a function of the pH, indicates that the maximum emission occurs at pH 8. The competition between Ru(bpy)2 3+ and the protonated TPrA for the ion-exchange sites of Nafion can determine whether the light emission occurs inside the LB coatings, at the coating/ solution interface or in the solution phase. Finally it is demonstrated that the control of the number of LB layers and the surface pressure allows one to control the amount of Ru(bpy)2 3+ loading and, as a consequence, the ECL emission.