Effect of the composition of Nafion deposition solutions on the ion-exchange properties of the Nafion films by quartz crystal microbalance sensor (QCM)

A quartz crystal microbalance (QCM) sensor system was employed to investigate the properties of Nafion films on a gold surface supported on a quartz-crystal as a function of the water content in the deposition solutions (0.5% Nafion in mixed ethanol/water). The rates of loading and unloading of the complex ion Ru(bpy)(3)(2+) through Nafion films were measured. A linear dependence of the frequency changes on the percentage of water in the deposition solution was observed for both loading and unloading. The ion-exchange distribution coefficients for Nafion films from various deposition solutions were calculated. We concluded that films cast from solutions of higher water content had more ;open' structures which allowed faster diffusion of ions. This conclusion was further supported by the results of SEM experiments.