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

Abstract

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.