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 inve stigate 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 a nd unloading of the complex ion Ru(bpy)(3)(2+) through Nafion films we re measured. A linear dependence of the frequency changes on the perce ntage of water in the deposition solution was observed for both loadin g 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 w as further supported by the results of SEM experiments. (C) 1998 Elsev ier Science B.V.