The Optimized SAW Humidity Sensor with Nanofilms of Graphene Oxide

Graphene oxide (GO) thin films with partial surface coating were deposited onto the surface of 160 MHz quartz SAW delay lines by SAW atomization of submicroliter droplets of GO aqueous dispersions. The delay lines were used as sensitive elements of the SAW relative humidity (RH) sensors for monitoring the process of saturation of vapor pressure of water in an enclosed volume. To explain the RH time dependence, we suggest a model, which takes into account two processes: fast adsorption of water molecules by the surface of GO, described by the first order kinetic equation, and slow volumetric adsorption, described by linear kinetic equation. The parameters of kinetic equations of the saturation process were estimated experimentally for the coatings obtained by different number of atomizations and for eleven different RH standards.