Enhanced Proton Conduction of Graphene Oxide by the Addition of ZIF-8 for Room Temperature Relative Humidity Sensors

Graphene oxide (GO) is proven to be a very versatile material in sensing devices. As a moisture-sensitive material, it finds a wide variety of applications from biomedical to environmental, which is mainly related to its fast response and low cost. Here a treatment to GO using the metalorganic framework ZIF-8 is applied for the realization and study of humidity sensing. An incremental increase in sensitivity is demonstrated as we move from pure GO to GO blended with ZIF-8 to ZIF-8 dispersed on the GO surface, with two and three order of magnitude change in relative DC current respectively. The particles of ZIF-8 are uniformly dispersed on the GO surface with an average size of 200 nm contributing to ionic conductivity and improving the sensing capabilities. The dynamic analysis reveals that behind the enhanced sensitivity of the surface treated GO lays the fact that, in contrast to GO, the proton ion hopping mechanism kicks in from the lowest relative humidity values and the resistance follows the
${R}\sim {f}^{-1}$
law throughout the whole relative humidity range, while at the same time it signifies the superficial origin of the sensing mechanism.