Role of trapped water on electroresponsive characteristic of silica-graphene oxide composite microspheres

Abstract

Electroresponsive microspheres containing nanosilica and graphene oxide (GO) sheets have been achieved by the one-step evaporation induced assembly of mixed colloids using spray drying. The interlocking of the nanostructured constituents by the attractive capillary force during drying of dispersion droplets results in the formation of powder grains with correlated nanoparticles and nanosheets. The presence of GO sheets arrests the buckling of the drying droplets during evaporative assembly and results in well-defined spherical shaped grains. Interestingly, this approach of random jamming in colloidal droplets is capable of preventing the spontaneous stacking of the GO sheets and, therefore, facilitates a way to confine the atomic-thick GO sheet in the solid matrix. A plausible mechanism for the formation of silica-GO binary composite microspheres is elucidated. Microspheres dispersed in insulating oil show interesting electroresponsive characteristics where the microspheres form a chainlike percolation path under the applied electric field. It has been established that the adsorbed water in the microspheres plays a profound role as far its electroresponsive behavior is concerned. GO sheets in the microspheres allow for tuning of electroresponse strength owing to the increased interaction of water molecules to the oxygen-containing functional groups anchored on the GO sheets.