Strongly-coupled freestanding hybrid films of graphene and layered titanate nanosheets: An effective way to tailor the physicochemical and antibacterial properties of graphene film

An effective way to tailor the physicochemical properties of graphene film is developed by combining colloidal suspensions of reduced graphene oxide (rG-O) nanosheets and exfoliated layered titanate nanosheets for the fabrication of freestanding hybrid films comprised of stacked and overlapped nanosheets. A flow-directed filtration of such mixed colloidal suspensions yields freestanding hybrid films comprised of strongly-coupled rG-O and titanate nanosheets with tunable chemical composition. This is the first example of highly flexible hybrid films composed of graphene and metal oxide nanosheets. The intimate incorporation of layered titanate nanosheets into the graphene film gives rise not only to an increase of mechanical strength but also to increased surface roughness, chemical stability, and hydrophilicity; thus, the physicochemical properties of the graphene film can be tuned by hybridization with inorganic nanosheets. These freestanding hybrid films of rG-O-layered titanate show unprecedentedly high antibacterial property, resulting in the complete sterilization of Escherichia coli O157:H7 (≈100%) in the very short time of 15 min. The antibacterial activity of the hybrid film is far superior to that of the pure graphene film, underscoring the beneficial effect of the layered metal oxide nanosheets in improving the functionality of the graphene film.