Photografting Graphene Oxide to Inert Membrane Materials to Impart Antibacterial Activity

Surface modification with bactericides is a promising approach to imparting membrane materials with biofouling resistance. However, chemical modification of membranes made from inert materials, such as polyvinylidene fluoride (PVDF) and polysulfone, is challenging because of the absence of reactive functional groups on these materials. In this study, we develop a facile procedure using benzophenone as an anchor to graft biocidal graphene oxide (GO) to chemically inactive membrane materials. GO nanosheets are first functionalized with benzophenone through an amide coupling reaction. Then, benzophenone-functionalized GO nanosheets are irreversibly grafted to the inert membrane surfaces via benzophenone-initiated cross-linking under ultraviolet irradiation. The binding of GO to the membrane surface is confirmed by scanning electron microscopy and Raman spectroscopy. When exposed to a model bacterium (Escherichia coli), GO-functionalized PVDF and polysulfone membranes exhibit strong antibacterial activity, reducing the number of viable cells by 90% and 75%, respectively, compared to the number with the pristine membranes. Notably, this bactericidal effect is imparted to the membranes without compromising membrane permeability or solute retention properties. Our results highlight the potential application of benzophenone chemistry in membrane surface modification as well as its promise in developing antimicrobial surfaces for a variety of environmental applications.