Water purification by improved polymeric and graphene-based membranes

Polymer-based porous membranes are widely used in many industrial and environmental processes for separations, and they are critical to the future of energy-related applications. Because permeability across a membrane scales inversely with the membrane's thickness, the "ultimate" membrane should be in the form of a one-Atom thick sheet with nanopores. Recently, nanoporous graphene (NPG) has been suggested for waste water purification, but new fabrication techniques that can be extended to large areas are required in view of its application. Herein we report a new fabrication strategy to obtain large area continuous NPGs-on-substrate combining graphene-on-substrate industrial techniques and swift-ion beam irradiation (SHI). Graphene membranes were synthesized on the Cu substrate and afterwards a 600nm layer of PMMA was spin-coated on the surface to complete the PMMA-Graphene-Cu stack.The PMMA-graphene-Cu trilayer was exposed to a flow of Au heavy ions that penetrate through the entire thickness of both polymer layer and the graphene sheet creating ion-Tracks and damages. A consecutive track-etching technique is used with an adequate revealing agent for PMMA, IsoPropylAlcohol(IPA), to selectively dissolve the latent tracks and damages created during SHI irradiation in the insulating material and the graphene sheet. Resulting from SHI irradiation and track-etching, the graphene nanopores are thus perfectly aligned to the PMMA nano-pores, providing, after cupper dissolution, a composite that features both well-defined and truly2-dimensional nanopores in the graphene layer but that can be handled as a normal polymer film.