Monday 27 October 2014

Water, water everywhere: How UV irradiation reversibly switches graphene between hydrophobic and hydrophilic states

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(Phys.org) —Scientists have long observed that the wettability of graphene – an essentially two-dimensional crystalline allotrope of carbon that it interacts oddly with light and with other materials – can be reversed between hydrophobic and hydrophilic states by applying ultraviolet (UV) irradiation. However, an explanation for this behavior has remained elusive. Recently, researchers at The University of New South Wales and University of Technology, Sydney investigating this phenomenon both experimentally and by calculations using density functional theory (DFT) – a computational quantum mechanical modeling method – finding that UV irradiation enables this reversible and controllable transition in graphene films having induced defects by water splitting adsorption on the graphene surface of H2O molecules in air. (Water splitting is the chemically dissociative reaction in which water is separated into hydroxyl and hydrogen; hydroxyl is a chemical functional group containing an oxygen atom connected by a covalent bond to a hydrogen atom; and adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface.)



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