Atomic structures of a H2O or an O2 molecule adsorbed on graphene with different types of defects. Credit: Xu, Z. et al. Reversible Hydrophobic to Hydrophilic Transition in Graphene via Water Splitting Induced by UV Irradiation. Sci. Rep. 4, 6450.
Read more at: http://phys.org/news/2014-10-uv-irradiation-reversibly-graphene-hydrophobic.html#jCp
(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.)
The scientists conclude that their discovery may provide new insights into the fundamental principles of water splitting with graphene-based materials, and could thereby lead to other applications – including electrocatalysis, nanomaterials; nanoelectromechanical systems, biomaterials, microfluidic devices, hybrid organic systems, and other advanced multifunctional systems.
2Reversible Transition of Graphene from Hydrophobic to Hydrophilic in the Presence of an Electric Field, Journal of Physical Chemistry C, 2012, 116 (36),doi:10.1021/jp3050466