Hydrophilic behavior of graphene and graphene-based materials

S. ACCORDINO; J. M. MONTES DE OCA; J. A. RODRÍGUEZ FRIS; G. A. APPIGNANESI

JOURNAL OF CHEMICAL PHYSICS

AMER INST PHYSICS

Lugar: American Institute of Physics; Año: 2015 vol. 143 p. 154704 - 154712

0021-9606

Graphene and the graphene-based materials like graphite, carbon nanotubes, and fullerenes are not only usually regarded as hydrophobic but also have been widely employed as paradigms for the investigation of the behavior of water under nonpolar confinement, a question of major concern for fieldsrangingfrombiologytomaterialsdesign.However,someexperimentalandtheoreticalinsights seem to contradict, at least partially, such a picture. In this work, we will provide firm evidence for a neat hydrophilic nature of graphene surfaces. Our molecular dynamics studies will demonstrate that parallelgraphenesheetspresentastrongtendencytoremainfullyhydratedformoderatelylongtimes (even when the equilibrium state is indeed the collapse of the plates), and thus, they are less prone to self-assembly than model hydrophobic surfaces we shall employ as control which readily undergo a hydrophobic collapse. Potential of mean force calculations will indeed make evident that the solvent exerts a repulsive contribution on the self-assembly of graphene surfaces. Moreover, we shall also quantify graphene hydrophilicity by means of the calculation of water density at two pressures and water density fluctuations. This latter study has never been performed on graphene and represents a means both to confirm and to quantify its neat hydrophilic behavior. We shall also make evident the relevance of the mildly attractive water-carbon interactions, since their artificial weakening will be showntorevertfromtypicallyhydrophilictotypicallyhydrophobicbehavior