The nature of free O-H stretching in water adsorbed on carbon nanosystems

Motivated by the existence of several recent works claiming for unusual hydrogen bonds in water adsorbed or confined in carbon nanostructures, we have analyzed the nature of a sharp O-H stretching at 3700 cm(-1) in H2O/graphene recorded in vibrational measurements. The interpretation of such mode is rather controversial. On the basis of a careful inspection of our spectroscopic data and of literature, we suggest that the interpretation of this feature as a fingerprint of surface hydrophobicity, electronic effects or disorder is astray. Instead, it merely arises from interface effects.