Influence of humidity on the graphene band gap

Influence of humidity on properties of graphene was investigated and a comparison of graphene and polymer humidity sensors was carried out. It is shown the graphene sensors have higher response in comparison with nanoporous polymer membranes. The resistance of the latter ones is 150 GOhm and decreases in 7.5 times in case of 60% relative humidity. The resistance of graphene decreases in 4 times from 100 kOhm. This was shown to be due to the expanding of band gap of graphene caused by the adsorbed water that may create the defects in the lattice or transfer the charge, the sign of which depends on the relative position of HOMO and LOMO of water and the Dirac point of graphene.