چكيده به لاتين
Doping is usually considered as a common approach for improving properties of substances. Theoretical studies on the graphene show that dipping can effectively change electrical properties of graphene and it causes the graphene to behave like a metal or semiconductor. In the present study doping of the fourth group elements of periodic table including Silicon, Germanium and Tin to the graphene lattice has been computationally studied. To this end mixed of quantum and simulation calculations have been used. Since elements of the 4th group have four valence electrons similar to Carbon hence it is expected that doping of these elements don't change bond hybridisation. How ever graphene is coverted from smooth state to pyramid wrinkle state on the doped site for reducing vander Waals repulsion because of the difference in size of the doped atom with carbon. In fact, amount of wrinke or in the other words height of created pyramid depends on size of the doped atom. If a hydrophilic substrate is coated by graphene monolayer, hydrophilic interaction can pass through graphene film and subsequent decreases the hydrophobicity of graphene monolayer. If instead of graphene , the doped graphene lay on a smooth hydrophilic substrate, from the face in weach doped atoms exit , carbon atoms will not directly lay on the substrate , hence , a distance between doped graphene carbon atoms and atoms of the substrate will be created. It is expected that the created distance between substrate and graphene prevent decrease of hydrophobicity. In this work, we developed a theoretical model to investigate effect of doping on hydrophobicity. we also performed molecular dynamic simulations on Coper and Gold coated by graphene and doped graphenes. The results of our simulation are very close to the results of the theoretical model and show that doping can increase graphene hydrophobicity.
