Stability of CH₃ molecules trapped on hydrogenated sites of graphene

We study the effect of a hydrogen atom on the thermal stability of a trapped CH₃ molecule on graphene using ReaxFF molecular dynamics simulations. Due to the hydrogen-molecule interaction, enhanced pinning of the CH₃ molecule is observed when it is positioned adjacent to the graphene site with the hydrogen atom. We discuss the formation process of such a stable configuration, which originates from different adhesion and migration energies of the hydrogen atom and the CH₃ molecule. We also studied the effect of the CH₃-H configuration on the electronic transport properties of graphene nanoribbons using first principles density-functional calculations. We found that the formation of the CH₃-H structure results in extra features in the transmission spectrum due to the formation of strongly localized states, which are absent when the CH₃ molecule is trapped on pristine graphene. Our findings will be useful in exploiting gas sensing properties of graphene, especially for selective detection of individual molecules.