Engineering Hydroxyl Functionalization Enables Atomically Precise ZnO Nucleation on Defective Graphene

The synergy between graphene and ZnO in creating hybrid nanomaterials with novel properties of interest for the technological industry requires the development of processes and techniques that enable their precise production at the nanoscale. Therefore, understanding the atomic and molecular mechanisms that lead to their creation is imperative for controlling each involved step in their formation, enhancing their efficiency. This work sheds light on the first atomic layer half-cycle for the growth of ZnO on graphene with a hydroxyl-functionalized monovacancy. We performed quantum mechanical calculations, considering a trapping-mediated mechanism and diethylzinc (DEZ) as the precursor. The results suggest that neighboring hydroxyl groups facilitate DEZ adsorption and minimize the activation energy. This is linked to the role of hydroxyl groups in the formation of noncovalent interactions such as weak van der Waals and C-H···O and O-H···O hydrogen bonds, which stabilize the systems and facilitate the first partial reaction. By comparing the response in systems with one, two, and three hydroxyl groups, it was found that as these functional groups increased in quantity, the reactions were both thermodynamically and kinetically more favorable. Thus, it can be concluded that incorporating hydroxyl groups on graphene through pretreatment may considerably increase the initial growth rate of ZnO.