Reversible Tuning of Surface Properties of Graphene-like Material via Covalently Functionalized Hydrophobic Layer

Nanoscale tuning of the surface properties of graphene-like materials is essential to optimize their application in electronic devices and protective technologies. The covalent modification method has recently been established as the most effective approach for tailoring the interface structure and properties, which are key aspects for fine-tuning the processability and performance of graphene-like materials. In this work, we demonstrate systematic exploration of the reversible covalent functionalization of a highly oriented pyrolytic graphite (HOPG) surface, a model system of multi-layered graphene, at the molecular scale. This is achieved using 3,5-trifluoromethyl benzenediazonum (3,5-TFD) and experimental investigations via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning tunneling microscopy (STM), and Raman spectroscopy. The degree of functionalization could be tuned by varying the concentration of 3,5-TFD dissolved in the grafting electrolyte. The covalently functionalized layer of 3,5-TFD was either locally degrafted by the STM tip or globally detracted upon thermal treatment, leaving the defect-free graphitic surfaces behind. Our findings open a new pathway for reversibly and robustly functionalizing graphene and other 2D materials for multiple uses in high-end applications.