Deterministic organic functionalization of monolayer graphene via high resolution surface engineering

Spatially-resolved organic functionalization of monolayer graphene with 1,3-dipolar cycloaddition of azomethine ylide is successfully achieved using low-energy electron beam irradiation. Indeed, the modification of the graphene honeycomb lattice obtained via electron beam irradiation yields a local increase of the graphene chemical reactivity. As a consequence, thanks to the high-spatially resolved generation of structural defects (similar to 100 nm), a chemical reactivity pattern has been designed over the graphene surface in a well-controlled way. Atomic force microscopy allows to investigate the two-dimensional spatial distribution of the structural defects and Raman spectroscopy reveals the new features that arise from the 1,3-dipolar cycloaddition, confirming the spatial selectivity of the graphene functionalization achieved via defect engineering. The Raman signature of the functionalized graphene is investigated both experimentally and via ab initio molecular dynamics simulations, computing the power spectrum. Furthermore, the organic functionalization is shown to be reversible thanks to the desorption of the azomethine ylide induced by focused laser irradiation. The selective and reversible functionalization of high quality graphene using 1,3-dipolar cycloaddition is a pivotal step for the design and realization of highly complex graphene-based devices and sensors at the nanoscale.