  Spatially-resolved organic functionalization of monolayer graphene is
successfully achieved by combining low-energy electron beam irradiation with
1,3-dipolar cycloaddition of azomethine ylide. Indeed, the modification of the
graphene honeycomb lattice obtained via electron beam irradiation yields to a
local increase of the graphene chemical reactivity. As a consequence, thanks to
the high-spatially resolved generation of structural defects (~ 100 nm),
chemical reactivity patterning has been designed over the graphene surface in a
well-controlled way. Atomic force microscopy and Raman spectroscopy allow to
investigate the two-dimensional spatial distribution of the structural defects
and 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 significant step towards
the controlled synthesis of graphene-based complex structures and devices at
the nanoscale.
