  Graphene modifications with oxygen or hydrogen are well known in contrast to
carbon attachment to the graphene lattice. The chemical modification of
graphene sheets with aromatic diazonium ions (carbon attachment) is analyzed by
confocal Raman spectroscopy. The temporal and spatial evolution of surface
adsorbed species allowed accurate tracking of the chemical reaction and
identification of intermediates. The controlled transformation of sp2 to sp3
carbon proceeds in two separate steps. The presented derivatization is
selective for single layer graphene and allows controlled transformation of
adsorbed diazonium reagents into covalently bound surface derivatives with
enhanced reactivity at the edge of single layer graphene. On bi-layer graphene
the derivatization proceeds to an adsorbed intermediate without further
reaction to form a covalent attachment on the carbon surface.
