Large Enhancement of the Nonlinear Optical Response of Fluorographene by Chemical Functionalization: The Case of Diethyl-amino-fluorographene

Fully fluorinated graphene (fluorographene) exhibits a weak nonlinear optical response, in contrast to its unfunctionalized counterpart, graphene. However, diethyl-amino-functionalized fluorographene is shown to exhibit a dramatic enhancement of its nonlinear optical response. Diethyl-amino-fluorographene is obtained by the reaction of fluorographene with lithium diethylamide. Partial nucleophilic substitution/reduction of the substrate results in sp3 carbons bonded to diethylamine or fluorine groups and in distinct sp2 domains. The diethylamine groups act as strong electron donors, the C–F groups as strong electron acceptors, and the sp2 domains as π-conjugated bridges, thus forming a donor−π bridge–acceptor nonlinear optical chromophore scheme. As such, the diethyl-amino-fluorographene displays a large enhancement of its nonlinear optical response compared to fluorographene and other fluorographene derivatives under ps, both visible and infrared laser excitation.