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 sp(3) carbons bonded to diethylamine or fluorine groups and in distinct sp(2) domains. The diethylamine groups act as strong electron donors, the C-F groups as strong electron acceptors, and the sp(2) domains as pi-conjugated bridges, thus forming a donor-pi bridge-acceptor nonlinear optical chromophore scheme. As such, the diethyl-aminofluorographene displays a large enhancement of its nonlinear optical response compared to fluorographene and other fluorographene derivatives under ps, both visible and infrared laser excitation.