Hydrogenated Fluorographene: A 2D Counterpart of Graphane with Enhanced Nonlinear Optical Properties

We describe the benign wet chemical synthesis, characterization, and third-order nonlinear optical properties of hydrogenated fluorographene, namely, of a new 2D counterpart of hydrogenated graphene (graphane). The presence of hydrogen in hydrogenated fluorographene was confirmed using infrared spectroscopy, X-ray photoelectron spectroscopy, and thermal gravimetric analysis coupled with evolved gas analysis. The nonlinear optical properties of the derivative were investigated in the visible and infrared using picosecond laser excitation and were compared to those of graphene and fluorographene. All samples were found to exhibit important nonlinear optical response, with hydrogenated fluorographene exhibiting the largest response under visible excitation (ca. 1 order of magnitude higher compared to graphene and fluorographene). This is among the highest recorded effects ever observed for any graphene-based materials, including graphene oxide presented elsewhere. The results reveal the importance of the nature of the functional group and the degree of functionalization (i.e., fluorination and hydrogenation) on the nonlinear optical properties of graphenes. It is likely that highly polarized donor-pi electron-acceptor regions within a layer result in such large optical nonlinearities.