The role of sp2/sp3 hybrid carbon regulation in the nonlinear optical properties of graphene oxide materials

Rational regulation of localized sp(2)/sp(3) hybrid carbon structure in graphene oxide systems plays a very important role in developing advanced carbon-based hybrid materials. Here, we report a simple ethanol solvothermal method toward precise control of the growth of the sp(2) hybrid carbon configurations/clusters in the sp(3) carbon matrix so as to regulate the structure of electronic energy bands in the graphene oxide system. The results of morphology observation, XPS, solid-state C-13 MAS NMR, FT-IR and Raman spectroscopy proved that controllable generation of the sp(2) hybrid carbon configurations/clusters can be achieved based on an executive oxidation/reduction strategy. Upon excitation by a 532 nm laser with 4 ns pulses, the obtained reduced graphene oxide (160-rGO-6) with a large number of sp(2) hybrid carbon configurations displays greater nonlinear reverse saturable absorption response and a higher nonlinear absorption coefficient b of 560 cm GW(-1) than graphene oxide with different oxidation degree (GO-X, X = 6, 8, 10 and 12), and reduced graphene oxide with relatively few sp(2) hybrid carbon configuration ratios (Y-rGO-6, Y = 80, 100, 120, 140 and 180). The significantly enhanced nonlinear reverse saturable absorption of 160-rGO-6 is attributed to the two photon absorption and excited state absorption originating from the sp(2) hybrid carbon configuration system.