The impact of functionalization modes on the third-order nonlinear optical properties of reduced graphene oxide

Covalent and noncovalent interaction mechanisms were implemented for the modification of reduced graphene oxide nanosheets through functionalization with zinc oxide nanoparticles employing chemical reduction and ultrasonication methods. The zinc oxide nanoparticles appear as hexagonal wurtzite structures in bare and composite. The partial removal of oxygen groups in rGO is further confirmed by the decline in d spacing in the XRD pattern. In Raman spectra, a reduction in defect ratio points to the restoration of the n conjugated system with the formation of the composite. The observed electronic spectra further confirmed the formation of composite and effective interaction between the components. The morphological analysis revealed that the zinc oxide nanoparticles dispersed over the layered reduced graphene oxide structure. The open aperture z-scan studies suggested increased absorption at the focus (Reverse saturable absorption), which was further exploited for analyzing the optical limiting behavior. The closed aperture z-scan curve implied the self-defocusing feature of the samples. The composite rGO/ZnO C has a beta value of 20.31 cmGW at an input intensity of 4.59 cm2GW and an optical limiting threshold value of 21.54 cm2J. These superior results are due to the effective interaction and charge conveyance among rGO and ZnO. The work focuses on analyzing the effect of interaction between components in the composite, input laser intensity, and sample concentration on the nonlinear optical properties. The obtained value of nonlinear optical parameters showed the importance of the functionalization mode in enhancing the optical limiting property of the composite. The results have implications for developing novel materials with improved nonlinear optical behavior.