Graphene oxide reduced and modified by soft nanoparticles and its catalysis of the Knoevenagel condensation

Abstract

An approach to prepare reduced graphene oxide (RGO) was developed using soft nanoparticles, amino-terminated poly(amidoanime) (PAMAM) dendrimers, as both a reducing agent and a stabilizing agent. Several factors that affect the reduction of graphene oxide (GO), including the PAMAM generation, the ratio of PAMAM/GO, the pH, and the reduction temperature were investigated. The reduced graphene oxide was characterized with UV-visible absorption spectroscopy, Raman spectroscopy, X-ray diffraction spectroscopy, thermo-gravimetric analysis, X-ray photoelectron spectroscopy and transmission electron microscopy. The PAMAM dendrimers efficiently reduced GO in a short time, and their adsorption onto the RGO nanosheets allows RGO to stably disperse in water and organic solvents, such as N,N-dimethyl formamide and dimethyl sulfoxide. PAMAM modified RGO can catalyze the Knoevenagel condensation with yields up to 99%, and thus is a very active organocatalyst.