Fabrication of thermo-responsive polymer functionalized reduced graphene oxide@Fe3O4@Au magnetic nanocomposites for enhanced catalytic applications

Abstract

A novel strategy was developed to fabricate thermo-responsive copolymer functionalized reduced graphene oxide@Fe₃O₄@Au magnetic nanocomposites (Au NPs@GFDP) for highly efficient catalysis. Superparamagnetic Fe₃O₄ nanoparticles (NPs) on reduced graphene oxide (RGO@Fe₃O₄) were obtained via a one-pot chemical functionalization method. RGO@Fe₃O₄ was coated with dopamine (DA) to generate polydopamine (PDA) modified RGO@Fe₃O₄ (GFD) through a combination of mussel inspired chemistry of dopamine in a weakly alkaline aqueous solution. The thermo-responsive polymer of poly(N-isopropylacrylamide-co-2,3-epithiopropyl methacrylate) P(NIPAM-co-ETMA) (P) was synthesized via a reversible addition fragmentation chain transfer (RAFT) polymerization and was facilely grafted onto the surface of GFD through a Michael addition reaction. The final gold nanoparticle (Au NP) functionalized GFDP nanocomposites were obtained through in situ reduction of gold precursors in GFDP solution using the episulfide groups of P(NIPAM-co-ETMA) as a ligand. The Au NPs@GFDP nanocomposite exhibited excellent dispersibility and stability in aqueous solutions. More importantly, the obtained nanocomposite also displayed easy recyclability because of the existence of Fe₃O₄ NPs and a higher catalytic efficiency for the reduction of nitrophenols over the Au NPs@RGO@Fe₃O₄ and Au NPs@GO without polymer modification. Au NPs@GFDP modified with PNIPAM also exhibited excellent temperature-responsive behavior for the catalytic reduction of nitrophenol. Therefore, the strategy described in this work may be of great potential for various industrial catalytic applications.