Bio-inspired fabrication of magnetic graphene-gold hybrid nanoclusters for catalytic dye degradation

Abstract

In this research work, we have synthesized a magnetic nickel nanoparticles-graphene-polydopamine-gold, NiNPs-G-PDA-Au composite for the photocatalytic degradation of organic dyes and other pollutants. Introduction of ferromagnetic nickel nanoparticles into the graphene, coated with polydopamine (PDA) and gold nanoparticles hybrid have made the catalyst easily separable after the reaction and thus recyclable. Moreover, NiNPs are well-known for their catalytic activity in numerous reactions. NiNPs have been prepared by the reduction of nickel(II) chloride using hydrazine monohydrate,N2H4.H2O and sodium hydroxide, NaOH. The prepared NiNPs have been then coated with graphene and then with polydopamine (PDA). PDA provides the catechol groups on the surface that are able to reduce the Au-salt and hold them strongly, inspired by marine mussels. The PDA layer has been loaded with AuNPs using chloroauric acid as the source of gold. The characterization of the hybrid material has been performed by conducting Fourier transform infrared (FTIR), x-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, transmission electron microscopy(TEM), thermogravimetric analysis (TGA). SEM study showed that the average size of the NiNPs are ~195 nm. Polydopamine coating and the presence of other chemical functionalities were also characterized by FTIR spectroscopy. The immobilized AuNPs on the composite materials showed high catalytic efficacy for the reduction of a model dye, methylene blue (MB), and 4-nitrophenol (4-NP). The reduction of methylene blue was facilitated by fast adsorption behavior of PDA for MB in aqueous systems. The fabricated NiNPs-G-PDA-Au nanocomposite materials exhibited synergistic capabilities of efficient catalytic reduction efficiency along with fast reduction kinetics as tested for MB and 4-NP dyes.