Graphene Oxide-Based Hydrogels\nto Make Metal Nanoparticle-Containing\nReduced Graphene Oxide-Based Functional Hybrid Hydrogels

Abstract

In this study, stable supramolecular hydrogels have been\nobtained\nfrom the assembly of graphene oxide (GO) in presence of polyamines\nincluding tris­(aminoethyl)­amine, spermine, and spermidine [biologically\nactive molecule]. One of these hydrogels has been well characterized\nby various techniques including field-emission scanning electron microscopy\n(FE-SEM), transmission electron microscopy (TEM), atomic force microscopy\n(AFM), X-ray diffraction (XRD) study, and Raman spectroscopy. TEM\nand AFM studies of one of these hydrogels have revealed the presence\nof a network structure of cross-linked nanosheets. This suggests the\nsupramolecular assembly of GO in the presence of polyamines using\nthe acid–base type electrostatic interaction. In presence of\na mild reducing agent (vitamin C), one of these GO hydrogels has been\ntransformed into a reduced graphene oxide (RGO)-based hydrogel by\na simple in situ reduction of GO sheets within the hydrogel matrix.\nMoreover, noble metal nanoparticle containing RGO based hybrid hydrogels\nhave been obtained using in situ and simultaneous co-reduction of\nGO and noble metal precursors within the GO gel matrix. The elegance\nof this method is in situ, “green chemical” and simultaneous\nreduction of GO and metal salts within the hydrogel matrix to form\nRGO-based hybrid gel and concomitant stabilization of metal nanoparticles\n(MNPs) within the gel system. The nascently formed MNPs are homogeneously\nand uniformly distributed on the surface of the RGO nanosheets within\nthe hybrid gel. Interestingly, this MNP containing RGO-based hybrid\nhydrogel matrix acts as a potential catalyst for the reduction of\naromatic nitro to amino group. The catalyst (hybrid gel matrix) can\nbe separated easily after the reaction and reused several times.