Green synthesis of Ag@Au bimetallic regenerated cellulose nanofibers for catalytic applications
Green synthesis of nanocomposites is attracted huge consideration in recent years due to its positive environmental-friendly impact. The present study reports the first bimetallic Ag-Au cellulose nanofibers composite (Ag@Au/CNCs) prepared via very simple green preparation method. Aqueous leaves extract of Moringa Oleifera was used to obtain the bimetallic Ag@Au/CNCs nanocomposite. High-resolution transmission electron microscopy (HRTEM) observation revealed the successful formation of triangle, hexagonal and spherical shapes of well combined Ag-Au nanoparticles on the regenerated cellulose nanofiber surface. Further the formation of Au-Ag bimetallic nanostructures were confirmed by X-ray photoelectron spectroscopy (XPS) and X-ray crystallography (XRD) results. The resultant bimetallic Ag@Au/CNCs catalyst is found to be remarkably good in the reduction of nitrophenols. The bimetallic Ag@Au/CNCs catalyst gave excellent kapp values of 15.59 and 22.83 × 10-3 s-1 for the 2- and 4-nitrophenol reduction process, respectively. To our delight, the Ag@Au/CNCs catalyst was found to perform well in the aza-Michael reaction. The catalytic activity of Ag@Au/CNCs was compared over mono metallic Ag/CNCs, Au/CNCs and other reported catalysts. Based on the results obtained, high synergy of Ag@Au/CNCs was explained. Possible mechanism has been proposed for the Ag@Au/CNCs catalyzed nitrophenol reduction and aza-Michael reactions.