Preparation and characterization of different shapes of Au–Ag bimetallic nanocomposites for enhanced physicochemical properties

Abstract

Abstract This paper reports the preparation and characterization of bimetallic Au core –Ag shell nanocomposites consisting, Ag shell of varied thickness (2–20 nm) and Au nanospheres and Au nanorods as cores for the selective catalytic reduction of nitro-organics. A significant blue-shift in the surface plasmon band, 529 nm of Au nanospheres, and 700 and 538 nm for Au nanorods to 400 nm, and 522 and 412 nm, respectively, was found with an increased thickness of Ag shell that led to a notable color change. The measured zeta potential of Au nanospheres (+26 mV) and Au nanorods (+22.4 mV) were also considerably increased due to the surface passivation with an Ag-shell over Au particles. It revealed that the catalytic reduction of 1,3-dinitrobenzene by the anisotropic Au nanorod core –Ag shell bimetallic nanocomposites produced a highly selective formation of 3-nitroaniline (74%) relative to 1,3-phenylenediamine by bare Au nanorod (64%), Au nanospheres (45%) and Au nanosphere core –Ag shell nanocomposites (76%). Whereas 53–60% aniline was obtained from the reduction of nitrobenzene by Au core –Ag shell compared to 34–41% yield by bare Au nanostructures. Thus, it was derived that the surface structural properties for the selective catalytic reduction of nitro-organics could be significantly tuned by varying the shape of the Au-core and Ag-shell thickness.