Robust Au–Ag/graphene bimetallic nanocatalyst for multifunctional activity with high synergism

Abstract

Gold nanorods (AuNRs) and silver nanoparticles (AgNPs) were fastened over single layer graphene (SLG) and successfully designated using microscopic (TEM and SEM–EDX) and spectroscopic (Raman, XRD, XPS and ICP) techniques. Salmon milt DNA stabilized the AgNPs and was also obliging in producing AuNRs. Bimetallic nanocatalyst (Au–Ag/SLG) was tremendously exerted as a versatile catalyst for hydroarylation, C-arylation and hydrophenoxylation reactions under mild and ligand-free conditions. But the mixture of monometallic nanocatalysts (Au/SLG and Ag/SLG) was unsuccessful in exposing their catalytic performance towards hydroarylation reaction. Initially the reaction conditions were optimized. 16 examples were fruitfully demonstrated for hydroarylation reaction in i-PrOH solvent with KOH. High synergistic effect was experienced with Au–Ag/SLG bimetallic nanocatalyst. Electron releasing group at the phenyl ring lead to the formation of 1,1-diphenylethylenes whereas the arenes with electron withdrawing functional group preferred hydrophenoxylation rather than hydroarylation. Consecutively C-arylation of hydroarylated products (1,1-diphenylethylenes) was achieved with iodobenzene by means of the same bimetallic nanocatalyst (Au–Ag/SLG). Leaching of metal nanoparticles during the course of the catalytic reaction was examined using heterogeneity test and ICP analysis. Reusability results confirmed the chemical stability of the proposed bimetallic Au–Ag/SLG nanocatalyst.