A novel environmentally sustainable synthesis of Au–Ag@AgCl nanocomposites and their application as an efficient and recyclable catalyst for quinoline synthesis

Abstract

This paper reports a facile, additive free, cost effective, green approach to the synthesis of Au–Ag@AgCl nanocomposites (NCs) using the tuber extract of Nephrolepis cordifolia. Au–Ag@AgCl NCs were fabricated by reducing cationic Ag and Au and simultaneously generating AgCl in the presence of plant material. The sizes of the dispersed NCs ranged from 10 to 50 nm (average diameter 30 nm). The synthesized NCs were found to catalyze multicomponent domino annulation–aromatization for quinoline synthesis. UV-visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy and thermogravimetric analysis (TGA) were used to determine the optical activity, functional groups present, crystallinity, size, oxidation state, weight loss and thermal stability, respectively, of the biosynthesized Au–Ag@AgCl NCs. These NCs exhibited excellent catalytic activities and high yields when used to synthesize pharmaceutically important quinolines via three-component coupling/hydroarylation/dehydrogenation of arylaldehyde, aniline, and phenyl acetylene derivatives. The nanocatalyst was easily recovered and recycled five times without significant loss of catalytic activity.