Microwave-assisted solid-state synthesis of Au nanoparticles, size-selective speciation, and their self-assembly into 2D-superlattice

Abstract

Novel methods for the synthesis of metal and alloy nanoparticles as well as their organized structures have been of much interest in nanoscience in recent years. In fact, the size-selective synthesis of nanoparticles below 5 nm is still of significant importance due to their high surface energy and reactivity. Herein, we report a simple, one-step, solid-state approach to synthesize Au nanoparticles of different sizes and shapes ranging from small nanoparticles of 3 nm to larger polyhedra of about 200 nm, by microwave-assisted reaction of a pasty mass formed by mixing Glucose powder with an aqueous solution of HAuCl4. It is shown that very small Au nanoparticles with an average particle size of 4.52 nm can be selectively speciated from the larger ones into an ethanolic dispersion of 1-decanethiol, which gets transformed into hexagonally close-packed two-dimensional superlattices upon drying-induced self-assembly.