Synthesis of Ag and Au nanostructures in an ionic liquid: thermodynamic and kinetic effects underlying nanoparticle, cluster and nanowire formation

Abstract

The in situ reduction of dissolved Ag⁺ or Au³⁺ to the zero valent state in the distillable ionic liquid DIMCARB is reported. The reduction process leads to both 1D and 3D nanostructure formation, i.e. nanoparticles and nanowires and clusters composed of nanoparticles. The nanostructures formed have been characterised using UV/vis spectroscopy, powder X-ray diffraction and atomic force microscopic (AFM) topographic and phase imaging. Ag nanostructure growth occurs as a solution based crystallisation process. However, real time AFM imaging of Ag nanostructures formed when poly(vinyl pyrrolidone) is present shows the growth of nanowires on a mica surface via a surface confined process involving Ag atom diffusion. The growth of Au nanowires also occurs via the surface diffusion process. Based on the experimental results, a nanostructure growth mechanism in DIMCARB is proposed and 1D or 3D nanostructure growth is related to either a thermodynamic or a kinetic pathway.