Dewetting of Au nanoparticle assemblies

Alhummiany, Haya and Jarvis, Samuel and Woolley, Richard A. J. and Stannard, Andrew and Blunt, Matthew and Moriarty, Philip (2011) Dewetting of Au nanoparticle assemblies. Journal of Materials Chemistry, 21 (42). pp. 16983-16989. ISSN 0959-9428

Abstract

Atomic force microscopy measurements as a function of annealing temperature, time of exposure to a high relative humidity environment, and scan duration/parameters have been used to ascertain the stability of assemblies of thiol-passivated Au nanoparticles on silicon substrates. Striking changes in the morphology of self-organised nanoparticle patterns are observed following the exposure of samples to atmospheres with a relative humidity of 80%. The nanoparticle film dewets the underlying silicon substrate on exposure to water, forming locally thicker regions. Time-lapse imaging shows that the dewetting proceeds via layer-by-layer growth, and there is no evidence for classical coarsening mechanisms involving self-similar film morphologies. Annealing at temperatures between 100 degrees C and 160 degrees C produces a rather different dewetting effect for the highest temperatures and/or annealing times, where significant nanoparticle sintering promotes the break-up of the two-dimensional assembly. The morphology of the initial 2D film plays a key role in determining the time scale on which annealing promotes nanoparticle dewetting. Dewetting can also be induced by a scanning probe such that localised (micron-scale) areas of the nanoparticle assembly can be converted from 2D to 3D character.