Growth of gold/zinc sulphide multilayer films using layer-by-layer assembly of colloidal nanoparticles

Fabrication of multilayer thin films through layer-by-layer (Ibl) deposition of charged nanoparticles on tin-doped indium oxide (ITO) coated and uncoated glass substrates are reported. The thin films were constructed by alternately dipping a substrate into a colloidal suspension of chitosan capped zinc sulphide (ZnS) nanoparticles (similar to 30 nm) and citrate stabilized colloidal gold (Au) nanoparticles (similar to 20 nm) leading to electrostatic interactions between the oppositely charged nanoparticle layers. Thin films consisting of up to 200 deposition cycles by multiple dipping have been studied and surface morphology, changes in the optical absorption characteristics, thickness, uniformity, toughness and electrical characteristics are reported. The niultilayered assemblies, attached to the surface by strong ionic bonds, were highly stable and could not be removed by moderate scratching. The current-voltage characteristics in the forward and reverse bias conditions demonstrated rectifying behaviors in the onset of conduction voltage which makes these films attractive for future electronic devices. (C) 2008 Elsevier B.V. All rights reserved.