Self-assembly of gold nanoparticles with crown ether derivatives at the liquid/liquid interface in the form of a stable nanocomposite film is reported. The metallic luster results from the electronic coupling of nanoparticles, suggesting the formation of closely-packed nanoparticle thin films. The interfacial film could be transferred to mica substrates and carbon-coated transmission electron microscopy (TEM) grids. The transferred films were very stable for prolonged time. The samples were characterized by UV-vis and IR spectroscopies, TEM, and thermogravimetric analysis. All the experimental results indicate the formation of nanoparticles monolayers at water/oil interfaces. (c) 2006 Elsevier B.V. All rights reserved.