Stable aqueous sols of gold or silver metathesize on contact with alkylamines in petroleum ether and form mono and bilayered films that spread over very large areas at the interface between water and petroleum ether. The films were characterized by UV-visible spectroscopy, transmission and scanning electron microscopy, and other techniques. The nature and properties of interfacial thin films depend on the alkylamines (butyl, octyl, or dodecyl) used. Tangible differences in electronic properties are discernible in the UV-visible spectra. © 2011 American Chemical Society.