Abstract: Composite monolayer films spontaneously adsorb onto the surface of Au from an ethanolic mixture of two mercaptans to form a nanoporous surface. The monolayers consist of an electron- transfer-retarding n-alkanethiol framework, which passivates the Au surface, and a much shorter aromatic mercaptan, which induces molecular-sized defects within the passivating framework. Electrochemical experiments indicate that the chemical nature of the template and the template/framework ratio in the deposition solution control the size, number, and chemical characteristics of the defects. For example, 4- hydroxythiophenol/1-hexadecanethiol mixed monolayers yield monolayer assemblies that admit Ru(NH3)63+ probe molecules but not Fe(CN)63-