Octadecyl mercaptan sub-monolayers on silver electrodeposited on gold quartz crystal microbalance electrodes

The objective of this work is to accurately and reproducibly control the amount of alkanethiol self-assembled onto the surface of a gold quartz crystal microbalance (QCM) electrode. This reaction is the first step in preparing bilayer membranes on gold electrodes that contain cytochrome c oxidase. In this work procedures for cleaning the surface of gold QCM electrodes, including use of an oxygen plasma, a UV surface cleaner, and aggressive chemical treatment of the surface, still led to rates of octadecyl mercaptan (OM) self-assembly that were highly irreproducible, varying over several orders of magnitude in time. Electrodeposition of a silver monolayer onto the surface of gold QCM electrodes affords a surface at which the OM self-assembly reaction can be easily controlled. Using the QCM to monitor the self-assembly reaction of OM on the silver-coated gold QCM electrode surface, a selected sub-monolayer coverage can be reliably prepared in about 10 min.