Au nanoparticle network-type thin films formed via mixed assembling and cross-linking route for biosensor application: Quartz crystal microbalance study

We have investigated a means of producing Au nanoparticle network-type thin films that are derived by a one-step mixed-assembly cross-linking route, can avoid nonspecific interactions, and provide maximum binding to a specific target. Although a stepwise layer-by-layer construction method exists, our goal is to seek an alternative and simpler pathway for preparing thin films such as electrode nanomaterials. The model system consisting of Au nanoparticles, 1,6-hexananedithiol (HDT) cross-linkers, and 3-mercaptopropionic acid (MPA) captures was studied. The mixing of these three components in solutions allowed sequential assembly, cross-linking, and eventual precipitation of the network-type thin films on a Au substrate. Characterization of the films was carried out using UV-visible spectroscopy, cyclic voltammetry, and a quartz crystal microbalance. Such a thin film can be useful in biosensing and surface-coating applications. By controlling the ratio of HDT and MPA, we made Au nanoparticle network-type thin films on which goat-anti-human IgG antibodies that were immobilized can bind specifically to IgG with negligible nonspecific binding.