Nanoparticle-structured ligand framework as electrode interfaces

Nanostructured thin film assemblies derived from metal or oxide nanocrystal cores and functionalized molecular shells provide large surface-to-volume ratio and three-dimensional ligand frameworks. In this article, we report results of an investigation of the nanostructured materials for electroanalysis. Monolayer-capped gold nanoparticles of 2-nm core diameter and carboxylic acid-functionalized alkyl thiols were assembled on electrode surfaces via an exchange-crosslinking-precipitation reaction route, and were studied as a model system. The network assemblies exhibit open frameworks in which the void space forms channels with the nanometer sized cores defining its size and the shell structures defining its chemical specificity. Such nanostructures were exploited to demonstrate the viability of responsive materials for interfacial incorporation and fluxes of ionic species. The nanomaterials were characterized by an array of techniques, including cyclic voltammetry, electrochemical quartz-crystal nanobalance, flow injection analysis, and surface infrared reflection spectroscopy. The current responses and mass loading as a result of the incorporation of ionic species into the nanostructure have been analyzed. The potential application of the nanostructured thin films for electrochemical detection in microfluidic systems is also discussed.