PNNL

Abstract

Organosilane based self-assembled monolayers are a valuable method for chemically modifying surfaces for catalysis, chemical separations and sensing/detection.1-3 These monolayers are readily terminated with a wide variety of ligands, making them ideally suited for chelating catalytic transition metal species. When this foundation is combined with nanostructured materials (e.g. nanoparticles or nanoporous materials), an ideal catalyst support is obtained, with high surface area, easy chemical accessiblity and high diffusion rates. In recent years, there has been a significant amount of interest in using silane functionalized nanomaterials as catalyst supports. In general, these studies have focused on the chemical identity of the monolayer interface and the role it plays in binding the metal center. However, the silane population density is also important, as this density is directly related to the lattice spacing of the terminal functionality at the monolayer interface. In order to use this spacing parameter to build complex moleclular recognition capability (e.g. chiral catalysis) it is necessary to have some baseline understanding of the spacing of these molecules within the monolayer. There have been measurements of this parameter in the past,4,5 but in general this measurement has been bypassed in favor of measurements that are easier to perform (e.g. film thickness by ellipsometry).