Molecular transport in thiacalix[4]arene-modified nanoporous colloidal films

The surface of nanopores in colloidal films assembled from 200 nm silica spheres was modified with thiacalix[4]arene moieties and transport of two redox-active species, ferrocene dimethanol and iron tris(bipyridyl) hexafluorophosphate, through the films has been studied using cyclic voltammetry. Evidence for two different molecular transport mechanisms was observed. Ferrocene dimethanol is transported via a simple diffusive mechanism while iron tris(bipyridyl) is transported via a surface-hopping mechanism. The difference in transport mechanisms is believed to result from different interaction strength between the diffusing species and the surface-bound organic moieties, and sheds light on transport mechanisms in nanoporous systems.