Light-controlled ion transport through spiropyran-modified nanoporous silica colloidal films

The transport of positively charged redox active species through spiropyran-modified nanopores in silica colloidal films was controlled using light. The silica colloidal films were comprised of 18 layers of face centered cubic (fcc)-packed 170 nm silica spheres. The surface of the films was first modified with amines, which were then used to attach the spiropyran moiety to the surface. The limiting current of a positively charged redox active species through the spiropyran-modified nanopore decreased after irradiation with UV light at pH 6.6. When the silica colloidal film was subsequently irradiated with visible light the initial limiting current was restored.