Electrode layers for electrochemical applications based on functionalized mesoporous silica films

Functionalized ordered mesoporous films of SiO2 have been used as electrode coatings for various electrochemical applications depending on the nature of introduced functional groups. The films functionalized with tetraalkylammonium cationic groups serve as a matrix for ionic immobilization of polyoxometalate- and hexacyanoferrate anions. The electroactive concentration of redox species within the layers achieves 90 and 260 mu mol/cm(3) for ionically bonded polyoxometalate and hexacyanoferrate, respectively, being several times higher comparing to a monolayer on an electrode. The films functionalized with protonable amino groups act as effective permselective membranes switchable by the change in pH. Depending on pH. they actuated or amplified the flux of hexacyanoferrate anions, while the flux of hexaaminoruthemum cations to the electrode surface was blocked. (C) 2006 Elsevier B.V. All rights reserved.