Functionalized Mesoporous Hybrid Thin Films as Selective Membranes

EUGENIO OTAL; PAULA C. ANGELOMÉ; SARA A. BILMES; GALO J. A. A. SOLER-ILLIA

ADVANCED MATERIALS

WILEY-V C H VERLAG GMBH

Año: 2006 vol. 18 p. 934 - 938

0935-9648

In this work we demonstrate the possibility of using titania based Mesoporous Hybrid Thin Films (MHTF) as selective functional membranes by exploiting a simple electrochemical technique, namely cyclic voltammetry (CV). This procedure allows a comparison of the diffusion values of electrochemical probes with different size and polarity (ferrocyanide (FCy), or ferrocene derivatives) in functionalized oxides when changing the functionality size or polarity. The exposed area of large-pore MHTFs deposited by dip-coating onto conducting substrates in contact with an electrolyte was evaluated by using an underpotential deposition (UPD) technique, which has been extensively used for the determination of the real surface area of polycrystalline Pt electrodes. While relatively small modifiers such as phenyl or glycerol partially block the pore system, the use of longerchain molecules, such as dihexadecylphosphate (DHDP), completely hinders diffusion of charged probes within the pores. In contrast, uncharged probes can permeate through these alkyl barriers, as demonstrated by the features of the electrochemical signals observed in CV measurements using ferrocene derivatives.