Electro-assisted generation of sol-gel thin films directed to electrochemical sensing

Alain Walcarius ,  Emilie Sibottier ,  Mathieu Etienne 

Laboratoire de Chimie Physique et Microbiologie pour l'Environnement (LCPME), 405, rue de Vandoeuvre, Nancy 54600, France

Abstract

Sol-gel electrochemistry has gained great popularity in the past decade, mostly because of the ease of formation of silica and organosilica films with tailor-made properties that can be advantageously exploited for several applications when coated on a suitable electrode surface [1-3]. The usual way to get such films involves either dip- or spin-coating a sol-gel medium containing the appropriate (organo)alkoxysilane precursor(s), which are hydrolyzed and (co)condensed on the electrode surface. Some years ago, Shacham and co-workers have developed a new and elegant electrochemically-driven deposition method for getting sol-gel thin films on conducting substrates [4]. The approach is based on altering the surface pH by applying a suitable potential to an electrode immersed in a sol-gel medium, inducing thereby the catalysis of the condensation process thus enhancing the rate of film deposition. The present lecture aims at presenting two extensions of this method: (1) the preparation of organosilica films containing thiol or amine ligands and its combination to the self-assembled monolayers technology to ensure good adhesion to the electrode surface; (2) the formation of well-ordered mesoporous silica films displaying a regular arrangement of mesopore channels oriented normal to the underlying electrode surface. The synthetic pathway involves basically the immersion of an electrode in a silica sol containing the hydrolyzed precursors, alone or in the presence of a surfactant template, where a cathodic potential is applied to increase pH locally at the electrode/solution interface and to induce co-condensation of the precursors. The films were characterized by various physico-chemical techniques (cyclic voltammetry, crystal quartz microbalance, atomic force microscopy, electron microscopy) and special attention was given to highlight the effect of the electro-deposition conditions. It was especially shown that film growth was first linear and then exponential [5], that mesostructuration can be effectively induced by the use of an appropriate surfactant template [6], and that both the amount of organic groups in the final material and its degree or organization greatly affected its permeation properties and the electroanalytical performance of the resulting film electrodes [6-8].

[1] O. Lev, Z. Wu, S. Bharathi, V. Glezer, A. Modestov, J. Gun, L. Rabinovich, S. Sampath,
Chem. Mater., 1997, 9, 2354.

[2] A. Walcarius, Chem. Mater., 2001, 13, 3351 & Electroanalysis, 2001, 13, 701.

[3] A. Walcarius, D. Mandler, J. Cox, M.M. Collinson, O. Lev, J. Mater. Chem., 2005, 15, 3663.

[4] R. Shacham, D. Avnir, D. Mandler, Adv. Mater., 1999, 11, 384.

[5] E. Sibottier, S. Sayen, F. Gaboriaud, A. Walcarius, Langmuir, 2006, 22, 8366.

[6] A. Walcarius, E. Sibottier, M. Etienne, J. Ghanbaja, Nature Mater. 2007, 6, 602.

[7] S. Sayen, A. Walcarius, Electrochem. Commun., 2003, 5, 341.

[8] A. Walcarius, E. Sibottier, Electroanalysis, 2005, 17, 1716.

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Presentation: Keynote lecture at SMCBS'2007 International Workshop, by Alain Walcarius
See On-line Journal of SMCBS'2007 International Workshop

Submitted: 2007-08-30 16:30
Revised:   2009-06-07 00:44
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