Clay-mesoporous silica composite films generated by electro-assisted self-assembly

This work describes the electro-assisted generation of clay-mesoporous silica composite films onto glassy carbon electrodes (GCEs). The method involved the deposition of clay particles by spin-coating on GCE and the subsequent growing of a surfactant-templated silica matrix around these particles by electro-assisted self-assembly (EASA). EASA typically consisted in applying a cathodic potential to the electrode immersed into a hydrolyzed sol (containing tetraethoxysilane, TEOS, as the silica source, and cetyltrimethylammonium bromide, CTAB, as surfactant) in order to generate the necessary hydroxyl catalysts inducing the formation of the mesoporous silica. In such conditions, alongside the silica deposition process, the inter-layer distance between the clay sheets was found to increase as a result of CTAB ion exchange. After removal of the surfactant template, the composite film became highly porous (i.e., to redox probes) and the clay recovered its pristine interlayer distance and cation exchange properties. This made it promising for application in preconcentration electroanalysis, as pointed out here using copper(II) as a model analyte, especially because it offered much better long-term operational stability than the conventional (i.e., without silica binder) clay film electrode. (C) 2013 Elsevier Ltd. All rights reserved.