Silica-based organic-inorganic hybrid materials have become increasingly attractive for analytical and electroanalytical purposes by exploiting their advanced properties in aqueous suspensions or at an electrode/solution interface.^1,2  In particular, those materials displaying a regular structure at the mesoporous level have been found to be very promising electrode modifiers because they ensure fast mass transport processes, which are often rate-determining in electrochemistry.^3,4 The aim of this lecture is to highlight and discuss some recent achievements performed with using such new materials in electroanalytical chemistry, especially by pointing out their advantages but also their limitations.

After a brief overview of the actual developments in this field, special attention will be given to two particular examples: (1) Hg^II preconcentration on mesoporous silica samples functionalized with thiol groups, and (2) Cu^II binding to amine-functionalized materials.  The first example will demonstrate the definite advantage of mesostructured organically-modified silicas over their non-ordered homologues, as a result of better accessibility to the binding sites and faster transport of the analyte because of unrestricted diffusion.^5,6 This can be exploited for the voltammetric detection of Hg^II species, in the anodic stripping mode subsequent to open-circuit accumulation.  The second example will point out some problems related to the poor chemical stability of silica adsorbents bearing alkaline functional groups (i.e., amine-containing ones)⁷ and will discuss some strategies to overcome such limitations by the resort to polyazamacrocycles attached to the silica surface via 1, 2, or 4 alkyl arms.^8,9

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1.   A. Walcarius, D. Mandler, J. Cox, M.M. Collinson, O. Lev, J. Mater. Chem. 15, 3663 (2005).

2.   A. Walcarius, M. M. Collinson, Annu. Rev. Anal. Chem. 2, 121 (2009).

3.   A. Walcarius, C.R. Chim. 8, 693 (2005).

4.   A. Walcarius, Electroanalysis 20, 711 (2008).

5.   A. Walcarius, M. Etienne, B. Lebeau, Chem. Mater. 15, 2161 (2003).

6.   A. Walcarius, M. Etienne, S. Sayen, B. Lebeau, Electroanalysis 15, 414 (2003).

7.   M. Etienne, A. Walcarius, Talanta 59, 1173 (2003).

8.   M. Etienne, S. Goubert-Renaudin, Y. Rousselin, C. Marichal, F. Denat, B. Lebeau, A. Walcarius, Langmuir 25, 3137 (2009).

9.   S. Goubert-Renaudin, M. Etienne, S. Brandès, M. Meyer, F. Denat, B. Lebeau, A. Walcarius, Langmuir 25, 9804 (2009).

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