Silica-based organic-inorganic materials combine the advantages of an inorganic backbone (mechanical stability, high porosity and possible control of pore size and 3D pore arrangement) and the chemical reactivity of organic groups [1]. Both organic and inorganic properties have strong influence on the adsorption of heavy metals in aqueous solution. Modifying electrodes with such materials can lead to an improvement of the sensitivity and selectivity of the sensor due to the preconcentration of the target analytes at open-circuit prior to their electrochemical detection by anodic stripping voltammetry [2,3]. Among polyazamacrocycles, cylam displays very interesting properties for sensing applications. It forms stable complexes with a large number of transition metals, in particular copper(II), and the complex properties can be tuned by a judicious choice of the organic groups attached to the macrocycle [4,5]. In the present work, cyclam molecules have been grafted onto the surface of silica materials displaying ordered (SBA15) and amorphous (K60) mesoporosity. Both hybrid materials have been dispersed in a carbon paste and the resulting modified electrodes have been successfully exploited for voltammetric detection of copper(II). The strong binding properties of cyclam towards Cu(II) species are kept when bound to silica and cyclam-functionalized silica acts as a powerful preconcentration agent. Surprisingly, a well-ordered silica does not improve significantly the electrode response, suggesting that the accumulation process may be restricted by chemical reactivity of immobilized cyclam towards Cu(II), rather than diffusion of the analyte into the silica network. The influence of interfering species (Co^II, Ni^II, Cr^III, …) on the electrochemical detection of Cu(II) and the analytical characteristics of the sensor have been studied.

[1] A. Walcarius, Chem. Mater., 13, 3351 (2001)

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

[3] M. Etienne, J. Bessière, A. Walcarius, Sens. Actuators B, 76, 531 (2001)

[4] F. Denat, S. Brandès, R. Guilard, Synlett., 561 (2000)

[5] M. Meyer, V. Dahaoui-Gindrey, C. Lecomte, R. Guilard, Coord. Chem. Rev., 1313, 178 (1998)

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