Full Paper Cyclam-Functionalized Silica-Modified Electrodes for Selective Determination of Cu(II) Ste ´phanie Goubert-Renaudin, a Mathieu Etienne, a Yoann Rousselin, b Franck Denat, b Be ´ne ´dicte Lebeau, c Alain Walcarius a * a Laboratoire de Chimie Physique et Microbiologie pour l)Environnement, UMR 7564, CNRS – Nancy-University, 405, rue de Vandoeuvre, F-54600 Villers-les-Nancy, France *e-mail: alain.walcarius@lcpme.cnrs-nancy.fr b Institut de Chimie Mole ´ culaire de l)Universite ´ de Bourgogne, UMR5260, CNRS-UNIV. BOURGOGNE, 9 Avenue Alain Savary, 21078 Dijon Cedex, France c Laboratoire de Mate ´riaux a ` Porosite ´ Contro ˆ le ´e, UMR 7016, CNRS-ENSCMu-UHA, 3 rue A. Werner, 68093 Mulhouse cedex, France Received: June 24, 2008 Accepted: August 25, 2008 Abstract Cyclam derivatives have been grafted via 1, 2 or 4 silylated arms to the surface of mesoporous silica and the resulting materials have been incorporated into carbon paste electrodes and applied to the preconcentration electroanalysis of Cu(II). Sensitive and selective detection of the target analyte was achieved owing to the attractive binding properties of this macrocyclic ligand towards Cu(II) species. Various parameters likely to affect the preconcentration and detection steps have been studied, including pH of the accumulation medium, composition of the detection solution, structure and composition of the adsorbent, accumulation time, or presence of potentially interfering species. In particular, the effect of the number of silylated groups linking the macrocycle to the silica network on the sensor performance was discussed. After optimization, Cu(II) can be determined in a linear concentration range extending from 2 nM to 100 mM. The method was validated by reliable Cu(II) determination in tap water. Keywords: Mesoporous silica, Cyclam, Carbon paste electrode, Copper, Voltammetry DOI: 10.1002/elan.200804378 1. Introduction Performance of any type of sensors lies in two key parameters: their sensitivity and selectivity towards the species to be quantified. In the field of electrochemical detectors, sensitivity can be improved by modifying the conventional electrode surface with a suitable chemical agent likely to preconcentrate, if possible selectively, the target analyte at the electrode/solution interface prior to its detection [1, 2]. This preconcentration step leads to a local increase in the analyte concentration at the electrode surface compared with that one in solution, which can be now detected at trace levels [3]. Due to their low cost, rapid renewability of their surface, low background currents and ease of preparation, chemi- cally modified carbon paste electrodes (CPEs) have been widely used for electroanalytical purposes [4, 5]. Never- theless, the main interest of these electrodes is probably linked to the fact that their modification appears to be universal as it allows to use almost all kinds of chemicals and materials as modifiers by simple dispersion in a carbon- binder mixture. Many examples have thus been reported dealing with dispersion of inorganic materials (e.g., zeolites, clays), organic and organometallic compounds, polymers, biological materials (enzymes, tissues and cells) and organ- ic-inorganic hybrid materials into CPEs [4]. Silica-based organic-inorganic hybrid materials are very attractive because they combine the mechanical properties of a rigid inorganic lattice (mechanical stability, high specific surface area, three-dimensional network) with the chemical reactivity of organo-functional groups bonded to the structure. This allows tuning of the chemical properties of the material, for instance inducing selectivity towards a target analyte [6 – 9]. (Organo)-silica modified electrodes have been applied to the voltammetric detection subsequent to open-circuit accumulation [10 – 12] and their sensitivity was demonstrated to be mainly controlled by the speed at which the analytes are reaching the binding sites in the porous material, leading to better performance using mesostructured adsorbents (obtained by surfactant tem- plated sol-gel assembly) in comparison to their non ordered homologues [13 – 15]. Grafted silicas and functionalized sol-gel materials have been exploited for Cu(II) electroanalysis. Except few examples dealing with silica-based thin film electrodes [10, 16, 17], most of the works were based on CPEs modified with these adsorbents. The functionalized materials used for that purpose were prepared either by postsynthesis grafting of silica samples or in one step by the sol-gel process. Several organo-functional groups likely to bind Cu(II) have been investigated, including amine groups [10, 16, 18, 19], phosphonic acid or urea derivatives [20, 21], dipeptide [15, 280 Electroanalysis 2009, 21, No. 3-5, 280 – 289 # 2009 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim