Abstract

Nano- and/or macro-structuration of electrode surfaces has recently emerged as a powerful mean to improve the performance of electrochemical devices by enhancing both molecular accessibility and rapid mass transport via diffusion, by increasing the electroactive surface areas in comparison to the geometric ones, and/or by providing confined platforms to host suitable reagents [1]. This lecture highlights how the template technology offers the benefits in terms of designing new types of porous electrodes, mostly based on thin films, functionalized or not, and discusses their interest in electroanalytical chemistry.

After describing the main strategies applied to combine template nanoscience and nanotechnology to electrochemistry by depicting the main types of micro- and nanostructured porous electrodes, special focus will be made on sol-gel-derived silica-based nanomaterials developed in my group. Electrochemistry is indeed likely to generate thin films of functionalized silica materials via an electrochemically-driven deposition method [2,3], which implies a local electrochemical tuning of pH at the electrode/solution interface to induce co-condensation of the precursors in a controlled way [4].

Even more interesting is the extension of this approach to the preparation of ordered and oriented mesoporous films with mesopore channels oriented perpendicular to the solid surface [5], which has proven to be very difficult by other ways [6]. The method combines the electrochemically-driven self-assembly of surfactants at solid/liquid interfaces [7] and the above electro-assisted generation process to produce sol-gel films [4], leading to perfect alignment of the nanoporous structures normal to the electrode surface [5]. Both preparation and characterization of the oriented mesoporous thin films have been thoroughly investigated and will be described [8]. The possibility to generate organically-functionalized oriented mesoporous thin films will be also discussed, showing notably the influence of the organic group type and content on the level of mesostructural order; for instance, highly ordered structures can be obtained up to 50% organosilane in the case of methyl groups [9] whereas it remained restricted to 10% for aminopropyl-functionalized films [10].

Their application in the field of electrochemical sensors will be exemplified in the case of Cu(II) detection subsequent to preconcentration at amine-functionalized silica film electrodes [10]. These novel mesostructures can be also used as secondary template for electrodeposition of nano-objects, as demonstrated for Prussian Blue [11].

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[11] A. Goux, J. Ghanbaja, A. Walcarius, J. Mater. Sci. 2009, 44, 6601.