Improved enzyme immobilization for enhanced bioelectrocatalytic activity of porous electrodes Rafael Szamocki a,b , Alexandra Velichko c , Frank Mu ¨ cklich c , Stephane Reculusa d , Serge Ravaine d , Sebastian Neugebauer e , Wolfgang Schuhmann e , Rolf Hempelmann b , Alexander Kuhn a, * a University Bordeaux 1, CNRS, ISM, Ecole Nationale Supe ´rieur de Chimie et Physique de Bordeaux, 16 Avenue Pey Berland, 33607 Pessac, France b Department of Physical Chemistry, Universita ¨ t des Saarlandes, 66123 Saarbru ¨ cken, Germany c Department of Material Science, Universita ¨ t des Saarlandes, 66123 Saarbru ¨ cken, Germany d Centre de Recherche Paul Pascal-CRPP, 115 Avenue du Dr. Schweitzer, 33600 Pessac, France e Department of Analytical Chemistry, Ruhr-Universita ¨ t Bochum, Universita ¨ tsstr. 150, 44780 Bochum, Germany Received 14 May 2007; received in revised form 30 May 2007; accepted 4 June 2007 Available online 13 June 2007 Abstract Porous electrodes with increased surface area have been prepared using a template route via colloidal crystals. The ordered porous structure and the interconnections between the pores have been quantitatively characterized by Focused Ion Beam Tomography. The internal surfaces of the electrodes have been biofunctionalized with two enzymatic systems for glucose oxidation. In order to increase significantly the stability, the biocatalysts have been immobilized either by crosslinking or by incorporation in an electrodeposition paint. The modified porous electrodes show an increased overall signal and therefore a better detection limit and a higher sensitivity when used as sensors, and a potentially higher power output when employed in biofuel cells. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Macroporous electrodes; Enzyme immobilization; Stability; Electrodeposition paint; Biosensors; Biofuel cells 1. Introduction Upgrading the performance of electrodes with electro- catalysts is a very active field of research. Classic examples are the modification of different electrode materials with inorganic catalysts for instance with noble metal nanopar- ticles for fuel cells or with transition metal oxides for elec- trochemical sensors. In the last few decades such conventional catalysts are more and more complemented by biochemical analogues like enzymes for devices such as biofuel cells [1–5] and biosensors [6], respectively. In all cases of electrocatalysis it is very important that the reaction rate per unit area is as high as possible to obtain a maximum signal or power output. This is especially important for miniaturized devices using ultramicroelec- trodes that have a very small geometric surface area. The increase of electrochemical signal or power output can be reached in different ways like using feedback reactions or electrodes with artificially increased active surface areas such as rough or porous electrodes. Techniques for the preparation and modification of macroporous electrodes with an increased active surface area were described in recent work [7–11]. Highly ordered macroporous electrodes were obtained by electrodeposit- ion of gold in colloidal crystals as templates. This method allows to control the pore diameter d and the thickness of the porous material with high precision. Also the pre- paration of macroporous ultramicroelectrodes can be achieved by this kind of template synthesis [12]. With these 1388-2481/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2007.06.008 * Corresponding author. Tel.: +33 5 40 00 65 73; fax: +33 5 40 00 27 17. E-mail address: kuhn@enscpb.fr (A. Kuhn). www.elsevier.com/locate/elecom Electrochemistry Communications 9 (2007) 2121–2127