Boosting the electrochemical properties of diamond electrodes using carbon nanotube scaffolds Cle ´ment He ´bert a, * , Jean Paul Mazellier b , Emmanuel Scorsone a , Michel Mermoux c , Philippe Bergonzo a a CEA-LIST, Diamond Sensors Laboratory, Gif-sur-Yvette 91191, France b Thales Research and Technology, Route De ´partementale 128, Palaiseau 91767, France c Laboratoire d’Electrochimie et de Physicochimie des Mate ´riaux et des Interfaces (LEPMI), UMR 5279, CNRS – Grenoble INP – Universite ´ de Savoie – Universite ´ Joseph Fourier, BP75, Saint Martin d’He `res 38402, France ARTICLE INFO Article history: Received 6 November 2013 Accepted 25 December 2013 Available online 5 January 2014 ABSTRACT Diamond is a very attractive electrode material for analytical measurements including for instance bio-sensing. However, it suffers from a relatively low double layer capacitance and high impedance when it comes to the development of supercapacitors or neural interfaces, applications for which it could also be extremely promising. One way to increase the dou- ble layer capacitance of the material is to increase its specific surface area. Here we propose here to use vertically aligned carbon nanotubes (VACNTs) with high surface areas as a template onto which boron doped diamond is grown. The resulting composite was found to exhibit a double layer capacitance as high as 0.58 mF cm 2 and very low impedance when compared to planar diamond electrodes in phosphate buffer saline solution. The influence of the VACNT length as well as of the thickness of the diamond coatings on the electrode performances were also investigated and are discussed in this paper. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Boron doped diamond (BDD) electrodes exhibit a number of superior electrochemical properties over more conventional electrodes, such as gold or platinum, that make them highly attractive for a wide range of analytical applications. In par- ticular, they feature a low background current resulting from an intrinsically low double layer capacitance, thus enabling high signal to noise electrochemical measurements [1]. Fur- thermore, their wide potential window in aqueous media, typically above 3 V, offers the possibility to detect a broad range of analytes that could not be addressed with other types of electrodes [1]. Finally, in addition to their antifouling capabilities and long term stability, Kiran et al. have demonstrated that they can be electrochemically reactivated in situ in biological fluids thus opening the way to continuous monitoring [2]. Due to the combination of those exceptional properties, BDD based electrochemical sensors have been reported e.g. for the detection of glucose [3], catecholamine [4], norepinephrine [5] etc. More recently, BDD electrodes have also been identified as a promising material for implantable stimulation electrodes [6]. Such electrodes are used to generate an electric field gradient that produces a compensating flux of charges toward the neurons and tissues surrounding the electrode, which is high enough to fire neurons. In this context, several studies have indicated that diamond is both biocompatible [7–8] and chemically inert, which are two prerequisites for 0008-6223/$ - see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.carbon.2013.12.083 * Corresponding author. E-mail address: clement.hebert@cea.fr (C. He ´ bert). CARBON 71 (2014) 27 – 33 Available at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/carbon