Novel disposable microfabricated antimony-ﬁlm electrodes for adsorptive stripping analysis of trace Ni(II) Christos Kokkinos a , Anastasios Economou a, * , Ioannis Raptis b , Thanasis Speliotis c a Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Panepistimiopolis, Athens 157 71, Athens, Greece b Institute of Microelectronics, NCSR ‘‘Demokritos”, P.O. Box 60228, Aghia Paraskevi, Athens 153 10, Greece c Institute of Material Science, NCSR ‘‘Demokritos”, P.O. Box 60228, Aghia Paraskevi, Athens 153 10, Greece article info Article history: Received 23 October 2008 Received in revised form 7 November 2008 Accepted 19 November 2008 Available online 28 November 2008 Keywords: Antimony-ﬁlm electrode Stripping analysis Ni detection abstract This work describes a novel type of antimony electrode for adsorptive stripping voltammetry (AdSV). The electrode was microfabricated by coating a silicon chip with a thin antimony-ﬁlm by means of sputtering and the active area of the electrode was deﬁned by photolithography. The resulting antimony-ﬁlm elec- trodes (SbFEs) were characterized by optical and electrochemical techniques. The sensors were tested for the detection of low concentrations of Ni(II) by AdSV in the presence of dimethylglyoxime. Well-formed stripping peaks and a linear dependence of the stripping peak current on the Ni(II) concentration were observed on the microfabricated SbFEs while comparative measurements attempted with electroplated SbFEs were unsuccessful. Utilizing thin-ﬁlm technology for the formation of the antimony-ﬁlm extends the scope of these devices as mercury-free sensors in AdSV. Ó 2008 Elsevier B.V. All rights reserved. 1. Introduction Electrodes consisting of thin metal-ﬁlms are commonly em- ployed in stripping analysis since their fabrication is simple and frequent regeneration of their surface is possible. Mercury-ﬁlm electrodes (MFEs) have been the most widely employed metal-ﬁlm electrodes in stripping analysis [1–3]. However, over the last few years research has focused on environmentally-friendly materials that could potentially substitute MFEs. Gold ﬁlms have been used but they are mostly limited to the detection of species with rather positive oxidation potentials (e.g. mercury and antimony) [4,5]. More recently, lead-ﬁlm electrodes have been reported but lead it- self is toxic and the useful potential window of these electrodes is limited [6]. A stannous-ﬁlm electrode has also been reported for anodic stripping voltammetry (ASV) but its drawback is the narrow anodic polarisation range [7]. Bismuth-ﬁm electrodes (BiFEs) have undoubtedly been the most promising sensors, exhibiting analyti- cal properties similar to MFEs in stripping analysis [8,9]. The use of antimony in electroanalysis is rather scarce. Antimony has been previously utilised for the fabrication of potentiometric pH sensors [10,11]. Also, an initial attempt has been made to use carbon paste electrodes modiﬁed with Sb 2 O 3 in combination with ASV [12]. More recently, a new promising type of metal-ﬁlm electrode, the antimony-ﬁlm electrode (SbFE), has been reported and has been claimed to perform on a par with MFEs and BiFEs in ASV [13– 15]. The available toxicological data regarding the health effects of antimony and its compounds are limited and inconclusive but toxicity is highly dependent on their speciation [16]. Antimony compounds are administered in oral drug formulations to treat Leishmaniasis [17] and, unlike their arsenic counterparts, inorganic antimony species are not methylated in vivo and their excretion from the organism is rapid [16]. The relevant data published by dif- ferent regulatory agencies indicate that antimony is much less toxic than mercury and therefore SbFEs are more environmen- tally-friendly than MFEs [18,19]. The approach commonly followed for the formation of BiFEs and SbFEs involves in situ or ex situ electrochemical plating by reduction of the respective metal cations to their metallic state on a suitable supporting material [8,9,13–15]. Recently, an alterna- tive microfabrication method for the preparation of BiFEs has been proposed, based on sputtering of a silicon substrate with bismuth [20,21]. These microfabricated devices have been successfully aplied to both ASV and AdSV [22,23]. In this work, we report on a novel type of SbFE fabricated by a photolithographic microfabrication process. The application of this thin-ﬁlm approach for the fabrication of SbFEs offers several advantages compared to electroplating: a plating solution or a con- ductive substrate are not required (resulting in a simpler, shorter and low-cost fabrication procedure), complications associated with the composition and the pH of the plating solution are avoided, reproducible surface area and morphology of the electrodes are en- sured and, ﬁnally, there is increase scope towards the mass-pro- duction of inexpensive and disposable devices with small size and with a variety of conﬁgurations. Initial results obtained for the analysis of Ni(II) using AdSV on the microfabricated SbFEs 1388-2481/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2008.11.022 * Corresponding author. E-mail address: aeconomo@chem.uoa.gr (A. Economou). Electrochemistry Communications 11 (2009) 250–253 Contents lists available at ScienceDirect Electrochemistry Communications journal homepage: www.elsevier.com/locate/elecom