Analytica Chimica Acta 516 (2004) 35–41 Electrochemical detection of carbohydrates using copper nanoparticles and carbon nanotubes Keith B. Male a , Sabahudin Hrapovic a , Yali Liu a , Dashan Wang b , John H.T. Luong a,∗ a Biotechnology Research Institute, National Research Council Canada, 6100 Royalmount Avenue, Montreal, Que., Canada H4P 2R2 b Institute of Chemical Process and Environmental Technology, National Research Council Canada, Ottawa, Ont., Canada K1A 0R6 Received 24 December 2003; received in revised form 24 March 2004; accepted 29 March 2004 Available online 18 May 2004 Abstract Copper (Cu) nanoparticles (4–8 nm in diameter), prepared by using sodium borohydride to reduce copper dodecyl sulfate (Cu(DS) 2 ), were used with single-wall carbon nanotubes (SWCNTs) to fabricate electrochemical sensors. Nafion, a perfluorosulfonated polymer, was able to solubilize SWCNTs and displayed interactions with Cu nanoparticles to form a network, connecting Cu nanoparticles to a glassy carbon (GC) or Cu electrode surface. Cyclic voltammetry confirmed an electrical contact through SWCNTs between Cu nanoparticles and the GC backing whereas TEM micrographs illustrated the deposition of Cu nanoparticles on the carbon nanotubes. The response time and the detection limit (S/N = 3) of the sensor for glucose were 10 s and 250 nM, respectively, i.e. a four-fold increase in the sensitivity compared to a bare Cu disk electrode. The response to interferents, such as acetaminophen, ascorbic acid and uric acid was suppressed in the presence of the SWCNT/Cu nanoparticle composite. © 2004 Elsevier B.V. All rights reserved. Keywords: Copper nanoparticles; Carbon nanotubes; Glucose; Amperometric detection; Nafion 1. Introduction Transition metals such as gold, platinum, silver, cop- per and nickel exhibit their high catalytic activities for many chemical reactions. With an ease of miniaturization to nanoscale dimensions, nanoparticles have been used in various chemical/biochemical sensing platforms. Indeed, electrochemical behavior and applications of nanoparti- cles have witnessed a significant growth in the last few years [1]. There are many simple procedures for the fab- rication of gold [2–4] and platinum [5–7] nanoparticles using various reducing agents coupled with a metal salt. Unlike these noble metals, copper nanoparticles can be easily oxidized to form copper oxide during the course of fabrication. These oxidation problems can be overcome to some extent by using reverse micelles [8,9] or microemul- sions using water-in-oil or gels [10,11] as well as radiation techniques [12,13]. Many of these procedures are complex ∗ Corresponding author. Tel.: +1-514-496-6175; fax: +1-514-496-6265. E-mail address: john.luong@cnrc-nrc.gc.ca (J.H.T. Luong). involving multiple solvent systems. Nevertheless, colloidal copper nanoparticles have been prepared in aqueous solu- tion via the reduction of copper dodecyl sulfate (Cu(DS) 2 ) by sodium borohydride [14]. Below the CMC (1.2 mM) of the Cu(DS) 2 , copper oxide particles are formed whereas above the CMC, surfactant aggregation leads to the for- mation of pure metallic particles, which decrease in size as the surfactant concentration increases. In order to keep the copper nanoparticles stable, it is critical to prevent their oxidation. Copper as an electrode material is of interest for analysis of carbohydrates and amino acids [15–18] because of the possibility of performing amperometric detection at a con- stant potential at high pHs. In comparison to Pt, Au, Ni, Ag and Co, Cu was reported to be superior in terms of range of response, detection limit, and especially stability [15]. The oxidation of carbohydrates using Au or Pt electrode in the direct amperometric detection mode encounters severe electrode poisoning, and must be overcome by pulsed am- perometric detection [19]. Cu-based microelectrodes have been used in capillary electrophoresis for analysis of carbo- hydrates [20]. 0003-2670/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2004.03.075