Please cite this article in press as: R. Bogdanowicz, et al., Amperometric sensing of chemical oxygen demand at glassy carbon and silicon electrodes modified with boron-doped diamond, Sens. Actuators B: Chem. (2013), http://dx.doi.org/10.1016/j.snb.2012.12.007 ARTICLE IN PRESS G Model SNB-14896; No. of Pages 7 Sensors and Actuators B xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect Sensors and Actuators B: Chemical journa l h o mepage: www.elsevier.com/locate/snb Amperometric sensing of chemical oxygen demand at glassy carbon and silicon electrodes modified with boron-doped diamond R. Bogdanowicz a,∗ , J. Czupryniak b , M. Gnyba b , J. Ryl c , T. Ossowski b , M. Sobaszek a , E.M. Siedlecka c , K. Darowicki d a Department of Metrology and Optoelectronics, Gdansk University of Technology, 11/12 G. Narutowicza Street, 80-233 Gdansk, Poland b Analytical Chemistry, Faculty of Chemistry, University of Gdansk, 18 Sobieskiego Street, 80-952 Gdansk, Poland c Environmental Engineering, Faculty of Chemistry, University of Gdansk, 18 Sobieskiego Street, 80-952 Gdansk, Poland d Department of Electrochemistry, Corrosion and Material Engineering, Gdansk University of Technology, 11/12 Narutowicza Street, 80 233 Gdansk, Poland a r t i c l e i n f o Article history: Available online xxx Keywords: Glassy carbon Boron-doped diamond Chemical oxygen demand Amperometric sensing Aprotic solvents a b s t r a c t A boron-doped diamond (BDD) sensor is proposed for effective detection of chemical oxygen demand (COD) by means of amperometric technique. Boron-doped diamond thin films, acting as active sensors, were deposited on both silicon wafer and glassy carbon (GC) substrates by microwave plasma assisted chemical vapour deposition. SEM micrographs showed that BDD–Si displays triangle-faceted crystal- lites ca. 0.5–3 m in size, while BDD–GC has triangle-faceted crystallites ranging from 0.5 to 3 m and also a small amount of square-faceted grains 0.5–1 m in size. The structure of BDD was confirmed by broad Raman bands centred at 483 cm -1 and 1216 cm -1 . Cyclic voltammograms were measured in tetrabutylammonium perchlorate/dimethyl sulfoxide solution to determine chemical oxygen demand by amperometric technique. The reduction of oxygen at boron-doped diamond predominantly involves the one electron reduction of oxygen to superoxide. The reduction of oxygen on BDD–Si and BDD–GC was found to be quasi-reversible (E = 59 - 100 mV). The lowest detection limit was about 0.9 mg l -1 . Two different types of electrochemical behaviour were observed at BDD–Si and BDD–GC electrodes which indicates a complexity of electroreduction of oxygen on the BDD surface. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Boron-doped diamond (BDD) electrodes have a plethora of applications and excellent chemical parameters therefore many researchers employ these tools to study various phenomena. Based on its excellent chemical stability, the authors had applied BDD for determining chemical oxygen demand (COD). COD in water and wastewater is a crucial parameter for water quality control and environmental monitoring. It has been proved that the BDD electrode is very effective in dissolution of var- ious organic pollutants including phenols [1], aromatic amines [2], chlorobenzene [3], quaternary ammonium salts [4] and oth- ers. The conventional dichromate methods of COD determination have several inherent drawbacks. They cause incomplete oxida- tion of volatile compounds and require the use of costly (Ag 2 SO 4 ) and toxic (Cr and Hg) compounds. Furthermore, the dichromate technique is time-consuming and the equipment should be oper- ated by skilled personnel to reduce analytical errors [5]. Yu et al. [6,7] employed boron-doped diamond deposited by HFCVD ∗ Corresponding author. Tel.: +48 58 347 1503; fax: +48 58 347 18 48. E-mail address: rbogdan@eti.pg.gda.pl (R. Bogdanowicz). on Ti substrate for chemical oxygen demand determination. They obtained the COD detection range of 20–9000 mg l -1 with a limit of 7.5 mg l -1 . The electrochemical measurements were carried out in 10 ml of sodium sulphate (0.1 M) solution. Potential rating for 50 M of glucose was from 2.2 V to 2.5 V (vs. SCE). A relationship between the COD values measured by a BDD sensor and the con- vectional dichromate method was linear. Wang et al. [8] optimised amperometric determination of chemical oxygen demand using a BDD electrode. Electrochemical process was run with different parameters as regards counter electrode, electrode gap, applied potential, electrolyte pH and temperature. The resulting measure- ments ranged widely from 19.2 to 11.600 mg l -1 COD, while the detection limit was low, i.e. 0.192 mg l -1 COD. The BDD sensor was made by HFCVD on p-type <1 0 0> silicon wafers with a growth time of 6 h and a B/C ratio of 5000 ppm. Szunerits et al. [9] reported the influence of the surface termination of BDD electrodes on the oxygen reduction reaction in alkaline solution. The NH 2 modified BDD surface displays a higher oxygen reduction current density and positive shift in the oxygen reduction potential compared to H- and H o - terminated BDD surfaces. Moreover, other authors employed different electrodes for determining chemical oxygen demand. Westbroek et al. [10] used rotating Pt ring – Pt/PbO 2 disc electrode with a detection limit of 0925-4005/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.snb.2012.12.007