Electroanalytical properties of screen printed shallow recessed electrodes Jonathan P. Metters, Fang Tan, Rashid O. Kadara and Craig E. Banks * Received 21st May 2012, Accepted 10th July 2012 DOI: 10.1039/c2ay25512j We report the fabrication of novel carbon based screen printed disc-shaped recessed electrodes (250 mm radius) which are electrochemically characterised and contrasted to other screen printed sensors previously reported upon within the literature. In these circumstances, the electrode is fabricated entirely through screen printing and the electrode geometry is defined by the dielectric (inert polymer) producing shallow recessed electrodes. In comparison to co-planar carbon screen printed electrodes, the shallow recessed screen printed electrodes exhibit a greater current density over the former. The potential electroanalytical applications of these carbon based disc-shaped shallow recessed electrodes are explored through the sensing of NADH and nitrite exhibiting analytically relevant limits of detection (3s) of 5.2 and 7.28 mM respectively. Additionally, the electroanalytical sensing of nitrite is further trialled in a canal water sample demonstrating the robust nature of the sensors analytical performance. Furthermore we explore the potential improvement of the shallow recessed electrodes through the fabrication of pentagon-shaped carbon based shallow recessed electrodes, which are compared and contrasted with shallow recessed disc electrodes towards the electroanalytical sensing of manganese(II); we believe this to be the first example of such an electrode geometry. In comparison of the observed current density the disc-shaped shallow recessed electrode offers greater sensitivity over co-planar screen printed electrode, whilst in addition to this, a pentagon-shaped recessed electrode offers improved sensitivity over even that of the disc-shaped shallow recessed screen printed electrode. The ultra-low nM sensing of manganese(II) is shown to be possible at both the disc and pentagon shallow recessed electrodes exhibiting limits of detection (3s) found to correspond to 63 and 36 nM respectively. Both the disc and pentagon-shaped shallow recessed screen printed electrodes are determined to offer greater analytical sensitivity as determined within this study and in comparison with previous literature using graphitic electrodes. The fabrication methodology of the shallow recessed electrodes is shown to be generic in nature such that the underlying carbon layer, which defines the composition of the shallow recessed working electrode, can be replaced with electrocatalytic surfaces. We demonstrate this with the fabrication of platinum disc-shaped shallow recessed screen printed electrodes, which are electrochemically characterised and explored towards the sensing of hydrazine and hydrogen peroxide displaying limits of detection (3s) of 26.3 and 44.3 mM respectively, which are found to be analytically useful. 1 Introduction Electrochemists are forever exploring new approaches to improve mass transport of the target analyte towards the elec- trode surface which consequently influences the observed elec- trochemical response. One such approach to improve mass transport is to use microelectrodes which have unique features of high mass flux, low ohmic drop, steady-state currents and minimal stirring dependence characteristics which are highly important with regard to the development of practical electro- chemical sensors. 1 The advantages offered by an electrochemical sensor which incorporates a microelectrode and consequently steady-state behaviour are: greater analytical sensitivities, increased current densities, and improved signal-to-noise ratios 2 which ultimately lead to enhancements in the electroanalytical performance towards the target analyte. 3,4 Various approaches have been reported for the fabrication of microelectrodes such as photoli- thography and sealing wires within glass. Another approach is the screen printing of microelectrodes which have the advantage of reproducibility, simplicity and ability to produce en mass at a low production cost; recently, Kadara and co-workers have reported the fabrication of screen printed microelectrodes, producing microelectrodes with radii of 60 to 100 mm. 5 Faculty of Science and Engineering, School of Chemistry and the Environment, Division of Chemistry and Environmental Science, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, Lancs, UK. E-mail: c.banks@mmu.ac.uk; Web: www. craigbanksresearch.com; Fax: +44 (0)1612476831; Tel: +44 (0) 1612471196 3140 | Anal. Methods, 2012, 4, 3140–3149 This journal is ª The Royal Society of Chemistry 2012 Dynamic Article Links C < Analytical Methods Cite this: Anal. Methods, 2012, 4, 3140 www.rsc.org/methods PAPER Published on 21 August 2012. Downloaded by Manchester Metropolitan University on 14/03/2015 10:54:53. View Article Online / Journal Homepage / Table of Contents for this issue