Electrocatalytic sensor devices: (I) cyclopentadienylnickel(II) thiolato Schiff base monolayer self-assembled on gold

The fabrication of a self-assembled monolayer (SAM) of a cyclopentadienylnickel(II)thiolato Schiff base compound, [Ni(SC6H4NC(H)C6H4OCH2CH2SMe)(eta(5)-C5H5)](2) on a gold electrode is described. Effective electronic communication between the Ni(II) centres and the gold surface was established by electrochemically cycling the Schiff base-doped An electrode in 0.1 M NaOH from -200mV to +600mV. The SAM-modified electrode exhibited quasi-reversible electrochemistry. The integrity of this electrocatalytic SAM, with respect to its ability to block and electro-catalyse certain Faradaic processes, was interrogated using cyclic voltammetric experiments. The formal potential, Edegrees', varied with pH to give a slope of about -30mVpH(-1). The surface concentration, G, of the nickel redox centres was found to be 1.548 x 10(-11) mol cm(-2). By electrostatically doping the SAM using an applied potential of +700mV versus Ag/AgCl, in the presence of horseradish peroxidase (HRP), it was fine-tuned for amperometric determination of H2O2. The electrocatalytic-type biosensor displayed typical Michaelis-Menten kinetics and the limit of detection was found to be 6.25 mM. (C) 2004 Elsevier B.V. All rights reserved.