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(SC(6)H(4)NC(H)C(6)H(4)OCH(2)CH(2)SMe)(eta(5)-C(5)H(5))](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 Au electrode in 0.1M 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, E degrees ', varied with pH to give a slope of about -30mVpH(-1). The surface concentration, G, of the nickel redox centres was found to be 1.548x10(-11)molcm(-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 H(2)O(2). The electrocatalytic-type biosensor displayed typical Michaelis-Menten kinetics and the limit of detection was found to be 6.25mM.