A nano-structured Ni(II)–ACDA modified gold nanoparticle self-assembled electrode for electrocatalytic oxidation and determination of tryptophan

A nano-structured Ni (II)/ACDA (2-amino-1-cyclopentene-1-dithiocarboxylic acid) film was electrodeposited on a gold nanoparticle–cysteine–gold electrode. The formation of Ni (II)/ACDA film and electrocatalytic oxidation of tryptophan on the surface of the modified electrode were investigated with cyclic voltammetric and chronoamperometric techniques. The hydrodynamic amperometry at rotating modified electrode was used for determination of tryptophan in the range of 0.085–43.0 μmol l−1. The detection limit was found to be 23 nmol l−1. The rate constant, transfer coefficient for the catalytic reaction and the diffusion coefficient of tryptophan in the solution were found to be 9.1 × 102 M−1 S−1, 0.52 and 1.09 × 10−5 cm2 s−1 respectively. It is worth noting that the as formed matrix in our work possesses a 3D porous network structure with a large effective surface area and high catalytic activity and behaves like microelectrode ensembles. The modified electrode indicated reproducible behavior and a high level stability during the experiments, making it particularly suitable for the analytical purposes.

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► Cysteine has been used to immobilize gold nanoparticles on a bulk gold electrode.
► The AuNPs were distributed evenly and formed almost a continuous monolayer on the surface of the Au.
► Cyclic voltammetric method was utilized for deposition of nano structure Ni–ACDA on the gold nanoparticle surface.
► The presence of AuNP supplied a larger surface area to allow more deposition of Ni(II)/ACDA complex.