Electrochemistry and electrocatalytic properties of mixed assemblies of horseradish peroxidase, poly(diallyl dimethylammonium chloride) and gold nanoparticles on a glassy carbon electrode

Poly(diallyldimethylammonium chloride), gold nanoparticles (Au-NPs; 2-5 nm) and horseradish peroxidase (HRP) were alternately self-assembled on a glassy carbon electrode. Due to the conducting wire effect of the Au-NPs, the HRP undergoes direct electrochemistry with a small peak-to-peak separation of 33 mV and a formal potential of -0.370 V (versus SCE). The reaction involves a single electron transfer coupled to a one-proton transfer reaction. Electrochemical impedance spectroscopy and cyclic voltammetry also were applied to characterize the self-assembly process and to study the electrochemical behavior of the immobilized HRP. Its good electrocatalytic response to the reduction of hydrogen peroxide resulted in a novel third-generation biosensor for this species.