Ultrasensitive Hydrogen Peroxide Biosensor Based on Enzyme Bound to Layered Nonoriented Multiwall Carbon Nanotubes/Polyelectrolyte Electrodes

A sensitive hydrogen peroxide sensor based on horseradish peroxidase covalently attached to layered nonoriented MWNTs modified electrode is presented. Cyclic voltammetry results gave quasi‐reversible Fe^III/Fe^II voltammetry. The electron transfer rate constant (k_s) and Michaelis–Menten constant (K_M) in pH 7 is 48.8±0.9 s^?1 and 0.13±0.05 mM respectively. A linear calibration curve for hydrogen peroxide was obtained up to 120 nM under the optimized conditions with a remarkable detection limit of (S/N=3) 1.5 nM. Results suggest that the nonoriented nanotubes act as electrical conductors and may also provide large surface area facilitating facile electron transfer and excellent electrochemical catalysis.