Electrocatalytic Properties of Heme Proteins in Layer‐by‐Layer Films Assembled with SiO2 Nanoparticles

Electrochemical and electrocatalytic properties of heme proteins, including myoglobin (Mb), hemoglobin (Hb), and horseradish peroxidase (HRP), in layer‐by‐layer films assembled with SiO2 nanoparticles were investigated at pyrolytic graphite (PG) electrodes. The stable layer‐by‐layer {SiO2/protein}n films showed a pair of well‐defined, nearly reversible cyclic voltammetric peaks at about −0.25 V (vs. SCE) at pH 5.5, characteristic of the protein heme FeIII/FeII redox couples. The proteins in the films displayed good electrocatalytic activities toward various substrates such as oxygen, hydrogen peroxide, trichloroacetic acid, and nitrite, and showed a potential applicability in fabricating the new kind of biosensors without using mediators. Electrochemical parameters of the protein films such as apparent heterogeneous electron transfer rate constant (ks) and formal potential (E°′) were estimated by square‐wave voltammetry and nonlinear regression analysis. The influencing factors like the number of bilayer and the pH of external solution were also investigated.