Direct electrochemistry and electrocatalysis of myoglobin based on silica-coated gold nanorods/room temperature ionic liquid/silica sol-gel composite film

A novel biosensor based on the silica-coated gold nanorods (GNRs@SiO₂) and hydrophilic room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium tetrafluroborate (bmim]BF₄]) was fabricated for the determination of hydrogen peroxide (H₂O₂) and nitrite. GNRs@SiO₂ can not only act as a binder to hinder bmim]BF₄] (RTIL) leaking from the electrode surface, but also provide a favorable microenvironment for direct electrochemistry of myoglobin (Mb). A pair of well-defined and quasi-reversible redox peaks of Mb was obtained at the GNRs@SiO₂-Mb/RTIL-sol-gel composite film modified GCE (GNRs@SiO₂-Mb/RTIL-sol-gel/GCE) through direct electron transfer between Mb and the underlying electrode. This biosensor showed an excellent electrocatalytic activity towards hydrogen peroxide and nitrite. The linear range for the determination of H₂O₂ was from 0.2 to 180 μM with a detection limit of 0.12 μM based on the signal-to-noise ratio of 3. In addition, the biosensor also exhibited high selectivity, good reproducibility, and long-term stability. Therefore, this kind of composite film can provide an ideal matrix for protein immobilization and biosensor fabrication.