An amperometric hydrogen peroxide biosensor based on immobilizing horseradish peroxidase to a nano-Au monolayer supported by sol–gel derived carbon ceramic electrode

A novel strategy for fabricating horseradish peroxidase (HRP)-based H2O2 sensor has been developed by combining the merits of carbon sol–gel supporting matrix and nano-scaled particulate gold (nano-Au) mediator. The thiol functional group-derived carbon ceramic electrode (CCE) was first constructed using (3-mercaptopropyl) trimethoxy silane as sol–gel monomer. Then, the stable nano-Au monolayer was obtained through covalent linkage between nano-Au and thiol group on the surface of CCE. The experimental results showed that nano-Au monolayer formed not only could steadily immobilize HRP but also efficiently retain its bioactivity. Hydrogen peroxide was detected with the aid of hydroquinone mediator to transfer electrons between the electrode and HRP. The process parameters for the fabrication of the enzyme electrode and various experimental variables such as the operating potential, mediator concentration and pH of background electrolyte were explored for optimum analytical performance of the enzyme electrode. The biosensor had a fast response of less than 8 s with linear range of 1.22×10−5 to 1.10×10−3mol l−1 and a detection limit of 6.1×10−6mol l−1. The sensitivity of the sensor for H2O2 was 0.29 A l mol−1 cm−2. The activation energy for enzyme reaction was calculated to be 10.1 kJ mol−1. The enzyme electrode retained 75% of its initial activity after 5 weeks storage in phosphate buffer at pH 7.