Amperometric phenol biosensor based on polyaniline

The catechol biosensor is constructed by cross-linking between polyphenol oxidase (PPO) and polyaniline (PANI) using glutaraldehyde as a cross-linking agent. The PANI, which is electrochemically synthesized in a solution containing ionic liquid, 1-ethyl-3-methylimidazolium ethyl sulfate, possesses good electroactivity and high conductivity above pH 6. In the presence of catechol as a substrate, the biosensor exhibits a linear range from 0.2 to 80 μmol dm^-3. The maximum response current (I_max) and the Michaelis-Menten constant (k^′_m) are 9.44 μA and 117 μmol dm^-3, respectively. The effects of pH and operating potential are also explored to optimize measurement conditions. The activation energy (E_a) of the PPO catalytic reaction is 30.23 kJ mol^-1 in the B-R buffer. Electrochemical impedance spectroscopy (EIS), UV-vis and SEM are used to characterize the PANI-PPO biosensor. The biosensor exhibits good long-term stability.