A hydrogen peroxide biosensor based on polyaniline/FTO

The hydrogen peroxide biosensor is constructed by cross-linking between horseradish peroxidase (HRP) and polyaniline (PANI) using glutaraldehyde as a cross-linking agent on F-doped tin oxide (FTO) electrode. The PANI synthesized in a solution containing ionic liquid, 1-ethyl-3-methylimidazolium ethyl sulfate (EMIES), is an electroactive polymer at pH over 6. The process of immobilized HRP is unrelated to isoelectric point of the enzyme and is particularly mild. The response current increases linearly with increasing hydrogen peroxide concentration up to 20 mmol dm^-3. The maximum response current (I_max) and the Michaelis-Menten constant (k^′_m) are 1.189 μA and 27.11 mmol dm^-3, respectively. The response current of the biosensor increases with increasing temperature below 40 °C. The activation energy (E_a) of the HRP catalytic reaction is 39.1 kJ mol^-1 in the B-R buffer. It is seen from UV-vis spectra that the main position of combination between HRP and PANI is located at the nitrogen site of the quinoid ring in polyaniline. The biosensor is also characterized with SEM and CV.