Highly sensitive amperometric biosensors for phenols based on polyaniline–ionic liquid–carbon nanofiber composite

A novel polyaniline–ionic liquid–carbon nanofiber (PANI–IL–CNF) composite was greenly prepared by in situ one-step electropolymerization of aniline in the presence of IL and CNF for fabrication of amperometric biosensors. The scanning electron micrographs confirmed that the PANI uniformly grew along with the structure of CNF and the PANI–IL–CNF composite film showed a fibrillar morphology with the diameter of around 95 nm. A phenol biosensor was constructed by immobilizing tyrosinase on the surface of the composite modified glassy carbon electrode via the cross-linking step with glutaraldehyde. The biosensor exhibited a wide linear response to catechol ranging from 4.0 × 10−10 to 2.1 × 10−6 M with a high sensitivity of 296 ± 4 A M−1 cm−2, a limit of detection down to 0.1 nM at the signal to noise ratio of 3 and applied potential of −0.05 V. According to the Arrhenius equation, the activation energy for enzymatic reaction was calculated to be 38.8 kJ mol−1 using catechol as the substrate. The apparent Michaelis–Menten constants of the enzyme electrode were estimated to be 1.44, 1.33, 1.16, 0.65 μM for catechol, p-cresol, phenol, m-cresol, respectively. The functionalization of CNF with PANI in IL provided good biocompatible platform for biosensing and biocatalysis.