A novel polyphenol oxidase immobilized polyglycine/reduced graphene oxide composite electrode for sensitive determination of catechol

In this study, we report a new type of flexible and free standing paper electrochemical sensor fabricated by integrating reduced graphene oxide (rGO), poly(glycine) and polyphenol oxidase (PPO) enzyme. For the sensor development, firstly, electrochemical polymerization of glycine at the rGO paper electrode was carried out by the cyclic voltammetric method, and then the poly(glycine)/rGO paper electrode was further utilized as a matrix to immobilize the PPO enzyme purified from potato. The developed PPO-poly(glycine)/rGO immobilized paper sensor was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Enzyme aggregation and distribution within the poly(glycine)/rGO paper electrode were studied using a fluorescence microscope. The electrochemical behavior of catechole (CC) on PPO-poly(glycine)/rGO immobilized paper electrode was investigated by cyclic voltammetry and amperometry. The sensor performed well in the concentration range of 0.1-800 mu M, with a detection limit of 0.07 mu M and a sensitivity of 0.0512 mA mu M cm(-2).