A novel nitromethane biosensor based on biocompatible conductive redox graphene-chitosan/hemoglobin/graphene/room temperature ionic liquid matrix

A novel amperometric biosensor for nitromethane (CH3NO2) based on immobilization of graphene (GR), chitosan (CS), hemoglobin (Hb) and room temperature ionic liquid (IL) on a glassy carbon electrode (GCE) was developed for the first time. The surface morphologies of a set of representative membranes were characterized by means of scanning electron microscopy (SEM). The electrochemical performance of the biosensor was evaluated by cyclic voltammetry (CV) and chronoamperometry. A pair of stable and well-defined redox peaks of Hb with a formal potential of −0.240 V was observed at the GR-CS/Hb/GR/IL/GCE. The effects of phosphate buffer pH, scan rate, and temperature on the biosensor were investigated to provide optimum analytical performance. Moreover, several electrochemical parameters, e.g., the heterogeneous electron transfer rate constant (ks), were calculated in detail. The presence of both GR and IL not only dramatically facilitated the electron transfer of Hb, but also greatly enhanced electrocatalytic activity towards CH3NO2. The apparent Michaelis–Menten constant was down to 0.16 μM, indicating that the biosensor possessed high affinity to CH3NO2. Besides this, the proposed biosensor exhibited fast amperometric response (<5 s), low detection limit (6.0 × 10−10 M), and excellent long-time storage stability for the determination of CH3NO2.