Sol–gel-derived amperometric biosensor for hydrogen peroxide based on methylene green incorporated in Nafion film

A hydrogen peroxide biosensor was fabricated by coating a sol–gel–peroxidase layer onto a Nafion-methylene green modified electrode. Immobilization of methylene green (MG) was attributed to the electrostatic force between MG+ and the negatively charged sulfonic acid groups in Nafion polymer, whereas immobilization of horseradish peroxidase was attributed to the encapsulation function of the silica sol–gel network. Cyclic voltammetry and chronoamperometry were employed to demonstrate the feasibility of electron transfer between sol–gel-immobilized peroxidase and a glassy carbon electrode. Performance of the sensor was evaluated with respect to response time, sensitivity as well as operational stability. The enzyme electrode has a sensitivity of 13.5 μA mM−1 with a detection limit of 1.0×10−7 M H2O2, and the sensor achieved 95% of the steady-state current within 20 s.