A novel protocol for covalent immobilization of thionine on glassy carbon electrode and its application in hydrogen peroxide biosensor

A novel protocol for effectively covalent immobilization of thionine (Th) was proposed, which was based on Schiff-base reaction between –NH2 of Th and –COH which was in situ generated on glassy carbon electrode (GCE) via simple potentiostatic activation in diluted nitric acid. GCE pretreated by potentiostatic activation possessed CHO-riched surface and microporous structure with high distribution density of electron transfer sites, and thus it became a good candidate for effective immobilization of Th through imine bond with high stability. The application of the resulting Th modified electrode in hydrogen peroxide biosensor was also investigated and it exhibited rapid response to H2O2 within 3 s. The linear calibration ranged from 5.0 × 10−7 to 5.8 × 10−3 M with a detection limit of 1.0 × 10−7 M. The effective immobilization of Th on potentiostatically activated GCE surface has deep significance in mediator immobilization, on which further researches based are under way.