Electrochemical sensor for H2O2 based on thionin immobilized 3-aminopropyltrimethoxy silane derived sol–gel thin film electrode

An electrochemical sensor using thionin as a mediator for hydrogen peroxide determination is described. The mediator was covalently immobilized with 3-aminopropyltrimethoxy silane (APTMOS) which is also used as the sol–gel precursor. The covalent immobilization of thionin to sol–gel matrix was achieved through glutaraldehyde cross-linking. This sol–gel matrix was coated as a thin film over the graphite rod and characterized using cyclic voltammetry. The performance of the modified electrode was examined on various supporting electrolytes, scan rates and pHs. The modified electrode showed good electrocatalytic activity towards the reduction of hydrogen peroxide at a reduced overpotential. The catalytic current is linear with hydrogen peroxide concentration ranging from 3.82 × 10−6 M to 4.07 × 10−3 M with a detection limit of 1.53 × 10−6 M and a correlation coefficient of 0.9951. Due to the covalent cross-linking of the mediator, the sensor showed a constant and reproducible response for more than 2 months.