Homogenous Thionine-SiO<SUB>2</SUB> Nanocomposite Spheres: Sonochemical Preparation, Characterization, and Application in H<SUB>2</SUB>O<SUB>2</SUB> Biosensor

The electrochemical properties of new homogenous thionine (TH)-doped silica nanoparticles as a mediator were studied. The nanocomposites were synthesized by using sonochemical method. The sonication induced the strong combination between dye molecules and silica in the construction of the composites. By controlling reaction condition, face rougher uniform spheres could be achieved. The as-prepared nanocomposites can be used as the mediator to construct the biosensors with horseradish peroxidase coimmobilized in the gelatine matrix and cross-linked with formaldehyde. The described experimental evidences show the different ratio of ethanol to water can induce the changes in their diameters. As a consequence, the resulting biosensors exhibited amperometric response decreased with the increase of the spherical size. The resulting biosensor mediated by the 100 nm diameter of TH-doped silica nanoparticles exhibited very fast amperometric response, good stability and could be effectively used for the study of the electrocatalytic properties.