Magnetic titania-silica composite-Polypyrrole core-shell spheres and their high sensitivity toward hydrogen peroxide as electrochemical sensor

A novel core-shell sphere with controlled shell thickness was synthesized by in situ chemical oxidative polymerization of pyrrole on FTS (Fe₂O₃/TiO₂/SiO₂ composite) surface. The dual porosity of 2-3 nm and 40-50 nm in FTS core particle provides the hybrids with a high surface area to volume ratio, which enormously facilitates the molecule diffusion process. Furthermore, the porous FTS particle encapsulate Fe₂O₃ and TiO₂ leading to its synergetic interaction with the PPy coating based on FTIR analysis. The unique structure and composition of the hybrid spheres result in new sensing property that is not available from their single counterparts. Cyclic voltammetry results demonstrate that the spheres with appropriate concentration of PPy exhibit enhanced electrocatalytic activity toward the reduction of H₂O₂ in 0.1 M phosphate buffer solution. The sensing performance tests show that the hybrids possess good linear response in wide H₂O₂ concentration range (10-4000 μM) and high sensitivity to H₂O₂ (0.653 A M⁻¹ cm⁻²) at room temperature. The formation mechanism of the spheres was proposed based on the fact that the FTS core was coated firstly by a smooth PPy layer and then PPy nanoparticles. The work reported here provides an alternative concept for preparation of functional materials with new nanostructures and properties.