Synthesis of IrO₂ decorated core-shell PS@PPyNH₂ microspheres for bio-interface application

In this paper, an effective approach is demonstrated for the fabrication of IrO₂-decorated polystyrene@functionalized polypyrrole (core@shell; PS@PPyNH₂) microspheres. The synthesis begins with the preparation of monodispersive PS microspheres with a diameter of 490 nm, by a process of emulsifier-free emulsion polymerization, followed by a copolymerization process involving pyrrole and PyNH₂ monomers in a PS microsphere aqueous suspension, to produce uniform PS@PPyNH₂ microspheres with a diameter of 536 nm. The loading of 2 nm IrO₂ nanoparticles onto the PS@PPyNH₂ microspheres can be easily adjusted by tuning the pH value of the IrO₂ colloidal solution and the PS@PPyNH₂ suspension. At pH 4, we successfully obtain IrO₂-decorated PS@PPyNH₂ microspheres via electrostatic attraction and hydrogen bonding simultaneously between the negatively-charged IrO₂ nanoparticles and the positively-charged PS@PPyNH₂ microspheres. These IrO₂-decorated PS@PPyNH₂ microspheres exhibit a characteristic cyclic voltammetric profile, similar to that of an IrO₂ thin film. The charge storage capacity is 5.19 mA cm^-2, a value almost five times greater than that of PS@PPyNH₂ microspheres. In addition, these IrO₂-decorated PS@PPyNH₂ microspheres exhibit excellent cell viability and biocompatibility.