Photonic crystals with tunable optical stop band through monodispersed silica–polypyrrole core-shell spheres

We prepared monodispersed silica–polypyrrole core-shell spheres (SiO2–Ppy) using adsorbed surfactant bilayers on silica as templates and demonstrated the construction of photonic crystal with tunable stop band from SiO2–Ppy core-shell spheres. Since the photonic stop band is very dependent on the refractive index, it can be tuned by simply changing the refractive index of Ppy shell via changing doping level. In fact, the stop band was shifted about 15 nm when the photonic crystal was exposed to fuming sulfuric acid due to the change of the doping level of Ppy shell.