Fabrication and simulation of inverse poly(ferrocenylmethylvinylsilane)/silica opal structures and their optical properties

Photonic crystal structures were fabricated by the formation of periodic arrays of poly(ferrocenylsilane) (PFS) derivations and silica spheres. Here, we present the primary steps of a simulation-driven design of photonic crystal based on PFS as a potentially stimuli-responsive polymer, which can present predesigned color when subjected to the visible light. The poly(ferrocenylmethylvinylsilane) (PFMVS) was synthesized by photolytic anionic ring opening polymerization of methylvinylsila[1]ferrocenophane monomer under controlled condition and monodisperse silica spheres were synthesized by the Stober process. Bare silica opal was prepared by the convective self-assembly process of different sizes of silica spheres on glass substrate followed by infiltration of PFMVS to obtain PFMVS/silica opal and finally removal of the silica spheres by acid washing to attain the inverse PFMVS opal. The particle size of silica spheres along with the refractive indices contrast of different components forming photonic crystal played an important role in obtaining the maximum reflectance wavelength of the desired opal. Photonic crystal prepared by 210, 270, and 330 nm monodisperse silica spheres represents the blue, green, and red color, respectively. Simulation analyses of these opal structures were investigated by using the plane-wave expansion (PWE) method to assess the photonic crystal behavior versus the visible light. According to the simulation results, the photonic crystal structure was designed. The experimental reflectance outcomes of the three opal structures were in good agreement with the simulation analysis.