| Photonic crystals（PCs）are also known as photonic bandgap materials.Due to the material with periodic dielectric structures the light propagation can be limited in a certain direction or trapped the light in a certain region.Generally,the PCs with on-demand band gap is a constant expectation of researchers after PCs were discovered and proposed.Importantly,there are two ways to regulate the photonic band gap（PBG）,change the effective refractive index or change the lattice constant.To our best knowledge,the change rate of PBG which induce by lattice constant always lower than the change of refractive index,but with larger variation range.Thus,our study on PBG was also based on the change of lattice constants.In this research,we successfully synthesized the monodispersed silica spheres with diameter ranges from 200 nm to 300 nm by a modified St?ber method.Two different inverse opal hydrogel photonic crystals（IOH）were prepared via a template sacrifice method and then their optical properties were studied,especially for PBG.The results are as follows:（1）Owning to the temperature is an important factor among the synthesis of silica particles,we precisely keep the temperature within 29oC to 35oC and synthesized the SiO2 particles with good dispersibility（200300 nm）.Then the silica spheres with a diameter of 220 nm were used as raw materials for the three-dimensional opal photonic crystal template preparation by a vertical self-assembly method.Followed,we used this silica template to prepare two different inverse opal hydrogels（methacrylic acid based inverse opal and azobenzene based inverse opal）,and then we did SEM and optical characterization of them.The examination results showed that the inverse opal structures with an ordered polymer scaffold and the air spheres were in an FCC arrangement over the entire sample with a close-packed plane（111）oriented parallel to the substrate as well as with narrower half peak width.（2）Typically,it was found that when the concentration of malachite green carbinol base（MGCB）was 0.48 mM,the pH of the solution reached the maximum at 9.2（input current was 20 A）.In addition,the cross-linker has a significant influence on the sensitivity of the inverse opal hydrogel.When the inverse opal with a cross-linker of10%,the photonic band gap could tuned from 443652 nm in 10 min.（3）In view of the need to immerse the methacrylic acid based inverse opal hydrogel in the MGCB solution to achieve the tunable photon band gap（209 nm）,the wide application of photonic crystals was greatly limited.Therefore,we induced the azobenzene and cyclodextrin derivatives into the inverse opal skeleton and expected that under the direct light stimulation,the supermolecule guest-host interaction could change the lattice parameters and lead to broad wavelength red-shift of photonic band gap.We have successfully prepared the pure azobenzene based inverse opal structures based on the synthesis of 4-azobenzene.After 10 minutes of UV（365 nm）exposure the photonic band gap was moved 19 nm. |
