Fabrication And Functionalization Of The SiO₂-based Structurally Colored Materials

Structural color is original from the interaction between lights and microstructures of materials.SiO₂ is one kind of ideal materials for the preparation of photonic crystals,due to its environmental friendly and cheap characteristics.Although rapid development has been achieved in recent years,there are still some problems needed to be resolved.First,the color saturation of colored films assembled by hollow spheres is very low and the color always looks whitish;Next,the bonding strength between nanospheres?films and substrates are very weak;In addition,when the colored films were in contact with liquids,the color will change due to the variation of periodicities.Based on this,the PS,PS@SiO₂,hollow SiO₂ and SiO₂ nanospheres were prepared respectively.The performances in differentr aspects have been improved through adjusting the arrangement of microspheres and fillers in the intervals between neighbouring nanospheres.The concrete research content is as follows:?1?Different sized monodisperse PS nanospheres were prepared by emulsion polymerization method;monodispersed PS@SiO₂ nanospheres were prepared by St?ber method.Photonic Crystals?PCs?films of PS@SiO₂ were prepared by a vertical deposition method.After calcination under reducing atmosphere,the hollow SiO₂ PCs films were obtained.The color variations and the role of carbon element were studied.SEM and TEM analysis showed that the size of PS and SiO₂ nanospheres are homogeneous;the shell thickness is uniform.Film analysis indicate that the microstructure are well ordered FCC close packing structures,the reflection peaks red shifted as the increase of particle size;EDS result showed that the PS nanoaspheres are partly carbonized and remained within the hollow SiO₂ microspheres after calcined in reduced atmosphere.By contrast,we found that the C element only improve the color saturation of hollow SiO₂ PCs without affect the structure colors.?2?Hollow SiO₂ PCs were obtained by removing PS templates under calcination.Hollow SiO₂-PDMS films were prepared by infiltrating PDMS into the open pores.The connection between color and the structures were analyzed,the roles of different compositions were discussed;the microstructure of the as-prepared materials,color saturation and hydrophobic effect have been characterized and discussed.SEM,TEM and reflection spectrum analysis showed that the microstructures of different PCs films are FCC close packed and highly ordered structures;when compared with PS@SiO₂ PCs,the reflection peaks of hollow SiO₂ PCs have a blue shift,the color saturation and peak intensity is decreased;after the PDMS were filled into the open pores,reflection peak intensity and color saturation increased again.Film analysis showed that: film strength was significantly increased after PDMS filled;when contact with the liquid,the liquid cannot destroy the microstructures and the color of the film is not changed.?3?SiO₂/TiO2/PDMS composite films were obtained after TiO2 sol and PDMS were infiltrated.The as-prepared colored films were characterized by reflection spectra and other test methods.The reason why they have the same color appearance and the difference between PS@SiO₂ and SiO₂/TiO2/PDMS composite films were discussed.SEM,EDS and XRD analysis showed that TiO2 sol has been successfully filled into the hollow SiO₂ PCs,the spectral reflectance and optical image analysis showed that the PS@SiO₂ PCs films and SiO₂/TiO2/PDMS films displayed the same color appearance.At the same time,the colors of SiO₂/TiO2/PDMS films do not change when in contact with different liquid.?4?Monodispersed SiO₂ nanospheres of different size were prepared by a St?ber method.Different colored coatings of SiO₂ were prepared by spray coating a mixture of SiO₂ nanospheres and carbon black.Superhydrophobic colored films were obtained after PDMS solutions were spray coated onto SiO₂ films and cured at 150 ? for 30 min.SEM analysis indicate that the microstructure of the film is amorphous,carbon black particles in this system are reunion together.Reflectance spectrum and optical image analysis showed that the colors are not changed with the viewing angles.Contact angle?CA?analysis showed that the prepared colored coatings are super-hydrophobic,the CA can reach to above 160 o and rolling angles less than 2°.