| Due to the characteristics of high refractive index,high thermal stability and photoinduced superhydrophilicity,TiO2 materials with different morphologies(including TiO2 nanoparticles(TiO2 NPs)and TiO2 core-shell microspheres)have exhibited obvious application advantages in the field of photonic crystals.However,there are still some problems in the applications of TiO2 NPs and TiO2 core-shell microspheres in photonic crystals.The composites of TiO2 NPs and photonic crystal usually needs to be calcined at high temperature to make amorphous TiO2 crystallize.It is difficult to accurately control the diameter and morphology of TiO2 core-shell microspheres,and the structure stability of the assembled photonic crystals is poor.Amorphous TiO2 core-shell microspheres will become agglomerated and ruptured and the dispersion will become worse when calcined at high temperature,which will affect the assembly of photonic crystals.In order to solve these problems,in this thesis,TiO2poly(hydroxyethyl acrylate)(PHEA)stabilized photonic crystal composites were prepared at room temperature.TiO2 core-shell microspheres with controllable particle size and morphology were synthesized,and structurally stable two-dimensional photonic crystals(2D PC)were prepared.Monodisperse TiO2@SiO2 hollow microspheres were prepared by silicon protected calcination method,and three-dimensional photonic crystals were assembled,which retained bright structural color after solvent infiltration.The anatase TiO2 NPs modified by triethanolamine were dispersed in hydroxyethyl acrylate(HEA)to prepare pre-polymerization dispersion.The pre-polymerization dispersion was filled and coated on the surface of PS photonic crystal by spin coating method.TiO2PHEA/PS photonic crystal composites were prepared by UV polymerization at room temperature.The structural stability of the composites was improved by locking the structure of TiO2 NPs and PS photonic crystals with PHEA.The composite had bright structural colors,and the water contact angle of the surface could be reduced to less than 5° in 0.3 s.The superhydrophilicity could be maintained in the laboratory environment for 180 days.The composites also had self-cleaning properties.P(St-MAA)@TiO2 microspheres with uniform size and regular morphology were prepared by using hexadecylamine as structure guiding agent and carboxyl-containing poly(styrenemethacrylic acid)(P(St-MAA))microspheres as core during the hydrolysis of titanium alkoxide precursors with high reaction activity.2D PC was prepared on glass substrates from P(StMAA)@TiO2 microspheres with diameters of 255 nm,308 nm,323 nm,339 nm and 360 nm,respectively,which showed angle-dependent structural colors.When the 2D PC was sealed in a transparent substrate,it was transparent in air and immediately showed bright structural colors in water.The structural colors of 2D PC could be adjusted by the change of refractive index of external medium,namely,the structural colors of 2D PC could be adjusted non-invasively.The mechanism of transparent-iridescent instant transformation could be explained by diffraction theory of 2D PC.Sealed 2D PC could be used as information encryption material to realize the function of the covert-overt transformation of QR code,patterns and text.Anatase TiO2@SiO2 hollow microspheres with regular morphology,uniform size and good dispersion were prepared by coating SiO2 thin layer on the surface of P(St-MAA)@TiO2 microspheres and calcined at 900℃.Opal photonic crystals with bright blue,cyan,green and orange were assembled from TiO2@SiO2 hollow microspheres with diameters of 220 nm,233 nm,262 nm and 277 nm,respectively.Due to the large refractive index contrast between the TiO2 shell and the hollow sphere,the reflection peak of the hollow TiO2@SiO2 photonic crystal was red-shifted and the brightness of the structural color was enhanced to a certain extent after the hollow TiO2@SiO2 photonic crystal was infiltrated by ethanol. |
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