Preparation And Property Studies Of Functionalized Photonic Crystal Films

Photonic crystal?PC?is a periodic structure composed of materials with different dielectric constants.The most important feature of PC is the photonic band gap?PBG?,and the PC materials can diffract structural colors when their PBGs are located in the visible region.Currently,PC-based materials have been widely used as functionalized optical materials.Among which,PC sensing materials are one of the main research directions due to the changable structural colors.In this thesis,two-dimensional?2D?and three-dimensional?3D?hydrogel PC films were prepared by using poly?vinyl alcohol??PVA?hydrogel as matrix.The color diffracting properties of PC films were investigated,and the applications in the field of sensor detection of such PC materials were also studied.For 2D PCs,firstly,monodispersed polystyrene?PS?colloidal microspheres were prepared by emulsifier-free emulsion polymerization.Then,a 2D PC film with invisible printing pattern was prepared by mask-assisted photopolymerization.The results showed that the transparent 2D PC film could reveal a high-resolution of the red pattern?632 nm?and the green background?540 nm?when immersed in water.Then,600 nm PS nanospheres and PVA hydrogel were utilized to prepare a 2D PC by physical cross-linking.The PC hydrogel was functionalized with 4-boron benzaldehyde?4-BBA?to make it glucose sensitive.The effect of cross-linking time on the sensitivity of the PC film was investigated.The results of the glucose sensing test in artificial tear fluids?ATF?showed that the diffraction wavelength of the PC film has a linear correlation with the glucose concentration in the low concentration range?0⁰.6 mM?.For 3D PCs,monodispersed poly?methylmethacrylate??PMMA?nanospheres were prepared by emulsifier-free emulsion polymerization.Nanospheres with different particle sizes were obtained by changing the feeding amount of methylmethacrylate?MMA?during polymerization.A PVA gel-based PC film with high transparency was prepared.The PBG of PVA-PCs can be adjusted to cover the ultraviolet?UV?and visible region by changing the particle size of the PMMA colloidal nanospheres.The results show that:PC-150 film has78.89%UV-365 shielding property with 85%transparency.At the same time,the PC film with the PBG in the visible light region has potential application in the field of color filter materials.Then,we studied the self-helable PVA hydrogel PC prepared by the freeze-thaw method.The PVA hydrogel prepared by freezing for 12 h and thawing for 1 h showed good mechanical properties as well as the self-healing properties.After that,we make PVA respond to Ni²⁺by modifing with maleic anhydride,and captured the reflection spectrum of the modified gel PC film respond to different Ni²⁺concentration under different pH conditions.The PC film showed the best responsiveness Ni²⁺at pH=5.