Preparation And Application Of Photoresponsive Fluorescent Photonic Crystal Materials

Photonic crystals（PCs）are a hot topic in the field of materials.Due to the periodic arrangement of particles in the material at the microscopic scale,the photonic crystal has special optical properties,including photonic band gap（PBG）and structural color.The typical materials for preparing photonic crystals are some monodisperse colloidal particles,such as polystyrene colloidal particles and silica colloidal particles.In recent years,photonic crystal materials with specific response properties have become a research hotspot by combining photonic crystals with stimulus response materials.The combination of photonic crystals with soft materials,photosensitive materials,conductive materials,thermal materials and other functional materials has attracted many researchers and expanded the application depth and breadth of photonic crystals.Stimulation-responsive photonic crystal materials have become a new hot research field.Photoresponsive fluorescent photonic crystals have become the focus of our attention due to their non-contact,reversibility and high sensitivity.Focusing on the optical properties of photoresponsive fluorescent photonic crystals,this paper combined the structural colors of colloidal photonic crystals with the ultraviolet fluorescence characteristics of spiropyan,designed and prepared fluorescent photonic crystal materials with multiple display modes and information coding functions,and studied its multiple response process.Its application value in multi-information coding,multi-responsiveness display and multi-mode display is explored.The main contents include:1.Preparation and response behavior of photoresponsive fluorescent photonic crystal materials.Based on the optical properties of the photonic crystal and spiropyran,the spiropyran modified photonic crystal materials were prepared.The material has both the structural color of photonic crystal and the fluorescence characteristics of spiropyran,according to which a multi-mode coding pattern was designed and prepared.Monodisperse polystyrene colloidal particles modified with spiropyran were prepared by semicontinent emulsion polymerization.Three kinds of polystyrene colloidal particles with fluorescence color were prepared.Red,green and blue fluorescent photonic crystals were rapidly prepared by spraying method.Due to the rapid spraying process,this kind of photonic crystal has loose particle arrangement and wide reflection peak,which manifests as short-range ordered and long-range disordered particle arrangement on the micro level,and non-angle-dependent structural color on the macro level.Because spiropyran molecules are grafted into the particles,the photonic crystal emits bright red fluorescence at 365 nm.Therefore,the photonic crystal exhibits a bright structural color under natural light and a red fluorescence under 365 nm light,showing dual display characteristics.We make use of this property to prepare double-sided encryption cards,which can display different patterns or text information under different light irradiation,and explore its application value in optical encryption and multi-mode information display.2.Preparation and research on the photo-magnetic response behavior of multicolor photonic crystal microbeads.Janus structural photonic crystal spheres with photomagnetic dual response were prepared by microfluidic method.The microspheres can fluoresce under ultraviolet light excitation and rotate under magnetic field stimulation.We prepared precursor solution composed of spiropyran modified polymer microspheres and Fe₃O₄ particles as well as precursor solution composed of ordinary polystyrene microspheres and Fe₃O₄ nanoparticles,then input the precursor solution and dimethyl silicone oil into the microfluidic chip respectively.The emulsion droplets of uniform size were prepared,and then placed in the oven to dry.The particles in the liquid would gradually self-assemble,and six different spherical photonic crystals were obtained.Fe₃O₄ nanoparticles were deposited in the lower part of the microbead due to their high density,while polymer microspheres were filled in the whole microbead and formed crystal structural,thus Janus structure photonic crystal microbeads were obtained.Because the polymer colloidal particles are grafted with spiropyran derivatives,they have ultraviolet fluorescence characteristics and produce red fluorescence under 365 nm light excitation.Based on the photomagnetic response characteristics of photonic crystal microbeads,a lattice pattern was constructed in black mold.By adjusting the external magnetic field,the microbead can be changed from the structural color surface to the black iron surface,so as to realize the display and hiding of structural color information.Under ultraviolet light,the structural color information is transformed into fluorescence color information.Based on the dual response characteristics of Janus photonic crystal microbeads,a variety of coding patterns are designed to realize multi-dimensional information coding,which expended the applications in information display,multiple response materials as well as in optical coding.