Color Functional Response Composites Based On Fe₃O₄ Photonic Crystals

Polymer matrix composites have excellent mechanical properties,so as the structural materials,they are widely used in civil construction,aerospace,military ships and other neighborhoods.While the development of composite materials as structural materials is more mature,the future development field of composite materials is to explore more functions applications of composite materials.Compared with shape memory composites,electroactive composites and self-repairing composites,photonic crystal composites are favored by many researchers because of their unique optical properties.For example,the internal composition of photonic crystal composites shows a highly ordered crystal structure,so that it shows a bright and stable photonic crystal structure color macroscopically.At the same time,external environmental stimulation can change the structure of photonic bandgap in photonic crystals,so that the color of photonic crystal composites can show dynamic and reversible changes in the visible light range.In many types of responsive photonic crystals,magnetic response photonic crystals can achieve fast response to the intensity of external magnetic field,which has the advantages of high efficiency and reversibility.Therefore,this paper mainly uses superparamagnetic Fe₃O₄ nanoparticles as the basic unit,uses Marangoni self-assembly method and magnetic induced impregnation method to prepare Fe₃O₄ photonic crystal color composites,at the same time,studies the specific functional response of Fe₃O₄ photonic crystal color composites.In this paper,ethylene glycol（EG）was used as the dispersion medium of solvothermal method,and surfactant sodium citrate（Na₃Cit）was added to prepare the saturation magnetization was 60.149 emu/g and with carboxyl modification superparamagnetic Fe₃O₄nanoparticles.The reaction time and the concentration of the surfactant Na₃Cit in the reaction system have significant effects on the morphology and particle size of the product Fe₃O₄nanoparticles.Using the balance between electrostatic repulsion and magnetic dipole attraction induced by external magnetic field,the Fe₃O₄ photonic crystal solution was prepared by using superparamagnetic Fe₃O₄ colloidal particles as the basic unit.Using the two-phase solvent system with different surface tension and boiling point,by introducing Marangoni effect to control the self-assembly of solute Fe₃O₄ colloidal particles in the process of solution evaporation and drying,uniform thickness and uniform color Fe₃O₄ photonic crystal color films were prepared.At the same time,it was found that due to the surface wettability of the substrate material is different,resulting in different deposition rates of Fe₃O₄colloidal particles on the surface of the substrate,then the color of Fe₃O₄ photonic crystal films was different.By using magnetic induced impregnation method,the superparamagnetic Fe₃O₄ colloidal particles were self-assembled on the surface of carbon fiber by the combined action of magnetic dipole interaction and electrostatic repulsion force between Fe₃O₄ colloidal particles to form Fe₃O₄ photonic crystal color carbon fiber with face centered cubic three-dimensional crystal structure.Based on the preparation principle of responsive photonic crystals,the photonic bandgap structure of Fe₃O₄ photonic crystals is directionally regulated to realize the functional response of Fe₃O₄ photonic crystal color composites.By adjusting the distance between the permanent magnet and the colorimetric dish,resulting in the distance increase between two Fe₃O₄ colloidal particles.Finally,the wavelength of the diffraction peak of the Fe₃O₄ photonic crystal solution shifted to the long wavelength,thus realizing the magnetic field intensity response of the Fe₃O₄ photonic crystal solution.By clockwise turning the Fe₃O₄ photonic crystal color film,the Bragg diffraction angleθin the crystal structure was gradually changed,so that the diffraction peak wavelength of the Fe₃O₄ photonic crystal color film shifted to the short wavelength,and the angular response of the Fe₃O₄ photonic crystal color film was realized.Fe₃O₄ photonic crystal color carbon fiber was placed on a self-made solvent response device to study the solvent response of Fe₃O₄ photonic crystal color carbon fiber.