Magnetic Assembly And Functionalization Of Nanominerals In Optical Field

Magnetic particles can be oriented along the magnetic field direction to achieve orderly arrangement under the magnetic field.Optical functional materials such as photonic crystal and liquid crystal can be obtained according to magnetic induced ordered nanostructure assembly.One-dimensional and two-dimensional natural nanominerals with unique structure,composition and properties can be used as structural base to prepare anisotropic magnetic nanoparticles by decorating with magnetic particles,achieving unique optical functional properties.In this paper,clay minerals@Fe3O4 nanocomposites,attapulgite@Fe3O4 nanorods,sepiolite@Fe₃O₄ nanowires and montmorillonite@Fe₃O₄ nanosheets,were prepared with core-shell structures by coprecipitation using three mineral materials?attapulgite,sepiolite and montmorillonite?,iron salts and polyethyleneimine.The resulting attapulgite@Fe₃O₄,sepiolite@Fe₃O₄ and montmorillonite@Fe₃O₄ are superparamagnetic.They can be oriented along the direction of the magnetic field and produce an instantaneously reversible response.These three magnetic composite mineral materials can be dispersed in a dilute acid solution of 0.001 mol/L to form stable colloid solutions.These stable colloid solutions produce a similar magnetically controlled liquid crystal with Bragg diffraction under an external magnetic field.Their optical properties are affected by magnetic field intensity,magnetic field direction and solid content.Since the building blocks of these three magnetically controlled liquid crystals are rod-shaped,fibrous,and sheet-like structures respectively,there are a lot of differences in orientation structures and optical properties between them.Under the external magnetic field,attapulgite@Fe₃O₄ and sepiolite@Fe₃O₄ can form a one-dimensional ordered structure on a solid substrate,while montmorillonite@Fe₃O₄ can form two-dimensional order structure.A bright Bragg diffraction light can be obtained by aligning attapulgite@Fe₃O₄ and montmorillonite@Fe₃O₄ sols on a solid substrate at a concentration of 0.0125 mg/mL,while sepiolite@Fe₃O₄ cannot.The light transmittance of the three liquid crystals is also different.Attapulgite@Fe₃O₄ is better than montmorillonite@Fe₃O₄,and montmorillonite@Fe₃O₄ is better than sepiolite@Fe₃O₄.The results show that the functionalization of attapulgite,montmorillonite and sepiolite has potential applications in display devices,photonic switches and other fields.