Preparation and optical properties of one-dimensional magnetically oriented halloysite@Fe3O4 nanomaterials

Abstract

Clay minerals with composite magnetic particles offer potential as magnetically oriented nanomaterials for application in inorganic liquid crystals. However, the instability of magnetically oriented clay@Fe₃O₄ materials, caused by the easy detachment of Fe₃O₄ particles from the clay minerals surfaces and the corrosivity of the HCl dispersant on Fe₃O₄ particles, has limited their development. In this work, hollow tubular halloysite (Hal) was used as the carrier for Fe₃O₄ particles to obtain halloysite@Fe₃O₄ (Hal@Fe₃O₄), in which Fe₃O₄ particles were uniformly coated on the outer surface of Hal and located in the Hal tubular lumen. In addition, LiCl was employed as a dispersant instead of HCl in Hal@Fe₃O₄ dispersions. They collaboratively enhanced the stability of magnetically oriented Hal@Fe₃O₄ nanomaterials compared to magnetically oriented palygorskite@Fe₃O₄ nanomaterials. The stable one-dimensional magnetically oriented Hal@Fe₃O₄ nanomaterials demonstrated liquid crystal properties that were adjustable by a magnetic field, and photonic crystal properties. As a result, these functional materials could be used in many fields, such as inorganic liquid crystals, photonic crystals, and photonic switches.