Synthesis of Controllable Superparamagnetic Nano Fe 3 O 4 Based on Reduction Method for Colloidal Clusters of Magnetically Responsive Photonic Crystals.

In this paper, we designed and investigated a reduction-based method to synthesize controllably monodisperse superparamagnetic nano Fe 3 O 4 colloidal clusters for magnetically responsive photonic crystals. It was shown that the addition of ascorbic acid (VC) to the system could synthesize monodisperse superparamagnetic nano Fe 3 O 4 and avoided the generation of γ-Fe 2 O 3 impurities, while the particle size and saturation magnetization intensity of nano Fe 3 O 4 gradually decreased with the increase of VC dosage. Nano Fe 3 O 4 could be rapidly assembled into photonic crystal dot matrix structures under a magnetic field, demonstrating tunability to various diffraction wavelengths. The nano Fe 3 O 4 modified by polyvinylpyrrolidone (PVP) and silicon coated could be stably dispersed in a variety of organic solvents and thus diffracted different wavelengths under a magnetic field. This is expected to be applied in various scenarios in the field of optical color development.