Single‐Stimulus‐Induced Modulation of Multiple Optical Properties

Abstract

Stimuli‐responsive smart optical materials hold great promise for applications in active optics, display, sensing, energy conversion, military camouflage, and artificial intelligence. However, their applications are greatly restricted by the difficulty of tuning different optical properties within the same material, especially by a single stimulus. Here, magnetic modulations of multiple optical properties are demonstrated in a crystalline colloidal array (CCA) of magnetic nanorods. Small‐angle X‐ray scattering studies reveal that these nanorods form an unusual monoclinic crystal in concentrated suspensions. The CCA exhibits optical anisotropy in the form of a photonic bandgap and birefringence, thus enabling magnetic tuning of the structural color and transmittance at a rate of 50 Hz. As a proof‐of‐concept, it is further demonstrated that the fabrication of a multifunctional device for display, anticounterfeiting, and smart‐window applications based on this multiple magneto‐optical effect. The study not only provides a new model system for understanding colloidal assembly, but also opens up opportunities for new applications of smart optical materials for various purposes.

Hierarchically Molecular Imprinted Porous Particles for Biomimetic Kidney Cleaning

“…Therefore, the resultant MIPIOPs possessed binding sites for not only lysozyme at the surface, but also urea and creatine in the interior. Because of the periodically ordered structure, the SCCBs, the hydrogel-filled hybrid SCCBs and the replicated MIPIOPs all showed brilliant structure colors, [46][47][48] as displayed in the optical microscopy images in Figure 2b-d and Figure S1 (Supporting Information). Such 3D ordered microstructures of these particles were confirmed by scanning electron microscopy (SEM), as shown in Figure 2e As a proof-of-concept experiment, the MIPIOPs were employed for the synchronous adsorption of macromolecule lysozyme and micromolecules urea and creatine.…”

Recent Advances in Colloidal Photonic Crystal-Based Anti-Counterfeiting Materials

“…Recently, Li and coworkers reported an anti-counterfeiting device based on a 3D colloidal PC structure self-assembled from uniform Fe 3 O 4 @SiO 2 nanorods in concentrated suspension [61]. Differently from the previously reported magnetic-responsive PC with 1D chain-like structures, these Fe 3 O 4 @SiO 2 nanorods could also form an ordered polycrystalline structure without an external magnetic field because the particle content was over the critical concentration in the suspension.…”

“…Moreover, the device shows different patterns when applying different shaped magnets, which is caused by the large brightness contrast between two regions under magnetic fields with different directions (Figure 3d). These rapid and reversible transitions, including color states, light and dark states, and pattern shapes, can be easily recognized by the naked eye, thereby making it a higher-level security material compared to anti-fake materials based on the transition in color states [61].…”

Structural Color Materials for Optical Anticounterfeiting

“…He and co‐workers reported a crystalline colloidal array by magnetic core–shell structured Fe 3 O 4 @SiO 2 nanorods in hundreds of nanometers with an aspect ratio round two. [ 109 ] Under a parallel magnetic field, the nanorods represented a rapid polycrystalline‐to‐single‐crystalline transition, with an alignment along the magnetic field because the nanorods tended to minimize the magnetic potential energy. The nanorod orientation led to not only anisotropic photonic stop bands as the anisotropic period in the array, but also significant birefringent properties leading to polarization dependence.…”