Janus Multicolored Photonic Crystal Beads for Real-Time Magnetic Responsive Patterns

Photonic Janus particles that can change colors in different stimuli have shown great promise in various applications, such as optical probes, catalyst supports, sensors, and display materials. However, it remains a challenge to produce Janus structural colored particles with a simple method. Inspired from ecsenius bicolors, a facile preparation of Janus structural colored beads (JSCBs) using sub-micrometer-sized colloidal particles and magnetic nanoparticles composed of Fe3O4 is established. A mixed emulsion is prepared by monodispersed colloidal particles and magnetic nanoparticles and initiator of PDMS precursor. Subsequent self-assembly of the emulsion in the room temperature environment provides two different structural colors, thanks to the gravity deposition of colloidal particles and Fe3O4 nanoparticles. The photonic bandgap of JSCBs can be precisely controlled with varying size of monodispersed colloidal nanoparticles, and the high optical quality and mechanical strength of the structural colored face are attributed to the existence of PDMS. In the presence of a magnet, the JSCBs can change their orientation simultaneously between two different structural colors. Moreover, the JSCBs are capable of encoding and angle-independent displaying, which are crucial to their applications in anticounterfeiting, information coding, and pattern display.