Fe3O4 Nanoparticle-Based Janus Photonic Crystal Microbeads with Multiple Fluorescence Colors for Information Coding

In this study, we fabricate magnetic Janus photonic crystalmicrobeadswith multiple fluorescence colors based on photonic crystals, Fe3O4 nanoparticles, and fluorescent dyes by a microfluidicdevice. We mix the poly(styrene-methyl methacrylate-acrylic acid)(p(St-MMA-AA)) nanoparticles, the Fe3O4 nanoparticles,and the fluorescent dyes. We use the mixture as the dispersed phaseand the silicone oil as the continuous phase. We get the Janus photoniccrystal microbeads after the self-assembly of the photonic crystals.Due to the greater density, the Fe3O4 nanoparticlessink to the bottom of the Janus microbeads, which are made up of photoniccrystals combined with p(St-MMA-AA) nanoparticles. The fluorescentdyes are distributed in the gaps of photonic crystals. The Janus photoniccrystal microbeads could rotate upside down under the action of magnetsbecause of the magnetism of the Fe3O4 nanoparticles.Moreover, they can fluoresce under UV light due to the fluorescentdyes. We combine Janus photonic crystal microbeads into arrays ofnumbers, letters, symbols, and patterns for information coding andanti-counterfeiting. The Janus microbeads have enormous potentialfor use in array displays, information coding, and anti-counterfeiting.