Electro-Responsive Janus Microspheres Composed of Photonic and Plasmonic Faces

Abstract

Plasmonic color comes from resonance between oscillation of free electrons on a metal surface and incident light, which are usually fabricated by lithographic methods on a flat substrate. It was realized on a microsphere by forming Pickering emulsion and depositing metal after removing particles, but a metal-absent hemisphere only shows whitish colors by scattering. Here, particles are crystallized not only at the surface but also inside the microsphere so that the metal-deposited hemisphere generates plasmonic colors and the other side photonic-crystal colors. The two colors can be dependently or independently controlled by using single or double emulsion templates, respectively. The particle anchoring and aging are compared on high-fraction and low-fraction cases in emulsions, and their time dependency is also analyzed. Photonic colors impart the color identity as a barcode on plasmonic sensors, or the microspheres serve as active color pixels for a dual-color reflective display.