Substrate-Enabled Plasmonic Color Switching with Colloidal Gold Nanorings

Plasmonic colors produced by metallic metasurfaces show subwavelength spatial resolution, material simplicity, and durability. Compared to the colors created by plasmonic metasurfaces, plasmonic colors generated by colloidal plasmonic nanostructures are of narrower spectral line widths and sharper and purer chromaticity. However, difficulties in the active control of plasmonic colors hinder the development from static plasmonic color pixels into dynamic plasmonic color devices. Moreover, functional plasmon-based applications usually involve plasmonic nanostructures supported on substrates that strongly alter the plasmonic far-field scattering properties. Au nanorings are emerging plasmonic nanostructures with an intriguing ring shape and controllable plasmon wavelengths. Herein, we report on a study of the substrate effect on the far-field scattering properties of colloidal Au nanorings. The in-plane and out-of-plane plasmon modes of the Au nanorings deposited on metallic films can be excited in varying proportions, which are dependent on the incidence angle of light, producing distinct, and controllable far-field scattering plasmonic colors. Color switching is further realized on the designed patterns made out of the Au nanorings by photolithography. Our study not only provides a fundamental understanding of the substrate effect on the plasmonic properties of uncommon metal nanostructures but also opens the possibility for creating new functional metallic nanostructures for dynamic color devices and anti-counterfeiting applications.