Abstract
Plasmonic metal nanostructures can simultaneously scatter and absorb light, with resonance wavelength and strength depending on their morphology and composition. This work demonstrates that unique dichroic effects and high-contrast colour-switching can be achieved by leveraging the resonant scattering and absorption of light by plasmonic nanostructures and the specular reflection of the resulting transmitted light. Using core/shell nanostructures comprising a metal core and a dielectric shell, we show that their spray coating on reflective substrates produces dichroic films that can display colour switching at different viewing angles. The high-contrast colour switching, high flexibility in designing multicolour patterns, and convenience for large-scale production promise their wide range of applications, including anticounterfeiting, mechanochromic sensing, colour display, and printing.