Bismuth nanogratings with narrow plasmon resonances for dynamic polarized color generation and colorimetric sensing

Abstract

Bismuth nanostructures are appealing for sustainable color generation and sunlight harvesting, thanks to their non-toxicity and their tunable visible-to-near infrared interband plasmon resonances. However, owing to their broad and polarization-insensitive spectral features, the nanostructures reported so far displayed a limited color tunability and were lacking other functionalities such as sensing. Herein, we report bismuth nanogratings with polarization-sensitive and narrow plasmon resonances (Q > 10). They were fabricated on the $cm^2$ scale following a lithography-free approach: conformal pulsed laser deposition of bismuth onto both the reflective and transparent nanostructured layers of DVDs. We characterized their specular reflectance for different orientations of the plane of incidence, angles of incidence, and polarizations of light. When light is polarized in the plane perpendicular to the lines, plasmon resonances occur and shift across the visible-to-near infrared upon changing the angle of incidence. In contrast, no such resonances occur when light is polarized in the plane parallel to the lines. This results in well-contrasted, polarization-sensitive colors, which are iridescent for the former orientation of polarization, and not for the latter. Resonances strongly shift upon changing the refractive index of the surrounding medium (> 500 nm/RIU), resulting in a marked change in the plasmonic color, e.g., from green in air to red in water. This showcases the potential of these nanogratings for dynamic polarized color generation and colorimetric sensing.