Metal Nanopillar Arrays Fabricated with Moth-Eye Films for Adjustable Plasmonic Colors and Colorimetric Plasmonic Sensing

The scalable fabrication of plasmonic metasurfaces that generate reflective plasmonic colors is achieved by using industrially manufactured antireflective moth-eye films. The periodically arranged dielectric nanopillar arrays on the moth-eye film serve as templates for fabricating ordered metal nanostructure arrays. The plasmonic colors exhibit angular independence and can be tuned by varying the species and thickness of the metal layer. Cross-sectional SEM observation and numerical simulations revealed that the changes in the reflection spectra related to the color generation are caused by the deformation of the metal layer, depending on its thickness. Furthermore, analysis of the electric field intensity distribution showed changes in the mode and wavelength of the plasmon resonance depending on the thickness of the metal layer. As a potential application, colorimetric plasmonic sensing was performed based on bulk refractive index measurements. The bulk refractive index sensitivity of the Ag-coated moth-eye film reached 347 nm/RIU (refractive index unit) and −730°/RIU using hue as an indicator of colors. The refractive index resolution of 2 × 10–5 RIU and the sensitivity obtained through colorimetric detection are superior to those of other colorimetric plasmonic sensors. The distinctive plasmonic colors produced by the metal-coated moth-eye films can be utilized to expand the application areas of plasmonic metasurfaces, such as colorimetric plasmonic biosensors and flexible displays, with their remarkable simplicity and affordability.