Structural colors based on TiO2 all-dielectric metasurfaces can be used for colorimetric refractive index sensing

Abstract

An all-dielectric metasurface-based structural color is presented in this study for colorimetric sensing of refractive index changes in environmental liquids ranging from 1.3 to 1.39. The TiO${}_2$ hollow rectangular column nanostructures designed are arranged on a polydimethylsiloxane (PDMS) substrate and can generate a single reflection peak with a full width at half maximum (FWHM) of approximately 2 nm under visible light irradiation, which is suitable for detecting extremely small refractive index changes. This is achieved by exciting a strong magnetic dipole (MD) resonance in the all-dielectric metasurface and effectively suppressing other multipole resonances using surface lattice resonances. In addition, due to the stretchability of the PDMS substrate, the metasurface can be actively and continuously tuned through 20% strain to achieve controlled frequency modulation, thereby achieving the effect of color change display. The metasurface composed of TiO${}_2$ nanostructures proposed can be used for dynamic colorimetric refractive index sensing, and can be applied to environmental detection and other fields by detecting the change in liquid refractive index through the chromaticity change displayed by it.