Rational design of colorimetric sensing for a customer-oriented index range using plasmonic substrates

Both beneficial matter and harmful matter widely spread in aqueous solutions. Various approaches have been developed to identify them qualitatively and quantitatively. In particular, colorimetric sensing, relying on an observable environment-induced color change, is a readily accessible approach to detect signals via our naked eyes, with no need for extra optoelectronic devices. Here we propose a colorimetric sensing scheme with enhanced performance using plasmonic metasurfaces. By judiciously selecting the structure parameters, the plasmonic resonance can be flexibly tuned at the entire visible range. Along with a pair of polarizers to filter the polarization states of the incident light and output reflection, a plasmonic metasurface, supporting bright colors, can serve as an efficient colorimetric sensing substrate. As an example, a figure of merit can be obtained as high as 1175 degrees/RIU in the demodulation of the hue. Significantly, the sensing capability can be designed according to the selected solvent with a specified refractive index, which promises a target-oriented colorimetric sensing scheme. (C) 2019 Optical Society of America