Abstract
The colorimetric detection of bio-agent targets has attracted considerable attention in nanosensor designs. This platform provides an easy to use, real-time, and rapid sensing approach, as the color change can be easily distinguished by the naked eye. In this Letter, we propose a large scale compatible fabrication route to realize colorimetric optical nanosensors with a novel configuration. For this purpose, we design and fabricate a tightly packed disordered arrangement of Fabry–Perot based metal–insulator–metal nanoantennas with a resonance frequency at visible light wavelengths. In this design, the adsorbed bio-agent changes the effective refractive index of the cavity, and this causes a shift in the resonance wavelength. The experimental data show that the proposed design can have sensitivity values $\gt\!{70}\;{{\rm nm}/{\rm refractive}}$ index unit. Unlike other optical sensing schemes that rely mainly on hot spot formation and field enhancement, this design has a large active area with relatively uniform patterns that make it a promising approach for low-level and reliable bio-detection.
© 2020 Optical Society of America
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