A Smartphone-Based Red–Green Dual Color Fiber Optic Surface Plasmon Resonance Sensor

A novel red–green dual color fiber optic surface plasmon resonance (SPR) sensor based on smartphone has been proposed. Instead of using narrowband filters or diffraction gratings to get spectral data as those smartphone-based SPR sensors reported so far, we propose to utilize the inherent color selectivity of phone cameras to monitor red and green color channels simultaneously, which can reduce the chance of false detection and improve the sensitivity. An Ag/Au bilayer structure SPR sensor was employed in order to perform SPR at the central region of the visible spectrum in aqueous environment and improve the sensitivity. Experimental results show that it has a quadratic response in the refractive index (RI) range of 1.325–1.344 (
$R^{2}=0.992$
) and a linear response in the RI range of 1.325–1.330, with a sensitivity of 18.59/RIU and a resolution of
$5.3\times 10^{-4}$
RIU. This novel SPR sensor has great potential as point-of-care and point-of-need platforms for healthcare, food safety, and environmental monitoring, especially in remote and rural areas.