Fano Resonance in Plasmonic Crystals Enables High-Sensitive Arsenite Detection

Fano resonance exhibiting characteristic asymmetric spectral line shape is a universal phenomenon, observed in diverse systems and is widely studied for its numerous potential applications. Here, we demonstrate a simple approach for high-sensitive arsenite detection using the changes in the spectral asymmetry of optical Fano resonance in precisely designed metamaterials, namely waveguided plasmonic crystals. For this purpose, we exploit selective binding of the toxic arsenite (As(III)) ions with optimized concentration of fluorescein-derived phenyl isothiocyanate molecules that are coated on top of a waveguided plasmonic crystal sample comprising of one dimensional periodic plasmonic gold grating on indium tin oxide waveguiding layer. The scattering spectra from the plasmonic crystal system with transverse magnetic (TM) polarization excitation show systematic changes in the Fano asymmetry parameter q with increasing concentration of arsenite, which is exploited for sensing arsenite down to a concentration of 1 ppm. Based on these results, we propose a robust plasmonic crystal metadevice that uses the polarized scattered intensities at two optimized wavelengths for high sensitive arsenite detection in natural aqueous environment.