  We discuss the possibility of implementing a novel bio-sensing platform based
on the observation of the shift of the leaky surface plasmon mode that occurs
at the edge of the plasmonic band gap of metal gratings when an analyte is
deposited on top of the metallic structure. We provide experimental proof of
the sensing capabilities of a two-dimensional array of gold nano-patches by
observing color variations in the diffracted field when the air overlayer is
replaced with a small quantity of Isopropyl Alcohol (IPA). Effects of rounded
corners and surface imperfections are also discussed. Finally, we also report
proof of changes in color intensities as a function of the air/filling ratio of
the structure and discuss their relation with the diffracted spectra.
