An optical sensing method with optical excitation in the ultraviolet (UV) range (200-400 nm wavelength) where biomolecules, which have inherent absorption lines in the UV range, adsorb on a plasmonic surface exhibiting coincident optical resonances in the UV, and the amplitude of the reflected/scattered/transmitted optical wave, which is strongly changed due to the presence of biomacromolecules or biomolecular structures, are measured or imaged to infer the presence and optical properties of the adsorbed biomolecular structures.