Infrared surface plasmon resonance hosts for sensors

A Surface Plasmon Resonance (SPR) biosensor that operates deep into the infrared (3-11 μm wavelengths) is potentially capable of biomolecule recognition based on both selective binding and characteristic vibrational modes. The goal is to operate such sensors at wavelengths where biological analytes are strongly differentiated by their IR absorption spectra and where the refractive index is increased by dispersion. This will provide enhanced selectivity and sensitivity, when biological analytes bind reversibly to biomolecular recognition elements attached to the sensor surface. This paper investigates potentially useful IR surface plasmon resonances hosts on lamellar gratings formed from various materials with plasma frequencies in the IR wavelength range. These materials include doped semiconductors, CuSnS, graphite and semimetal Bi and Sb. Theoretical results were compared with the experimental results. Penetration depth measurement from the experimental complex permeabilities values shows the tighter mode confinement than for usual Au giving better overlap with biological analytes.