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Nanoplasmonics have been exploited for a variety of applications ranging from optoelectronic devices to biodetection systems.[1–21] Techniques including surface-enhanced fluorescence, infrared absorption (SEIRA), Raman scattering (SERS) and refractive index (RI) based sensing employ distinct plasmonic properties of metallic structures to achieve ultra-high sensitivities.[22–41] In particular, surface enhanced absorption spectroscopy in Mid-infrared (Mid-IR) spectral range is of great interest as it provides direct access to rich vibrational information of most organic molecules and enables investigation of unique structural characteristics of biosamples. Mid-IR spectroscopy has been used as a label-free identification tool for obtaining fingerprints of molecules and complex macromolecules, eg, proteins and lipids.[42] However, the sensitivity of Mid-IR spectroscopy techniques is fundamentally limited by the …