Surface-enhanced infrared absorption studies towards a new optical biosensor

Abstract

Reflectometric interference spectroscopy (RIfS), which is well-established in the visual regime, measures the optical thickness change of a sensitive layer caused, e.g., by binding an analyte. When operated in the mid-infrared range the sensor provides additional information via weak absorption spectra (fingerprints). The originally poor spectra are magnified by surface-enhanced infrared absorption (SEIRA). This is demonstrated using the broad complex fluid water band at 3300 cm−1, which is caused by superposition of symmetric, antisymmetric stretching vibration, and the first overtone of the bending vibration under the influence of H-bonds and Fermi resonance effect. The results are compared with a similar experiment performed with an ATR (attenuated total reflectance) set-up.

Keywords

• attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR)
• direct optical sensing
• mid-infrared regime (MIR)
• reflectometric interference spectroscopy
• surface-enhanced infrared absorption (SEIRA)