Surface enhanced FTIR spectroscopy on membranes

The infrared absorption of molecules in the vicinity of small metal clusters is enhanced due to an electric field around the clusters. This phenomenon is known as surface enhanced IR absorption (SEIRA). The potential of SEIRA consists in the investigation of thin layers and of membranes. SEIRA was used to detect small and specific changes in the structure of biomembranes applying two configurations: underlay er and overlay er. In the underlayer configuraiton, IR transparent Ge crystals were coated with Ag clusters before vesicles were adsorbed. In the overlayer configuration, the vesicles were first absorbed on neat Ge crystals before a layer of Ag clusters was condensed on top. An intensity increase in the SEIRA spectra was observed for both configurations compared to FTIR spectra without Ag clusters.