Formation of Metallic Langmuir Film on the Water Surface with Fatty Acid and BEDO-TTF Molecules

The formation process of metallic Langmuir film on the water surface fabricated from BEDO-TTF (BO) and stearic acid (SA) is described. The in-situ observation by Brewster angle microscope revealed a creation of small islands after spreading the mixing solution on the water surface and then a formation of homogeneous Langmuir film by a coalescence of the islands with decreasing of the surface area. An appearance of mixed valence state of BO in both islands and Langmuir film was confirmed by polarization-modulated IR reflection absorption spectroscopy. A theoretical simulation of the spectra supports the bilayer model on the water surface, in which a metallic BO layer underlies between the SA layer and the water surface. An investigation on the Langmuir-Blodgett (LB) films transferred onto substrates by infrared spectroscopy implies the existence of hydrogen-bonded carboxylate groups of (R-COO———H———OOC-R)^- in the SA layer. Finally, the optical conductivity in the LB films can be compared with those of the superconductor crystal (BO)₂ReO₄(H₂O) through the Drude optical parameters obtained from the IR spectra fitting.