Grazing incidence diffraction of cadmium arachidate multilayers at the solid-liquid interface

Abstract

Abstract Using complementary X-ray reflectivity (XR) and grazing incidence X-ray diffraction (GIXD), we report structural studies of supported thin-organic layers in contact with water and air. Using a monochromatic synchrotron beam to penetrate 10 mm of liquid, we have characterized buried films composed of 12.5 repeating bilayers of arachidic acid (C20H40O2) complexed with cadmium ions (cadmium arachidate, CdAr2). We found that the layered structure of the CdAr2 multilayers do not exhibit rearrangement after exposure to water with negligible water penetration into the inner layers when compared to their dry state. These findings are consistent with the formation of extremely robust CdAr2 multilayers that can withstand multiple rinses in strong organic solvents, acid, and mechanical wear. The second goal was to demonstrate the feasibility of similar experiments to study much thinner single bilayer bio-membranes. These studies are the first successful GIXD experiments of ultra thin-organic film composed of a few layers at the solid-liquid interface.