A fatty-acid Langmuir-Blodgett (LB) monolayer ionically adsorbed to the substrate has been prepared by adopting ZnO based conductor and pure water respectively as the substrate and subphase Ionization of the fatty acid molecules has been detected by infrared reflection-absorption spectroscopy (IR-RAS) which is enabled by the condensed free electrons in the doped ZnO substrate On the contrary IR-RAS measurements have indicated that fatty-acid molecules transferred onto Au and indium-tin-oxide substrates from a pure-water surface are not ionized In addition it has been demonstrated that these ionically bonded fatty-acid monolayers protect the ZnO transparent electrode from chemical attack by NH3 gas Since the LB technique is a simple method applicable to a wide variety of materials the present results may lead to a new way of obtaining functional organic-inorganic nanosystems (C) 2010 Elsevier Inc All rights reserved