X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) have been used to investigate physicochemical properties of mixed Langmuir-films made of carboxylic ionophores and phospholipids. The selective monolayers were deposited onto semiconductor, structures. Differences found in various experiments of friction force corresponded well with those found from XPS spectra. The cation detection by the monolayer was also proved by XPS studies and confirmed by significative sensitivities found with functionalised ion-sensitive field effect transistors (ISFETs). (C) 2003 Elsevier B.V. All rights reserved.