Langmuir-Blodgett films of alkylpyridines as metal ion sensors

Abstract

Monolayers of nonadecylpyridine (NDP) were studied at the water-air interface by measuring surface pressure-and surface potential-area isotherms. The conditions of preparation of Langmuir-Blodgett (LB) film of NDP on quartz were studied and the physicochemical properties of the film then examined. UV-visible and FTIR/ATR spectroscopy were used to characterize the dry LB film. Ellipsometry was also used to measure the layer thickness as a function of the number of transferred layers, the monolayer composition and the compression of the film. Transfer of the film from pure water subphase on substrates of different natures and hydrophobicity, i.e. quartz, glass, chromium, germanium and polymers, was also studied comparatively. The interactions of the monolayer with the metal cation Ni 2+ solubilized in the aqueous subphase were investigated by recording the surface pressure and surface potential at the water-air interface both in the presence and in the absence of the metal ion in subphases of the same ionic strength. The transfer was then performed using subphases containing the metal ion and the resulting LB films were characterized by ESCA spectroscopy and reported techniques. Absorption spectra were recorded for LB films of NDP immersed in water or in contact with the metal ion solutions. Complexation of metal cations from the subphase was studied by monitoring the absorption spectra of solutions containing the metal ion when the LB film was immersed in the solution.