Optical Ion Sensors Based on LB Films

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In order to design a multi-channel sensing system based on pattern recognition, fluorescence response of bilayr membranes having octadecylrhodamine B to various inorganic anions were investigated. Fourteen cationic amphiphiles, double chain amphiphiles and single chain amphiphiles with a rigid aromatic segment, were used as the sensing bilayr membranes. Fluorescence response of bilayr membranes was strongly depend not only on inorganic anions but also on the chemical structure of the bilayr forming amphiphile. Fluid bilayr membranes were more sensitive than those of gel state. Iodide ion act as a fluorescence quencher of the most bilayr membranes. Carbonate ions specifically enhanced fluorescence intensity of the bilayr membrane of a single chain viologen amphiphile. Based on the results of the bilayr membranes fluorescence responses of Langmuir-Blodgett films of the cationic amphiphiles complexed with counter charged polyelectrolites, Poly(stirenesulfonate), poly(vinylsulfate), and carboxymethyl-cellulose, were investigated. The chemical structure of the counter charged polymer strongly affected the fluorescence response even if the same amphiphile was used as a monolayr forming compound. A large variety of the fluorescence of the molecular films is essential to the molecular design of the multi-channel ion sensors.