INTERACTION OF COPPER IONS WITH STEARIC-A CID LANGMUIR MONOLAYER AND FORMATION OF CLUSTER STRUCTURES IN MONOLAYERS AND LANGMUIR-BLODGETT-FILMS

The interaction of copper ions with the stearic acid Lagmuir monolayer resulting in an extremely high level of copper binding to monolayer i n quantities that significantly exceeded the amount of stearic acid mo lecules in the monolayer was studied. The shape of the pressure-area i sotherm changed drastically upon the pH changes from 4 to 6 in the pre sence of copper ions in aqueous phase (at concentrations from 10(-5) t o 10(-3) M) or upon the addition of copper ions to the aqueous phase u nder different monolayer compression. The bulk phase copper ion concen tration changes, caused by binding to the monolayer, were studied with the use of EPR at the equilibrium after intensive mixing of the bulk phase and were found to depend on the aqueous phase pH and monolayer c ompression extent. The highest level of binding (up to 100 copper ions per one stearic acid molecule, pH 5.6, initial copper concentration 5 . 10(-4) M) was observed at the surface pressure of about 20 mN/m; fu rther monolayer compression and the corresponding increase in the surf ace pressure caused the reverse growth of the aqueos phase copper ion concentration. At collapse (monolayer fracture and destruction) the co pper ion concentration in the bulk phase was similar to that with abse nce of monolayer. The EPR spectra and SAXS difractograms of copper-con taining stearic acid multilayers confirmed the high copper content in the obtained LB films. STM study of pure stearic acid and the copper-c ontaining monolayer LB films, transferred to graphite wafers from the water subphase surface (pH 5.4) with various copper concentration, dis covered nanosized (about 5 nm) cluster formation an the monolayer surf ace. The obtained data point out that interaction of the charged Langm uir monolayer with copper ions and formation of copper containing nano structures depended on the monolayer compression and was determined by arrangement, order, mobility of the monolayer stearic acid molecules and by electrostatics at the interface.