Properties of mixed monolayer and LB films of chiral amino acid porphyrin

Abstract

Mixed monolayers of a new chiral amino acid porphyrin (Py) and arachidic acid (AA) at the air/water interface were studied The diagrams obtained by plotting the mean area per molecule as a function of molar fraction of Py showed positive deviations from ideal conditions at low surface pressure ( π) such as π=5 and 15 mN m −1 and showed ideal miscible behavior at high surface pressures, such as π=25 mN m −1. Vertical uniformity of the mixed LB films was demonstrated by UV–visible and fluorescence spectra. Aggregates were present when the mixed film was transferred at various surface pressures and at different molar ratios of Py and AA. When the molar ratio of Py was increased from 0.05 to 1.00, the absorption peak of the Soret band bathochromically shifted ca. 5.3 nm. When the deposited pressure is increased from 5 to 30 mN m −1, the absorption peak of Soret band of 1:4 Py–AA mixed LB film bathochromically shifted ca. 3.7 nm, and the absorbance increased linearly. Low angle X-ray diffraction results showed that the mixed LB films had a periodic layer structure with a layer spacing of ca. 5.5 nm.