Excited state proton transfer of pyranine in octadecylamine Langmuir–Blodgett films of different structures

The structure and orientation of pyranine-adsorbed octadecylamine (ODA) LB films were investigated by several spectroscopic methods (UV–vis and fluorescence) and X-ray diffraction. Depending on preparation manners (deposition of a mixed monolayer of ODA and pyranine at the air/water interface or immersion of ODA LB films into a pyranine solution), pyranine-adsorbed films, respectively, exhibit unique structures and photo-excited relaxation processes. The excited state proton transfer (ESPT) in the pyranine-adsorbed ODA LB films was investigated by measurement of fluorescence lifetimes. From the results, the effect of π–π stacking interaction upon the ESPT in the LB films is considered to be similar to the one of the electron-withdrawing substitute in the bulk solution.