Role of various LB parameters on the optical characteristics of mixed Langmuir–Blodgett films

This communication reports the spectroscopic characterizations of mixed Langmuir–Blodgett (LB) films of non-amphiphilic N,N-bis (2,5-di-tert-butylphenyl)3,4,9-perylenedicarboximide (DBPI) molecules, mixed with polymethyl methacrylate (PMMA) and stearic acid (SA). Jaggregates of DBPI molecules in the mixed LB films have been confirmed by UV–Vis absorption spectroscopic study. Formation of organized structure of molecular stacking in the mixed LB films gives rise to the strong excimeric emission, which is manifested by a broad structureless band in the longer wavelength region of the fluorescence spectra and is confirmed by excitation spectroscopic study. A weak hump at around 576 nm due to monomeric emission is observed in the fluorescence spectra of 0.1M of DBPI-PMMA mixed LB films of lower number of layers. The intensity of the 0–0 band at 530 nm in the fluorescence spectra is observed to be a function of the molefraction, number of layers, surface pressure of lifting and the matrix materials. r 2006 Elsevier Ltd. All rights reserved.