Spectroscopic characterizations of the mixed Langmuir-Blodgett (LB) films of 2,2'-biquinoline molecules: evidence of dimer formation

摘要

This communication reports the -A isotherms and spectroscopiccharacterizations of mixed Langmuir and Langmuir-Blodgett (LB) films ofnonamphiphilic 2, -biquinoline (BQ) molecules, mixed with polymethylmethacrylate (PMMA) and stearic acid (SA). The pi-A isotherms and molefractionversus area per molecule studies indicate complete immiscibility of sample (BQ)and matrix (PMMA or SA) molecules. This immiscibility may lead to the formationof microcrystalline aggregates of BQ molecules in the mixed LB films. Thescanning electron micrograph gives the visual evidence of microcrystallineaggregates of BQ molecules in the mixed LB films. UV-Vis absorption,fluorescence and excitation spectroscopic studies reveal the nature of thesemicrocrystalline aggregates. LB films lifted at higher surface pressureindicate the formation of dimer or higher order n-mers.