A spectroscopic study of water-soluble pyronin B and pyronin Y in Langmuir–Blodgett films mixed with stearic acid

Mono and multilayer of water-soluble pyronin B (PyB) and pyronin Y (PyY) mixed with stearic acid (SA) have been incorporated in Langmuir–Blodgett (LB) films. The surface pressure–area (π–A) isotherm studies pointed out that pure PyB and PyY are incapable of forming stable films at air–water interface and collapsed readily at low surface pressures. However, mixture of PyB or PyY with SA easily formed stable films at the air–water interface and they were easily transferred onto solid substrates. The average area per molecule of mixed films of PyB and PyY at the air–water interface was observed to decrease with increasing concentrations of PyB and PyY. The spectroscopic characteristics of PyB and PyY in chloroform, in SA containing chloroform and in LB films have also been investigated by using absorption and steady-state and time-resolved fluorescence spectroscopy techniques. The morphology of the LB film surfaces has been characterized by using atomic force microscopy (AFM).