Preparation and characterization of mixed monolayers and Langmuir−Blodgett films of merocyanine 540/octadecylamine mixture

Mixed monolayer of merocyanine 540 (MC540) dye and octadecylamine (ODA) at the air/water interface has been prepared using the co-spreading method. The pressure–area (π–A) isotherm studies revealed that the mixtures of MC540/ODA at a different ratio formed a stable monolayer at the air/water interface and these floating layers were easily transferred onto hydrophilic substrates as the Y-type Langmuir–Blodgett (LB) film. The specific area per molecule in the π–A isotherm of the mixed monolayer of MC540/ODA was larger than that of the pristine ODA. The area can also get increased up to 40 mN/m surface pressure by the increase of the dye concentration in the mixtures. The LB films of MC540/ODA mixture were formed at 30 mN/m surface pressure by transferring the mixed monolayer at the air/water interface on hydrophilic glass substrate via vertical dip-coating as mono- and multilayer films. The photophysical properties of MC540 in chloroform and LB films have been investigated using the absorption, steady-state and time-resolved fluorescence spectroscopy techniques. H-aggregate formation of MC540 both in chloroform and LB film were concluded from the spectroscopic results. The morphology of the one-layer mixed LB film of MC540/ODA on the glass substrate has been characterized by AFM (atomic force microscopy). The non-contact mode AFM image of the one-layer mixed LB film showed that the film surface consisted of MC540/ODA nanoclusters. In conclusion, our results contribute to understanding the strong interaction between MC540 and ODA at the air/water interface, and show the effects of some parameters on the mixed LB films of MC540.

Langmuir–Blodgett films (LB) of merocyanine 540 (MC540) mixed with amphiphilic octadecylamine (ODA) on glass substrate are fabricated by co-spreading method. The formation of stable LB film of MC540 mixed with ODA on water subphase is checked by surface pressure–area (π–A) isotherm.Figure optionsDownload as PowerPoint slideHighlights
► Langmuir–Blodgett films of merocyanine 540/octadecylamine mixture were fabricated.
► Photophysical properties of merocyanine 540 were followed as spectroscopic.
► H-aggregate formation of merocyanine 540 at solid and liquid phases was characterized.
► Surface morphology of thin film was examined by using atomic force microscopy.