Invited feature articleClay induced changes in the aggregation pattern of Safranine-O in hybrid Langmuir-Blogdgett (LB) films

•Absorption spectra of concentrated aqueous solution of SO shows prominent H-dimeric band.•Formation of H-dimeric sites of SO reduced its fluorescence efficiency.•Prominent J-aggregation occurs in the clay induced hybrid LB films.•J-aggregation enhances the fluorescence intensity of SO molecules, used as a fluorescence probe.•In-situ BAM images gave the visual evidence for the formation of aggregation of SO.

In the present communication, detailed investigation has been carried out to study the clay mineral induced changes in aggregation of a well known cationic fluorescent dye Safranine-O (SO) in aqueous solution as well as in organo-clay hybrid Langmuir-Blodgett (LB) films. At higher dye concentration in aqueous solution, Safranine-O (SO) formed both H-dimers and J-aggregates and the corresponding UV-vis absorption spectra got distorted with increasing solution concentration. In clay mineral Laponite dispersed aqueous solution SO formed J-aggregates with increasing Laponite concentration resulting in an increase in fluorescence intensity. H-dimeric sites were also sufficiently decreased in organo-clay hybrid LB films of SO. UV-vis absorption and fluorescence spectroscopic as well as in-situ Brewster Angle Microscopic (BAM) studies were employed in our investigation.

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