Enhanced fluorescence efficiency of an organo-clay hybrid Langmuir-Blodgett film

In this communication the photophysical characterizations of the complex and hybrid Langmuir-Blodgett (LB) films of a cationic water soluble phenothiazine dye Toluidine Blue O (TBO) were represented. Being water soluble, TBO cannot form Langmuir monolayers or LB film. Cationic TBO molecules can interact with anionic stearic acid (SA) on adsorption and form TBO-SA complex film. Cationic TBO molecules can be incorporated in anionic nano laminates of Laponite followed by adsorption onto preformed cationic Octadecylamine (ODA) film to form TBO-Clay-ODA hybrid film. The Langmuir monolayers have been characterized by surface pressure vs. area per molecule isotherms and in-situ Brewster-angle-Microscopic studies (BAM). Spectroscopic characterizations have been employed to study the LB films. Interestingly the hybrid organo-clay film at higher concentration of clay showed a significant decrease of H-aggregated sites which is non-fluorescent in nature. This resulted in high fluorescence efficiency as observed in the clay incorporated hybrid LB films of TBO. It was also observed that the three layered hybrid LB film showed maximum fluorescence intensity which was two times greater than even the solution fluorescence intensity. This investigation showed the possibility of efficient use of the hybrid organo-clay LB films of TBO as biological fluorescent marker and in various opto-electronic devices.