Study of polydiacetylenes and rhodamine-800 mixed film at air–water interface and onto solid support: Trace of fluorescence resonance energy transfer (FRET).

Here, we report the mixing behaviour of diacetylene monomer 10, 12-tricosadiynoic acid (TCDA) and rhodamine-800 (Rh8) using Langmuir–Blodgett (LB) technique. The presence of Rh8 affected the structures, phase behaviour as well as colorimetric properties of TCDA in the mixed films at air–water interface and onto solid support. The mixed LB films having TCDA molefraction ≥ 0.5 leads to multilayer formation, whereas multilayer formation was hardly observed for the films containing TCDA molefraction less than 0.5. It was observed that polymerization as well as phase change (blue to red) was possible only for multilayered films. Brewster angle microscopy, atomic force microscopy, and fluorescence inverted microscopy studies confirmed the formation of definite structures in the polymerized TCDA/Rh8 mixed films at air–water interface and onto solid support. Structure of TCDA polymer strands was largely influenced by the presence of Rh8 in the mixed films. Interestingly, energy transfer occurred from TCDA in red phase to Rh8 in the mixed films with TCDA molefraction greater than 0.4. Maximum energy transfer efficiency was found to be 47.3% for the mixed LB film with TCDA molefraction 0.9. [ABSTRACT FROM AUTHOR]