Laponite elementary sheets assisted fluorescence resonance energy transfer: A demonstration by Langmuir-Blodgett technique

Abstract The fluorescence resonance energy transfer (FRET) between donor-acceptor molecules of fluorescein (FL) and rhodamine B (RhB) was enhanced by clay sheets of laponite. This enhancement was implemented by the Langmuir-Blodgett (LB) technique. Hybrid films were prepared by incorporating elementary clay sheets into dye molecules (FL and RhB for different molar ratios) at the air/water interface. The spectroscopic measurements (UV–Vis absorption and photoluminescence) of these mixture systems (FL, RhB and clay mineral) were analyzed both in colloidal dispersion and LB films. A high efficiency (92%) of FRET from FL to RhB was achieved with presence of laponite. Characterizations such as surface pressure versus area (π-A) isotherms, atomic force microscopy (AFM) and contact angle measurements were used to confirm the successful incorporation of clay sheets in hybrid films with loaded dye molecules. The clay incorporation were indicated to shorten the distance between donor and acceptor chromophores (Forster radius), which was realized by the tightly bounded dye molecules on clay sheets and self-assembly of dye molecule pairs.