Intralayer and Interlayer Energy Transfer between Octadecyl Substituted Pyronine and Crystal Violet Incorporated in Langmuir−Blodgett Films: A Time-Resolved Study

Abstract

The intralayer and interlayer excitation energy transfer between dioctadecylpyronine (PYR18) and dioctadecyl crystal violet (CV18) in alternating multilayer Langmuir−Blodgett (LB) films has been examined with picosecond time-resolved fluorescence decay measurements. The PYR18 fluorescence is efficiently quenched by energy transfer to CV18. The critical transfer distances of 65 and 67 Å for intralayer and interlayer energy transfer, respectively, were calculated from spectral overlap. For the intralayer energy transfer system the fluorescence decay can be fitted with a two-dimensional Förster energy transfer equation, whereas for the interlayer energy transfer system it was necessary to allow the dimension to float in the Förster equation. By use of global analysis, a “fractal dimension” equal to 2.6 was obtained. With single-curve analysis the two-dimensional system is seen to approach the three-dimensional one with increasing CV18 concentration.