INTRALAYER AND INTERLAYER ENERGY-TRANSFER BETWEEN OCTADECYL SUBSTITUTED PYRONINE AND CRYSTAL VIOLET INCORPORATED IN LANGMUIR-BLODGETT-FILMS- A TIME-RESOLVED STUDY

The intralayer and interlayer excitation energy transfer between dioct adecylpyronine (PYR18) and dioctadecyl crystal violet (CV18) in altern ating multilayer Langmuir-Blodgett (LB) films has been examined with p icosecond time-resolved fluorescence decay measurements. The PYR18 flu orescence is efficiently quenched by energy transfer to CV18. The crit ical transfer distances of 65 and 67 Angstrom for intralayer and inter layer energy transfer, respectively, were calculated from spectral ove rlap. For the intralayer energy transfer system the fluorescence decay can be fitted with a two-dimensional Forster energy transfer equation , whereas for the interlayer energy transfer system it was necessary t o allow the dimension to float in the Forster equation. By use of glob al analysis, a ''fractal dimension'' equal to 2.6 was obtained. With s ingle-curve analysis the two-dimensional system is seen to approach th e three-dimensional one with increasing CV18 concentration.