Preparation and luminescence properties of the J aggregate of cyanine dyes in phospholipid Langmuir- Blodgett films

Abstract

The J aggregate of two cyanine dyes—dye I (5,6,5′,6′-dibenzo-1,1′-diethyl-2,2′- cyanine chloride) and dye II (5,5′-dichloro-3,3′-diethyl-9-phenyl-thiacarbocyanine chloride)—can be incorporated into acidic-phospholipid-containing Langmuir- Blodgett (LB) films. Dipalmitoyl-phosphatidylcholine (DPPC) and dipalmitoyl- phosphatidic acid (DPPA) were used for preparation of the LB films. An observation that J aggregation was difficult in the absence of negatively charged lipid species (DPPA) in the membrane reconfirms the importance of electrostatic interaction between negative charge at the matrix molecules and positive charge at the chromophore. The luminescence properties of the J aggregate in the more elaborate LB films with dye I and dye II aggregates at the same lipid surface were examined and interpreted in terms of excitation energy transfer from dye I to dye II aggregates.