Aggregation features of molecules in various types of Langmuir-Blodgett (LB) multilayers were investigated by using the steady-state and time-resolved fluorescence techniques. The fluorescence peak of interleaving hemicyanine/arachidic acid multilayers is at 598nm which shows a significant blue shift with respect to that of hemicyanine(615nm) in solution. As the interlayer interactions were screened by arachidic acid layers

intralayer interaction of hemicyanine molecules caused the formation of H-aggregates in interleaving hemicyanine/arachidic acid multilayers. However

the fluorescence peaks of pure Y and Z-type hemicyanine multilayers are at 645nm and 635nm

respectively. It indicated that the molecules mainly formed J-aggregates which lead to a significant red shift of fluorescence band due to the stronger interlayer interactions. It indicated that the interlayer interaction would be stronger than the intralayer interaction because of the lack of the screening of AA and the inclination angle θ would be reduced (close to 0)

which caused J-type aggregation. The temporal profile could be well fitted by the model. The lifetime

relative amplitudes of the components and molecular numbers in an aggregate were deduced

Notice that the molecular numbers and amplitudes of the aggregates in the pure hemicyanine samples were larger than that in LB interleaving films.