Formation of fluorescent H aggregates of a cyanine dye in LB films and   its effect on energy transfer
  Here we report the formation of fluorescent H aggregates of a cyanine dye Oxa18 in ultrathin film and its effect on energy transfer between Oxa18 and sRhb. Ideally H aggregate do not fluoresce. However, due to imperfect stacking of Oxa18 molecules in the aggregates, fluorescence occurred from Oxa18 H aggregates. This H aggregated band has substantial effect on the enhancement of energy transfer from Oxa18 to sRhb both in solution and in ultrathin film. 
Santanu Chakraborty, Pintu Debnath, Dibyendu Dey, D. Bhattacharjee,   Syed Arshad Hussain
cond-mat.mtrl-sci