Laser-induced self-assembly of pseudoisocyanine J-aggregates

This letter describes that the appearance and growth of J-aggregate are clearly accelerated by focusing a near-infrared laser beam into an aqueous solution of psudoisocyanine while gradually increasing the concentration by solvent evaporation. The J-aggregate formed in the laser focus shows a narrower fluorescence bandwidth compared to those obtained by simple concentration increase. This indicates that the growth of the highly ordered J-aggregates is preferentially enhanced in the laser focus, which is the first demonstration showing laser-induced self-assembly of psudoisocyanine J-aggregates. Furthermore, we discuss the mechanism of the laser-induced self-assembly on the basis of thermodynamic equilibrium between the in and out of optical trapping potential produced by the focused laser beam.