Aqueous Dispersion of J-Aggregates Prepared by Polyion Complexation and Its Two-Photon Excited Fluorescence Property

An aqueous dispersion of J-aggregates was prepared by the complexation between an anionic cyanine dye and a polycation. 5-chloro-2-[[5-chloro-3-(3-sulfopropyl)-2(3H)-benzothiazolylidene]methyl]-3-(3-suflopropyl)benzothiazolium hydroxide sodium salt and poly(allylamine hydrochloride) were used as the anionic dye and the polycation, respectively. Upon mixture of the aqueous solutions of these materials under a certain condition, a transparent aqueous dispersion with a sharp J-aggregate absorption band at 460 nm was obtained, and the J-aggregates in the dispersion exhibited no dissociation even after 30-fold dilution with water, indicating that the J-aggregates were stable in aqueous media. The two-photon excited fluorescence action cross section (sigma(TPEF)) of the aqueous dispersion of J-aggregates was observed in the excitation wavelength range from 800 to 900 nm, and the maximum value of sigma(TPEF) was evaluated to be 92 GM. The sigma(TPEF) values of the monomeric and aggregated cyanine dye molecules were compared, and it was revealed that the sigma(TPEF) was enhanced by similar to 1300 times upon J-aggregation. (C) 2010 The Japan Society of Applied Physics