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

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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 ($\sigma_{\text{TPEF}}$) of the aqueous dispersion of J-aggregates was observed in the excitation wavelength range from 800 to 900 nm, and the maximum value of $\sigma_{\text{TPEF}}$ was evaluated to be 92 GM. The $\sigma_{\text{TPEF}}$ values of the monomeric and aggregated cyanine dye molecules were compared, and it was revealed that the $\sigma_{\text{TPEF}}$ was enhanced by ${\sim}1300$ times upon J-aggregation.
2010-03-25