Nontemplated Approach to Tuning the Spectral Properties of Cyanine-Based Fluorescent NanoGUMBOS

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• 作者：Susmita Das ; David Bwambok ; Bilal El-Zahab ; Joshua Monk ; Sergio L. de Rooy ; Santhosh Challa ; Min Li ; Francisco R. Hung ; Gary A. Baker ; Isiah M. Warner
• 刊名：Langmuir
• 出版年：2010
• 出版时间：August 3, 2010
• 年：2010
• 卷：26
• 期：15
• 页码：12867-12876
• 全文大小：1138K
• 年卷期：v.26,no.15(August 3, 2010)
• ISSN：1520-5827

文摘

Template-free controlled aggregation and spectral properties in fluorescent organic nanoparticles (FONs) is highly desirable for various applications. Herein, we report a nontemplated method for controlling the aggregation in near-infrared (NIR) cyanine-based nanoparticles derived from a group of uniform materials based on organic salts (GUMBOS). Cationic heptamethine cyanine dye 1,1′,3,3,3′,3′-hexamethylindotricarbocyanine (HMT) was coupled with five different anions, viz., [NTf₂⁻], [BETI⁻], [TFPB⁻], [AOT⁻], and [TFP4B⁻], by an ion-exchange method to obtain the respective GUMBOS. The nanoGUMBOS obtained via a reprecipitation method were primarily amorphous and spherical (30−100 nm) as suggested by selected area electron diffraction (SAED) and transmission electron microscopy (TEM). The formation of tunable self-assemblies within the nanoGUMBOS was characterized using absorption and fluorescence spectroscopy in conjunction with molecular dynamics simulations. Counterion-controlled spectral properties observed in the nanoGUMBOS were attributed to variations in J/H ratios with different anions. Association with the [AOT⁻] anion afforded predominant J aggregation enabling the highest fluorescence intensity, whereas [TFP4B⁻] disabled the fluorescence due to predominant H aggregation in the nanoparticles. Analyses of the stacking angle of the cations based on molecular dynamic simulation results in [HMT][NTf₂], [HMT][BETI], and [HMT][AOT] dispersed in water and a visual analysis of the representative simulation snapshots also imply that the type of aggregation was controlled through the counterion associated with the dye cation.