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论文类型：期刊论文

发表时间：2017-06-01

发表刊物：DYES AND PIGMENTS

收录刊物：SCIE、EI、Scopus

卷号：141

页面范围：379-387

ISSN号：0143-7208

关键字：Aminocyanine dyes; Dual fluorescence; Different viscosity sensitivities; Density functional calculations

摘要：A systematic spectral analysis is presented for a heptaaminocyanine dye (Cy7-NCY) and pentaaminocyanine dye (Cy5-NHY). The dyes displayed near infrared and ratiometric dual-fluorescence in viscous environments. Computational studies on these dyes revealed the origin of dual-fluorescence and the nature of the difference in viscous-sensitivity for these dyes. In low-viscous solvents, the amino group can be described as a rotor and was decoupled with the polymethine chain by photo-excitation, displaying an emission peak with long wavelength. In high-viscous solutions, on the contrary, the amino group is almost parallel to the parent polymethine chain and the lone-pair of the amino group is in an appropriate orientation for efficient overlap with the polymethine chain, resulting in an emission peak with short wavelength. The overall balance of the rotating ability for the substituted amino group and the polymethine chain affects the competition between radiative and non-radiative transition processes in a viscous environment. (C) 2017 Elsevier Ltd. All rights reserved.