期刊
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
卷 18, 期 28, 页码 18750-18757出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c6cp00881j
关键词
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资金
- 973 Program [2013CB834604]
- NSFCs [21173235, 21127003, 21333012, 21373232]
- Strategic Priority Research Program of the Chinese Academy of Sciences [XDB12020200]
Excited state solvation plays a very important role in modulating the emission behavior of fluorophores upon excitation. Here, the solvation effects on the local micro-environment around a fluorophore are proposed by investigating the fantastic emission behavior of a novel amyloid fibril marker, NIAD-4, in different alcoholic and aprotic solvents. In alcoholic solvents, high solvent viscosity causes an obvious enhancement of fluorescence because of the restriction of torsion of NIAD-4, where the formation of a non-fluorescent twist intramolecular charge transfer (TICT) state is suppressed. In aprotic solvents, high solvent polarity leads to a remarkable redshift of the emission spectra suggesting strong solvation. Surprisingly, an abnormal fluorescence enhancement of NIAD-4 is observed with increasing solvent polarity of the aprotic solvents, whereas solvent viscosity plays little role in influencing the fluorescence intensity. We conclude that such an abnormal phenomenon is originated from a solvation induced micro-viscosity enhancement around the fluorophore upon excitation which restricts the torsion of NIAD-4. Femtosecond transient absorption results further prove such a micro-viscosity increasing mechanism. We believe that this solvation induced micro-viscosity enhancement effect on fluorescence could widely exist for most donor-pi-acceptor (D-pi-A) compounds in polar solvents, which should be carefully taken into consideration when probing the micro-viscosity in polar environments, especially in complex bioenvironments.
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