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Iodide as a Fluorescence Quencher and Promoter-Mechanisms and Possible Implications
KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics.
2010 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 34, 11282-11291 p.Article in journal (Refereed) Published
Abstract [en]

In this work, fluorescence correlation spectroscopy (FCS) was used to investigate the effects of potassium iodide (KI) on the electronic-state population kinetics of a range of organic dyes in the visible wavelength range. Apart from a heavy atom effect promoting intersystem crossing to the triplet states in all dyes, KI was also found to enhance the triplet-state decay rate by a charge-coupled deactivation. This deactivation was only found for dyes with excitation maximum in the blue range, not for those with excitation maxima at wavelengths in the green range or longer. Consequently, under excitation conditions sufficient for triplet state formation, KI can promote the triplet state buildup of one dye and reduce it for another, red-shifted dye. This anticorrelated, spectrally separable response of two different dyes to the presence of one and the same agent may provide a useful readout for biomolecular interaction and microenvironmental monitoring studies. In contrast to the typical notion of KI as a fluorescence quencher, the FCS measurements also revealed that when added in micromolar concentrations KI can act as an antioxidant, promoting the recovery of photo-oxidized fluorophores. However, in millimolar concentrations KI also reduces intact, fluorescently viable fluorophores to a considerable extent. In aqueous solutions, for the dye Rhodamine Green, an optimal concentration of KI of approximately 5 mM can be defined at which the fluorescence signal is maximized. This concentration is not high enough to allow full triplet state quenching. Therefore, as a fluorescence enhancement agent, it is primarily the antioxidative properties of KI that play a role.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2010. Vol. 114, no 34, 11282-11291 p.
Keyword [en]
National Category
Physical Sciences Biophysics Physical Chemistry
Research subject
Biological Physics
URN: urn:nbn:se:kth:diva-26847DOI: 10.1021/jp103837fISI: 000281128700039ScopusID: 2-s2.0-77956071048OAI: diva2:374577
Swedish Research Council, VR-NT 2009-3134EU, FP7, Seventh Framework Programme, 201 837

QC 20101206

Available from: 2010-12-06 Created: 2010-11-29 Last updated: 2016-03-10Bibliographically approved

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