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- Armstrong, Emily J., et al.
(författare)
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A ground-state complex between methyl viologen and the fluorescent whitening agent 4,4 '-bis(2-sulfostyryl)-biphenyl disodium salt : a fluorescence spectroscopy study
- 2021
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Ingår i: Canadian journal of chemistry (Print). - : Canadian science publishing. - 0008-4042 .- 1480-3291. ; 99:7, s. 563-569
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Tidskriftsartikel (refereegranskat)abstract
- This study explores the quenching of the dianionic fluorescent whitening agent, NFW, by various substances, including methyl viologen (MV), in water and in the presence of beta-cyclodextrin (beta-CD). Results of a fluorescence spectro-scopic examination of the beta-CD-NFW system are presented. It was found that NFW forms a 1:1 inclusion complex with b-CD with an association constant of 2540 +/- 380 M-1. The included NFW fluorescent state is protected by the beta-CD cavity from a range of water-based quenchers (neutral, anionic, and cationic). Quenching proceeds near the diffusion-controlled limit in water for the quenchers tested with the exception of the dicationic MV. Methyl viologen is an extremely efficient quencher of NFW fluorescence with a nominal K-SV similar to 5.0 x 10(3) M-1 in water alone, corresponding to a nominal k(q) of similar to 4 x 10(12) M-1 s(-1), which exceeds the diffusion-controlled limit in this solvent. The quenching efficiency of MV is strongly suppressed in the presence of 10 mM beta-CD (K-SV = 105 +/- 12 M-1) and in the presence of NaCl (K-SV = 106 +/- 9 M-1 at 0.5 M salt). In the absence of CD or salt, there is a strong contribution from static quenching in the MV system; the presence of these additives suppresses the static quenching. Various results suggest the static quenching is due to formation of a ground-state complex between the dianion NFW and the dication MV.
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