Cargando…
Effect of Urea on Solvation Dynamics and Rotational Relaxation of Coumarin 480 in Aqueous Micelles of Cationic Gemini Surfactants with Different Spacer Groups
[Image: see text] The present work highlights the effect of urea on solvation dynamics and the rotational relaxation of Coumarin 480 (C-480) in the Stern layer of aqueous micelles of cationic gemini surfactants, 12-4(OH)(n)-12 (n = 0, 1, 2). UV–visible absorption, steady-state fluorescence and fluor...
Autores principales: | , , , , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Chemical Society
2018
|
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6044790/ https://www.ncbi.nlm.nih.gov/pubmed/30023859 http://dx.doi.org/10.1021/acsomega.7b01747 |
_version_ | 1783339542875471872 |
---|---|
author | Kumari, Sunita Sonu, Halder, Sayantan Aggrawal, Rishika Sundar, Ganapathisubramanian Saha, Subit K. |
author_facet | Kumari, Sunita Sonu, Halder, Sayantan Aggrawal, Rishika Sundar, Ganapathisubramanian Saha, Subit K. |
author_sort | Kumari, Sunita |
collection | PubMed |
description | [Image: see text] The present work highlights the effect of urea on solvation dynamics and the rotational relaxation of Coumarin 480 (C-480) in the Stern layer of aqueous micelles of cationic gemini surfactants, 12-4(OH)(n)-12 (n = 0, 1, 2). UV–visible absorption, steady-state fluorescence and fluorescence anisotropy, time-resolved fluorescence and fluorescence anisotropy, and dynamic light scattering measurements have been carried out for this study. The formation of micelles becomes disfavored in the presence of urea at high concentration. Solvation dynamics is bimodal in nature with fast solvation as a major component. The average solvation time increases, reaches a maximum, and then decreases with increasing concentration of urea because the degree of counterion dissociation also follows the same order with the addition of urea in the micellar solution. With increased degree of counterion dissociation, the extent of clustering of water molecules is increased, resulting in slower solvation process. The −OH group present in the spacer group of gemini surfactant controls the rate of solvation by shielding the water molecules from the probe molecules forming hydrogen bond. The microviscosity of micelles is decreased with increasing concentration of urea, as a result of which the rotational relaxation process becomes faster. In the presence of the −OH group in the spacer group, the microviscosity of micelles is enhanced, resulting in longer rotational relaxation time. Rotational relaxation process is bimodal in nature with the major contribution from the fast component to the fluorescence depolarization. Slow rotational relaxation is mainly due to the lateral diffusion of C-480 molecules along the surface of the micelle. The tumbling motion of the micelle as a whole is much slower than the lateral diffusion of C-480. Wobbling motion of C-480 becomes faster with increasing concentration of urea as a result of decreased microviscosity of micelles. The alignment of C-480 molecules in micelles might change with changing microviscosity. |
format | Online Article Text |
id | pubmed-6044790 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | American Chemical Society |
record_format | MEDLINE/PubMed |
spelling | pubmed-60447902018-07-16 Effect of Urea on Solvation Dynamics and Rotational Relaxation of Coumarin 480 in Aqueous Micelles of Cationic Gemini Surfactants with Different Spacer Groups Kumari, Sunita Sonu, Halder, Sayantan Aggrawal, Rishika Sundar, Ganapathisubramanian Saha, Subit K. ACS Omega [Image: see text] The present work highlights the effect of urea on solvation dynamics and the rotational relaxation of Coumarin 480 (C-480) in the Stern layer of aqueous micelles of cationic gemini surfactants, 12-4(OH)(n)-12 (n = 0, 1, 2). UV–visible absorption, steady-state fluorescence and fluorescence anisotropy, time-resolved fluorescence and fluorescence anisotropy, and dynamic light scattering measurements have been carried out for this study. The formation of micelles becomes disfavored in the presence of urea at high concentration. Solvation dynamics is bimodal in nature with fast solvation as a major component. The average solvation time increases, reaches a maximum, and then decreases with increasing concentration of urea because the degree of counterion dissociation also follows the same order with the addition of urea in the micellar solution. With increased degree of counterion dissociation, the extent of clustering of water molecules is increased, resulting in slower solvation process. The −OH group present in the spacer group of gemini surfactant controls the rate of solvation by shielding the water molecules from the probe molecules forming hydrogen bond. The microviscosity of micelles is decreased with increasing concentration of urea, as a result of which the rotational relaxation process becomes faster. In the presence of the −OH group in the spacer group, the microviscosity of micelles is enhanced, resulting in longer rotational relaxation time. Rotational relaxation process is bimodal in nature with the major contribution from the fast component to the fluorescence depolarization. Slow rotational relaxation is mainly due to the lateral diffusion of C-480 molecules along the surface of the micelle. The tumbling motion of the micelle as a whole is much slower than the lateral diffusion of C-480. Wobbling motion of C-480 becomes faster with increasing concentration of urea as a result of decreased microviscosity of micelles. The alignment of C-480 molecules in micelles might change with changing microviscosity. American Chemical Society 2018-03-14 /pmc/articles/PMC6044790/ /pubmed/30023859 http://dx.doi.org/10.1021/acsomega.7b01747 Text en Copyright © 2018 American Chemical Society This is an open access article published under an ACS AuthorChoice License (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html) , which permits copying and redistribution of the article or any adaptations for non-commercial purposes. |
spellingShingle | Kumari, Sunita Sonu, Halder, Sayantan Aggrawal, Rishika Sundar, Ganapathisubramanian Saha, Subit K. Effect of Urea on Solvation Dynamics and Rotational Relaxation of Coumarin 480 in Aqueous Micelles of Cationic Gemini Surfactants with Different Spacer Groups |
title | Effect of Urea on Solvation Dynamics and Rotational
Relaxation of Coumarin 480 in Aqueous Micelles of Cationic Gemini
Surfactants with Different Spacer Groups |
title_full | Effect of Urea on Solvation Dynamics and Rotational
Relaxation of Coumarin 480 in Aqueous Micelles of Cationic Gemini
Surfactants with Different Spacer Groups |
title_fullStr | Effect of Urea on Solvation Dynamics and Rotational
Relaxation of Coumarin 480 in Aqueous Micelles of Cationic Gemini
Surfactants with Different Spacer Groups |
title_full_unstemmed | Effect of Urea on Solvation Dynamics and Rotational
Relaxation of Coumarin 480 in Aqueous Micelles of Cationic Gemini
Surfactants with Different Spacer Groups |
title_short | Effect of Urea on Solvation Dynamics and Rotational
Relaxation of Coumarin 480 in Aqueous Micelles of Cationic Gemini
Surfactants with Different Spacer Groups |
title_sort | effect of urea on solvation dynamics and rotational
relaxation of coumarin 480 in aqueous micelles of cationic gemini
surfactants with different spacer groups |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6044790/ https://www.ncbi.nlm.nih.gov/pubmed/30023859 http://dx.doi.org/10.1021/acsomega.7b01747 |
work_keys_str_mv | AT kumarisunita effectofureaonsolvationdynamicsandrotationalrelaxationofcoumarin480inaqueousmicellesofcationicgeminisurfactantswithdifferentspacergroups AT sonu effectofureaonsolvationdynamicsandrotationalrelaxationofcoumarin480inaqueousmicellesofcationicgeminisurfactantswithdifferentspacergroups AT haldersayantan effectofureaonsolvationdynamicsandrotationalrelaxationofcoumarin480inaqueousmicellesofcationicgeminisurfactantswithdifferentspacergroups AT aggrawalrishika effectofureaonsolvationdynamicsandrotationalrelaxationofcoumarin480inaqueousmicellesofcationicgeminisurfactantswithdifferentspacergroups AT sundarganapathisubramanian effectofureaonsolvationdynamicsandrotationalrelaxationofcoumarin480inaqueousmicellesofcationicgeminisurfactantswithdifferentspacergroups AT sahasubitk effectofureaonsolvationdynamicsandrotationalrelaxationofcoumarin480inaqueousmicellesofcationicgeminisurfactantswithdifferentspacergroups |