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Self-assembled aggregates of the carotenoid zeaxanthin: time-resolved study of excited states

Billsten, Helena LU ; Sundström, Villy LU and Polivka, Tomas LU (2005) In The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory 109(8). p.1521-1529
Abstract
In this study, we present a way of controlling the formation of the two types of zeaxanthin aggregates in hydrated ethanol: J-zeaxanthin (head-to-tail aggregate, characteristic absorption band at 530 nm) and H-zeaxanthin (card-pack aggregate, characteristic absorption band at 400 run). To control whether J- or H-zeaxanthin is formed, three parameters are important: (1) pH, that is, the ability to form a hydrogen bond; (2) the initial concentration of zeaxanthin, that is, the distance between zeaxanthin molecules; and (3) the ratio of ethanol/water. To create H-aggregates, the ability to form hydrogen bonds is crucial, while J-aggregates are preferentially formed when hydrogen-bond formation is prevented. Further, the formation of... (More)
In this study, we present a way of controlling the formation of the two types of zeaxanthin aggregates in hydrated ethanol: J-zeaxanthin (head-to-tail aggregate, characteristic absorption band at 530 nm) and H-zeaxanthin (card-pack aggregate, characteristic absorption band at 400 run). To control whether J- or H-zeaxanthin is formed, three parameters are important: (1) pH, that is, the ability to form a hydrogen bond; (2) the initial concentration of zeaxanthin, that is, the distance between zeaxanthin molecules; and (3) the ratio of ethanol/water. To create H-aggregates, the ability to form hydrogen bonds is crucial, while J-aggregates are preferentially formed when hydrogen-bond formation is prevented. Further, the formation of J-aggregates requires a high initial zeaxanthin concentration and a high ethanol/water ratio, while H-aggregates are formed under the opposite conditions. Time-resolved experiments revealed that excitation of the 530-nm band of J-zeaxanthin produces a different relaxation pattern than excitation at 485 and 400 run, showing that the 530-nm band is not a vibrational band of the S-2 state but a separate excited state formed by J-type aggregation. The excited-state dynamics of zeaxanthin aggregates are affected by annihilation that occurs in both J- and H-aggregates. In H-aggregates, the dominant annihilation component is on the subpicosecond time scale, while the main annihilation component for the J-a-gregate is 5 ps. The S-1 lifetimes of aggregates are longer than in solution, yielding 20 and 30 ps for H- and J-zeaxanthin, respectively. In addition, H-type aggregation promotes a new relaxation channel that forms the zeaxanthin triplet state. (Less)
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author
organization
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Contribution to journal
publication status
published
subject
in
The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
volume
109
issue
8
pages
1521 - 1529
publisher
The American Chemical Society
external identifiers
  • wos:000227247900005
  • scopus:14844363437
ISSN
1520-5215
DOI
10.1021/jp044847j
language
English
LU publication?
yes
id
b57e4c11-e639-4388-aadc-b7c01a09e750 (old id 151977)
date added to LUP
2007-07-03 10:46:13
date last changed
2017-09-17 07:21:34
@article{b57e4c11-e639-4388-aadc-b7c01a09e750,
  abstract     = {In this study, we present a way of controlling the formation of the two types of zeaxanthin aggregates in hydrated ethanol: J-zeaxanthin (head-to-tail aggregate, characteristic absorption band at 530 nm) and H-zeaxanthin (card-pack aggregate, characteristic absorption band at 400 run). To control whether J- or H-zeaxanthin is formed, three parameters are important: (1) pH, that is, the ability to form a hydrogen bond; (2) the initial concentration of zeaxanthin, that is, the distance between zeaxanthin molecules; and (3) the ratio of ethanol/water. To create H-aggregates, the ability to form hydrogen bonds is crucial, while J-aggregates are preferentially formed when hydrogen-bond formation is prevented. Further, the formation of J-aggregates requires a high initial zeaxanthin concentration and a high ethanol/water ratio, while H-aggregates are formed under the opposite conditions. Time-resolved experiments revealed that excitation of the 530-nm band of J-zeaxanthin produces a different relaxation pattern than excitation at 485 and 400 run, showing that the 530-nm band is not a vibrational band of the S-2 state but a separate excited state formed by J-type aggregation. The excited-state dynamics of zeaxanthin aggregates are affected by annihilation that occurs in both J- and H-aggregates. In H-aggregates, the dominant annihilation component is on the subpicosecond time scale, while the main annihilation component for the J-a-gregate is 5 ps. The S-1 lifetimes of aggregates are longer than in solution, yielding 20 and 30 ps for H- and J-zeaxanthin, respectively. In addition, H-type aggregation promotes a new relaxation channel that forms the zeaxanthin triplet state.},
  author       = {Billsten, Helena and Sundström, Villy and Polivka, Tomas},
  issn         = {1520-5215},
  language     = {eng},
  number       = {8},
  pages        = {1521--1529},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory},
  title        = {Self-assembled aggregates of the carotenoid zeaxanthin: time-resolved study of excited states},
  url          = {http://dx.doi.org/10.1021/jp044847j},
  volume       = {109},
  year         = {2005},
}