Self-assembled aggregates of the carotenoid zeaxanthin:: time-resolved study of excited states
Self-assembled aggregates of the carotenoid zeaxanthin:: time-resolved study of excited states
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DOI：
10.1021/jp044847j
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发表时间：
2005-03-03
影响因子：
2.9
通讯作者：
Polívka, T
中科院分区：
文献类型：
--
作者：
Billsten, HH;Sundström, V;Polívka, T
在本研究中，我们提出了一种控制水合乙醇中两种类型玉米黄质聚集体形成的方法：j -玉米黄质（头尾聚集体，530 nm处的特征吸收带）和h -玉米黄质（卡包聚集体，400 nm处的特征吸收带）。要控制是否形成J-或h -玉米黄质，有三个参数很重要：(1)pH，即形成氢键的能力；(2)玉米黄质初始浓度，即玉米黄质分子之间的距离；(3)乙醇/水比。要形成h聚集体，形成氢键的能力至关重要，而j聚集体在氢键形成受阻时优先形成。此外，j团聚体的形成需要较高的初始玉米黄质浓度和较高的乙醇/水比，而h团聚体的形成条件相反。时间分辨实验表明，j -玉米黄质在530nm激发时产生的弛豫模式与485和400运行时产生的弛豫模式不同，表明530nm波段不是S-2态的振动带，而是由j型聚集形成的单独激发态。玉米黄质聚集体的激发态动力学受到发生在J-和h -聚集体中的湮灭的影响。在H-团聚体中，主要湮灭组分在亚皮秒时间尺度上，而j -a-团聚体的主要湮灭组分为5 ps。团聚体的S-1寿命比溶液中的长，H-玉米黄质和j -玉米黄质分别产生20和30 ps。此外，h型聚集促进了一个新的弛豫通道，形成玉米黄质三重态。
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.