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首页> 外文期刊>Chemistry: A European journal >Exciton-coupled charge-transfer dynamics in a porphyrin J-aggregate/TiO_2 complex
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Exciton-coupled charge-transfer dynamics in a porphyrin J-aggregate/TiO_2 complex

机译：卟啉J-聚集体/ TiO_2复合物中激子耦合的电荷转移动力学

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摘要

Exciton-coupled charge-transfer (CT) dynamics in TiO_2 nanoparticles (NP) sensitized with porphyrin J-aggregates has been studied by femtosecond time-resolved transient absorption spectroscopy. J-aggregates of 5,10,15-triphenyl-20-(3,4-dihydroxyphenyl) porphyrin (TPPcat) form CT complexes on TiO_2 NP surfaces. Catechol-mediated strong CT coupling between J-aggregate and TiO_2 NP facilitates interfacial exciton dissociation for electron injection into the conduction band of the TiO_2 nanoparticle in pulse width limited time (<80fs). Here, the electron-transfer (<80fs) process dominates over the intrinsic exciton-relaxation process (J-aggregates: ca. 200fs) on account of exciton-coupled CT interaction. The parent hole on J-aggregates is delocalized through J-aggregate excitonic coherence. As a result, holes immobilized on J-aggregates are spatially less accessible to electrons injected into TiO_2, and thus the back electron transfer (BET) process is slower than that of the monomer/TiO _2 system. The J-aggregate/porphyrin system shows exciton spectral and temporal properties for better charge separation in strongly coupled composite systems. Free charge-carrier generation in the Frenkel exciton-coupled porphyrin catechol J-aggregate/semiconductor (TiO_2) composite system is accomplished through an interfacial exciton-dissociation process. The separated hole is delocalized through excitonic coherence of the J-aggregate. The immobilized hole is spatially less accessible to electrons injected into TiO_2 and thus leads to slower back electron transfer (BET; see schematic).
机译：飞秒时间分辨瞬态吸收光谱研究了卟啉J-聚集体敏化的TiO_2纳米粒子（NP）中的激子耦合电荷转移（CT）动力学。 5,10,15-三苯基-20-（3,4-二羟基苯基）卟啉（TPPcat）的J聚集体在TiO_2 NP表面上形成CT络合物。邻苯二酚介导的J-聚集体与TiO_2 NP之间的强CT耦合促进了电子在TiO_2纳米粒子的导带中在脉冲宽度有限的时间内（<80fs）注入电子时的界面激子解离。在这里，由于激子耦合的CT相互作用，电子传递（<80fs）过程比固有的激子弛豫过程（J-aggregates：ca. 200fs）更为重要。 J聚集体上的母孔通过J聚集体的激子相干性而异位。结果，固定在J-聚集体上的空穴在空间上不容易注入到TiO_2中的电子进入，因此背电子转移（BET）过程比单体/ TiO _2系统的过程慢。 J-聚集体/卟啉系统显示出激子光谱和时间特性，可在强耦合复合系统中实现更好的电荷分离。 Frenkel激子偶联的卟啉邻苯二酚J聚集体/半导体（TiO_2）复合体系中的自由电荷载流子生成是通过界面激子离解过程完成的。分离的孔通过J聚集体的激子相干而脱位。固定化的空穴在空间上不易注入TiO_2中，因此导致反向电子传输较慢（BET;参见示意图）。

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