Li Chao, Liu Tao, Thwaites Owen, Gardner Adrian M, Sazanovich Igor V, Yang Haofan, Li Xiaobo, Cooper Andrew I, Cowan Alexander J
Stephenson Institute for Renewable Energy and Department of Chemistry, University of Liverpool L69 7ZF UK
Leverhulme Research Centre for Functional Materials Design, Materials Innovation Factory and Department of Chemistry, University of Liverpool Liverpool L7 3NY UK.
Chem Sci. 2024 Sep 13;15(39):16133-41. doi: 10.1039/d4sc03825h.
The controlled aggregation of organic chromophores into supramolecular structures offers a way to control and tune photocatalytic activity. However, the underlying mechanisms of charge transfer and accumulation are still unclear. Time-resolved vibrational spectroscopy is a powerful structural probe for studying photogenerated intermediates. Here, we employ time-resolved infrared (TRIR) spectroscopy to study CNP (2,6-bis(4-cyanophenyl)-4-(9-phenyl-9-carbazol-3-yl)pyridine-3,5-dicarbonitrile) and its supramolecular aggregates. We show that excitation of the charge transfer (CT) band of semi-crystalline nanofibers (CNP-f) gives rise to long-lived delocalised polarons, which form within the instrument response timescale. By contrast the CNP nanospheres (CNP-s) give rise to a shorter lived polaron that appears to have a greater degree of localization. CNP-f and CNP-s are known to show markedly different levels of photocatalytic activity for hydrogen and hydrogen peroxide formation which are rationalised owing to these differences in photodynamics immediately following photon absorption.
将有机发色团可控聚合成超分子结构为控制和调节光催化活性提供了一种方法。然而，电荷转移和积累的潜在机制仍不清楚。时间分辨振动光谱是研究光生中间体的一种强大的结构探测手段。在此，我们采用时间分辨红外（TRIR）光谱来研究CNP（2,6-双（4-氰基苯基）-4-（9-苯基-9-咔唑-3-基）吡啶-3,5-二甲腈）及其超分子聚集体。我们表明，半结晶纳米纤维（CNP-f）的电荷转移（CT）带的激发产生了长寿命的离域极化子，其在仪器响应时间尺度内形成。相比之下，CNP纳米球（CNP-s）产生的极化子寿命较短，似乎具有更高程度的局域化。已知CNP-f和CNP-s在氢气和过氧化氢生成方面表现出明显不同的光催化活性水平，这归因于光子吸收后这些光动力学差异。
