Wei Yaxiong, Wang Ye, Zhou Qiaohui, Zhang Song, Zhang Bing, Zhou Xiaoguo, Liu Shilin
Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
Phys Chem Chem Phys. 2020 Nov 25;22(45):26372-26382. doi: 10.1039/d0cp04230g.
The solvent effect usually plays an important role in triplet-triplet annihilation (TTA) upconversion processes. In this work, we have studied the TTA upconversion kinetics of perylene with Bodipy-phenyl-C60 as the triplet photosensitizer in five solvents, 1,4-dioxane, dichlorobenzene, chlorobenzene, toluene, and tetrahydrofuran (THF). Although no significant solvent effect was observed in steady-state absorption and fluorescence emission spectra, the overall TTA upconversion quantum yields showed a profound dependence on solvent properties, i.e. 4.9% in 1,4-dioxane, 7.1% in dichlorobenzene, 6.7% in chlorobenzene, 4.6% in toluene, and 2.2% in THF (the maximum of 50%). Each elementary reaction step involved in the overall process was analyzed by applying femtosecond and nanosecond time-resolved transient absorption spectroscopy, revealing that the fluorescence emission of perylene was more significantly affected by the solvents in contrast to the other steps. Moreover, an extra intramolecular energy-transfer pathway of Bodipy-phenyl-C60 was found via the formation of charge-separated states in dichlorobenzene, chlorobenzene, and THF solvents, once being excited. These conclusions provide valuable clues to choose the most favorable solvent for the higher TTA upconversion efficiency in related applications.
溶剂效应通常在三重态-三重态湮灭（TTA）上转换过程中起着重要作用。在这项工作中，我们研究了以Bodipy-苯基-C60作为三重态光敏剂的苝在1,4-二氧六环、二氯苯、氯苯、甲苯和四氢呋喃（THF）这五种溶剂中的TTA上转换动力学。尽管在稳态吸收光谱和荧光发射光谱中未观察到明显的溶剂效应，但TTA上转换的整体量子产率对溶剂性质有很大的依赖性，即在1,4-二氧六环中为4.9%，在二氯苯中为7.1%，在氯苯中为6.7%，在甲苯中为4.6%，在THF中为2.2%（最大值为50%）。通过应用飞秒和纳秒时间分辨瞬态吸收光谱对整个过程中涉及的每个基本反应步骤进行了分析，结果表明，与其他步骤相比，苝的荧光发射受溶剂的影响更为显著。此外，发现在二氯苯、氯苯和THF溶剂中，Bodipy-苯基-C60一旦被激发，会通过形成电荷分离态产生一条额外的分子内能量转移途径。这些结论为在相关应用中选择最有利于提高TTA上转换效率的溶剂提供了有价值的线索。
