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Lifetime of Triplet Photosensitizers in Aerosol Using Time-Resolved Photoelectric Activity
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2020-06-29 , DOI: 10.1021/acsearthspacechem.0c00141 Ephraim Woods 1 , Oliver T. Harris 1 , William E. Leiter 1 , Nora E. Burner 1 , Pomaa Ofosuhene 1 , Alexandra Krez 1 , Mark A. Hilton 1 , Kathleen A. Burke 1
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2020-06-29 , DOI: 10.1021/acsearthspacechem.0c00141 Ephraim Woods 1 , Oliver T. Harris 1 , William E. Leiter 1 , Nora E. Burner 1 , Pomaa Ofosuhene 1 , Alexandra Krez 1 , Mark A. Hilton 1 , Kathleen A. Burke 1
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Time-resolved photoelectric activity of aerosol (TPEAA) experiments measure the kinetics of photochemically initiated reactions near the surface of aerosol particles. In the demonstration presented here, TPEAA experiments monitor the evolution of excited triplet states, which are key intermediates in the photochemical formation of secondary organic aerosol (SOA). One example is the decay of the triplet excited state of imidazole-2-carboxaldehyde (IC) in aqueous NaCl aerosol particles. The decay of the triplet IC shows two distinct timescales, indicative of two populations of IC in the particles: aqueous and pure IC. The lifetime in the pure-IC phase is less than 20 ns, and the lifetime associated with aqueous IC is limited by reaction with chloride ions (k = 5.6 × 105 M–1 s–1). The results demonstrate how phase separation in aerosol particles can control reaction pathways and kinetics. In another example, TPEAA monitors the decay of the triplet anthraquinone-2-sulfonate (AQ2S) anion in aqueous NaCl aerosol. The AQ2S triplet reacts with water (k′ = 8.7 × 106 s–1) to produce adduct species. In this case, tuning the wavelength of the photoemission laser permits the preferential observation of the triplet or a combination of the AQ2S triplet and the water adduct. These results bridge a gap between aerosol phase measurements, which are normally steady-state and bulk-phase transient absorption measurements, which typically probe homogeneous phases.
中文翻译：
三重态光敏剂在气溶胶中使用时间分辨光电活性的寿命
时间分辨的气溶胶光电活性（TPEAA）实验测量了气溶胶颗粒表面附近的光化学引发反应的动力学。在此处展示的演示中，TPEAA实验监测了激发三重态的演化，该态是次级有机气溶胶（SOA）光化学形成中的关键中间体。一个例子是NaCl气溶胶颗粒中咪唑-2-甲醛（IC）的三重激发态的衰减。三重态IC的衰减显示出两个不同的时标，表明颗粒中有两个IC种群：水性和纯IC。纯IC相的寿命小于20 ns，与水性IC相关的寿命受到与氯离子反应的限制（k = 5.6×10 5 M –1s –1）。结果表明，气溶胶颗粒中的相分离如何控制反应路径和动力学。在另一个示例中，TPEAA监控三氯化碳蒽醌-2-磺酸盐（AQ2S）阴离子在NaCl气溶胶中的衰减。AQ2S三重态与水（k '= 8.7×10 6 s –1）反应生成加合物。在这种情况下，调整光发射激光器的波长可以优先观察三重态或AQ2S三重态与水加合物的组合。这些结果弥合了通常为稳态的气溶胶相测量与通常探测均相的本体相瞬态吸收测量之间的差距。
更新日期：2020-08-20
中文翻译：
三重态光敏剂在气溶胶中使用时间分辨光电活性的寿命
时间分辨的气溶胶光电活性（TPEAA）实验测量了气溶胶颗粒表面附近的光化学引发反应的动力学。在此处展示的演示中，TPEAA实验监测了激发三重态的演化，该态是次级有机气溶胶（SOA）光化学形成中的关键中间体。一个例子是NaCl气溶胶颗粒中咪唑-2-甲醛（IC）的三重激发态的衰减。三重态IC的衰减显示出两个不同的时标，表明颗粒中有两个IC种群：水性和纯IC。纯IC相的寿命小于20 ns，与水性IC相关的寿命受到与氯离子反应的限制（k = 5.6×10 5 M –1s –1）。结果表明，气溶胶颗粒中的相分离如何控制反应路径和动力学。在另一个示例中，TPEAA监控三氯化碳蒽醌-2-磺酸盐（AQ2S）阴离子在NaCl气溶胶中的衰减。AQ2S三重态与水（k '= 8.7×10 6 s –1）反应生成加合物。在这种情况下，调整光发射激光器的波长可以优先观察三重态或AQ2S三重态与水加合物的组合。这些结果弥合了通常为稳态的气溶胶相测量与通常探测均相的本体相瞬态吸收测量之间的差距。
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