Abstract We studied spectral properties of 5-Bromoindole (5-BrI) in poly (vinyl alcohol) (PVA) film. The fluorescence of 5-BrI in PVA films is similar to indole in PVA film but strongly quenched compared to unsubstituted indole. The quantum yield of 5-BrI is only 0.0034 comparing to 0.26 of indole. In contrast, phosphorescence of 5-BrI in PVA is comparable to indole phosphorescence in magnitude and lifetime but its emission shifted towards longer wavelengths by 50 nm for a maximum at 530 nm. The phosphorescence of 5-BrI in PVA can be effectively excited at longer wavelengths (450–500 nm). The maximum of phosphorescence excitation spectrum of the 5-BrI in PVA is at about 480 nm. This direct excitation to the triplet state results in high positive phosphorescence anisotropy of 0.2. Although the S0 → T1 absorption transition is only about 800 fold weaker from the main 280 nm UV absorption band yielding measurable trace of absorption for 5-BrI in PVA film in the visible/blue range. We believe this is a first report of singlet-triplet absorption (S0 → T1) at room temperature, not involving external heavy atoms or oxygen presence. The comparison of phosphorescence of 5-BrI in PVA film to Rhodamine 6G in ethanol fluorescence allows us to estimate the phosphorescence quantum yield of 5-BrI in PVA to be ~0.02. We measured independently fluorescence and phosphorescence lifetimes and quantum yields as well as phosphorescence excitation spectrum across all wavelengths from UV to the visible range. These measurements were used to determine rate constants for all processes involved the in 5-BrI in PVA excited state deactivation.

中文翻译：

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室温下 PVA 薄膜中 5-溴吲哚的发光特性：直接三重态激发

摘要 我们研究了聚乙烯醇 (PVA) 薄膜中 5-溴吲哚 (5-BrI) 的光谱特性。PVA 薄膜中 5-BrI 的荧光类似于 PVA 薄膜中的吲哚，但与未取代的吲哚相比，它的荧光被强烈淬灭。与吲哚的 0.26 相比，5-BrI 的量子产率仅为 0.0034。相比之下，PVA 中 5-BrI 的磷光在强度和寿命上与吲哚磷光相当，但其发射向更长的波长偏移 50 nm，最大波长为 530 nm。PVA 中 5-BrI 的磷光可以在更长的波长（450-500 nm）下有效激发。PVA 中 5-BrI 的磷光激发光谱的最大值约为 480 nm。这种对三重态的直接激发导致 0.2 的高正磷光各向异性。尽管 S0 → T1 吸收转变仅比主 280 nm 紫外吸收带弱约 800 倍，但在可见光/蓝色范围内产生了 PVA 膜中 5-BrI 的可测量吸收痕迹。我们相信这是室温下单线态-三线态吸收（S0 → T1）的首次报告，不涉及外部重原子或氧的存在。PVA 薄膜中 5-BrI 的磷光与乙醇荧光中的罗丹明 6G 的比较使我们能够估计 PVA 中 5-BrI 的磷光量子产率约为 0.02。我们独立测量了从紫外到可见光范围的所有波长的荧光和磷光寿命和量子产率以及磷光激发光谱。这些测量值用于确定 PVA 激发态失活中 5-BrI 中涉及的所有过程的速率常数。