Department of Chemistry, Johannes Gutenberg-University, Duesbergweg 10-14, 55099 Mainz, Germany.
J Am Chem Soc. 2022 Aug 10;144(31):14053-14056. doi: 10.1021/jacs.2c07188. Epub 2022 Jul 29.
Internal conversion (IC) often is the dominating relaxation pathway in NIR emitters, lowering their fluorescence quantum yield. Here, we investigate dibenzoterrylene (DBT) by bulk and single molecule spectroscopy. With increasing solvent polarity, the S-S energy gap decreases leading to a decrease of the fluorescence quantum yield and an increase of the IC rate in full accordance with the energy gap law. Making use of the unexpectedly strong fluorescence solvatochromism of this aromatic hydrocarbon, the validity of the energy gap law could also be demonstrated at the single molecule level. The S-S energy gap not only controls the fluorescence lifetime and quantum yield of single molecules but also dictates how these quantities develop during spectral fluctuations. Our results open new avenues into unexplored single molecule photophysics and appear as a promising tool for nanoscale probing of dynamic heterogeneities.
内部转换（IC）通常是近红外辐射体中占主导地位的弛豫途径，降低了它们的荧光量子产率。在这里，我们通过体相和单分子光谱研究了二苯并噻吩（DBT）。随着溶剂极性的增加，S-S 能隙减小，导致荧光量子产率降低，IC 速率增加，这完全符合能隙定律。利用这种芳烃出人意料的强荧光溶剂化变色性，也可以在单分子水平上证明能隙定律的有效性。S-S 能隙不仅控制着单分子的荧光寿命和量子产率，还决定了这些量在光谱波动过程中的发展情况。我们的研究结果为探索单分子光物理开辟了新的途径，并为纳米尺度探测动态不均匀性提供了一种很有前途的工具。
