Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, USA.
J Phys Chem B. 2013 Apr 25;117(16):4313-24. doi: 10.1021/jp306392e. Epub 2012 Sep 4.
The role of proton transfer in the photoluminescence intermittency (PI) of single molecules of violamine R (VR) overgrown in potassium acid phthalate (KAP) crystals is evaluated in comparisons of protonated (KAP) and deuterated (DKAP) mixed crystals between 23 and 60 °C. The PI is analyzed by the construction of cumulative distribution functions that are statistically compared. We find that the on- and off-interval duration distributions change with isotopic substitution consistent with proton transfer contributing to the PI of VR. The on- and off-interval duration distributions have distinct temperature dependencies consistent with different mechanisms for dark state production and decay. Additional evidence for proton-transfer is provided by distributions of single molecule emission-energy maxima that reflect emission from protonated and deprotonated VR. A mechanism for the PI of KAP is presented, where the dark state is assigned to formation of the colorless, leuco form of VR, formed by proton transfer from VR to the KAP lattice, and decay of the dark state involves ring-opening promoted by proton transfer from KAP to VR. The distributed kinetics for dark-state production and decay are modeled using a log-normal distribution for the PI data in preference to a power-law previously assumed. A discussion of the log-normal distribution with regards to PI and proton transfer is presented.
在 23 至 60°C 温度范围内，通过比较质子化（KAP）和氘代（DKAP）混合晶体，评估质子转移在酸式邻苯二甲酸钾（KAP）晶体中生长的Violamine R（VR）单分子光致发光不连续性（PI）中的作用。通过构建统计比较的累积分布函数来分析 PI。我们发现，随着同位素取代，开和关间隔持续时间分布发生变化，这与质子转移对 VR 的 PI 有贡献一致。开和关间隔持续时间分布具有不同的温度依赖性，这与暗态产生和衰减的不同机制一致。质子转移的额外证据来自单分子发射能量最大值的分布，该分布反映了质子化和去质子化 VR 的发射。提出了一种 KAP 的 PI 机制，其中暗态被分配给 VR 从 VR 向 KAP 晶格转移质子形成的无色、隐色形式的形成，而暗态的衰减涉及由 KAP 向 VR 转移质子促进的开环。使用对数正态分布对 PI 数据进行模型化，而不是以前假设的幂律分布，以更好地模拟暗态产生和衰减的分布式动力学。本文还讨论了对数正态分布与 PI 和质子转移的关系。
