Wang Jian-Xin, Fang Ye-Guang, Li Chun-Xiang, Niu Li-Ya, Fang Wei-Hai, Cui Ganglong, Yang Qing-Zheng
Institution Key Laboratory of Radiopharmaceuticals, College of Chemistry, Beijing Normal University, Beijing, 100875, P. R. China.
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing, 100875, P. R. China.
Angew Chem Int Ed Engl. 2020 Jun 15;59(25):10032-10036. doi: 10.1002/anie.202001141. Epub 2020 Mar 4.
An organic crystal of 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (pCBP) exhibits time-dependent afterglow color from blue to orange over 1 s. Both experimental and computational data confirm that the color evolution results from well-separated, long-persistent thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) with different but comparable decay rates. TADF is enabled by a small S -T energy gap of 0.7 kcal mol . The good separation of TADF and RTP is due to a 11.8 kcal mol difference in the S energies of the S and T structures, indicating that apart from the excited-state properties, tuning the ground state is also important for luminescence properties. This afterglow color evolution of pCBP allows its applications in anticounterfeiting and data encryption with high security levels.
4,4'-双（N-咔唑基）-1,1'-联苯（pCBP）的有机晶体在1秒内呈现出从蓝色到橙色的时间依赖性余辉颜色。实验和计算数据均证实，颜色演变源于具有不同但可比衰减率的、分离良好的长寿命热激活延迟荧光（TADF）和室温磷光（RTP）。TADF由0.7千卡·摩尔的小S - T能隙实现。TADF和RTP的良好分离归因于S和T结构的S能量存在11.8千卡·摩尔的差异，这表明除了激发态性质外，调节基态对发光性质也很重要。pCBP的这种余辉颜色演变使其能够应用于具有高安全级别的防伪和数据加密。
