Shi Weicai, Guan Li, Ren Xiaojie, Zhang Jianen, Luo Tao, Liu Chunzhi, Lan Youshi, Chen Zhijuan, Chen Xiaobo, Li Xu
Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China.
Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, PR China.
J Colloid Interface Sci. 2024 Apr;659:213-224. doi: 10.1016/j.jcis.2023.12.058. Epub 2023 Dec 21.
The effect of aggregation configuration of molecular fluorophore citrazinic acid (CZA) on the photoluminescence (PL) properties of carbon dots (CDs) has been investigated using first-principles method. The structural stability of all aggregates has been analyzed, and the results show that the most stable structures are J-type CZA aggregates with head-to-tail configurations and the CZA/CD aggregates are bonded by replacing H atoms on the CD edges with de-OH from the pyridine ring of CZA. The luminescent properties of CZA/CD aggregates are mainly affected by the binding modes and binding sites. When the sites belong to electron-donating groups, electron-withdrawing groups or sp domain, the PL spectra of CDs are shifted and the luminescent intensities are significantly enhanced. The results suggest that covalently bonded CZA/CD aggregates are responsible for the high fluorescence quantum yield of CD. Moreover, the distance between the centers of the two pyridine rings in H-type CZA dimers less than 3.5 Å is prone to π-π stacking, leading to fluorescence quenching of aggregates. The present work is helpful in understanding the effect of molecular fluorophores on the PL properties of CDs and provides theoretical guidance for the controllable synthesis of CDs.
采用第一性原理方法研究了分子荧光团柠嗪酸（CZA）的聚集构型对碳点（CDs）光致发光（PL）性质的影响。分析了所有聚集体的结构稳定性，结果表明，最稳定的结构是具有头对尾构型的J型CZA聚集体，且CZA/CD聚集体是通过用CZA吡啶环上的去OH取代CD边缘的H原子而键合的。CZA/CD聚集体的发光性质主要受结合模式和结合位点的影响。当这些位点属于供电子基团、吸电子基团或sp域时，CDs的PL光谱会发生位移，发光强度显著增强。结果表明，共价键合的CZA/CD聚集体是CDs具有高荧光量子产率的原因。此外，H型CZA二聚体中两个吡啶环中心之间的距离小于3.5 Å时容易发生π-π堆积，导致聚集体荧光猝灭。本工作有助于理解分子荧光团对CDs PL性质的影响，并为CDs的可控合成提供理论指导。
