First-principles study on the modulation mechanism of solvent effect on the fluorescence emission of carbon dots

• Published in: Journal of molecular liquids 2024-06, Vol.403, p.124872, Article 124872
• Main Authors: Ren, Xiaojie, Guan, Li, Shi, Weicai, Zhang, Jianen, Chen, Mingjun, Luo, Tao, Liu, Chunzhi, Lan, Youshi, Chen, Zhijuan, Chen, Xiaobo, Li, Xu
• Format: Article
• Language: English
• Subjects: Carbon dots; First-principles method; Fluorescence spectra; Solvatochromism phenomena; Solvent effect
• ISSN: 0167-7322
• DOI: 10.1016/j.molliq.2024.124872

The modulation mechanism of CDs fluorescence emission by solvent effects was investigated using a first-principles method. The results indicate that solvent polarity and the interaction between solvents and CDs synergistically affect the fluorescence properties of CDs. Specifically, hydrogen bonding has a more significant influence on modulating the fluorescence spectra of CDs compared to solvent polarity. [Display omitted] •Calculation of solvent effect by microsolvent-Solvation model based on density model.•The effect of electron donating or withdrawing ability of functional groups on solvent effect was analyzed.•Simulated solvatochromism phenomena of carbon dots and compared with experimental results.•The interaction between carbon dots and solvent was studied by Independent Gradient Model Based on Hirshfeld Partition method. Solvent effect is one of the effective pathways to regulate the fluorescence emission spectra of carbon dots (CDs). In this work, the solvent effect on fluorescence emission of CDs with functional groups has been investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. Solvation model based on density (SMD) and microsolvent-SMD models have been employed to simulate the solvent effects. The electron donating or withdrawing ability of the surface functional groups of CDs, the polarity of the solvent, and the interaction between solvent molecules and CDs were analyzed. The results indicate that microsolvent-SMD model comprehensively considers the solvent polarity and the interaction between solvent molecules and functional groups, which is more advantageous to revealing the physical nature of solvent molecules participating in fluorescence emission, resulting in the calculated fluorescence spectra closer to experimental results. The hydrogen bonds can modulate the fluorescence spectra of CDs more significantly than the solvent polarity, when the CDs are primarily characterized by n-π* transitions, hydrogen bonding induces a blue shift in the fluorescence spectrum, whereas when the CDs mainly undergo π-π* transitions, hydrogen bonding causes a red shift in the spectrum. This work provides theoretical guidance to exploit the solvent effect to achieve effective modulation of the fluorescence properties of CDs.