高质量红光碳点的制备及机理探索 | Science Bulletin封面文章

ScienceBulletin 2023-03-29

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速递

Photoluminescence mechanisms of red-emissive carbon dots derived from non-conjugated molecules

Xin Yang, Lin Ai, Jingkun Yu, Geoffrey I. N. Waterhouse, Laizhi Sui, Jie Ding, Baowei Zhang, Xue Yong, Siyu Lu

Science Bulletin, 2022, 67(14): 1450–1457

doi: 10.1016/j.scib.2022.06.013

简介

在碳点基发光材料中, 红光和近红外波长发射性质的开发一直是目前研究的热点和难点, 其在生物学领域和显示领域等具有广阔的应用前景；然而, 红光碳点的形成过程和荧光机理均不明确, 这使得高品质红光碳点的制备依然面临巨大挑战. 针对上述难题, 研究人员提出氮(N)诱导芳构化的策略, 精准调控碳点中五元芳环和六元芳环的形成过程, 并通过高分辨制质谱结合密度泛函理论计算深度解析了柠檬酸基红光碳点的荧光发射中心. 他们选取柠檬酸和一系列类柠檬酸分子, 如乌头酸、酒石酸、天冬氨酸、苹果酸和顺丁烯二酸等作为反应前驱体进行探究, 结果表明, 柠檬酸类似物种碳链长度的不同会影响所制备碳点的荧光发射波长, 前体碳链长度会影响N参与的扣环形式, 从而导致不同程度的红移. 其中, 柠檬酸基碳点可形成N掺杂六元芳环, 从而实现荧光发射波长从无N掺杂的423 nm到有N掺杂的667 nm, 高达244 nm的大幅度红移. 这项工作揭示了柠檬酸或类柠檬酸等非共轭小分子为碳源制备红光碳点的生长过程和其荧光发射中心, 并为其他类型碳点的荧光机制探索和结构分析提供了创新思路.

图文导读

Fig. 1 Schematic of the fabrication of CA-BCDs and CA-RCDs (a). CA-BCDs: TEM and HRTEM (b) and AFM (c). CA-RCDs: TEM and HRTEM (d) and AFM (e). CA-BCDs and CA-RCDs: XRD (f); FTIR spectra (g); XPS survey scans; and narrow scan C 1s, N 1s, and O 1s XPS spectra (h–k); 1H NMR (l); and mass spectra (m).

Fig. 2 Excitation-dependent spectra of CA-BCDs (a) and CA-RCDs (e); PL dynamics of CA-BCDs (b) and CA-RCDs (f); variable-temperature PL spectra of CA-BCDs (c, d) and CA-RCDs (g, h); 2D pseudocolor map of TA spectra expressed in ΔOD as functions of delay time and probe wavelength for CDs with a pump wavelength of 400 nm: CA-BCDs (i) and CA-RCDs (k); TA spectra of A-BCDs (j) and CA-RCDs (l) at indicated delay time from 0.5 to 1000 ps.

Fig. 3 (a) Reaction routes from precursor molecules to a target molecule with m/z 508. (b) Second stage in the formation of CA-RCDs: dehydration aggregation. (c) Third stage in the formation of CA-RCDs: crosslinking carbonization. (d) DFT of the target molecular model and PL.

Fig. 4 TEM (a–e), AFM (f−j), 1H NMR (k), MS (l), and reaction scheme (m) of AC-RCDs, TA-RCDs, AA-RCDs, MI-RCDs, and ME-RCDs.

Fig. 5 (a–e) PL images of AC-BCDs, AC-RCDs, TA-BCDs, TA-RCDs, AA-BCDs, AA-RCDs MI-BCDs, MI-RCDs, ME-BCDs, and ME-RCDs. (f−j) DFT models for AC-RCDs, TA-RCDs, AA-RCDs, MI-RCDs, and ME-RCDs. (k–o) DFT emission of AC-RCDs, TA-RCDs, AA-RCDs, MI-RCDs, and ME-RCDs. (p) Schematic diagram of the formation of CDs through pyrolysis.