碳点(CD)由于其独特的光学性质和潜在的应用,在许多应用领域受到了相当大的关注;然而,荧光机制是其应用的障碍。在这里,通过调节乙醇和二甲基甲酰胺(DMF)的比例,由单一邻苯二胺(oPD)制备三色发射CD。这些CD的荧光机制被提出为分子态荧光。使用液相色谱-质谱(LC-MS)和1H核磁共振(NMR)光谱鉴定反应中间体。1H-苯并[d]咪唑(BI),2,3-二氨基吩嗪(DAP),和5,14-二氢喹喔啉并[2,3-b]吩嗪(DHQP)被认为是蓝色的荧光团,绿色,和红色发射CD通过比较它们的光学特性。根据LC-MS和1H-NMR分析,具有红色发射的DHQP倾向于由纯乙醇中的DAP和oPD形成。通过添加DMF,BI形成增强并且DHQP形成被抑制。制备的CD显示出具有DAP的绿色发射。当DMF用量>50%时,BI的形成得到了相当大的促进,导致DAP形成被抑制。具有蓝色发射的BI然后变成CD的荧光团。这一结果为我们提供了对基于oPD的CD的荧光机理的更好理解,指导我们设计CD的结构和光学特性。
Carbon dots (CDs) have received considerable attention in many application areas owing to their unique optical properties and potential applications; however, the fluorescent mechanism is an obstacle to their applications. Herein, three-color emissive CDs are prepared from single o-phenylenediamine (oPD) by regulating the ratio of ethanol and dimethylformamide (DMF). Fluorescent mechanism of these CDs is proposed as molecular state fluorescence. Reaction intermediates are identified using liquid chromatrography-mass spectroscopy (LC-MS) and 1H nuclear magnetic resonance (NMR) spectra. 1H-Benzo[d]imidazole (BI), 2,3-diaminophenazine (DAP), and 5,14-dihydroquinoxalino[2,3-b] phenazine (DHQP) are proposed to be the fluorophores of blue, green, and red emissive CDs by comparing their optical properties. As per the LC-MS and 1H-NMR analysis, DHQP with red emission tends to form from DAP and oPD in pure ethanol. By adding DMF, BI formation is enhanced and DHQP formation is suppressed. The prepared CDs exhibit green emission with DAP. When the DMF amount is >50%, BI formation is considerably promoted, resulting in DAP formation being suppressed. BI with blue emission then turns into the
fluorophore of CDs. This result provides us an improved understanding of the fluorescent mechanism of oPD-based CDs, which guides us in designing the structure and optical properties of CDs.