Effect of lignin molecular weight on the formation and properties of carbon quantum dots

Green Chemistry 2024

The effect of lignin molecular weight on the formation and properties of carbon quantum dots.

Xiaoli Liu,   Siyu Zhao, Xinrui Chen,   Xing Han,   Junhua Zhang,   Min Wu,   Xueping Song *   and   Zhanying Zhang.   

摘要：It is generally believed that the formation of lignin-based carbon quantum dots (L-CQDs) includes lignin depolymerization and repolymerization. However, the detailed mechanism has not been well understood. In this study, the effect of lignin molecular weight on the properties of L-CQDs is studied to elucidate the formation mechanism of L-CQDs. Firstly, alkaline lignin is sequentially fractionated into five lignin samples with a molecular weight range of 7100–2000 using a continuous organic solvent precipitation method. Then, the five lignin fractions are used to prepare five L-CQDs numbered from 1 to 5, corresponding to the lignin fractions from high to low, respectively. L-CQDs-3 that was prepared from the lignin fraction with an intermediate molecular weight of 5042 g mol−1 has a 1.86-fold increase in fluorescence intensity compared to the L-CQDs-0 prepared from pristine alkaline lignin. It is found that this lignin fraction with a molecular weight of 5042 g mol−1 can depolymerize into a large number of vanillin and benzaldehyde (2,4-dihydroxy-6-methyl) units. These low molecular weight units can easily form highly conjugated carbon core structures, thus improving the fluorescence performance of L-CQDs-3. In addition, the present study confirms the excellent imaging ability of L-CQDs-3 in the L02, HepG2 and Escherichia coli cells. This study not only supplements the existing L-CQD formation mechanism, but also provides a simple method for the preparation of L-CQDs with high fluorescence performance.

DOI：https://doi.org/10.1039/D3GC04694J