Comparison of N-doped carbon dots synthesized from the main components of plants including cellulose, lignin, and xylose: Characterized, fluorescence mechanism, and potential applications

In this study, N-doped carbon dots (N-CDs) synthesized from the main components of plants, including cellulose (N-cCDs), lignin (N-ICDs), and xylose (N-xCDs), were compared. TEM, XRD, FT-IR, and XPS were carried out to characterize their morphology and chemical composition. Results show that the three obtained N-CDs contained N-doped sp(2) and sp(3) hybrid carbon core, which was surrounded by oxygen- and nitrogen-containing functional groups. The three N-CDs exhibited a novel double excitation-one emission phenomenon, and their fluorescence were significantly enhanced by N-doping. Moreover, this study indicated that high lignin-containing biomass is not appropriate for producing CDs by hydrothermal method. Cellulose is conducive to produce CDs, while it needs a relatively high temperature and a long time. Low-molecular carbohydrate-rich biomass and nitrogen-containing biomass is the better carbon source to produce the CDs. Also, this study revealed that N-cCDs and N-xCDs are excellent candidates for fluorescent ink, fabrics identifying, temperature sensing, and Hg2+ sensing. Due to its poor fluorescence property, N-ICDs is not suitable for fluorescent ink and fabrics identification.