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Colloidal carbon dots (C-dots) have excellent optical properties and they have been widely used for various types of applications. Compared to the C-dots prepared using chemicals, the Biomass-derived C-dots have attracted a great of attention because of their environmental friendliness and biocompatibility. However, currently obtained C-dots using biomass have low quantum yield. In this work, we demonstrated an efficient precursor of Magnolia flower for synthesizing high-quantum yield C-dots via hydrothermal approach. High performance liquid chromatography and Bradford assay were used to analyze the compositions of the Magnolia flower, which determine the quality of the C-dots. The typical emission bands of the as-prepared C-dots cover from 400 to 550 nm at different excitation wavelengths. The C-dots synthesized using violet Magnolia flower have the QY as high as 11.9%, which is higher than that of 10.4% (white Magnolia flower), because the violet color gives the higher content of the N. The as-obtained C-dots have excitation-dependent color and high quantum yield, showing a great potential for the use of the anti-counterfeiting system. • The components of carbon and nitrogen in the two colors of Magnolia flowers were briefly analyzed. • The synthesized self-doped carbon dots of violet one had a higher quantum yield and the luminescence could reach in the green region. • The carbon dots had good efficacy for anti-counterfeiting. [ABSTRACT FROM AUTHOR]

The traditional textile degumming process produces abundant wastewater, which contains a lot of monosaccharides and oligosaccharides. It is of great economic and environmental significance to utilize these carbohydrates in high value. In this study, high performance liquid chromatography (HPLC) was used to analyze the carbohydrate components in kenaf degumming wastewater, and then the production of C-dots using the wastewater was explored. The results showed that the types and content in the degumming wastewater were monosaccharides (glucose, xylose and arabinose) and oligosaccharides (dextran, xylan and araban). The carbohydrate (mainly glucan and xylan) content in wastewater accounted for 91.16 % of the total carbohydrates weight loss in kenaf degumming process. By using hydrolysis and hydrothermal reaction on kenaf degumming wastewater, blue-green carbon dots (C-dots) with good performance were prepared and successfully applied to anti-counterfeiting printing. In particular, the as-prepared C-dots prepared from kenaf degumming wastewater with urea added (WUC-dots) showed an excitation-dependent photoluminescence (PL) spectrum and quantum yield (QY) of 2.4 % in aqueous solution. The fluorescent code exhibited a clear outline, excitation-tunable color and good stability, showing a great potential for anti-counterfeiting system. [ABSTRACT FROM AUTHOR]