Biomass materials have abundant natural resources, renewability and good biochemical compatibility, so biomass-based fluorescent materials prepared from biomass materials have gradually become a research hotspot. In particular, the low cost...

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Fluorescent carbon quantum dots are a new type of nano‐fluorescent probe material, which overcomes some deficiencies of organic fluorescent materials and semiconductor quantum dots. In addition, they also have excellent optical properties, biocompatibility, and good application potential in environmental detection and other fields. To realize the special functions of carbon quantum dots, various functionalized composite carbon quantum dots have also been gradually developed. Lignin is a kind of natural polymer material rich in aromatic ring structure, which has abundant π electrons and a large number of easily functionalized active groups. Therefore, lignin is gradually used as a fluorescent probe material. In this article, sulfadiazine, p‐aminobenzenesulfonic acid, ammonium sulfamate as the amination reagents were used to modify lignin, and then citric acid was used as raw material to prepare carbon quantum dots (CQDs), and finally sulfadiazine lignin composite carbon quantum dots (PSA‐L‐CQDs), sulfamic acid lignin composite carbon quantum dots (BSA‐L‐CQDs), and sulfamate amine lignin composite carbon quantum dots (ASA‐L‐CQD) were prepared. Their structure and fluorescence characteristics were analyzed. The selectivity and sensitivity of PSA‐L‐CQDs to metal ions were tested by fluorescence spectroscopy. The experimental results show that PSA‐L‐CQDs have good selectivity and high sensitivity to Fe3+. The detection limit of Fe3+ was 29.5634 nmol/L. The composite carbon quantum dots have the advantages of low cost, simple manufacture, high selectivity, and high sensitivity.

As a typical heavy metal pollutant, chromium has caused great harm to the natural environment. Chromium mainly exists in trivalent and hexavalent compounds in nature, among which Cr(VI) is more toxic. As an outstanding fluorescent material, carbon quantum dots (CQDs) have the advantages of easy preparation, low cost, good optical stability, good biocompatibility, and low toxicity. The composite carbon quantum dots formed by compounding carbon quantum dots with other functional molecules can not only effectively reduce the preparation cost but also have stable fluorescence emission and metal ion recognition functions. In this paper, l‐arginine modified lignin composite carbon quantum dots (Arg‐l‐CQDs) are synthesized, their fluorescence responsiveness to a series of metal ions is analyzed, and their feasibility for Cr(VI) detection is analyzed. The results show that the Arg‐l‐CQDs can be used as a fluorescent probe to achieve specific fluorescence response, high selectivity, and anti‐interference to Cr(VI). There is a certain linear relationship between the concentration and the fluorescence intensity of the fluorescent probe. The linear equation is F/F0 = 0.5568‐0.0012C[Cr(VI)], the linear correlation coefficient is 0.9945, and the detection limit of the fluorescent probe is 0.8625 µmol L−1.