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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 [pi] 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 (PSAL-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 [Fe.sup.3+]. The detection limit of [Fe.sup.3+] was 29.5634 nmol/L. The composite carbon quantum dots have the advantages of low cost, simple manufacture, high selectivity, and high sensitivity. KEYWORDS composite carbon quantum dots, environmental detection, lignin, metal ions, sulfamidated lignin, 1 | INTRODUCTION With the continuous improvement of living standards, people begin to pay more attention to their health problems. Due to the heavy metals play a great role in [...]

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. [ABSTRACT FROM AUTHOR]

New P,N sp3 bidentate ligands containing two chiral carbon centers were developed and applied to palladium-catalyzed asymmetric allylic substitution reactions. Good generalities with various nucleophiles, including carbon, nitrogen and oxygen containing nucleophiles, were achieved with up to 96% ee and 98% yield. This reaction provides an efficient method for the asymmetric formation of C-C, C-N and C-O bonds.