RT Journal Article A1 Zheng Yang,Tiantian Xu,Shaobing Zhang,Hui Li,Yali Ji,Xiaodan Jia,Jianli Li; AD 合成与天然功能分子教育部重点实验室, 中国 ; 化学化工学院, 中国 ; 国土资源部煤炭资源勘查与综合利用重点实验室, 中国 ; 化学化工学院, 中国 ; 化学化工学院, 中国 ; 合成与天然功能分子教育部重点实验室, 中国 ; 化学化工学院, 中国 ; 合成与天然功能分子教育部重点实验室, 中国 ; 化学化工学院, 中国 ; 国土资源部煤炭资源勘查与综合利用重点实验室, 中国 ; 合成与天然功能分子教育部重点实验室, 中国 T1 Multifunctional N,S-doped and methionine functionalized carbon dots for on−off−on Fe3+ and ascorbic acid sensing, cell imaging, and fluorescent ink applying YR 2023 IS 4 vo 16 OP 5401-OP 5411 K1 carbon dots;ascorbic acid;fluorescent sensors;Fe3+;fluorescent ink;message encryption AB Fluorescent carbon dots (CDs) have been identified as potential nanosensors and attracted tremendous research interests in wide areas including anti-counterfeiting, environmental and biological sensing and imaging in considering of the attractive optical properties. In this work, we present a CDs based fluorescent sensor from polyvinylpyrrolidone, citric acid, and methionine as precursors by hydrothermal approach. The selective quantifying of Fe3+ and ascorbic acid (AA) are based on the fluorescent on–off–on process, in which the fluorescent quenching is induced by the coordination of the Fe3+ on the surface of the CDs, while the fluorescence recovery is mainly attributed to redox reaction between Fe3+ and AA, breaking the coordination and bringing the fluorescence back. Inspired by the good water solubility and biocompatibility, significant photostability, superior photobleaching resistance as well as high selectivity, sensitivity, and interference immunity, which are constructed mainly from the N,S-doping and methionine surface functionalization, the CDs have not only been employed as fluorescence ink in multiple anti-counterfeiting printing and confidential document writing or transmitting, but also been developed as promising fluorescence sensors in solution and solid by CDs doped test strips and hydrogels for effectively monitoring and removing of Fe3+ and AA in environmental aqueous solution. The CDs have been also implemented as effective diagnostic candidates for imaging and tracking of Fe3+ and AA in living cells, accelerating the understanding of their function and importance in related biological processes for the prevention and treatment specific diseases. SN 1998-0124 LA EN