Carbon dots with high quantum yields used for Fe3+ detection, information encryption and anti-counterfeiting

Carbon dots (CDs) are a new type of nanomaterial, and their excellent properties such as superior optical properties, good water solubility, and easy-to-modify surface make them promising in various practical applications. Carbon dots with multiple functions are "interdisciplinary talents" among the candidates and are more favorable. However, low quantum yields limit the widespread use of carbon dots. Therefore, the development of multi-functional carbon dots with high quantum yields is of great significance. In this work, nitrogen doped blue fluorescent CDs (B-CDs) were prepared using a microwave assisted hydrothermal method with citric acid (CA) and o-phenylenediamine (OPD) as raw materials. The obtained B-CDs emit strong blue fluorescence in aqueous solution, and the relative quantum yield is as high as 87.07%. A highly sensitive fluorescent probe was developed for detecting Fe3+. The concentration range for Fe3+ detection was found to be linear in the range of 0.8 to 80 mu M, with a limit of detection of 0.095 mu M. In addition, the fluorescence of B-CDs can be quenched by Fe(3+ )and restored by l-cysteine (l-Cys), resulting in an 'on-off-on' phenomenon, which makes them potential candidates for application in information encryption and anti-counterfeiting, thereby expanding their applications.