Chiral CDs-based fluorescence sensor for rapid and specific sensing K₄[Fe(CN)₆] in table salt and salted food

Potassium ferricyanide (K₄[Fe(CN)₆]) as anti-caking agent plays an important role in avoiding the formation of chunks for fine particulate solids. However, inappropriate and excessive addition and decomposition of K₄[Fe(CN)₆] are detrimental to physical health. At present, appropriate strategies for convenient and accurate analysis of K₄[Fe(CN)₆] in table salt and pickled food are desirable. Herein, an efficient "ON-OFF-ON" fluorescent sensor based on chiral carbon dots was prepared by a simple one-step hydrothermal method. The chiral CDs with L-Tryptophan and D-Tryptophan as chiral source were named as L-CDs and D-CDs. Notably, the bright fluorescence of L/D-CDs could be effectively quenched by K₄[Fe(CN)₆] through dynamic quenching mechanism. This fluorescent sensor achieved excellent sensitive and selective detection of K₄[Fe(CN)₆] with a limit of detection (LOD) of 25.0 ng·mL^-1. In addition, the L/D-CDs could be applied not only for selective fluorescent recognition of K₄[Fe(CN)₆] by the methods of portable filter paper and hydrogels, but also as fluorescent dye for repeated message encryption and decryption.