Dual-response ratiometric fluorescence based ligand-functionalized CsPbBr3 perovskite quantum dots for sensitive detection of trace water in edible oils

The sensitive and accurate detection of trace water in edible oils is of significance for the protection of their quality and safety. Herein, a kind of novel dual-emission CsPbBr3 perovskite quantum dots modified with a functional ligand dimethyl aminoterephthalate (CsPbBr3 @DMT-NH2 QDs) was synthesized at low temperature. The QDs display highly-sensitive fluorescence turn-on/off dual response and distinct fluorescence color change from green to blue in the presence of water. Thus, both the ratiometric fluorescence sensing and the visual ratiometric chromaticity detection method were established for water assay with the ultralow limit of detection of 0.006% (v/v) and 0.01% (v/v), respectively, and they can realize the accurate detection (recovery of 93.0%–108.0%, relative error ≤ 5.33%) of trace water in edible oils. Furthermore, it is found that the high polarity levels of protic solvents disintegrate the QDs, and the relatively-low polarity levels are conducive to the aggregation of the QDs, which ultimately lead to green fluorescence quenching. Meanwhile, the deprotonation and polarity of water promote the excited-state intramolecular proton transfer and intramolecular charge transfer of DMT-NH2, so enhancing its blue fluorescence. To our knowledge, this is the first report on dual-response ratiometric fluorescence perovskite QDs for ultrasensitive water detection in edible oils.