GR5 DNAzyme and difunctional carbon dots-encapsulated zeolitic imidazolate framework for ratiometric fluorescence detection of Pb(II) in fish and water.

Accurate and rapid detection of lead ions in food and environment is urgently needed for human health. Herein, we have developed a ratiometric fluorescence system grounded in GR5 DNAzyme and carbon dots-embedded ZIF-8 nanocomposite (CDs@ZIF-8) to achieve the self-calibration detection of lead ions (Pb). GR5 DNAzyme, which acts as a molecular recognition element, is adsorbed onto the surface belonging to CDs@ZIF-8. Pb-induced cleavage of DNAzyme results in the desorption of short FAM-labeled single-stranded DNA, which triggers a detectable change in the FAM fluorescence. Meanwhile, CDs@ZIF-8 provides an unchanging reference signal through the self-luminescence of encapsulated blue-emitting CDs. The ratiometric fluorescence signal blocks the environmental interference. This method achieves a hypersensitized and specific monitoring method of Pb in 60 min through a simple mixing process, with a minimum detectable limit of 0.1 nM. The use of self-calibrating multifunctional nanomaterials is expected to enable the development of more reliable and accurate sensors compared to single-functional nanomaterials, with the resulting sensors having broader application prospects.