Rational design for enhancing sensitivity and robustness of a probe via encapsulation of carbon dots into a zeolitic imidazolate framework-8 for quantification of tetracycline in milk with greenness evaluation

Tetracycline (TC) is a vital class of broad-spectrum antibiotics widely employed. However, its extensive use raises associated concerns. Due to its persistent nature, there is a risk of trace amounts of TC contaminating food. The complex composition of food samples has sparked considerable interest in developing selective and sensitive TC sensors. Here, a novel sensing material, gCDs@ZIF-8, where ZIF-8 is a metal–organic framework composed of Zn²⁺ and 2-methylimidazole, was developed by incorporating fluorescent green carbon dots (gCDs) into the ZIF-8 for TC detection. Consequently, the synthesized gCDs exhibited green emission and a specific response to tetracycline. The incorporation of gCDs into ZIF-8 enhances sensitivity, making it a valuable probe for the quantification of TC. The detection limit for gCDs alone was 0.42 µM, and when encapsulated in ZIF-8, the sensitivity increased, resulting in a limit of detection of 157 nM. Quantifying tetracycline in milk samples demonstrated spike recoveries ranging from 95 to 105 percent. The assay displayed excellent precision, with a relative standard deviation (RSD, n = 3) of less than 2% at each concentration point. The robustness and ruggedness of the assay were evident through the probe's stable shelf life, water stability, and a broad working pH range. Validation tests confirmed the gCDs@MOF-based sensing system's capability to detect tetracycline in various sample matrices. The method's environmental friendliness was assessed using three metric tools (AGREE, AGREEprep, and the Complex GAPI), all confirming its superior eco-friendliness.