A Novel Tetranuclear Copper(I) Iodide Metal-Organic Cluster [Cu4I4(Ligand)(5)] with Highly Selective Luminescence Detection of Antibiotic

Antibiotics in wastewater are very harmful to the environment and human health; their effective detection is important but still challenging. Herein, the first copper(I) iodine-based antibiotic sensor [Cu4I4(EBT)(5)] (denoted as UJN-Cu, EBT = 3-ethyl-1,3-benzothiazole-2-thione) was prepared through a facile solvothermal synthesis method and structurally determined by single crystal X-ray diffraction. The molecular structure of UJN-Cu adopts a chair-like structure of [Cu4I4 (Ligand)(5)], which is distinctly different from the reported cubane- or chair-like [Cu4I4(Ligand)(4)] tetranuclear configurations. Theoretical calculations indicate that the greenish yellow fluorescent emission of UJN-Cu arises from the charge transition between the [Cu4I4] core and EBT ligand. The hydrophobic EBT as a shell of the [Cu4I4] core and the formation of three-dimensional supramolecular structure are responsible for the excellent stability of UJN-Cu in various antibiotic aqueous solutions. UJN-Cu behaves as a sensitive luminescence sensor for detection of tetracycline hydrochloride (TCH) in an aqueous system, and the limit of detection reaches as low as 10 mu M. The obvious quenching effect of a tablet of UJN-Cu toward TCH at low concentrations can be obviously detected by the naked eye. Remarkably, the sensor is highly selective for TCH with quenching efficiency 6 times larger than other antibiotics, and can be reused for at least five cycles with the quenching efficiency nearly constant. This study not only represents the first copper(I) iodine cluster-based sensor for antibiotic detection but also revealed molecular copper(I) iodine materials are of significance in monitoring water quality.