A highly sensitive dual-signal detection of oxytetracycline via catalyzed hairpin assembly-mediated G-quadruplex formation coupled with CsPbBr3@SiO2 nanocomposites.

As a broad-spectrum antibiotic, excessive use of oxytetracycline (OTC) could raise significant concerns to both human health and ecological environment. Cesium lead bromide perovskite nanocrystals (CsPbBr3 NCs), known for their luminescent properties, are an effective candidate for chemical sensing. Nevertheless, their limited stability restricts their application in polar solvents. Herein, a series of CsPbX3 (X = Cl, Br)/silica nanocomposites with tunable-wavelengths were successfully prepared through in-situ crystallization of CsPbX3 nanocrystals within the mesoporous framework of silica nanospheres, and the dense silica matrix provides high stability to the CsPbX3 NCs. Subsequently, a sensitive, label-free dual-signal detection strategy for oxytetracycline was constructed by integrating high-luminescence CsPbBr3@SiO2, magnetic separation and catalyzed hairpin assembly (CHA). The detection of OTC was accomplished by measuring the absorption and fluorescence signals with limits of detection 0.017 and 0.012 nM, respectively. Additionally, the sensing strategy was employed to detect OTC in aquatic products with satisfactory results.