Synthesis of stable copper nanoclusters with different emission wavelengths for oxytetracycline determination

Red-emitting copper nanoclusters (Cu NC-1) and orange-emitting copper nanoclusters (Cu NC-2) were prepared by using polydentate ligands bearing functional groups with different electronic effects. The decomposition temperatures of Cu NC-1 and Cu NC-2 are 573 K and 553 K. Their photoluminescence quantum yields are 15.5% and 52.7%, respectively. In the temperature range 398-498 K, the photoluminescence intensity of Cu NC-1 shows a linear relationship with temperature. A ratiometric fluorescence probe based on Cu NC-1 for determination of oxytetracycline (OTC) was constructed by introducing magnesium ions. Spectroscopic test results show that the inner filter effect leads to the emission quenching of Cu NC-1. The detection limit is 6.0 nM, and the linear range is 0-5 µM. The detection unit of this probe can also use a smartphone, with a detection limit of 0.44 µM. The recoveries for the determination of OTC in river water, tap water and milk are in the range 97.7%-103.6%.