Luminescent sensor based on colloidal Ag₂S quantum dots for oxytetracycline detection in milk

The paper presents the study results of luminescent sensor, based on colloidal Ag₂S quantum dots, passivated with L-cysteine molecules (Ag₂S/L-Cys QDs) for oxytetracycline (OTC) detection in raw milk. Its work is based on QDs luminescence quenching in the spectral region, which is free from the intrinsic luminescence of the raw milk and OTC (725 nm). A working sensor mechanism was proposed. It is based on the formation of a non-luminescent complex with charge transfer between OTC and Ag₂S/L-Cys QDs due to binding the antibiotic with passivator. The sensor parameters were established. The limit of detection (LOD) is 0.53 μM in milk, limit of quantitative detection (LOQ) is 1.16 μM, linear range is 0-20 μM. These parameters are comparable with known luminescent sensor analogs for raw milk.