Luminescent properties of colloidal quantum dots Ag$_2$S passivated by thioglycolic acid molecules in the presence of oxtetracycline

It was found that in the presence of oxytetracycline molecules, the spectral absorption and luminescence profiles of colloidal Ag$_2$S quantum dots passivated with thioglycolic acid (TGA) molecules are transformed. When mixing a colloidal solution of Ag$_2$S/TGA quantum dots with antibiotic molecules, a peak with a maximum at 820 nm appears in the absorption spectrum, and a shift in the luminescence maximum to the short-wave region (from 940 to 860 nm) accompanied by an increase in its intensity is observed in the luminescence spectrum. The observed patterns are due to a change in the state of the Ag$_2$S/TGA quantum dots interface due to binding to the oxytetracycline molecule through the interaction of the tricarbonyl group with dangling bonds on the surface of the quantum dots and passivator molecules, providing the formation of new radiative recombination centers. The obtained results indicate the possibility of practical application of a colloidal solution of Ag$_2$S/TGA quantum dots as a luminescent receptor for the presence of tetracycline antibiotics in solution.