D‑Penicillamine‑Stabilized Gold Nanoclusters as a Selective Fluorescent Sensor for Tetracyclines.

The development of simple, rapid, and cost‑effective sensing methods for monitoring antibiotic residues in water is crucial due to the widespread use of antibiotics in livestock farming and the consequent risk of environmental contamination. In this study, we present a facile synthesis of gold nanoclusters (AuNCs) stabilized with D‑penicillamine (AuNC@D‑Pen), a thiolated ligand that provides excellent colloidal stability and supports strong photoluminescent properties. The synthetic protocol affords highly uniform nanoclusters whose fluorescence emission, centered at approximately 650 nm, is both intense and stable under typical environmental conditions.The fluorescence of AuNC@D‑Pen undergoes progressive quenching in the presence of tetracycline, enabling a sensitive and reliable optical detection strategy. The detection limit (LOD) was determined to be 2.0 µM (0.9 ppm), with a linear response range extending from 0.5 to 220 µM, which positions this system as a promising tool for practical analytical applications, including routine water‑quality monitoring. In addition, the sensor exhibits excellent selectivity for tetracyclines over common potentially interfering species such as anions, metal ions, and amino acids, highlighting the robustness of the sensing mechanism. Overall, the AuNC‑based probe represents an efficient platform for the rapid, selective, and affordable detection of antibiotic contaminants in aqueous environments.