A novel functionalized nitrogen- and sulfur-co-doped nanocarbon dots for the fluorescence detection and photocatalysis degradation of tetracycline antibiotics.

Monitoring and eliminating pollutants are critical for environmental remediation. In this study, nitrogen- and sulfur-co-doped nanocarbon dots (NS-NCDs) were synthesized via a hydrothermal method using ascorbic acid and thiosemicarbazide as precursors. The introduction of nitrogen and sulfur atoms through doping altered the electron configuration and nanostructure of the carbon dots, resulting in strong blue fluorescence (quantum yield: 11.32 %). These NS-NCDs functioned as dual-functional agents for both detecting and degrading tetracycline antibiotics (TCs). Under UV light, the fluorescence color of the NS-NCDs transitioned from blue to colorless with increasing TCs concentration. Fluorescence quenching of NS-NCDs by TCs was mediated synergistically by the inner filter effect (IFE) and electron transfer, with IFE contributing 76 %, 75 %, and 71 % of the total quenching efficiency for tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC), respectively. This dual-mechanism enabled ultrasensitive detection of TCs, achieving limits of detection (LODs) as low as 0.21 μM (TC), 0.28 μM (OTC), and 0.16 μM (CTC), which are well below regulatory thresholds for environmental antibiotic residues. The NS-NCDs probe also exhibited high selectivity and anti-interference performance in complex matrices. Furthermore, NS-NCDs serve as a catalyst to rapidly activate peroxymonosulfate (PMS) under sunlight for the degradation of TCs, achieving degradation rates exceeding 90 % within 60 min. TCs degradation is driven by the oxidation of free radicals and electron transfer from TCs to PMS, facilitated by NS-NCDs. This study demonstrates the bifunctional role of NS-NCDs in real-time monitoring and photocatalytic degradation of TCs, providing an innovative strategy to combat antibiotic contamination.