Practical and robust SERS platform based on ag/COF composites for on-site quantification of antibiotic contaminants...

The widespread misuse of antibiotics has raised serious concerns regarding food safety and environmental health, necessitating rapid and ultrasensitive detection methods. Herein, we report a covalent organic framework composite decorated with optimally loaded silver nanoparticles (30Ag-Func-COF) as a high-performance SERS substrate for multiplexed detection of antibiotic residues. The 30Ag-Func-COF substrate exhibited ultrahigh sensitivity, achieving detection limits as low as 10^-12 M for MB dye molecules, high reproducibility (RSD < 5%), and remarkable long-term stability (> 90% after four months). Its general applicability was confirmed with standard Raman probes (methylene blue and 4-mercaptobenzoic acid) and further extended to structurally distinct antibiotics, chloramphenicol and spiramycin, with excellent linearity (R² ≥ 0.98). In situ detection in complex matrices, including milk, tap water, and fruit juices, was successfully demonstrated with minimal pretreatment, yielding detection limits comparable to standard solutions. Mechanistic investigations combining density functional theory and electromagnetic field simulations revealed a synergistic enhancement mechanism, involving strong analyte-substrate charge transfer and localized plasmonic "hot spots". Collectively, this work establishes 30Ag-Func-COF as a robust and practical SERS platform for rapid, multiplexed, and on-site monitoring of antibiotic contamination, with significant implications for food safety, environmental surveillance, and beyond.