β-CD-Ag nanoparticles combined with ordered Au nanoshells array as a dual-substrate SERS platform for antibiotic detection

Integrating β-CD-AgNPs and AuNSs arrays enables rapid, quantitative SERS sensing of antibiotic residues. • The system detects AMP, CIP, ENR, NFX individually and in mixtures with high sensitivity. • The combined substrate enabled accurate, applicable antibiotic detection in real waters. β-Cyclodextrin-functionalized Ag nanoparticles (β-CD-AgNPs) were synthesized via a one-step method and integrated with ordered Au nanoshells (AuNSs) arrays to construct a highly sensitive surface-enhanced Raman scattering (SERS) sensor for antibiotic detection. The specific dimensions of the β-CD-AgNPs enable selective binding, drawing antibiotic molecules into close proximity with the AgNPs surface. This proximity generates plasmonic hot spots, significantly amplifying the Raman signals. In this design, the β-CD-AgNPs serve a dual role as both the primary SERS substrate and an internal standard. A strong linear relationship was established between the concentration of antibiotics and the intensity ratio of the characteristic antibiotic peak to the β-CD-AgNPs peak. Based on this principle, we achieved sensitive detection of both individual antibiotics and their mixtures, and validated the method through spike-and-recovery experiments in environmental water samples. The calibration plots were established by linearly fitting the intensity ratio (antibiotic characteristic peak/internal standard peak) against the concentration of Ampicillin (AMP), Ciprofloxacin (CIP), Enrofloxacin (ENR), and Norfloxacin (NFX) solutions, all exhibiting excellent linearity (R 2  > 0.99), as well as for binary mixtures of CIP and AMP, with R 2 values of 0.9942 and 0.9953, respectively. The limits of detection (LODs) for these antibiotics ranged from 0.0827 to 0.3365 μmol·L −1 , and the limits of quantification (LOQs) ranged from 0.27 to 1.11 μmol·L −1 . The linear working ranges were 0.61–5.00, 0.55–12.00, 0.48–12.00, and 1.11–12.00 μmol·L −1 for AMP, CIP, ENR, and NFX, respectively. In environmental water samples, apparent recovery rates of individual antibiotics ranged from 98.84% (±0.03%) to 100.02% (±0.01%), with relative standard deviations (RSDs) between 1.32% and 4.92%. For CIP and AMP mixtures in similar samples, recoveries ranged from 98.53% (±0.01%) to 111.29% (±0.04%), with RSDs between 1.15% and 5.71%. These results demonstrate that the proposed SERS sensor enables efficient and accurate antibiotic detection, offering a viable approach for the rapid and highly sensitive monitoring of antibiotic contaminants in the environment. Download: Download high-res image (188KB) Download: Download full-size image