Zr-MOF-based substrate with inherent internal standards facilitates reliable SERS analysis of sulfonamide antibiotics

A multifunctional structure comprising gold nanoparticles immobilized within a zirconium-based metal-organic framework (AuNPs/Zr-MOF) was systematically designed. With the capabilities of analyte enrichment, Raman signal enhancement and internal standard calibration, the as-prepared AuNPs/Zr-MOF substrates demonstrate the outstanding SERS sensing performance toward the representative sulfonamide antibiotics (SAs), sulfadiazine, sulfamerazine, sulfamethazine and sulfaquinoxaline. For the first time, these four SAs are detected by SERS in real honey samples at levels of 2.8 ∼ 5.2 ng·g⁻¹ within 10 min. The extensive π-bond conjugated system of Zr-MOF significantly enhances the concentration of SAs through π-π interactions. The entrapped SAs are adsorbed perpendicularly onto the surface of Au via coordinated interactions between Au and two oxygen atoms, or between Au and the terminal amino group. To achieve reliable quantitative analysis, the inherent vibration of the Zr-MOF structure was used as an internal standard label. Combined with a simple clean-up protocol, the established SERE sensing method is superior to conventional methods in terms of time, while achieving the impressive sensitivity. This study presents a robust SERS-based approach for the rapid detection and monitoring of multiple analytes.