Exclusive core-satellite composite based on sandwich Ag-MOF-Ag nanoshell with abundant hotspots for sensitive monitoring of antibiotic and pesticide residues in milk

Exploring robust, sensitive and reliable surface-enhanced Raman spectroscopy (SERS) substrates largely depends on creating a high density of hot spots. Hererin, we present the fabrication of a unique core-satellite composite, consisting of sandwich Ag/MOF/Ag nanoshells, achieved by constructing two layers of dense Ag satellites with a MOF interlayer on PMAA nanospheres. These innovative sandwich Ag/MOF/Ag nanoshells create two distinct types of plasmonic nanogaps: the interstitial space between the Ag nanoshell layers and the internanogaps between adjacent Ag satellites. This structure significantly increases the number of hot spots compared to traditional core-monolayer metal satellites, leading to enhanced SERS activity. As expected, the composites exhibit an impressive enhancement factor of 3.85 × 10 6 and a low detection limit (LOD) of 10 −9 mol/L for methylene blue. The SERS sensing performance is further validated by successfully quantifying ciprofloxacin (CIP) and paraquat (PQ) in real milk samples with LODs of 3.28 × 10 −7 mol/L for CIP and 1.71 × 10 −8 mol/L for PQ, demonstrating strong potential for ultra-sensitive detection of hazardous pollutants in foods.