Magnetic nanozymes for dual-modal SERS-colorimetric detection of hydrogen peroxide in foods

Excessive hydrogen peroxide (H₂O₂) residues in food endanger human health, through a stepwise synthesis method, multifunctional magnetic core-shell structured Fe₃O₄@SiO₂@Ag-CuO (FSAC) nanoparticles were prepared. This was done to construct a SERS sensor that does not require enzyme participation, for the detection of H₂O₂. Leveraging FSAC's intrinsic peroxidase-mimetic activity, H₂O₂ mediates 3,3',5,5'-tetramethylbenzidine (TMB) oxidation to Raman-active oxTMB, with quantitative detection based on oxTMB's 1604 cm^-1 characteristic peak. Structural characterization verified the well-defined core-shell architecture, and the Ag-CuO heterojunction generated dense SERS "hotspots" to achieve a high enhancement factor (3.77 × 10⁶). The sensor exhibited a wide linear range (0-40 μM, R² = 0.980) and the low detection limit (30 nM), along with excellent homogeneity (RSD ≤ 9.22%), 21-day stability and 7-cycle magnetic recyclability. Practical applicability was validated in milk, yogurt and juices, with recoveries of 89.3-104.6% (RSD ≤ 11.4%), providing a robust strategy for rapid H₂O₂ monitoring in foodstuffs.