Magnetic nanoparticle SERS sensor for rapid and selective detection of ClO^- in drinking water

A selective detection strategy is  proposed for the determination of residual hypochlorite in drinking water. Flower-like Fe₃O₄@SiO₂@Ag magnetic nanoparticles can aggregate on a silver film-coated magnetic substrate surface under a magnetic field, enabling the separation and enrichment of the analyte from the sample. 4-Mercaptophenol is functionalized on magnetic nanoparticles enabling quantitative detection of ClO^- through a "signal off" mechanism. This substrate exhibits high sensitivity, with an analytical enhancement factor calculated using Rhodamine B (RhB) as an example reaching 1.89 × 10⁵, and a detection limit for ClO^- as low as 0.0125 mg/L. The substrate also demonstrates good uniformity, reproducibility, and selectivity. Detection in actual drinking water samples indicates the potential application of this detection strategy in food safety.