Magnetic Field Induced Dielectric Polarization to Enhance Raman Detection of Nitrite by NiFe₂O₄@Ag

Abstract Rapid and accurate detection of nitrite in the aqueous environment is extremely important for ecological safety and human health. In this paper, the Raman detection of nitrite by a NiFe₂O₄@Ag sensor in water is enhanced by an extra magnetic field collaborated with surface plasma. Most importantly, it is demonstrated that the magnetic field enhances the Raman peak intensity through not only the effect of magnetic aggregation but also the magnetic field‐induced dielectric polarization effect. In this way, the NO₂⁻ can be detected in a wide linear range from 10⁻⁸ to 10⁻³ mol L⁻¹, and the limit of detection (LOD) can reach as low as 1.25 × 10⁻⁹ mol L⁻¹, which is 5.69 times lower than that in the absence of an external magnetic field. Similarly, the sensitivity under the magnetic field is 2.65 times that without the magnetic field. In addition, the sensor also shows superior detection ability to NO₂⁻ in real samples. Given the excellent capability of the magnetic field‐enhanced Raman spectra, the reported strategy offers new thoughts on how to enhance the detection ability by an external magnetic field and show the great application potential in real water bodies.