Enhanced Raman Detection of Nitrite by Ag/NH ₂ ‐Ni‐MOFs: Synergistic Polarization of Internal and External Electric Fields

Abstract Excessive nitrites present in water pose a severe threat to human health. Given its high solubility, nitrite is hard to eliminate. Thus, it is crucial to assess the nitrite concentration in water bodies to avoid risk in advance. In this study, an enhanced Raman detection method through augmenting the polarization for nitrite in water is reported, which is triggered by the synergistic effect of internal and external electric fields. The nitrite is transformed into azo compounds for Raman detection on the substrate of Ag/NH 2 ‐Ni‐MOFs. By the polarization induced by the internal and external electric fields, the Raman peak intensity of azo compounds increases by 2.20 times. The method is capable of reproducibly and selectively detecting nitrite within the concentration range of 10 −8 –10 −3 mol L −1 , and achieving a limit of detection (LOD) of 3.76 × 10 −9 mol L −1 , which is substantially below the national standard (0.71 × 10 −3 mol L −1 ). In addition, this strategy has found application in evaluating the solutions containing methylene (MB) and U(VI), etc. This work puts forward an effective approach to devising high‐performance and highly selective techniques for assessing solution pollutants, which demonstrates outstanding detection capabilities in practical applications.