SERS Nanosensor for the Detection of Ag(I) Ions under High-Chloride Environment: Breaking Chloride Masking Effect

The use of chemical sensors for the detection of Ag(I) ions under a chloride (Cl^–) environment is extremely difficult due to the chloride masking effect. Herein, a surface-enhanced Raman scattering (SERS) nanosensor using p-aminothiophenol (PATP) as probe molecules has been developed for the detection of Ag(I) ions under high concentrations of Cl^– ions. The peak intensity ratio I₄₃₈/I₃₉₀ was used as the basis for the quantitative analysis, showing a high selectivity for Ag(I) ions. Corroborating with DFT simulations, the origin of the sensing mechanism is the existence of coordination between Ag(I) ions and PATP. To enhance the sensitivity of the SERS nanosensors, we propose a sequence-dependent probe modification method by decreasing the Raman signal from the isolated probe molecules in the nanogaps of nanoparticles. More significantly, this breakthrough SERS sensor addresses a long-standing issue of conventional Ag(I) sensors for the detection of total Ag(I) ions under a high-chloride environment. Even at ultrahigh concentrations (up to 500 mM) of Cl^– ions, this method still breaks the chloride masking effect and exhibits outstanding sensitivity with a limit of detection (LOD) of 0.07 μM for Ag(I) ions. In addition, the successful detection of Ag(I) ions in the real samples with Cl^– ions indicates that our method has promise for practical applications. These findings have significant implications for future research on heavy-metal analysis in complex samples.