Unraveling the structural evolution of silver plasmonic hotspots for the detection of oxidative ONOO radicals via SERS probe decay.

Peroxynitrite (ONOO) plays a pivotal role in environmental pollution and ecosystem health, necessitating its detection for assessing ecological impacts and risks. Surface-enhanced Raman scattering (SERS) offers high sensitivity but is often limited by narrow Raman cross sections of analytes. Specialized molecules can aid SERS detection, but are complex to design and may cause nonspecific reactions in biological systems. Therefore, developing new SERS strategies is crucial for simpler, more accurate ONOO detection. Herein, the shape instability of Ag nanomaterials in the hotspots, due to oxidation and dissolution of Ag atoms at the edges and corners, is investigated, and the detection of ONOO is performed by SERS probes. ONOO reacts first with the (111) facet, especially at the edges and corners. Consequently, the SERS signal of the adsorbed probe, Rhodamine 6G in hotspots can be used to monitor edge and corner dissolution that positively related to the ONOO concentration. As a result, ONOO concentration from 0.1 to 25 μM was detected, achieving a coefficient of determination of R = 0.9896. The method exhibits good reproducibility (RSD < 3.25%) and stability (> 7 days), and quantitative detection of ONOO was achieved in bovine serum samples. Ag nanocubes exhibited an eightfold stronger response and higher precision compared to Ag nanoparticles in ONOO detection. This simple detection technique offers a promising method for the accurate, quantitative detection of ONOO in wide range of biological systems.