Ph-dependent SERS performance of Ag-glutathione substrate for rapid detection of thiram in apples

Modifying nanoparticle assembly can alter the electric field strength within “hot spots,” offering promise for enhancing surface-enhanced Raman scattering (SERS) performance. In this work, by modifying the surface of Ag nanoparticles (AgNPs) with glutathione (GSH), a pH-responsive substrate, Ag-GSH nanoparticles (AGGNPs), was prepared. Under acidic conditions, hydrogen bonds form between protonated GSH molecules, inducing aggregation of AGGNPs and causing a red shift in the absorption peak. The SERS enhancement factor (EF) increased from 5.6 × 10 5 to 1.36 × 10⁶ and exhibited a good linear relationship with pH. In practical apple sample detection, the natural acidic environment of the fruit pulp enabled SERS self-optimization. Without external acid addition, the signal for thiram at 1383 cm −1 was significantly enhanced, achieving a minimum detection concentration of 10 −11 M. This approach effectively provides a novel pathway for developing highly efficient SERS sensing strategies and offers fresh insights for expanding SERS applications in agricultural detection.