Template-guided silver nanoassemblies for reliable surface-enhanced Raman scattering (SERS) detection of environmental toxicants

• Reproducible monitoring platform for environmental toxicant detection. • Silver-ammonia complex enables uniform silver nanoassemblies growth. • High analytical reproducibility achieved with low relative standard deviation. Plasmonic nanoparticles (NPs), owing to their highly amplified electromagnetic fields, have emerged as powerful platforms for diverse surface-enhanced Raman scattering (SERS) applications. However, achieving reliable and quantitative SERS detection remains challenging due to poor reproducibility and batch-to-batch variability of plasmonic substrates. Herein, we report a robust and reproducible silver growth strategy using an Ag-ammonia complex ([Ag(NH 3 ) 2 ] + ) to fabricate uniform silver nanoassemblies (SNAs). The slow and controlled complex-mediated growth enables homogeneous Ag NP deposition (9.5–24.9 nm in diameter), precise nanogap engineering, and highly reproducible SERS responses. Furthermore, the SNAs enabled label-free detection of representative environmental toxicants, including thiram, crystal violet, and malachite green, with detection limits of 5.31 × 10 −6 M, 2.14 × 10 −6 M, and 2.74 × 10 −6 M, respectively. Notably, crystal violet detection exhibited highly uniform and reproducible SERS responses, achieving spot-to-spot and batch-to-batch relative standard deviations of 11.30 % and 5.02 %, respectively. In addition, further modulation of Ag NP diameter enabled markedly enhanced sensitivity, achieving a detection limit as low as 7.3 × 10 −9 M. This engineered SERS platform enhances analytical reliability and shows strong potential for practical environmental monitoring.