Abstract
Abstract Green synthesis based on plant extracts offers a sustainable route for obtaining silver nanoparticles (AgNPs) under mild conditions and for exploring their multifunctional behavior in chemically relevant agricultural contexts. Here, aqueous extract of Paullinia cupana mediated AgNPs formation, evidenced by the emergence of a surface plasmon resonance band at 418–420 nm and the progressive color change of the reaction medium. The resulting AgNPs were immobilized on carbon by in situ and ex situ routes to generate AgNPs@C materials, which were characterized by UV–Vis spectroscopy, X-ray diffraction, FTIR, thermogravimetric analysis, SEM/EDS, TEM, and BET surface-area measurements. The precursor aqueous AgNP dispersion was additionally characterized by dynamic light scattering and zeta-potential analysis. The aqueous AgNP dispersion showed a mean hydrodynamic diameter of 429.5 ± 14.0 nm, a polydispersity index of 0.229 ± 0.010, and a zeta potential of − 10.93 ± 1.56 mV. Electrochemical assays were conducted using the commercial emulsifiable concentrate Decis 25 EC as the deltamethrin source. Both AgNPs@C materials showed irreversible cathodic processes in the presence of the formulation, with scan-rate dependence consistent with diffusion-influenced electrochemical behavior. In parallel, germination assays with gherkin and coriander seeds revealed contrasting concentration- and species-related responses. The lower AgNP concentration preserved selected germination-related parameters or produced responses comparable to the controls, whereas the higher concentration was inhibitory, especially for root growth. These results support P. cupana-mediated AgNP systems as green multifunctional materials that connect sustainable synthesis, electrochemical behavior in pesticide-containing media, and concentration-related biological effects on seeds.