Interfacial Chemical Bonding-Driven Charge Transfer from Silver Nanoparticles to Doped Graphene for Electrochemical Sensing of Metribuzin

Abstract Understanding charge transfer at the metal−support interface is crucial for optimizing the electrochemical activity of metal sites. Herein, a series of silver nanoparticles (Ag NP)/heteroatom-doped graphene composites (Ag/G-X, where X = N, P, or S) was designed and prepared. Ag/G-S with an average Ag NP size of 4.5 ± 0.7 nm enables rapid electron transfer required for two-electron metribuzin (MB) electroreduction. The Ag/G-S modified glassy carbon electrode (GCE) delivers better MB sensing performance than Ag/G-N/GCE and Ag/G-P/GCE, achieving a limit of detection (LOD) of 0.53 ng mL−1 and a limit of quantification (LOQ) of 1.77 ng mL−1, with a sensitivity of 44.612 μA mL μg−1 cm−2. The Ag/G-S/GCE displays a linear range of 0.001−16 μg mL−1 (R2 = 0.99), along with stability over 2000 cyclic voltammetry cycles, reproducibility beyond 30 days, anti-interference capability against common inorganic ions and a recovery rate of 94.1% to 101.84% in real samples. Theoretical analysis reveals that Ag/G-X features an interfacial chemical bonding consisting of σ-type donation and d-π* back-donation, which governs charge transfer from Ag to the G-X substrate. Furthermore, the S-guided interfacial orbital interaction is more beneficial than that guided by N and P in regulating the d-band center of Ag NPs, thereby endowing the exposed Ag sites with optimized adsorption energetics for key intermediates in the MB reduction. This work demonstrates the role of interfacial chemical bonding-driven charge transfer in Ag/G-X for the two-electron electrochemical reduction of MB on Ag NP surfaces, and offers a strategy for developing Ag-based sensing nanomaterials.