Controlled synthesis of Ag-Au alloy nanoparticles for optimizing surface enhanced Raman scattering-based detection of antibiotic and pesticide residues

Developing effective analytical techniques for detecting amoxicillin and fenobucarb residues, primary components of antibiotics and pesticides with sustantial health and environmental impacts, remains challenging. Surface-Enhanced Raman Scattering (SERS) is a rapid, simple, and highly sensitive analytical method with the potential integration into compact, handheld devices for real-time, on-site monitoring. In this work, Ag-Au alloy nanoparticles for SERS-based sensor materials with uniform structures, tunable composition, and adjustable plasmon resonance bands are proposed. The findings show that a silver fraction of 0.8 is optimal for detecting amoxicillin and fenobucarb by SERS, attributable to the synergistic effects of enhanced Raman scattering capabilities of Ag and Au compared to their single-element counterparts. Density Functional Theory (DFT) calculations indicated that electron transfer occurs from the ligands to the clusters during adsorption, which is related to the SERS chemical enhancement mechanism. SERS spectra analysis and Mulliken charge calculations for metallic atoms illustrate the highest electron transfer from ligands to the Ag4Au2 bimetallic cluster, underscoring the superior enhancement capability of the alloyed surface compared to pure Ag6 and Au6 clusters. Our work offers an effective route to find suitable SERS substrate for each analyte.