Evaluating the SERS Enhancement Efficiency of Silver, Gold, Copper, and Their Bimetallic (Ag-Au, Au-Cu) Nanoparticles

Currently, silver nanoparticles remain one of the most prevalent substrates for surface-enhanced Raman spectroscopy (SERS), owing to their high enhancement efficiency across a broad range of excitation wavelengths. However, their practical application is limited by inherent drawbacks, including poor biocompatibility and a propensity for oxidation. To address these limitations, this study investigates the efficacy and stability of bimetallic alloy nanoparticles as alternative SERS substrates. Spherical silver-gold (Ag-Au) and gold-copper (Au-Cu) alloy nanoparticles were synthesized via laser ablation in aqueous media, a versatile technique chosen for its applicability to various compositions, unlike many conventional methods that are often material-specific. Among the synthesized alloys, the Ag-Au (2:1) composition demonstrated the highest SERS activity, exhibiting an enhancement factor only 1.5 times lower than that of pure silver nanoparticles. Furthermore, the Au-Cu (1:1) sample displayed greater enhancement efficiency at an excitation wavelength of 488 nm compared to monometallic gold or copper nanoparticles, while concurrently demonstrating superior stability. These findings indicate that bimetallic alloy nanoparticles are promising candidates for SERS applications, with their performance potentially surpassing that of their constituent pure metals.