Laser‐Based Synthesis of Pt–Au Bimetallic Alloy/Core‐Shell Nanoparticles and Their SERS Sensitivity Analysis

In this study, Pt–Au bimetallic alloy nanoparticles (NPs) are synthesized through laser exposure of a mixture of Pt and Au NPs. Monometallic Pt and Au colloidal NPs are initially synthesized using 1064 nm nanosecond laser ablation of Pt/Au in deionized water. Then, colloidal solutions of Pt and Au NPs, combined in equal volumes, are illuminated with a 532 nm nanosecond laser. The Pt–Au alloy NP formation dynamics are investigated by tuning the incident laser fluence. Our results suggest that the alloy process is highly fluence‐ dependent, with no alloy observed for fluence in the 300–400 J cm −2 range. The optimum fluence and exposure duration for synthesizing bimetallic alloy NP are 100–200 J cm −2 and 20 min, respectively. Furthermore, Pt–Au bimetallic NPs are utilized as surface‐enhanced Raman scattering (SERS) platforms in detecting the probe molecule Rhodamine 6G (10 −7 M concentration). Pt–Au NP colloidal mixture irradiated at a fluence of 100 mJ cm −2 demonstrated significantly amplified SERS signals for Rhodamine 6G, and this enhancement is ascribed to the core‐shell character of Pt–Au NPs along with the plasmonic effect of Pt and Au NPs. Rhodamine 6G also exhibited strong SERS signals on interacting with Pt–Au NPs irradiated at a fluence of 200 mJ cm −2 because of the Pt–Au alloy character.