Fabrication of a Bimetallic Au–Ag Nanoparticle-Based Photonic Chip via Excimer Laser Irradiation for Water Pollutant Detection and Enhanced Raman Sensing

This paper presents the fabrication of photonic chips incorporating gold-silver (Au-Ag) bimetallic nanoparticles via a laser-induced method. Thin films of Au-Ag were deposited on polycarbonate substrates and subsequently irradiated with an ArF excimer laser. During laser exposure, an external electric field of 10 ⁵ V/m was applied to study its influence on nanostructure formation. The morphological development and properties of the resulting nanostructures were systematically investigated under both the presence and absence of the electric field. The results show that the diameters of the fabricated nanostructures in both conditions predominantly ranged from 40 to 100 nm. Notably, the application of the external electric field promoted the formation of larger linear clusters compared to samples formed without the electric field. Raman spectroscopy of a low concentration (10⁻⁴ M) Rhodamine B solution in the presence of bimetallic nanoparticles fabricated without the electric field demonstrated excellent Surface-Enhanced Raman Spectrum and SERS activity. Furthermore, optical sensing tests for water pollutant detection confirmed the suitability of both samples, with sensitivities of 933.5 nm/RIU and 663.1 nm/RIU for nanostructures produced without and with the external electric field, respectively.