SERS tags based on polymer microspheres decorated by gold nanoparticles: layer-by-layer deposition vs. aggregation from quasi-stable colloidal solution

Abstract

Surface-enhanced Raman scattering (SERS) tags based on polymer microspheres (PMS) show significant promise for applications in liquid environments, particularly in the study of biological systems. The core principle of this fabrication method is to concentrate gold nanoparticles within a single point, with dimensions comparable to the diameter of the laser spot. These tags remain clearly visible in the solution and, owing to the formation of interparticle hot spots, yield enhanced SERS signals. In this work, we developed gold nanoparticle (AuNP) decorated polymer microspheres (PMS) for use as efficient SERS tags. A well-established layer-by-layer deposition technique was compared with nanoparticle aggregation from quasi-stable colloidal solution to fabricate SERS tags. The SERS performance of these AuNP-decorated PMS was evaluated using rhodamine 6G as a non-resonant model molecule. Structures fabricated by the aggregation method showed a higher surface filling factor (FF = 32%) and notably greater analytical enhancement (AEF of 1.4 × 10⁴), significantly outperforming those from layer-by-layer deposition (14% FF, 7.5 × 10³ AEF). Furthermore, the practical applicability of these SERS tags was validated through two applications: the quality assessment of motor oil in the non-aqueous environment and the quantitative analysis of 2,4-dinitrophenol in the aqueous solution. These results underscore the potential of the AuNP-decorated PMS SERS tags for diverse analytical and quality control applications.