Versatile methodology for the synthesis of stable magnetic SERS-encoded clusters for sensing applications

Surface-enhanced Raman scattering (SERS) substrates are garnering increasing interest for ultrasensitive high-throughput sensing. Notably, SERS-encoded nanostructures stand out due to their potential for nearly unlimited codification with excellent optical properties. In this paper we report a simple, versatile and cost-effective method for preparing SERS-encoded clusters. These clusters consist of encoded silver nanoparticles assembled onto magnetic microparticles, which are externally coated with oxide-based structures. We propose and compare diverse shell materials, including SiO₂, ZnO and TiO₂. This design results in a stable and robust system with excellent magnetic and optical properties, suitable for being used in multiple media and conditions. To enhance usability, the external coating was functionalized with dopamine, facilitating further modifications. Additionally, we developed a data analysis method based on machine learning and artificial neural networks, utilizing self-organizing maps to automate particle identification. This study provides valuable information for selecting the most appropriate magnetic SERS-encoded cluster for multiplex sensing applications.