Ultrasensitive Geosmin Sensing Using Reusable SERS-Active Porous Silicon Microarray

Cyanobacteria (blue-green algae) produce geosmin, a volatile organic compound associated with ecological imbalance that adversely affects aquatic organisms by impairing growth and reproduction, weakening immune responses, and reducing aquaculture yields and quality. Herein, we developed a rapid, portable and ultrasensitive approach for geosmin detection based on an aptamer-modified silver-coated porous silicon (Ag-pSi) microarray that serves as a surface-enhanced Raman spectroscopy (SERS) transducer. The Ag-pSi substrate, characterized by a high surface area that efficiently distributed noble metal nanoparticles across the thin film, significantly enhanced Raman scattering, yielding an analytical enhancement factor of 2.17 × 108. The microarray scaffold, comprising 25 discrete sensing spots, exhibited a linear response across geosmin concentrations from 0.001 to 10 μg L–1, with an exceptionally low detection limit of 0.1 ng L–1. The performance evaluation demonstrated high reusability, storage stability and high selectivity, as evidenced by 9 successful regeneration cycles, a 7 week shelf life and negligible interference from coexisting metabolites. The scientific feasibility of the fabricated SERS array was further confirmed across various aqueous media, with recovery rates ranging from 94% to 103%, consistent with the benchmark approach. Overall, the integrated SERS-based approach offers a transformative and practical solution for sensitive monitoring of off-flavor contaminants across aquaculture, food safety, and environmental contexts.