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.