Plasmonic Ag/Au Alloy Aerogels with Hierarchical Mesoporosity for Ultrasensitive and Stable SERS Detection of Illicit Drugs

Three-dimensional (3D) plasmonic Ag/Au alloy aerogels with hierarchical porosity and interconnected networks were fabricated via a facile one-pot reduction–gelation strategy. This approach enables simultaneous reduction, alloying, and self-assembly of Ag and Au, producing aerogels with tunable composition, uniform mesoporosity, and abundant plasmonic hotspots. Structural and optical characterizations confirm homogeneous alloying within a robust 3D framework, broadband plasmonic resonance, enhanced electromagnetic field localization, and minimal charge transfer resistance, collectively enabling ultrasensitive and reproducible surface-enhanced Raman spectroscopy (SERS) detection. Systematic tuning of Au content identifies Ag-1Au as optimal, balancing plasmonic enhancement, chemical stability, and long-term durability. The aerogels allow qualitative and quantitative detection of illicit drugs, including amphetamine, ketamine, morphine, tetrahydrocannabinol (THC), and synthetic cannabinoids, with detection limits down to 10 –9 to 10 –11 M and excellent reproducibility. Moreover, the platform effectively detects cannabinoids in complex matrices, such as electronic cigarette liquids, demonstrating practical applicability. This work establishes a facile, scalable, and highly controllable strategy to construct high-performance Ag/Au aerogels for ultrasensitive chemical sensing and forensic applications.