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.