Autonomous nanocomposite electrochemical sensing of antibiotics across aquatic ecosystems

Antibiotics are pervasive in aquatic environments, driving antimicrobial resistance and threatening ecosystem and human health, yet monitoring still depends on laboratory-based methods that preclude real-time, large-scale surveillance. Here we report an autonomous electrochemical sensing platform based on a stabilized MXene (Ti₃C₂Tₓ) nanocomposite that enables selective, ultrasensitive, and long-term monitoring of antibiotics directly in natural waters. A controlled in situ electrochemical oxidation strategy converts Ti₃C₂Tₓ into a Ti₃C₂Tₓ-TiO₂ heterostructure while preserving electrical conductivity, producing a chemically robust and catalytically active sensing interface. When integrated with reduced graphene oxide and silver nanowires, the resulting hierarchical electrode generates multi-site molecular recognition that yields distinct electrochemical fingerprints for ciprofloxacin and sulfamethoxazole. The sensor achieves nanomolar detection limits (45 nM for ciprofloxacin and 4 nM for sulfamethoxazole), maintains > 98% signal retention over 30 days, and discriminates target antibiotics from structurally related compounds and complex matrix interferents. Machine-learning analysis of time- and voltage-resolved electrochemical features enables 96.7% classification accuracy, while density functional theory reveals fundamentally different adsorption and charge-transfer mechanisms for the two antibiotics. Field validation across lakes, rivers, aquaculture effluents, and synthetic biological fluids shows strong agreement with LC-MS/MS measurements (R ²  = 0.987). When deployed on an unmanned surface vessel, the system enables continuous, autonomous monitoring over > 10 km ² for 72 hours. Together, these results establish electrochemical fingerprinting on stabilized MXene nanocomposites as a scalable strategy for real-time surveillance of antibiotic pollution in aquatic ecosystems.