Ultrasensitive ZnO/GO/PTH Nanocomposite Electrode for Selective Electrochemical Detection of Ciprofloxacin in Environmental Waters

A novel ternary nanocomposite of zinc oxide, graphene oxide, and polythiophene (ZnO/GO/PTH) was synthesized via a sonochemical method for ultrasensitive electrochemical detection of ciprofloxacin (CIP) in environmental waters. Comprehensive characterization using XRD, FT-IR, BET (surface area: 28.20 m²/g), FE-SEM/HR-TEM (average particle size: 3.42 nm), and EDS confirmed successful component integration with enhanced interfacial synergy. The ZnO/GO/PTH-modified electrode demonstrated 6.4-fold higher electrocatalytic activity toward CIP oxidation compared to bare GCE, attributed to synergistic π-π stacking interactions, Zn–S coordination, and charge-transfer enhancement. The optimized sensor exhibited outstanding analytical performance: (1) a broad linear range (0.015–6 μM, R² = 0.998), (2) high sensitivity (0.075 μA·μM⁻¹·cm⁻²), and (3) ultralow detection limit (LOD: 0.008 μmol/L, S/N = 3). Remarkably, the sensor retained 95.6% of its initial response after 25 days of storage and showed minimal signal variation (<3.0%) against 20–50-fold excess interferents (Ca²⁺, ofloxacin, etc.). Validated in real water samples (river, lake, tap water), the sensor achieved recoveries of 90.3–102.5% (RSD ≤ 5.7%, n = 5), demonstrating reliability for monitoring environmentally relevant CIP concentrations. This work provides a cost-effective and robust platform for on-site antibiotic surveillance in aquatic ecosystems.