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 a bare glassy carbon electrode (GCE), attributed to synergistic $\pi $ - $\pi $ stacking interactions, Zn–S coordination, and charge-transfer enhancement. The optimized sensor exhibited outstanding analytical performance: 1) a broad linear range (0.015– $6~\mu $ M, ${R} ^{{2}} =0.998$ ); 2) high sensitivity ( $0.075~\mu \text {A}\cdot \mu $ M ${}^{{1}}\cdot \text {cm}^{{2}}\text {)}$ ; and 3) ultralow limit of detection (LOD): $0.008~\mu $ mol/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 (Ca ${}^{{2}+}$ , ofloxacin, etc). Validated in real water samples (river, lake, tap water), the sensor achieved recoveries of 90.3%–102.5% (RSD $\le 5.7$ %, ${n} =5$ ), 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.