MXene-Supported Single-Atom Fe–Co Nanozyme Nanocomposites for Electrochemical Detection of Antibiotic Residues in Water

The increasing occurrence of antibiotic residues in aquatic environments poses significant risks to ecosystem integrity and public health, necessitating the development of rapid, sensitive, and portable analytical technologies. Herein, a MXene-supported dual single-atom Fe–Co nanozyme nanocomposite (FeCo-SA/MXene) is proposed as a high-performance electrocatalytic platform for the ultrasensitive electrochemical detection of antibiotic contaminants in water. The nanocomposite integrates the exceptional electrical conductivity and abundant surface functionalities of Ti₃C₂Tₓ MXene with atomically dispersed Fe–N₄ and Co–N₄ catalytic sites, enabling accelerated electron transfer and enhanced electrocatalytic activity. The structural characterization confirmed successful formation of isolated Fe–Co active sites without detectable metal nanoparticles, while electrochemical impedance spectroscopy indicated a substantial reduction in charge-transfer resistance from 185 Ω for the bare glassy carbon electrode to 26 Ω after FeCo-SA/MXene modification, accompanied by a 3.5-fold increase in electrochemically active surface area. The proposed sensor exhibited wide linear detection ranges of 0.5 nM–100 μM for tetracycline, 1 nM–80 μM for ciprofloxacin, 2 nM–100 μM for sulfamethoxazole, and 5 nM–120 μM for chloramphenicol, with corresponding detection limits of 0.12, 0.28, 0.45, and 0.83 nM, respectively. The sensor further demonstrated excellent selectivity against common interfering species, retained 96% of its initial response after 30 consecutive measurements and 94% after 4 weeks of storage, and achieved recoveries of 95.9–103.1% with relative standard deviations below 3.5% in environmental water samples. These findings demonstrate the potential of FeCo-SA/MXene nanozyme nanocomposites as a promising platform for developing next-generation electrochemical sensors for rapid, ultrasensitive, and reliable monitoring of emerging antibiotic contaminants in aquatic environments.