N-doped carbon nanotubes as electron transport promoter by bridging MnFe2O4 and carbon cloth for simultaneous detection of heavy metal ions (Cd2+ and Pb2+)

Herein, multi-layer composite electrodes of MnFe 2 O 4 @carbon nanotubes/carbon cloth (MFO@CNT/CC) are prepared by dip coating and the subsequent hydrothermal method. Flexible conductive carbon cloth (CC) substrate provides a 3D strong base support. The carbon nanotubes (CNT) connected by CC form a conductive network with a large specific area, which is also conducive to electron transfer. The modified MnFe 2 O 4 nanoparticles have abundant active sites, which can enhance the electrochemical activity. CNT and MnFe 2 O 4 nanoparticles form a tandem structure beneficial to increase the active site and promote the response to heavy metal ions. The MFO@CNT/CC electrode has good detection performance for Cd 2+ (0.25–12 ppm) and Pb 2+ (0.25–12 ppm) and a low detection limit of 0.25 ppm. In the presence of interfering ions, it exhibits a highly selective response to the target ion, with minimal current changes and a range of variations (−3.48–5.59 %). The actual detection recovery is in the range of 97.33–101.17 %, suggesting its practical reliability. Furthermore, we propose a detection and analysis method that combines electrochemistry with machine learning; the model attains a perfect classification accuracy of 100 % for both Pb 2+ and Cd 2+ , underscoring the robustness of the classification. Overall, this work provides innovative composites and performance explorations for advancing high-performance simultaneous detection of heavy metal ions.