Electrochemical detection of phosphate in agricultural fertilizers using a polypyrrole/carbon nanorod–molybdenum dioxide composite electrode

In this work, we designed a new composite sensor for the sensitive and selective detection of phosphate ions (PO₄³⁻) by using polypyrrole (PPy), carbon nanorods (CNRs), and molybdenum dioxide (MoO₂) as the electrode material. Carbon nanorods were fabricated by the carbonization of electrospun polyacrylonitrile nanofibers and the composite electrode was prepared by simple electrodeposition. The synergistic effect of PPy, MoO₂, and CNRs improved the electrochemical responses of the sensor. The sensor displayed a broad linear range between 3 and 1065 μM with a low detection limit of 0.015 μM, and it showed outstanding selectivity, stability, and repeatability, thereby enabling trace-level detection of phosphate in agricultural fertilizers and environmental samples. This PPy/CNR–MoO₂ sensor can be potentially used for environmental monitoring and agricultural management with the goal to decrease phosphate-related pollution in practice.