Electrochemical malathion sensors based on phytic acid-doped polyaniline and overoxidized polyaniline nanorods

In this work, polyaniline (PANI) and overoxidized polyaniline (oPANI) nanorods doped by phytic acid (PA) with uniform size of 60–100 nm were prepared and modified on glassy carbon electrode (GCE) as non-enzymatic malathion sensors. Doping of PA has deep influence on structural and morphological properties, conductivity and detection performance of electrode materials. The obtained PANI nanorods doped with PA (PA-PANI) possess high affinity toward malathion, and thus the redox reaction of PANI molecules could be hindered and redox currents were inhibited. The electrode reaction process on PA-PANI/GCE is a typical adsorption-controlled process. By contrast, the oPANI nanorods doped with PA (PA-oPANI) presents good catalytic performance to malathion and the electron transfer process was enhanced and redox currents increased. Correspondingly, the electrochemical reduction process on PA-oPANI/GCE is a typical diffusion-controlled process. Both enzyme-free electrochemical sensors exhibit good stability, anti-interference ability, recovery in real samples and excellent detection performance, with a wide linear range of 0.01–200 ppb and low detection limit (1.58 ppt for PA-PANI and 2.23 ppt for PA-oPANI, respectively), indicating that PA-PANI and PA-oPANI could be used as an excellent malathion sensor. Moreover, the PA-oPANI sensor has some degree of reproducibility through further anodic polarity processing, and the detailed application needs to be further explored.