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.