Nano-size cobalt-doped cerium oxide particles embedded into graphitic carbon nitride for enhanced electrochemical sensing of insecticide fenitrothion in environmental samples: An experimental study with the theoretical elucidation of redox events

In the present work, a nanocomposite, based on embedding Co-doped CeO2 nanoparticles into graphitic carbon nitride (g-C3N4), was applied to functionalize commercial glassy carbon paste. This is the first application of the electrochemical sensor, developed through the proposed procedure, in electrochemical sensing. The sensor was utilized for the electrochemical determination of organophosphate pesticide fenitrothion (FNT). Cyclic voltam-metry identified reversible oxidation of FNT (oxidation at 0.18 V and reduction at 0.13 V) and additional reduction at-0.62 V vs. Ag/AgCl in HCl solution (pH = 1). Theoretical calculations were carried out to model and elucidate experimentally observed redox processes. Special attention was devoted to modeling experimental conditions, and based on the obtained results, a detailed redox mechanism of the investigated analyte was proposed. This represents the first complete and unambiguous elucidation of the FNT redox mechanism, sup-ported by joined experimental and theoretical data. Square wave voltammetry (SWV) was utilized for quanti-fication, whereby the FNT oxidation peak was chosen for monitoring the analyte concentration. The developed sensor provided a nanomolar detection limit (3.2 nmol L-1), a wide linear concentration range (from 0.01 to 13.7 mu mol L-1), and good precision, repeatability, and selectivity towards FNT. Practical application possibility was explored by testing the sensor performance for examining tap water and apple samples. Recovery tests, conducted during the FNT-spiked sample assays, showed a great application capability of the developed sensor for real-time monitoring of FNT traces in environmental samples.

Automated summary

In this study, a nanocomposite based on Co-doped CeO2 nanoparticles embedded into graphitic carbon nitride was developed and applied to functionalize commercial glassy carbon paste. The electrochemical sensor based on this nanocomposite was utilized for the detection and quantification of organophosphate pesticide fenitrothion. The oxidation and reduction processes of fenitrothion were experimentally observed and theoretically modeled, leading to a detailed understanding of its redox mechanism. The developed sensor exhibited nanomolar detection limit, wide linear concentration range, and good precision, repeatability, and selectivity towards fenitrothion. Furthermore, the sensor showed great potential for real-time monitoring of fenitrothion traces in environmental samples.