Revolutionising pesticide detection: a high-sensitivity electrochemical sensor with CdS/g-C₃N₄/MWCNTs for paraquat monitoring

ABSTRACT

Over a decade, the Malaysia National Poison Centre found that 40% of pesticide poisoning cases may be linked to excessive paraquat (PQ) in water, soil, or food, underscoring the widespread impact on public health and emphasising the importance of detecting even trace amounts of PQ residues in the environment. Thus, this study presents a novel electrochemical sensor based on multiwalled carbon nanotubes (MWCNTs) reinforced cadmium sulphide co-anchoring on graphitic carbon nitride (CdS/g-C₃N₄) nanocomposites for PQ detection. The CdS/g-C₃N₄ nanocomposite was successfully synthesised and characterised through FTIR, XRD, EDX, FESEM and TEM analysis. The modified electrode (CdS/g-C₃N₄/MWCNTs PE) exhibited improved electrocatalytic activity, as demonstrated by cyclic voltammetry (CV) and impedance spectroscopy. The CdS/g-C₃N₄/MWCNTs PE displayed a high CV peak and low R_ct value which corresponded to a higher electron transfer rate, reduced charge transfer resistance and enhanced mass transport properties. The electrochemical sensor’s performance was evaluated for the detection of PQ, and it demonstrated a linear response in a range of 1.0 µM to 0.1 mM with a limit of detection of 0.14 μM. Furthermore, the sensor exhibited selectivity with a less than 16% potential interference from various organic chemicals and inorganic ions. The sensor’s applicability was tested by quantifying PQ in real water samples, showing excellent recovery percentages ranging from 98.9% to 102.0%. The developed electrochemical sensor provides a practical solution for the rapid and accurate monitoring of PQ levels in the environment. This work establishes the foundation for the development of a selective electrochemical sensor for pesticide analysis, addressing both public health and environmental concerns.

Research Highlights

1. A novel electrochemical sensor based on CdS/g-C₃N₄/MWCNTs nanocomposites was developed, showing improved electrocatalytic activity.

2. The CdS/g-C₃N₄/MWCNTs modified electrode displayed enhanced electron transfer rate and mass transport properties, reducing charge transfer resistance.

3. The developed electrochemical sensor exhibited high sensitivity, with a low detection limit of 0.14 μM for paraquat (PQ).

4. The sensor demonstrated excellent selectivity, remaining unaffected by potential interference from various organic chemicals and inorganic ions.

5. The sensor’s practical applicability was validated by quantifying PQ levels in real water samples, achieving excellent recovery percentages ranging from 98.9% to 102.0%.

KEYWORDS:

• Cadmium sulphide
• electrochemical sensor
• environmental monitoring
• graphite nitride
• paraquat

Acknowledgments

The authors would like to thank the Ministry of Education Malaysia and Universiti Pendidikan Sultan Idris for providing financial support (Grant no.: GPUF 2020-0193-103-01) for this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Universiti Pendidikan Sultan Idris [GPUF 2020-0193-103-01].