In modern agriculture, extensive use of pesticides to preserve crops from pests has raised serious environmental and food safety problems because of the harm for our healthiness. As one of important branches of the instrumental analysis in modern days, electrochemical analysis technology shows great potential and advantages in analysis fields and more applications in pesticide residues.

In this work, a hybrid nanocomposite consisting of copper nanowires (Cu NWs) and Graphene(GR)/CTS was prepared as an excellent catalyst for methyl parathion electrooxidation. Through a simple way to obtain a mixed Cu NWs/GNs-Chit hybrid nanocomposites, the combination of them formed structure similar to a overhead network, to provide a beneficial platform for the detection. The electrochemical characterization of the Cu NWs/GNs-Chit modified electrode and its application for determination of methyl parathion via specific adsorption were evaluated using Cyclic voltammetry(CV) and Square ave oltammetry(SWV).Under the optimized operational conditions, the developed electrochemical sensor showed a specific and excellent performance with a good sensitivity, selectivity and wide dynamic range toward the quantification of methyl parathion. The results implicate the applicability of CuNWs/GNs-Chit hybrid nanocomposites for fast, simple, sensitive and elective analysis of OPs, which may open a new avenue in monitoring Ops.

Result and discussion

1. SEM image of Cu NWs-Graphene hybrid composit

The Cu NWs has an average diameter of 150 nm and length of 30 nm, and the surface is very smooth, which was calculated from 30 randomly selected Cu NWs in SEM image. Figure 1C ,Cu NWs were well dispersed on the surface of GR and Some Cu NWs inserted into the sheets structure of GR.

2. Electrochemical Behavior of the Modified Electrodes

Fig.2 show the difference is Cu NWs/GNs-Chit/GCE showed the highest normalized signal/response, compared with Nafion/Cu NWs/GCE and GNs-Chit/GCE.

3. Optimization for methyl parathion detection at Cu NWs/GNs-Chit/GCE

Cu NWs with GNs-Chit ratio of 1:2 (v/v) and 10 μl hybrid nanocomposites loading gives the highest normalized signal/response under the tested conditions, so these were selected for subsequent experiments.

4. Square wave voltammetry quantification of methyl parathion

The response of Cu NWs/GNs-Chit/GCE could cover a broad dynamic range in methyl parathion detection from 0.05-5 ppm. A sensitivity as high as 69.2 μA. cm⁻². ppm⁻¹ and a limit of detection as low as 50 ppb methyl parathion were obtained.

5. Reproducibility, interference and selectivity study

  Good selectivity is very important to evaluate a sensor. Interferences arising from other pesticides such as nitrobenzene, p-nitrophenol, inorganic ions such as PO₄^3-, SO₄^2-, NO₃^- and ascorbic acid(AA) that exist in fruits and vegetables were also examined to evaluate the selectivity of nafion/Cu NWs/GCE electrodes.

Conclusion

A new non-enzymatic electrochemical sensor based on Cu NWs/GNs-Chit hybrid nanocomposites for methyl parathion detection has been developed. The hybrid composite modified electrode displayed distinctly enhanced electrocatalytic activity towards methyl parathion electrooxidation. Under the optimized operating conditions, square wave oltammetry was employed for methyl parathion detection, which shows a wide dynamic detection range from 0.2 ppm to 5 ppm, a high sensitivity (69.2·cm^-2·ppm^-1) and the detection limit as low as 50 ppb. It had specific detection to the methyl parathion residues and had good reproducibility and stability. These results demonstrate that the developed Cu NWs/GNs-Chit hybrid nanocomposites have great potential for fast, simple, sensitive and selective analysis of methyl parathion.

References

Chen, D.; Wang, J.; Xu, Y.; Li, D.; Highlysensitive detection of organophosphorus pesticides by acetylcholinesterase-coated thin film bulk acoustic resonator mass-loading sensor[J]. Biosensors and Bioelectronics 2013, 41, 163-167.

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