Construction Of Carbon Nanotube Hybrid Materials Based Electrochemical Sensor For Detection Of Pesticide Residues

Pesticides is agricultural production.According to statistics,China’s annual pesticide usage has exceeded 410,000 tons.Pesticides act as a"protective umbrella"for crops.Reasonable use of pesticides can control and prevent crop diseases,pests and weeds,and improve crop yield and quality,ensuring food security and farmers’income.However,excessive use of pesticides can cause environmental pollution and pose a potential threat to human health.Hence,it is crucial to swiftly and accurately detect pesticide residues in agricultural products,as it has a crucial role in safeguarding public health,promoting the scientific and modern development of agriculture,as well as social stability and sustainable development.Electrochemical analysis,especially electrochemical sensor,has become a promising method for pesticide residue detection due to its advantages of low operation cost,fast response,high sensitivity,high selectivity,easy to device and miniaturization.Carbon nanotubes（CNTs）are one-dimensional nanomaterials with a hexagonal ordered arrangement.They possess a large specific surface area,rich catalytic active sites,excellent electrical conductivity,and other properties that make them ideal materials for constructing working electrode structures.Although the properties of CNTs,such as their compact structure and excellent mechanical properties,have enabled them to demonstrate advantages in the field of electrochemical sensing,theπelectron cloud also leads to increased mutual attraction.The van der Waals interaction between tubes will make them form a structure similar to a cluster,which leads to a wide range of binding of CNTs in practical applications,thus reducing the surface area of CNTs and affecting their sensing performance.Therefore,this paper proposes to introduce functional materials as dispersants through ultrasonic method,cross-linking method and electrostatic assembly method using CNTs as base materials.In this paper,CNTs based nanocomposites are used as modifying materials and applied to the detection of pesticide residues in environmental water sources and agricultural products.The details are as follows:（1）A simple electrostatic self-assembly method was employed to prepare carbon nanohorns-modified multi-walled carbon nanotubes（CNHs@MWCNTs）composite material and used as electrode material for electrochemical detection of Niclosamide（NA）.The MWCNT modified with CNHs has improved dispersibility,and the composite material not only possesses better conductivity,but also has a larger surface area and higher catalytic activity,which significantly enhances the electrochemical behavior of NA oxidation.Due to the synergistic effect of CNHs and MWCNT,the sensor presents a low detection limit of 2.0 n M and a wide linear range of 7.0 n M to10.0μM.Additionally,the sensor exhibits excellent selectivity,good reproducibility,and long-term stability,and demonstrates good accuracy in detecting NA in real sample analysis.（2）Polydopamine（PDA）functionalized graphdiyne（GDY）was prepared via self-polymerization,and amino-functionalized multi-walled carbon nanotubes（MWCNTs-NH₂）were stable connected to the surface of GDY@PDA via in-situ cross-linking approach.The resulting GDY@PDA/MWCNTs-NH₂/GCE was directly used as an electrochemical sensor for detecting Benomyl（Ben）.The stable connection of MWCNTs-NH₂on the surface of GDY@PDA prevented the self-aggregation of MWCNTs-NH₂,and provided a highly efficient and rapid electron transfer pathway for the electrochemical oxidation of Ben.The synergistic effect between GDY and MWCNTs-NH₂ significantly promoted the electron transfer,increased effective surface area and enrichment ability,thereby enhancing the sensing sensitivity.According to the experimental results,the sensor exhibited excellent analytical performance with a low detection limit down to 1.8 n M and a linear range of 7.0 n M to 10.0μM.Furthermore,the sensor demonstrated good stability and acceptable reproducibility,providing a feasible approach for the rapid and accurate detection of Ben in real sample analysis.（3）Copper nanoparticles（Cu NPs）modified covalent organic frameworks（COFs）using in-situ reduction and convenient ultrasonic approach together with carboxylated multi-walled carbon nanotubes（MWCNTs-COOH）were prepared and used as electrode material to construct an electrochemical sensor for sensitive detection of carbendazim（CBZ）.Firstly,COFs were synthesized through the amine-aldehyde condensation reaction.Then,Cu NPs with electrocatalytic activity were constrained in COFs using sodium borohydride as reducing agent.Finally,MWCNTs-COOH was combined with Cu NPs@COFs throughπ-πinteraction to serve as a conductive agent.The results showed that the prepared Cu NPs@COF/MWCNTs-COOH composite material had a large specific surface area,abundant active sites and strong adsorption ability for CBZ.The Cu NPs@COF/MWCNTs-COOH electrode exhibited excellent electrocatalytic performance for detecting CBZ with a linear range of 0.3 n M to 10.0μM and a detection limit of 0.1 n M.Additionally,the sensor not only demonstrated excellent stability and reproducibility but also achieved successful detection of CBZ in vegetables and fruits.