The Construction Of Electrochemical Sensors Based Co-nanomaterial For The Detection Of Cd²⁺ And Pb²⁺

Heavy metal pollution is currently a hot issue in the field of food safety,and cadmium and lead are one of the common heavy metal pollution particles.Cadmium ions(Cd²⁺)and lead ions(Pb²⁺)continue to accumulate in the human body with biological chains,causing great damage to human health.Therefore,the accurate and rapid detection of Cd²⁺and Pb²⁺in actual samples is important for food safety prevention and monitoring.important meaning.However,there are very few Cd²⁺and Pb²⁺and many other interfering substances（pesticides,other metal ions and so on）which bring great challenges to the rapid monitoring of target ions in the actual samples.With the rapid development of nanomaterial science,electrochemical sensing technology has also been rapidly developed.By optimizing the electrochemical sensing interface morphology,size,composition and structure,the construction of high sensitivity,strong anti-interference ability and reproducible electrochemical sensor.We constructed a composite nanosensing interface with high sensitivity,large specific surface area and good repeatability based based on paper-based conductive carbon paper,synthesized in this paper.In order to achieve rapid detection of target ions,the different enrichment principles are used to achieve the enrichment of target ions on the surface of the sensing electrode.The specific work is as follows:Firstly,Co（OH）₂ was grown on the surface of conductive carbon paper（CP）by electrodeposition,and then subjected to high-temperature dehydration treatment to obtain a sensing electrode based on Co₃O₄ nanosheets.Among them,the three-dimensional carbon fiber structure of conductive carbon paper provides sufficient growth sites for Co₃O₄ nanosheets and can greatly increase the electron transmission rate.At the same time,the Co₃O₄ nanosheets have a large specific surface area and can provide sufficient sites for Cd²⁺pre-enrichment.The Co₃O₄-CP sensor electrode prepared in this study showed good sensing performance in Cd²⁺detection,and showed a good linear relationship in the concentration range of 1 n M～1200 n M Cd²⁺,and its detection limit was as low as 0.63 n M,which is comparable to other traditional detections.Compared with methods,electrochemical sensing technology has a lower detection limit and a wider detection range,and its anti-interference and repeatability are also excellent.In addition,the sensor electrode has been successfully used in the spiked detection of actual samples,indicating that the prepared Co₃O₄-CP sensor electrode has practical application potential.The sheet-like cobalt-based metal-organic framework materials（Co MOF）was grown on the surface of CP and obtain CP/Co MOF electrodes.The gold nanoparticles（Au NPs）was electrodeposited on CP/Co MOF that can greatly increase the conductivity of the sensing electrode and obtained CP/Co MOF/Au NPs electrode.At the same time,glutathione（GSH）can be modified to the surface of the sensing electrode through the Au-S bond to obtain a CP/Co MOF/Au NPs-GSH sensing electrode.When Cd²⁺is present in the detection system,the-COOH of GSH on the surface of the sensing electrode will chelate with Cd²⁺to form a COO-Cd-OOC structure,so that Cd²⁺can be enriched in the CP/Co MOF/Au NPs-GSH sensing electrode Surface,and there will be a characteristic peak near-0.8 V.As a result,a highly sensitive electrochemical sensor for detecting Cd²⁺was established.Under optimal conditions,the established electrochemical sensor can detect Cd²⁺as low as 1 n M,and its detection range is:1n M～1μM,1μM～20μM.The sensor electrode was applied to the actual sample recovery test and showed a good recovery rate.The sensor uses CP as a conductive substrate to build an electrochemical sensor to detect Cd²⁺in a sensitive and portable manner,which is expected to solve the shortcomings of traditional methods that rely on large instruments.An ultrasensitive,real-time and fast electrochemical Cd²⁺and Pb²⁺analysis CP-r GO-Co Zn MOF sensor electrode is successfully developed by integrating r GO and Co Zn MOF.Reduced graphene oxide（r GO）can not only enhance the conductivity of the sensing electrode,but also provide a firm site for the subsequent bimetallic MOF（Co Zn MOF）growth.After the Co Zn MOF is subjected to high temperature treatment,it presents a loose pore structure,which can effectively increase the contact area between the electrode and the detection system,and increase the enrichment site of the target detection object.Because bismuth ions(Bi³⁺)can form alloys with Cd²⁺and Pb²⁺respectively,and then are respectively enriched on the surface of the sensing electrode,corresponding characteristic peaks appear at different potentials,thereby achieving the purpose of simultaneous detection.Under the best experimental conditions,the linear detection ranges of CP-r GO-Co Zn MOF sensing electrodes for Cd²⁺and Pb²⁺are:1n M～3μM,6μM～35μM(Cd²⁺)and 1 n M～2μM,3μM～35μM(Pb²⁺).The limit of detection（LOD）（S/N=3）is as low as 0.565 n M(Cd²⁺)and 0.0588 n M(Pb²⁺).The sensing electrode exhibits excellent anti-interference performance and repeatability,and also performs well in actual sample detection,indicating that the sensing electrode has good detection performance.