Research On Highly Sensitive Electrochemical Sensors For Heavy Metal Ions Based On Carbon Nanocomposites

With the rapid development of metallurgy,chemical industry,and agriculture,many heavy metal minerals have been exploited and utilized,which caused environmental and food pollution problems though they provided convenience for human life.Therefore,it is necessary to develop sensitive and rapid detection methods for heavy metal ions.Traditional detection methods for heavy metal ions have the disadvantages of expensive instrument,large volume,long detection time and complicated operation,while electrochemical sensors are low cost,portable,rapid and simple.In this study,electrochemical sensors based on novel carbon nanocomposites were constructed to realize the rapid detection of heavy metal ions in water and food.Besides,the repeatability,reproducibility,specificity and stability of methods were evaluated.The main results are as follows:（1）A sensitive electrochemical sensor based on AuNPs/PANI-MWCNTs for Zn²⁺Pb²⁺and Cu²⁺detection.In this study,a simple and sensitive electrochemical sensor was fabricated for the simultaneous detection of Zn²⁺,Pb²⁺and Cu²⁺.PANI-MWCNTs and AuNPs were deposited on the electrode surface by electrochemical deposition,and then the performance of the sensor was evaluated by cyclic voltammetry,electrochemical impedance spectroscopy and square wave stripping voltammetry.The results show that the proposed sensor exhibited three independent peaks for Zn²⁺,Pb²⁺,and Cu²⁺,and showed wide linear ranges from 1 to180μg L^-1 for each.The detection limits（S/N=3）of Zn²⁺,Pb²⁺and Cu²⁺were 0.039μg L^-1,0.037μg L^-1 and 0.017μg L^-1,respectively,which are lower than the minimum limits set by the standards for drinking water quality in China.In addition,the sensor exhibited excellent repeatability,reproducibility,stability and selectivity.Finally,the feasibility of the analytical method was verified by the determination of trace Zn²⁺,Pb²⁺and Cu²⁺in water and food samples,and the results obtained by this method were consistent with the ICP-MS determination.（2）A highly sensitive electrochemical aptasensor based on 3D-rGO/AuNPs for Hg²⁺detection.In this study,based on the stable structure of T-Hg²⁺-T,an electrochemical sensor for rapid and highly sensitive detection of Hg²⁺in water and food was developed.The three-dimensional reduced graphene oxide-modified gold nanoparticles（3D-rGO/AuNPs）was served as support material,which offered more immobilization sites for thiolated probe（P1）.In the presence of Hg²⁺,P1 could interact with another probe（P2）by forming T-Hg²⁺-T structure.Further,the partial sequence of P2 that did not interact with P1 was employed as an initiator sequence,which resulted in the formation of the extended double-stranded DNA through the hybridization chain reaction（HCR）between two harpin DNA strands（HP1 and HP2）.In this process,toluidine blue（TB）was used to interact with the double-stranded DNA and bring in effective electrochemical responses.Under the optimal experimental conditions,the aptasensor exhibited pronounced electrochemical signals towards Hg²⁺ranging from 10fM to 50 nM,with a low detection limit of 3.3 f M.Besides,the aptasensor showed excellent performance in lake water and food for Hg²⁺determination.