Studies Of Electrochemical Sensors For Heavy Metal Ions Based On Functional Organic Ligands

This paper systematicly summarizes environmental pollution caused by lead ions(Pb²⁺),current detection methods of lead ions,carrier types of lead ions,synthesis of new lead ionophores,and fast scanning cyclic voltammetry.Lead ionophores are carriers that specifically identify lead ions in related lead ion detection.Lead ionophores can achieve specific recognition of lead ions through forces such as hydrogen bonding,van der waals forces,electrostatic forces,and stacking forces.In this thesis,electrochemical sensors were constructed based on two different types of lead ionophores,and high-sensitivity detection of lead ions was achieved by fast scanning cyclic voltammetry.The details are as follows:1.Synthesis of new lead ionophores by metal-free radical coupling reactionBased on the green organic synthesis method,a new lead ionophore-2,4,6-trimethylthiosulfonate（MTF）was synthesized.It is synthesized through a metal-free radical coupling reaction,which avoids the use of metal catalysts and related additives,it is environmentally friendly,with simple and mild reaction conditions,a wide range of substrates can be used and a series of thiosulfonates with different substituent groups are developed under standard conditions.The synthesized lead ionophor is within the framework of density functional theory（DFT）,the energy value of the attachment of lead ions to the carrier is calculated according to relevant theory,and the most suitable lead ionophore among a series of synthesized thiosulfonates is selected.This synthetic method is green and efficient,and computational chemistry has also been successfully used in this research,providing strong preliminary theoretical support.2.Selective measurement of picomolar levels of lead ions based on new lead ionophore electrochemical sensorsIn this work,a Nafion/MTF/GCE electrochemical sensor based on2,4,6-trimethylthiosulfonate（MTF）was developed,which realized detection of Pb²⁺.Firstly,the prepared sensor was preconcentrated by enriching Pb²⁺with an electrochemical workstation,and then Pb²⁺was detected by rapid scanning anode stripping voltammetry（FSASV）.The experimental results show that when the scan rate is 100 V/s,the prepared sensor shows that there is a good linear relationship between the Pb²⁺dissolution peak current and the logarithm of Pb²⁺concentration between 10 nmol/L and 0.1 pmol/L,and the detection limit（LOD）can reach 0.1pmol/L through FSASV.This method was successfully applied to the determination of Pb²⁺in spiked tap water samples,and the recovery rate was between 97.8 and 106.2%,and the relative standard deviation RSD was 4.2 to 6.7%.Therefore,the combination of MTF-based sensors and FSASV is a fast,economical and sensitive method for detecting Pb²⁺.3.An Electrochemical sensor based on new calixarene and fast scanning voltammetry for rapid and high sensitivity detection of lead ionsBased on a new calixarene and fast scanning voltammetry,an efficient and convenient electrochemical sensor was developed for the detection of Pb²⁺.Based on TCA,through organic reaction,calixarene is combined with L-cysteine（Cys）,obtaining a new calixarene（NTCA）,which contains four sulfhydryl groups（-SH）at the bottom.The new calixarene was fixed on the surface of the gold electrode by Au-S bond,forming an electrochemical sensor for detecting Pb²⁺.The sensor achieves highly sensitive detection of Pb²⁺by fast scanning anodic stripping voltammetry（FSASV）.There is a good linear relationship between logarithm of the peak current and the concentration of Pb²⁺within the concentration range of 1×10^-6mol/L to 1×10^-12mol/L.The detection limit is 10^-12mol/L.Calculations based on relevant theory have also verified that the new calixarene has a specific adsorption effect on Pb²⁺.This method was successfully applied to the measurement of Pb²⁺in spiked water samples with a recycling range of 98.2 to 104.8%and a relative standard deviation RSD of 3.6 to 5.2%.This method is efficient,sensitive and convenient,the constructed electrochemical sensor has broad application prospects in safety detection and field detection of water environment.