Construction And Performance Of Three Phenolic Electrochemical Sensors

With the rapid development of economy,people are becoming more and more aware of environmental protection and health.At present,phenolic substances widely exist in our food,pharmaceutical and industrial production.Phenolic substances will not only pollute the environment but also affect human health.Therefore,an effective and rapid analytical method is needed to detect the food and environment in our lives.The electrochemical sensor has the advantages of simple operation,convenient portability,high sensitivity,short detection time,low cost and low detection limit,which is suitable for the detection of phenolic substances.Therefore,we constructed three electrochemical sensors for the detection of thymol,hydroquinone and catechol.The experimental contents are as follows:1)Thymol electrochemical sensor based on PdNPs@MoO₃-MWCNTs composite material.Molybdenum（VI）oxide（MoO₃）material was synthesized by a simple hydrothermal method,and PdNPs and MWCNTs were combined with MoO₃material.Then the prepared PdNPs@MoO₃-MWCNTs composite material was used to construct the modified electrode to complete the detection of thymol.Cyclic voltammetry（CV）,electrochemical impedance spectroscopy（EIS）and differential pulse voltammetry（DPV）were used to prove that PdNPs@MoO₃-MWCNTs composite had good electrocatalytic effect on thymol in solution.At the same time,the sensor prepared under the best experimental conditions completed the detection performance of thymol in honey samples.2)Thymol electrochemical sensor based on Pt NPs@CPOFs-MWCNTs composite material.In this study,using the idea of polyoxometalates and covalent organic frameworks,the preparation of covalent polyoxometalate organic frameworks（CPOFs）was introduced in this study.Firstly,the prepared polyoxometalate was functionalized with amine group（NH₂-POM-NH₂）,and then the CPOFs was prepared by solvothermal Schiff base reaction with NH₂-POM-NH₂and 2,4,6-Trihydroxybenzene-1,3,5-tricarbaldehyde as monomers.After incorporation of Pt NPs and MWCNTs into the CPOFs material,the Pt NPs@CPOFs-MWCNTs nanocomposite that possessed excellent catalytic activity and electrical conductivity was formed and utilized as new electrode material for electrochemical thymol sensors.The obtained Pt NPs@CPOFs-MWCNTs composite exhibited excellent activity toward thymol,which was attributable to its large special surface area,good conductivity,and the synergistic catalysis of each component.3)Electrochemical sensor for Simultaneous detection of hydroquinone and catechol based on Pt NPs@CPOFs-MWCNTs composite material.Based on the previous chapter,the second CPOFs was synthesized from NH₂-POM-NH₂and another monomer,2,5-dimethoxybenzene-1,4-diformaldehyde under the same conditions.An electrochemical sensor based on Pt NPs@CPOFs-MWCNTs was constructed for simultaneous detection of hydroquinone and catechol.The electrochemical behavior of the modified electrode was studied by electrochemical tests and the experimental conditions were optimized.Under the best experimental conditions,the sensor could distinguish the oxidation peak potential of hydroquinone and catechol well.At the same time,the stability and selectivity of the prepared electrochemical sensor were studied.