Preparation Of MXene Based Iron Rich Nanocomposite Modified Electrode And Highly Sensitive Detection Of Arsenic（Ⅲ） In Water

The heavy metal arsenic（As）seriously harms the environment and threatens the lives of hundreds of millions of people.Therefore,it is of great significance to explore a highly sensitive detection method for arsenic in water environment.Currently reported inorganic arsenic analysis methods are usually costly and time-consuming,so it is urgent to seek sensitive and rapid analytical methods for arsenic detection.Electrochemical analysis methods have been widely concerned in the sensing field due to their advantages of high sensitivity,good selectivity,simple operation and fast analysis speed.Nanomaterials with high specific surface area and many active sites are widely used as electrode modification materials for electrochemical analysis.In particular,two-dimensional metallic carbide Ti₃C₂T_X（MXene）nanomaterial is an ideal nanomaterial for preparing modified electrodes because of its unique layered structure,good electrical conductivity and abundant active sites.Materials rich in iron（Fe）can form Fe-O-As bonds with arsenic,so they are ideal materials for arsenic adsorption and sensing.In this work,MXene was used as the sensing material matrix,and iron rich material Fe-Co layered dihydroxide（Fe-Co-LDH）and amino functionalized iron foundation organic framework（Fe-MOF）were used to compound MXene,respectively,to improve the sensitivity of the composite material to arsenic detection through synergistic effect.The highly sensitive response mechanism is revealed by various techniques,which provides a basic theoretical basis for the construction of efficient sensors.The main research results are as follows:（1）Fe-Co-LDH/MXene material was obtained by depositing ferrous sulfate and cobalt nitrate on the surface of MXene by hydrothermal reaction in the presence of urea and ammonium fluoride with MXene as the substrate.X-ray diffraction（XRD）analysis showed that Fe-Co-LDH/MXene was successfully synthesized.Scanning electron microscopy（SEM）characterization revealed that the synthesized Fe-Co-LDH materials were in the form of rods with a uniform size of about 2μm and were uniformly distributed/deposited on the surface of MXene sheets.Cyclic voltammetry（CV）and electrochemical impedances（EIS）results showed excellent electrochemical activity and good electrical conductivity of Fe-Co-LDH/Mxene,which was mainly attributed to the good electrical conductivity,large specific surface area and abundant active sites of MXene.The results of X-ray photoelectron spectroscopy（XPS）analysis showed that the adsorption enrichment of Fe-Co-LDH/MXene materials is mainly through the bonding of OH groups to arsenic on the surface.The results of electrochemical tests on arsenic by SWASV showed that the Fe-Co-LDH/MXene modified electrode has good linearity in the concentration range of 1～10 ppt and 10～1000 ppt.The electrochemical sensor in this study possesses a high sensitivity(0.22μA·cm^-2·ppt^-1)and a low detection limit（0.9 ppt）due to its good conductivity,high specific surface area and strong adsorption effect on arsenic.The test process is not interfered by other heavy metal ions,and the reproducibility and stability are good.The modified electrode showed good recovery of As（Ⅲ）content in real water samples.（2）Fe-MOF/MXene composite nanomaterials were prepared by adjusting the mass ratio of Fe Cl₃·6H₂O to MXene in the dispersion containing MXene under hydrothermal conditions.XRD results showed that Fe-MOF/MXene was successfully synthesized.SEM results show that Fe-MOF particles are about 250 nm and uniformly deposited on the surface of MXene.CV analysis showed that the redox activity of Fe atoms in the center of Fe-MOF/MXene was enhanced due to the presence of MXene.SWASV showed that the Fe-MOF/MXene modified electrode had a highly sensitive response to arsenic.XPS proved that the response mechanism was mainly the combination of Fe-O-As bond on MOF surface and OH and As bond on MXene surface.The synergistic effect of the two improved the sensitivity of arsenic adsorption detection.The linear correction curves of Fe-MOF/MXene modified electrodes for arsenic ranged from 1～10 ppt and from 10～100 ppt.The electrochemical sensor in this study possessed a very high sensitivity(1.367μA·cm^-2·ppt^-1)and the lowest detection limit（0.58 ppt）.The analysis of interference test shows that the heavy metal ions such as Cu（Ⅱ）,Pb（Ⅱ）,Hg（Ⅱ）do not interferent the detection of As（Ⅲ）,and the electrode has good reproducibility and stability.The modified electrode showed high recovery of As（Ⅲ）content in real water samples.