The Construction Of Composite Interfaces Based On Metal Organic Framework Or Molybdenum Disulfide And Its Electrochemical Sensing Application

Metal-organic frameworks?MOFs?,also known as porous coordination polymers?PCPs?,have attracted widespread interest in recent years and have become one of the most developing rapidly materials in the chemistry and materials fields.As we all know,MOFs as a new type of star material have a porous structure and a large specific surface area.In addition,there are many types of metal ions and ligands that can be selected,which also makes the structure of MOFs diverse.Due to its unique properties,it can be widely used in adsorption,supercapacitor,catalysis,sensing and other fields.Molybdenum disulfide?MoS₂?,a two-dimensional layered nano-material,has attracted extensive interest of researchers because of its unique morphology,structure and high specific surface area,and has been gradually known and explored by researchers.However,the electrical conductivity of MoS₂ and MOFs is not very good,which also limits its application in electrochemistry.In general,the combination of MOFs or MoS₂nanomaterials and other materials with good conductivity can achieve better performance,which can break the limitations of single material in application.In this paper,MOFs or MoS₂ materials were used as the substrate to prepare composites by electropolymerization or solvothermal method,and the composites have good electrochemical properties.The composites were applied to construct electrochemical sensing of the heavy metals ion and nitrophenol.The work is mainly divided into the following four parts:?1?Au-ZIF-8 material was synthesized by certain method.In order to further improve the conductivity and increase the specific surface area of the composites,RGO-Au-ZIF-8 nanocomposites were prepared by combining reduced graphene oxide?RGO?on the basis of Au-ZIF-8 material.RGO-Au-ZIF-8 nanocomposites were characterized by FT-IR,SEM,TEM,XRD and electrochemical properties.The optimum detection conditions were determined by optimizing the proportion of materials and the experimental conditions.Compared with single material modified glassy carbon electrode and bare glassy carbon electrode,the nanocomposites has superior electrochemical properties and can be used to simultaneously detect two heavy metal ions of Pb²⁺ and Cu²⁺.In the detection range of 0.01?M-10?M,the oxidation peak current vs the concentrationofPb²⁺ and Cu²⁺showedgoodlinearrelationships:Y??A?=1.71X??M?+1.2885,R²=0.9954;Y??A?=1.08X??M?+0.8123,R²=0.9960,respectively.In addition,the sensor has good anti-interference.?2?Cu?tpa? MOF with certain electroactivity was synthesized by solvothermal method.In order to further enhance the conductivity and catalytic ability of the material,AuNPs were dispersed in the solution of Cu?tpa? MOF by simple ultrasonic dispersion method,and Au-Cu?tpa? composites were prepared.Cu?tpa? and Au-Cu?tpa? composites were characterized by particle-size,FT-IR,TEM,UV-Vis and electrochemical methods.Compared with single material modified glassy carbon electrode and bare glassy carbon electrode,the prepared composite material modified electrode has large specific surface area,good electrical conductivity and certain electrocatalytic ability,which can accelerate the electron transfer on the electrode surface.Pb²⁺ was detected by differential pulse anodic stripping voltammetry with high sensitivity and selectivity.In the detection range of 0.01?M-10?M,the oxidation peak current vs the concentration of Pb²⁺ showed good linear relationships,the detection limit was as low as 3.3 nM?S/N=3?.In addition,the sensor has good selectivity and good separation of oxidation peak potential for various heavy metal ion.So,Pb²⁺,Cu²⁺ and Hg²⁺ were detected simultaneously.The linear regression equations are obtained,the linear regression equations are Y??A?=1.3395X??M?+1.2879,R²=0.9966(Pb²⁺);Y??A?=1.11X??M?+0.9954,R²=0.9985(Cu²⁺);Y??A?=0.8307X??M?+1.0025,R²=0.9950(Hg²⁺)respectively.?3?So far,it is not common to prepare MOFs-based polymers by electropolymerization.Based on the characteristics of thionine?Th?such as good chemical stability and good electron transfer ability,the polythionine/metal-organic frameworks?PTh/Cu?tpa??was prepared by electropolymerization to combine MOFs with Th,which was used to detect 4-nitrophenol sensitively.The results showed that PTh/Cu?tpa?composite modified electrode had the good electrochemical response to 4-nitrophenol,this may be attributed to the large specific surface area of Cu?tpa?,and the existence of PTh increases the conductivity of Cu?tpa?.Therefore,the PTh/Cu?tpa? composite possesses the property of large specific surface area and good electronic conductivity.In addition,PTh also has a certain catalytic effect,so that the reduction peak potential of4-nitrophenol shifts to the positive.Under the optimal conditions,4-nitrophenol was detected by differential pulse voltammetry,the reduction peak current vs the concentration of 4-nitrophenol exhibits a linear relation with the concentration range from0.3?M-10?M,and the limit of detection was determined to be 7.1×10^-88 M.?4?Sulfonated polyaniline material was prepared,and a novel molybdenum disulfide/sulfonated polyaniline composite material?SAT-MoS₂? was prepared by combining with molybdenum disulfide.A 4-nitrophenol sensor was constructed for the highly sensitive detection of 4-nitrophenol.The analysis shows that?1?SAT is dispersed on the MoS₂ nano-sheets,which effectively prevents the stacking between the MoS₂ nano-sheets and increases the effective surface area of the electrode.?2?SAT has good conductivity and accelerates the electron transfer on the electrode surface;Based on the synergistic effect between SAT and MoS₂,the composite has good electrochemical properties.In addition,there is hydrogen bond and strong electrostatic binding between SAT and p-nitrophenol,which can adsorb more p-nitrophenol to the electrode surface and play the role of preconcentration.The optimum experimental system was determined by optimizing the experimental conditions.Using the reduction peak signal of 4-nitrophenol as the detection signal,the sensitivity detection of 4-nitrophenol can be achieved by differential pulse voltammetry.