Construction Of Highly Sensitive Electrochemical Sensor Based On Transition Metal Organic Frameworks

Compared with traditional detection methods,electrochemical sensing technology has the advantages of simplicity,rapid response,low cost,and online real-time monitoring.It has excellent prospects for future social development.The response properties of the sensing material to the target molecule determine the performance of the electrochemical sensor.Current reports on sensor materials focus on carbon nanomaterials and precious metal nanomaterials,but carbon nanomaterials lack specificity,and precious metal nanomaterials are expensive.How to unify the two or seek alternative new nanomaterials has become the key to the continued development of the electrochemical sensing field.Metal-organic frameworks（MOFs）are formed by coordinating metal atom nodes and organic ligands with periodic structural units.They have a high specific surface area,adjustable pores,and good biocompatibility,widely used in energy storage and conversion,drug controlled release and other fields.However,MOFs have not been studied in depth in the field of electrochemical sensing.In this paper,a simple and effective synthesis process of nanomaterials is used to control the morphology structure or phase composition of MOFs and to study the influence of its structure and phase composition on electrochemical sensing performance.The main contents are as follows:（1）Construct a three-dimensional network of Ni-MOF@AgNWs for electrochemical glucose sensing.Combined with the analysis of the morphology and structure of Ni-MOF and Ni-MOF@AgNWs and the corresponding electrochemical sensing performance of glucose.It is found that the original Ni-MOF is in a disordered accumulation state,and only the surface active sites are exposed during the electrochemical sensing process.Moreover,hinder the diffusion and delivery of glucose molecules.Using AgNWs as the Ni-MOF growth framework,Ni-MOF grows tightly along the surface of AgNWs to form Ni-MOF@AgNWs with a three-dimensional network structure.This structure enhances the diffusion and transfer process of glucose molecules and electron transferability,which significantly exposes deep active sites.Finally,the linear detection range of Ni-MOF@AgNWs for glucose is 1-1000μM,the sensitivity is 32.3μAμM^-1,and the lowest detection limit（LOD）is 0.024μM.The prepared Co-MOF@AgNWs and Fe-MOF@AgNWs have greatly improved glucose electrochemical sensing performance compared with the original corresponding MOFs,which proves that the strategy of introducing conductive nanomaterials to control the morphology and structure of MOFs has universal.（2）Construct AuNPs/Co-MOF/MWCNT as nitrite electrochemical sensor.Improving the mass and current transfer capacity in the electrochemical sensing process is the key to improving the sensing performance.Therefore,Co-MOF/MWCNT with good mass transfer and electronic transmission capabilities were prepared by using the above-mentioned composite strategy.To reduce the working voltage in the electrochemical sensing process of nitrite,a large number of highly dispersed,small-sized（2-4 nm）AuNPs were deposited on Co-MOF/MWCNT by using Co-MOF to confine the growth of precious metal nanoparticles.Finally,the three-dimensional composite material composed of three low-dimensional materials has a nitrite electrochemical sensing sensitivity of 0.223μAμM^-1,a linear detection range of 1-1000μM,and a LOD of 0.4μM at a lower working voltage（0.72 V）.（3）The ZIF-67 derived carbon material was constructed for multiple heavy metal ions electrochemical sensor,and the influence of the morphology and phase composition obtained by different carbonization temperatures on the sensing performance was studied.After ZIF-67 is carbonized at 600 or 700°C,it maintains a specific morphology and structure,and its size decreases sharply as the temperature rises,and the phase composition is all Co₃O₄.When ZIF-67 is carbonized at 800°C,its appearance is severely collapsed,and the phase composition is elemental Co.After testing the sensing performance of Co₃O₄/C-600,Co₃O₄/C-700,and Co/C-800,it is found that as the carbonization temperature increases,the sensing performance decreases accordingly.Maintaining a specific morphology and size is conducive to the adsorption and reduction of heavy metal ions.Simultaneously,Co₃O₄ is conducive to the deposition and reduction of heavy metal ions and inhibits the hydrogen evolution reaction,while elemental Co is the opposite.Under the optimal test conditions,the linear detection range of Co₃O₄/C-600 for Cd²⁺,Pb²⁺,and Cu²⁺is 0.1-1.5μM,the sensitivity of Cd²⁺is 33.68μAμM^-1,the LOD is 0.01μM;the sensitivity of Pb²⁺is 457.332μAμM^-1,LOD is 0.002μM;Cu²⁺has a sensitivity of 169.42μAμM^-1,and LOD is 0.004μM.