| In electroanalytical chemistry,electrochemical sensors as the"core"have become the focus of research for electrochemists.Compared with the traditional liquid-filled ion-selective electrodes,screen-printed electrodes(SPEs),are favored by electrochemists because they of their relatively simple fabrication,low cost,faster detection speed,more convenient use,and easy commercialization.The solid contact electrode is developed on the basis of liquid contact electrode,which improves the problem of high detection limit of liquid contact electrode and greatly reduces the detection limit of the test.One of the solid contact electrodes is screen-printed electrode,which is a multi-electrode system and is more convenient and cheaper to operate than the commonly used single-electrode solid electrode.In the past,solid electrodes and liquid film electrodes used in electrochemical experiments can only be used as working electrodes alone,and must be connected to reference electrodes for normal testing,which obviously increases the difficulty and difficulty of operation.The screen-printed electrode of two-electrode system has changed the problem of inconvenient operation and the need of external reference electrode for the traditional electrode single-electrode system,which undoubtedly promotes the application of solid electrode in environmental testing.In this thesis,the sensitivity,stability and response performance of dipolar screen-printed electrode potentiometric sensors are improved,and the main research explores the dipolar screen-printed electrode potentiometric sensors based on single-walled carbon nanotube materials,and the dipolar screen-printed electrode potentiometric sensors with silver powder modified as the conduction layer.(1)Preparation of the conduction layer of screen-printed electrodes using a mixture of single-walled carbon nanotubes and epoxy resin conductive adhesive.In the current situation,screen-printed electrodes(SPEs)based on nanomaterials are gradually being used in daily work and life in the environmental and biological fields.However,in the actual detection and application,these electrodes also reveal many problems affecting the detection performance,the more obvious problem is that the poor adhesion of nanomaterials due to their own characteristics leads to the poor adhesion of nanomaterials when involved in the preparation of the conductive layer,the conductive layer is easy to separate from the electrode and affect the use.Therefore,the adhesion of the solid contact layer for screen-printed electrodes was optimized by combining the characteristics of epoxy conductive adhesive(CA)and screen-printed electrodes.In this experiment,an epoxy resin conductive adhesive(CA)with adhesion and conductivity was used as the binder for the solid contact layer,and single-walled carbon nanotubes(SWCNT),a nanomaterial,was selected as the base material for the conduction layer,and a method for fabricating screen-printed electrodes(SPEs)with improved disadvantages of nanomaterials was constructed based on lead ion-selective electrodes.The linear response range of the constructed electrode based on CA-SWCNT as the solid contact layer is 1.0×10-7?1.0×10-3M,and the detection limit is 1.9×10-7 M.Through experiments and data analysis,we found that the electrochemical properties of the constructed screen-printed electrode based on the mixture of epoxy resin conductive adhesive and single-walled carbon nanotubes as the conductive layer are different from those of the constructed electrode in terms of resistivity,electrode response stability and capacitance.In terms of resistivity,response stability and capacitance,we found that the screen-printed electrode with a mixture of epoxy resin and single-walled carbon nanotubes as the conductive layer and the screen-printed electrode without the addition of epoxy resin did not show significant differences in these aspects.We also found that the electrode with the epoxy resin conductive gel added did not show a more obvious water layer with a more stable potential response.In summary,the addition of epoxy resin conductive adhesive in the conduction layer can effectively improve the performance of the electrode.(2)The use of modified silver powder and epoxy resin conductive glue mixed conductive layer to build screen printing electrode.As a functional powder material with some special physical and chemical properties,silver powder has a wide range of applications in chemical applications,biomedical,environmental,energy,and electronic technology,etc.,and is receiving more and more attention in scientific research.Along with the rapid development of electronic technology and photovoltaic industry,the requirements and demand for silver powder are also getting higher and higher.The traditional conductive silver powder is mainly in the form of flakes and spheres,which has the problem of unsatisfactory resistivity and loose packing density.In this paper,the performance of the existing conductive silver powder is optimized by modifying it to have better electrical conductivity,which can be better used in screen printing electrodes.Combining the excellent properties of the modified silver powder with the aim of improving the sensitivity,stability and response performance of the screen-printed electrode potentiometric sensors,a high stability screen-printed electrode potentiometric sensor based on the new conductive silver powder material is investigated using conductive adhesive(CA)as the binder of the solid contact layer and the new conductive silver powder as the solid contact layer.The linear range of the screen-printed electrode based on the new conductive silver powder material is 1.0×10-7?1.0×10-3M,and the detection limit is 2.2×10-7M.The screen-printed electrode constructed with this conductive layer performs better in all aspects based on the excellent performance of the matrix material,and exhibits better hydrophobicity than the conductive layer prepared from a single material.This research system provides a new solid conduction layer and lays the foundation for further research on screen-printed electrodes. |
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