New Synthesis And Purification Technology Of Silver Nanowires

Silver Nanowires（hereafter called AgNWs）are one-dimensional nanomaterials restricted to less than 200 nm laterally.They have attracted extensive attention due to their excellent properties in optoelectronics and mechanics.Compared with traditional indium tin oxide（ITO）transparent conductive materials,AgNWs networks perform better in optoelectronics,mechanical properties and stability.The application of AgNWs depends on its size effect.Ultra-fine AgNWs has excellent light transmittance and electrical conductivity,and is suitable for the manufacture of display,touch screen and other devices.Relatively large diameter AgNWs have more outstanding electric heating response and high temperature resistance,and are widely used in electric heaters,chemical sensing and biological sterilization.The preparation cost of AgNWs is relatively high.When the macro quantitative preparation of AgNWs is realized,the preparation cost of AgNWs gradually decreases and enters the commercialization stage.Whether it is flexible electrode,touch screen or electric heater parts,AgNWs account for a relatively high cost in the device.This paper aims to reduce the application cost of AgNWs in flexible devices through the preparation and purification of AgNWs.The main research contents are as follows:Chapter 1 Preparation of AgNWs with urea as control agent and reducing agentUsing urea instead of halogen as control agent and reducing agent,the molar ratio of PVP,urea and AgNO₃ was optimized,the reaction time,the injection rate of AgNO₃,the molecular weight of PVP were adjusted,the reaction steps were optimized,the amount of ethylene glycol organic reactants was reduced,and the synthesis time was shortened.The average diameter of synthetic AgNWs was 84 nm and the average length was 40μm.The optimized AgNWs were characterized by TEM,XRD and UV-Vis,and the possible mechanism of the synthesis of AgNWs with urea as control agent was briefly explained.Chapter 2 Study on the purification process of AgNWsFor the main impurity silver nanoparticles（AgNPs）and silver nanorods（AgNRs）that appeared in the synthesis of AgNWs,we purified AgNWs by centrifugation,extraction and filtration,and co-dissolution.Most of the AgNPs and AgNRs smaller than 40nm were removed by centrifugation at 4000 rpm for 20 min.When the diameter of metal filter is 30μm,three layers of filter are superimposed to remove AgNRs in the range of 5-15μm,and the uniformity of the length of AgNWs is improved.The concentration of sodium borohydride and formamide was optimized,which played a good role in the removal of PVP on the surface of AgNWs.The combination of these three methods provides a new idea for the purification of AgNWs.Chapter 3 Preparation and performance study of AgNWs electric heater conductive filmBy adjusting the viscosity and uniformity of the prepared and purified AgNWs inks,we prepared the transparent conductive film of AgNWs through the spin coating method,and explored the changes of the light transmittance and square resistance of the film under different concentrations of AgNWs inks,which laid a foundation for the preparation of the electric heater in the next step.