The Controllable Preparation And Properties Of Silver Nanoparticles

The reaction rate and diffusion rate are two important factors that affect the morphology of nanomaterials.In this paper,silver nanomaterials were selected as the target material,silver nanoparticles with different morphology were prepared at different diffusion rates,and the conductive properties of the prepared silver nanowires were investigated.At the same time,dendritic,flower-like and spherical silver nanoparticles were obtained at different reaction rates and the catalytic properties of these three kinds of particles were investigated.The study obtained the following main conclusions:The electrolytic deposition reaction was carried out by using 6 mM silver nitrate solution as the reaction solution,and the diffusion rate was adjusted by changing the volume fraction of glycerin in the solution.When the the volume fraction of glycerin in the solution is 80%,the resulting products are silver nanowires having a diameter of about 90 nm.The silver nanowires were transferred to the Mixed Cellulose Ester substrate by vacuum filtration to form a conductive film,and then the film was subjected to an acetone fumigation treatment to strengthen the adhesion between the silver wire and the substrate.In the following,the film was chemically “welded” to enhance the connection between the silver wires and to reduce the resistance of the entire silver film.The sheet resistance of the composite film was regulated by adjusting the density of the nanosilver wires.Finally,a conductive film with a sheet resistance of only 2.746 ?/sq was obtained,and the sample had excellent flexibility.After 1000 bending tests,the conductivity of the film remained unchanged.In the bending angle test,when the bending angle reached 90°,the sheet resistance remained stable.The film obtained also had a very high stability,and the electrical conductivity of the film remained stable at 210 °C for 210 days.The redox reaction was performed in the mixture of 5 mM silver nitrate solution and 10 mM hydroxylamine solution,and the reaction rate was adjusted by changing the amount of the complexing agent glycine added.With the increase of added glycine,the reaction rate gradually slowed down,and dendritic,flower-like and spherical silver nanoparticles were obtained.Through the structural characterization of the three types of silver nanoparticles,the relationship between the exposure ratio of the(111)facets of the three nanoparticles was found to be: dendritic silver?flower-like silver?spherical silver.In the industrial reaction of epoxidation of ethylene to ethylene oxide,the active component of the catalyst used is mainly silver.The prepared silver particles with different morphologies were added into the silver slurry to prepare the industrial EO silver catalyst.In the process of catalyst evaluation,when the catalyst was activated,the nanosilver particles existed in the form of agglomerates on the outer surface of the catalyst.As the reaction progressed,the nano-silver crystals on the surface were melted and then adhered to each other to form silver clusters.In the cross section of the catalyst,as the reaction progressed,the initial spherical particles diffused at a high temperature and combined with each other to form spherical particles of a larger diameter.When the additive of cesium was added,the catalyst with dendritic silver nanoparticles had the highest EO selectivity.On the other hand,the catalyst with spherical silver nanoparticles had the lowest EO selectivity because it had the lowest(111)crystal surface exposure ratio.The stability and selectivity of the silver catalyst containing silver dendrites are better than others which indicates that dendritic silver particle has a great application potential in the industry.