Role Of Interface Concentration Field On The Growth Of Silver Particles

Sliver nanomaterials have shown potential applications in many fields including optics,electricity,catalysis and medical treatment.Owe to the strong dependence of silver morphology on the properties of particles,silver particles with different structures were synthesized by regulating reaction temperature,chemical concentration and other experimental parameters.However,the rational synthesis and scale up of silver particles remain a challenge due to the lack of the understanding on their growth process and the control mechanism.From the view of chemical engineering,the growth of materials is accompanied by the reaction and mass transfer process at the interface.In the previous studies of our group,silver particles with different morphologies were largely synthesized by controlling the reaction and mass transfer process,finding the role of the interface concentration field on the morphology evolution of silver particles.On the basis of previous studies,this paper further investigated the role of the interface concentration field on the growth process of silver particles by directly regulating the local concentration of silver ions.The main findings are as follows:(1)In the process of synthesizing silver particles through electrodeposition method,the in-situ experimental device was used to observe the growth of silver particles.By controlling the potential applied to the synthesis,silver oxides as by-products were produced in the solution.They migrated to the growth front of crystal,which is driven by the electric field.It was found that the mass transfer of silver ions was promoted with the increase of migration speed of colloid particles.The diffusion layer became thinner and the concentration gradient became sharper at the growth front of silver particles.The morphology of silver particles changed from spherical nanocrystals to aggregates,disordered branches and dendritic structures with the increase of migration speed of colloid particles.Among them,the growth rate of silver particles is positively correlated with the mass transfer of silver ions,which indicated that the formation of silver crystal is limited by the mass transfer.The role of interface concentration field on the evolution of silver particle morphology was confirmed by the Lattice Boltzmann simulation and the regulation mechanism was discussed.(2)To further discover the role of interface concentration on the growth of silver particles,the change of interface concentration was regulated in special directions,in which the growth direction of silver particles was expected to change with the interface concentration.The replacement reaction method was employed to generate silver rods.The in-situ experimental device was used to observe the growth process of silver rods in a real time.It was found that the silver rods grew from single direction growth at first to multiple directions as a result of the enhancement of the mass transfer.When there was an anisotropic distribution of silver ions,silver rods tended to grow to the rich sides of silver ions.Furthermore,silver cross was formed with the enhancement of silver ions diffusion at front of growth.