Controlled Synthesis Of Au@Ag Composite Nanoparticles,Their Formation Mechanism And Optical Absorption Property

Au,Ag nanomaterials have been one of the most important fields and focuses of nanomaterials due to their unique physical,chemical properties,and important applications in sensor devices,catalysis,optoelectronic devices,and biomedicine ctc...With the development of society,single-component nanomaterials has been unable to meet people's needs,composite nanomaterials emerged.The optical absorption properties and conductivity of Ag nanoparticles are very excellent,but the stability of Ag nanoparticles is very poor,compared with this,the stability and dispersibility of Au nanoparticles are good,so in order to combine the advantages of both,the preparation of Au@Ag Nanoparticles aroused great interest,Among the Au@Ag composite nanoparticles,the optical absorption properties of Au@Ag nano-composite rods are most prominent,therefore,controlled synthesis of the Au@Ag nano-composite rods is significant to uncover their properties and achieve their practical applications.For the problems existing in the preparation of Au@Ag composite nanorods,we can synthesize Au@Ag heterogeneous nanorods with good morphology and high purity using seed growth method,what's more,we can control the length,diameter and structure of the Au@Ag heterogeneous nanorods by adjusting appropriate parameters.The main work and achivevments are summarized as follows:1 We synthesize Au decahedron with edge length of 30 nm using polyol reduction method,and synthesize Au nanorods with ratio of 8.4(length 110 nm,diameter 13 nm),and then characterize their optical absorption properties.These Au nanoparticles are purposed to provide seed(precursor)for further preparation of Au@Ag nano-composite nanoparticles.2 We synthesize Au@Ag heterogeneous nanorods with good morphology and high purity rapidly using Au decahedron as seed,what's more,we can control the length,diameter and structure of the Au@Ag heterogeneous nanorods by adjusting appropriate parameters.The results show that the reduction rate plays a very important role of the growth of Ag atoms on the Au decahedron,the reduction rate is determined by the ascorbic acid and klkaline of the system,when the reduction rate is low,Au decahedron locate at one end of the Au@Ag heterogeneous nanorods,and Au decahedron will move towards the center of the Au@Ag heterogeneous nanorods with promotion of the the reduction rate,In these two phases,the diameter of the Au@Ag heterogeneous nanorods is determined by the size of the Au decahedron,and then the diameter of the Au@Ag heterogeneous nanorods becomes thick with promotion of the the reduction rate,when the reduction rate is too fast,Ag atoms nucleates themselves.3 We synthesize Au@Ag core-shell nanorods using Au nanorods as seed,by controlling the reduction rate of the reaction system,we achieved the anisotropic growth of Ag atoms on Au nanorods.