The Study Of Synthesis,Assembly And Properties Of Monodisperse Gold Nanoparticles

Compared with bulk materials,nanomaterials have many special properties that are closely related to their sizes and shapes.In recent years,people have been working to explore the relationship between them.During the experiment,there are many unexpected by-products.In order to explore the relationship between properties and morphology better,it is necessary to minimize the appearance of by-products and improve the monodispersity of the products.At present,there are two main types of methods.One is to make better the synthetic methods,and the other one is to post-treat the products.In this paper,we prepared gold nanoparticles using chemical liquid-phase method,and then purified the primary products through post-treatment to improve the monodispersity of the products,and explored the relationship between the properties and the sizes/shapes of gold nanoparticles.The products were characterized by transmission electron microscopy,scanning electron microscopy,X-ray powder diffraction,UV-Vis absorption spectroscopy,and Raman scattering spectroscopy.For characterization,the morphology,size,crystallinity,and optical properties of the gold nanoparticles were obtained.The research content of this paper mainly includes the following aspects:(1)In cyclohexane,a mixture of gold nanoparticles(Au NPs)and gold nanowires(Au NWs)was obtained by reducing chloroauric acid with oleylamine.They were separated by centrifugation and characterized by different analytical methods.The results showed that Au NPs and Au NWs can be effectively separated by centrifugation.And the surface-enhanced Raman scattering effect(SERS)of Au NWs is better than that of Au NPs.(2)In the solution of dodecyldimethylammonium bromide(DDAB)in toluene,the mixture of gold nanoplates(Au NPTs)and Au NPs were synthesized by reducing chloroauric acid with borane-tert-butylamine.They were then separated by density gradient centrifugation and their morphology and structure were characterized.The experimental results showed that Au NPTs and Au NPs can be effectively separated by the density gradient centrifugation,and pure single components can be obtained.In addition,Au NPTs exhibit stronger SERS abilityrelative to that of Au NPs.(3)The synthesis of small gold seeds was performed by reducing triphenylphosphine chloride with a borane-tert-butylamine complex in toluene.And then a series of Au NPs with different sizes were obtained by seed growth method.In addition,it was found that the SERS intensity increases with increasing particle size.Finally,the different types of superlattice structures were obtained by self-assembling nanoparticles: single-component gold nanoparticles can be assembled into layered films and three-dimensional spherical aggregates,while the two components of different sizes can self-assemble to form binary superlattice structure.