Synthesis And Self-assembly Of Gold、Silver Nanoparticles

Metal nanoparticles have attracted intensive attentions by the scientists due to their unique properties different from the body materials,and have potential applications in many fields such as catalysis,biological medicine,storage devices and sensors.Besides the size,the properties of metal nanoparticles is related to their morphology.To research the synthesis of monodisperse noble metal nanoparticles can not only help us understand their properties better,also be the fundation of noble metal nanoparticles self-assembly which will further service in constructing nano-devices.In this thesis,we utilize a single step single phase method and hot injection method to synthesize monodisperse gold,silver nanoparticles respectively.At the same time,the self-assembly of both individual gold 、 silver nanoparticles and binary nanoparticles through interfacial self-assembly method and solvent-evaporation induced method has been attempted.Some instruments such as ultraviolet-visible spectrophotometer(UV-Vis)and transmission electron microscopy(TEM)have been used to characterize the products,and discuss the influence factors in the synthesis and self-assembly process.The main research contents are as follows.Monodisperse Au nanoparticles with a size of 6 nm and 4.5 nm can be obtained by the reaction involving chlorotriphenylphosphine gold(Ⅰ),tert-butylamine borane complex and 1-dodecanethiol served as coating agent at 100℃ for 5 minutes.1-dodecanethiol can play a key role in making gold nanoparticles have regular shape.The size of gold nanoparticles decreases with the increase in the amount of 1-dodecanethiol.Using different solvents dispersing gold nanoparticles,UV-Vis indicated that the same size of gold nanoparticles,the movement of the SPR is related to the type of solvents.We use a single oil phase to synthesize gold nanoparticles with regular morphology,uniform size and deviation less than 7%.The dispersion and stability of gold nanoparticles prepared by single oil phase is better than the water phase.Only the gold nanoparticles with regular morphology and uniform size can be able to realize a long range order,close-packed structure,and uniform film with a single-layer nanoparticles thickness.Monodisperse silver nanoparticles with a size of 4.5 nm can be obtained by the reaction involving silver nitrate,1,2-dodecanediol and coating agents such as oleylamine and 1-dodecanethiol at 180℃ for 3 minutes.A small amount of dodecanthiol(20 μL of dodecanethiol per 10 mg of silver nanoparticles)is added to the suspension of silver nanoparticles coated with oleylamine,and the mixture is kept under vigorous stirring for 1 h.Thus,silver nanoparticles coated with dodecanethiol can be obtained.With the different coating agents,the size deviation of silver nanoparticles is too little to making size selection.Meanwhile,from the relationship between optical properties and the type of solvents,we knew that the movement of SPR was influenced by the kind of coating agents and solvents.Interfacial self-assembly method and solvent-evaporation induced method have been used to realize the transferable single-layer membranes of gold and silver nanoparticles,i.e.,2D ordered nanoparticle superlattice.At the same time,The Au/Ag binary nanoparticles have been grown successfully.To grow single-layer membranes,we spread a drop of hexane or toluene solution containing gold or silver nanoparticles with selected concertrations over the surface of subphase in a Teflon well.The well was covered with a glass slide and hexane or toluene was allowed to evaporate over 15-30 minutes,resulting in a solid film supported on the subphase surface.In this way,centimeter-scale single-layer film can be readily transferred to the substrate.Replaced toluene with hexane,the self-assembly process can be finished in 15-30 minutes.