Surface Chemistry Of Non-spherical Nanoparticles Controls Their Assembly Behavior At The Interface

Self-assembly is a process in which multiple elements form specific structures through weak interactions,and it exists widely in nature and organisms.Whether it is molecular self-assembly or nano-self-assembly,it provides a basis for us to understand the interaction between microscopic substances,The superlattice structure assembled by inorganic nanoparticles coated with organic ligands through weak interaction can present potential synergistic effect of nanoparticles,and endow the assembly with unique collective behavior and function.Among them,non-spherical nanoparticles have different sizes in three dimensions,and nanoparticles have size effect,so the properties of non-spherical nanoparticles in different dimensions are quite different.The purpose of this paper is to explore the assembly of controllable synthesized non-spherical nanoparticles at the interface,which will promote the study of the behavior of non-spherical nanoparticles at the interface and help us to understand the assembly mechanism deeply.The research content mainly includes the following four parts:(1)The first part mainly includes the controllable synthesis of CdSe nanorods and CdSe quantum dots.CdSe quantum dots and nanorods have attracted wide interest of researchers because of their excellent optical properties.In the first part,we first synthesized quantum dots by thermal injection method,and found that their size is about 3 nm.Then,after referring to previous work,we synthesized CdSe nanorods(CdSe NRs).For the synthesis of CdSe NRs,we explored the reaction time,reaction ligand and the ratio of two precursors in the reaction,and obtained nanorods with a length ranging from?5 nm to??90nm and a diameter of?3 nm(except for changing the treatment method of reaction ligand).(2)Using the synthesized CdSe nanorods,the synthesized nanorods were pretreated firstly.We explored the spectral influence and stability of pretreatment,and characterized their optical properties,morphology and phase,which proved that their composition did not change after ligand exchange.Then,we chose to assemble CdSe nanorods on the oil-water interface under the condition of limited emulsion.By changing the aspect ratio of assembly unit,we got the qualitative relationship between aspect ratio and assembly effect.Then we explored adding some small molecules such as linear amines,carboxylic acids,alcohols and aliphatic hydrocarbons,and found that they have some special effects on assembly,and different molecules have different effects on assembly.For example,linear amine molecules can change the assembly effect by changing their chain length.Then,we explored the mechanism that adding small molecules affects the assembly mode,and proved that amphiphilic molecules play a special role in the assembly process.(3)In the third part,we explored the controllable synthesis of gold nanoparticles(Au NPs)and silver nanoparticles(Ag NPs),and the controllable adjustment of nanoparticle size can be realized by changing ligands or adding seeds for secondary growth.M(M=Au,Ag)-PbS heterostructure nanoparticles were synthesized by using it as seeds.For the synthesis of Au-PbS NPs,different morphologies of heterostructure nanoparticles were obtained by using seed growth method under the condition of changing the diameter and reaction time of gold nanoparticles previously synthesized.(4)On the basis of the previous topic,we proposed whether nanoparticles can be directly modified to make them hydrophilic and lipophilic at the same time,and then assembled on the interface.Therefore,we chose the gold-lead sulfide nano-heterostructure(Au-PbS NPs)because of the different affinity of these two components for some ligands.The nanoparticles were modified asymmetrically on the surface,which made them have hydrophilic-lipophilic functions similar to surfactants.We assembled the nanoparticles on the oil-water interface to form stable anti-fusion droplets.By adjusting the synthesis method,we changed the sizes of Au and PbS components of Au-PbS nanoparticles,and constructed droplets with nanoparticles with different size ratios,and deeply discussed the influence of nanoparticle component structure on the droplets.We find that in heterostructure,with the increase of one end size of Au,it will aggregate on the surface of droplets during the assembly process,forming a double-layer aggregate,which is not conducive to the stability of droplets.