Self-assembly Of Nanoparticles Induced By Light,Magnetic Field And Poor Solvent

With the development of nanotechnology,the design and modification of nanoparticles have attracted wide attention.Under the combined action of thermodynamics and kinetics,nanoparticles can spontaneously assemble into ordered structures,and then develop materials with brand-new functions and properties.The self-assembly process is influenced by solvent type,temperature,emulsifying time and surfactant.Therefore,in order to effectively enlarge the self-assemblyrocess and apply it to industry,it is necessary to analyze the self-assembly process to achieve accurate control.In this paper,the effects of light,magnetic field and bad solvent on the assembly of nanoparticles were studied.1.Self-assembly of azobenzene functionalized nanoparticles under light control.First,we successfully synthesized the ligand molecule AZO with azobenzene and catechol and isotropic spherical Fe3O4 nanoparticles.Trans-azobenzene will be isomerized to cis-azobenzene under ultraviolet light irradiation,while cis-azobenzene will be isomerized to trans-azobenzene under visible light irradiation.Azo molecules were modified on the surface of Fe3O4 nanoparticles by ligand exchange,which endows the nanoparticles with photoresponsibility;Photoresponsive Fe3O4 nanoparticles will aggregate due to the dipole-dipole interaction between cis-azobenzenes under the irradiation of ultraviolet light,and the aggregated nanoparticles will depolymerize under the irradiation of visible light.Finally,the photoresponse of Fe3O4 was characterized by TEM,UV-Vis and DLS.2.Light and magnetic fields induced azobenzene functionalized nanoparticles to self-assemble into emulsion.At first,we took advantage of the difference in polarity between cis-azobenzene and trans-azobenzene,and added a small amount of polar solvent N,N-dimethylformamide(DMF)to the system to study Fe3O4 nanoparticles the process by which aggregates assemble into an emulsion during depolymerization.Then,rhodamine 6g was added into the system,which confirmed that the emulsion was filled with DMF inside and toluene solution outside.Then,the influence of the ratio of ligand and polar solvent on the surface of the nanoparticles on the formation of droplets was explored;during the formation of the droplets,an external magnetic field was applied to explore the changes in the morphology of the droplets under the action of the magnetic field;finally,we used TEM,UV-Vis,DLS,etc.to characterize the dynamic process of droplet formation.3.Selective self-assembly of Au-Fe3O4 binary nanoparticles induced by light and poor solvent.First,we synthesized a photoresponsive azobenzene ligand with a mercapto group as the end group;Au-Fe3O4 particles with different particle size ratios can be synthesized by changing the amount of Au nanoparticles,iron acetylacetonate,oleic acid,oleylamine,etc.Then,the Au nanoparticles in the Au-Fe3O4 particles were modified by ligand exchange;the Au-Fe3O4 particles after the ligand exchange would aggregate under ultraviolet light,and at this time,it was the aggregation between gold nanoparticles.Finally,we used the hydrosilation reaction of 4-methoxybenzaldehyde and dimethylphenylsilane as a model to explore the effect of the aggregation of Au nanoparticles on the reaction efficiency under light.4.Poor solvent-induced assembly of CdSe nanoplateletsIn this chapter,we chose sheet-like nanoparticles as the research object.First,we synthesized uniform CdSe nanoplatelets which were easy to aggregate and synthesized sulfhydryl polystyrene molecules with different molecular weights through anionic polymerization.Then,sulfhydryl polystyrene molecules with different chain lengths were modified to the surface of CdSe nanoplatelets by means of ligand exchange,the CdSe nanoplatelets after ligand exchange were relatively stable.Finally,we assembled the ligand-exchanged CdSe nanoplatelets by adding a poor solvent,and explored that when the molecular weight,the type and concentration of the poor solvent were changed,a spherical,long-chain,and fibrous assembly morphologies can be obtained.