Mechanism Study For The Interfacial Assembling Of Micro/nano Size Particles

Interfacial self-assembly of micro/nano size particles, especially oil-waterinterfacial self-assembly, has attracted considerable attention due to its highlycontrollable process, small disturbances, universality, simplicity, high efficiency andthe films assembled have excellent quality. In recent years, its investigation just wasconfined to experimental study. Au, Ag, Pt, SiO2, CoPt3nanoparticles,1Dnanostructures,2D nanoplatelets have been successfully self-assembled at theoil-water interface, forming closely-packed ordered nanofilms. However, they paylittle attention to the process and mechanism of the formation about the films at theinterface. Meanwhile, their researches hardly focus on the fabrication time, theconcentration of suspension in depth and systematically. Hence, this paper aimed atthe relationship of results and related factors in the assembling process, phasetransformation, the reason of generating point defect、line defect and planar defect tocarry out my research. The outcome may play a key role in achieving micro/nano sizeparticles large area ordered fabrication and constructing nanometre devices.The maincontent and results achieved in this paper are summarized as follows:1. The preparation of highly monodispersed micro/nano size particles. SiO2sphere,through modified stober method. Then we obtained core-shell SiO2@Ag compositematerials by a simple sol-gel method. The SiO2spheres have uniform size of300nm(standard deviation is about5%) and good monodispersity, which are suitable to befabricated. SiO2@Ag nanomaterials have good monodispersity with a uniform size of350nm. The Ag nanoparticles on the surface of SiO2have particle size range from10to50nm with crystalline state.2. The conditions and mechanism of fabricating micro/nano size particle atoil-water interface in the open condition. Monodispersed SiO2,SiO2@Ag, PSnanoparticles have been fabricated at oil-water interface in an appropriate glassculture dish. Different inducers ethanol and water also were used to find out thepossible effects for the results. The reason why the defects existed and the mechanism were discussed. We mainly considered several factors that affected the films such asthe fabrication time, the concentration of suspension. The results showed that weobtained large-area close-packed monolayer hexagonal SiO2、SiO2@Ag films whenthe fabrication time was30min. About50cm2ordered films were achieved using theethanol as inducer after fabricating1min while more ordered films were developedwith water as inducer. We found when the mass fraction of PS suspension is0.5%,the films show more excellent morphology with less line defect. As a result,monodispersed SiO2,PS nanoparticles are the ideal materials to assemble at theinterface, forming monolayer films. They also can be considered as templates toconstruct nanometre devices. As to the SiO2@Ag nanoparticles, it is not appropriateto got highly quality films because of the Ag nanoparticles on the surface of SiO2distributed not uniformly and symmetrically, leading to big vacancy and defects.3. The process and mechanism of fabricating micro/nano size particle at oil-waterinterface in the confined condition. Real-time observation and study on the wholeself-assembly process of PS spheres. As for the specific mechanism of the formationof PS monolayer film at toluene-water interface is investigated deeply from the pointof thermodynamics and kinetics.We mainly investigated that the concentration ofsuspension and different amounts of surfactant affected the quality of films obtained.The films fabricated firstly showed tetragonal or amorphous phase structure, thentetragonal and hexagonal mixed phase appeared when adding ethanol to the system,resulting in hexagonal closely packed phase in single layer film totally.We foundwhen the mass fraction of PS suspension is0.5%, the concentration of sodiumdodecyl benzene sulfonate is0.05mol/L, the films show more excellent morphology.