Synthesis, Characterization And Growth Mechanism Of Novel Nanomaterials In Emulsion System

With the development of high-tech and the requirement of practical application,the design and preparation of functional nanomaterials with novel structures and the invention of diverse synthesis methods are becoming more and more important.Recently,various synthesis routes have been extensively used to prepare different nanomaterials,and the corresponding characterization technologies for structure and property have been improved.Moreover,the growth mechanism of nanomaterials has been proposed preliminarily.To some extent,the theoretic and technical bases have been found to the practical application.At the same time,the more controllable method and the detailed explanation of growth mechanism are needed urgently.Regarding the requirements mentioned above,the synthesis of novel nanomaterials was investigated,and the fundamental growth mechanism was explored through the controllable synthesis of different nanomaterials and nanostructures in emulsion system. The main works of this paper were as followed: 1,Microemulsion method,a biomimetic mineralization route,was used to investigate the scientific issues from biomineralization process,so these issues could be solved by the basic theories and the analytic technologies in chemistry.As a result,the biomineralization mechanism could be understood more clearly.A series of rare earth carbonate and phosphate nanostructures were synthesized and the influences of experimental conditions on the growth of the products were investigated.Combined with the classical crystal theory and the interface effect between crystal and surfactant,the growth mechanism of nanomaterials in microemulsion system was proposed.With the increase in the atomic number and the decrease in the ionic radii of rare earth elements,the morphologies of the corresponding carbonates changed from simple one-dimensional structures to complex fan-like superstructures,and then to ellipse-like mesocrystals. The morphology evolvement indicated a change of the interactions between rare earth ion and the template molecule as well as possible conformational effects on the long chain template molecules.The intensive interaction of the interface between crystal and surfactant led to the similar morphologies of rear earth phosphates.In addition,the crystallization process could also be influenced by the degree of supersaturation.2,Taking advantage of the merits of microemulsion method(including mild reaction conditions and more control parameters),different nanostructured materials of rare earth compounds were synthesized.The lanthanide-doped nanofibers had a mean diameter of 5 nm and a narrow size distribution.The dopant of europium resulted in the distortion of the crystal lattice,which led the fluorescence properties of the ultrafine LaPO₄:Eu nanofibers were different from that of the large diameter ones. The quantum yield of terbium-doped nanofibers was relative high.In addition,different mesoporous ceria nanostructures were successfully synthesized by the microemulsion method.The experiment measurements showed that both the SBET and the Vp of the ceria nanobelts were higher than those of the nanowires.Because of the size effect,the blue-shifting of the absorption band was observed in UV-Vis spectra.The formation mechanism of cefia mesoporous structure was also proposed.Maybe,the precursors had the similar composition and structure characters with the biomineralization products.The organic surfactant molecule,existing in the precursor,resulted in the formation of mesoporous structure.In addition, LaCoO₃ nanoparticles were synthesized and the relationship between experimental condition and structure was studied.Using sunlight as irradiator,the photocatalytic activity of LaCoO₃ was investigated.3,Based on the controllable synthesis of different nanomaterials and the relative perfect crystallization mechanism of the usual emulsion method, high temperature emulsion system was used for the preparation of novel nanomaterials and nanostructures.Maybe,the high temperature emulsion system has the merits both from usual emulsion and hydrothermal method, including more control parameters,narrow size distribution of the products, quick crystallization rate and so on.Moreover,the synergy effect of the two methods maybe appears.Cu₂O nanoplate array and CeO₂ nanofilm were in-situ synthesized and the formation mechanism was investigated in the high temperature emulsion system.Under the similar condition, ellipsoid-like CEO(CO₃)₂ nanomaterials were prepared.Using CEO(CO₃)₂ as support,a quite good catalysis was realized in the desulfur of diesel. Through the change of different surfactants,nanoclusters of CeO₂ were prepared,and the relationship between the Raman scatter property and the special structure was investigated.In addition,a new general method was invented for the preparation of hollow microsphere,and a series of different microspheres were synthesized.