Preparation Of Ceria And Its Composite Nanoparticles By Using Block Copolymers As Templates

Ceria(CeO2) as a kind of rare earth elements to form oxides have many unique characteristics. Cerium mainly exists in two valence states, namely the Ce3+and Ce4+. In actual research, the cerium can shift between Ce3+and Ce4+and able to block the surface space,which provides a convenient way the vacancies for the oxygen transfer on the surface of the ceria. So the cerium oxide can be used as oxygen donor and favor in a large number of applications, such as: solid fuel cell, catalysts, biological medicine, etc. Block copolymer micelles as a new nanoreactor, due to its adjustment to the morphology and size of nanoparticles, so caused the very widespread attention. This thesis mainly studies the use of block copolymer template to fabricate cerium oxide and its composite nanoparticles. Using poly(styrene)- b- poly(2- vinyl pyridine)(SVP) micelles as the template, by hydrazine reduction-oxidation, ultraviolet irradiation, calcination method for the preparation of CeO2 nanoparticles and the Au/CeO2 composite nanoparticles.(1) Using the SVP micelles as the template, by hydrazine reduction and oxidation of the fabrication of CeO2 nanoparticles. Experiment with hydrazine reduction-oxidation to transform cerium nitrate precursor into ceria nanoparticles. This approach yields ultrasmall nanoparticles or spherical aggregates of CeO2 by simply changing the solubility of the solvents. The CeO2 nanoparticles are stable in organic solvents. The resultant CeO2 colloidal nanoparticles can self-assembly into porous nanostructures after removal block copolymers,which endow the catalyst with greatly enhanced photocatalytic activity. The CeO2 nanoparticles and their assembly are expected to have potential applications in the areas of photocatalysis, hybrid inorganic-organic nanocomposite and others.(2) By ultraviolet irradiation to fabricate CeO2 and the Au/CeO2 nanoparticles. Using block copolymer SVP micelles in selective solvent formed by self-assembly as the template.Chloroauric acid and cerium nitrate can complex into the micelles. After UV irradiation, the cerium nitrate is reduced. Under the action of oxygen in the air, the reduced ceria become cerium oxide. Particle size of spherical CeO2 nanoparticles was about 25 nm. At the same time,examines the influence of nanoparticles’ morphology and size by DMF’s content. The XRD is used to analyse the composition of CeO2 nanoparticles. Then introduce chloroauric acid intothe system. Through UV irradiation synthesis the Au/CeO2 composite nanoparticles with the dumbbell structure.(3) Experiments using SVP micelles formed by self-assembly as the template. After the cerium nitrate and chloroauric acid complexing into the micelles, cerium nitrate transform into cerium hydroxide by ammonia fume. After high temperature calcinations, the cerium hydroxide and chloroauric acid transform into cerium oxide and gold. By then, XRD characterization confirms that the Au@CeO2 nanoparticles with core-shell structure is obtained. The appropriate calcination condition to prepare Au@CeO2 nanoparticles with core-shell structure, is 2h under 400℃.