Preparation Of Oxide Nanoparticles By Insoluble Carboxyl-containing Grafted Starch

Because of its many particular properties in optics , electricity, magnetism,heat, catalysis , mechanics, chemical activity etc, and its great potential high technology applied prospects, nanoparticle has become one of the quite hot problems in material research fields, it gains much attention of the scientists from all the world. Various methods have been used for the preparation of nanoparticles, however some intriguing questions remain unanswered even now. It is still a challenging research area to prepare novel functional nanostructured materials with interesting and useful properties, so it is even important to explore new methods for synthesis of nanomaterials with controllable size and shape and to understand the mechanism and rule of the growth process of nanomaterials for further application. In this work, we developed an easy, inexpensive method to synthesize a fine and homogeneous metal oxide nanoparticles.This thesis consists of four sections as follows:First, some methods for synthesis of grafted starch were introduced in this paper, and the reaction mechanism was also described. The influence of initiator concentration, monomer concentration, reaction temperature, and reaction time on grafting parameters of starch graft copolymers was discussed. Finally, by using Ce⁴⁺ as initiator we investigated graft emulsion copolymerization of acrylonitrile onto starch. The structure of the grafted starch was investigated with FTIR.Perovskite type complex oxide LaMnCh are promising ceramic materials used as electrode materials in solid-oxide fuel cell or as the catalysts. But they usually possess low specific surface areas, generally<10m² ? g-1, so the potential application of these materials as catalysts are limited. In order to increase the specific surface areas, the best way is to prepare nanometer-scale powders. A new method was used to prepare well-separated and spherical LaMnO3 nanosized particles. The overall process involves three steps: preparation of insoluble carboxyl-containing grafted starch copolymer (ISC); formation of presursor (ISC-M); decomposition of ISC-M, and phase transition of LaMnO₃ nano-particles. Infrared spectra for ISC and ISC-M were discussed. The decomposition of the precursor was studied by DTA-TG. The crystalline phase was characterized by XRD. The size distribution and shape of particles were observed by TEM. The average particle size is less than 20 nm. Furthermore, this processcould be carried out at low temperature (about 600 ℃) and further investigation showed that LaMnO3.15 exhibited evidently catalytic activity for oxidation of cinnamaldehyde at moderate temperatures.Zinc oxide (ZnO) is a versatile semiconductor material with hexagonal wurtzite structure and has a band gap of 3.3 eV and a large excition binding energy of 60 meV at room temperature. It has attracted much attention like GaN due to the application of UV emission. In the past, the structure and optical properties of ZnO film has been investigated extensively. In this dissertation, insoluble carboxyl-containing grafted starch copolymer (ISC) was used to prepare ZnO nanoparticles. The crystal type, morphology and particle size, the distribution of particle size and purity of product was characterized by XRD, FTIR, DTA-TG, TEM. The results showed that spherical, well-separated nanoparticles with the narrow distribution could be obtained by this method.Insoluble carboxyl-containing grafted starch copolymer (ISC) was used to prepare NiO, CO₃O₄ nanoparticles. Their crystal type, morphology and particle size, the distribution of particle size and purity of product was characterized by XRD, FTIR, DTA-TG, TEM.