利用嵌段共聚物为模板制备氧化铈及其复合纳米粒子
发布时间：2018-10-13 10:23
【摘要】：二氧化铈(CeO2)作为一种稀土元素形成的氧化物具有许多独特的特点。铈主要以两种价态存在,即Ce3+和Ce4。在实际研究中,由于铈能够在Ce3+和Ce4之间转变而能够在固体表面形成空位,这些空位为氧在二氧化铈表面传递提供了便利的途径。所以氧化铈可以作为氧的供体而在大量实际应用中受到人们的青睐,例如:固体燃料电池、催化剂、生化药物等。嵌段共聚物胶束作为一种新型的纳米反应器,具有能够控制纳米粒子的形貌和尺寸的优点而引起广泛关注。本论文主要研究了利用嵌段共聚物为模板制备氧化铈及其复合纳米粒子。利用聚苯乙烯-b-聚(2-乙烯吡啶)(PS-b-P2VP)胶束为模板,通过肼还原与氧化、紫外辐照、煅烧等方法来制备CeO2纳米粒子和Au/CeO2复合纳米粒子,并对产物进行了表征以及光催化性能研究。(1)利用PS-b-P2VP胶束为模板,通过肼还原-氧化法制备出CeO2纳米粒子。将PS-b-P2VP/硝酸铈复合胶束与肼反应,将铈离子还原成单质铈,经进一步氧化生成二氧化铈纳米粒子。实验合成出的CeO2纳米粒子能够在有机溶剂中稳定存在。通过简单改变溶剂的溶解性可以制备出单分散的CeO2纳米粒子或尺寸较大的球形CeO2聚集体。将嵌段共聚物除去后,实验制得的CeO2胶体粒子能够自组装为多孔的纳米结构,这种结构能够大幅提升样品的催化性能。实验制得的CeO2纳米粒子在光催化、有机—无机复合纳米材料等领域有潜在的应用价值。(2)通过紫外辐照法制备出CeO2及Au/CeO2纳米粒子。利用PS-b-P2VP形成的胶束为模板,将硝酸铈通过络合作用引入到胶束之中。利用紫外光辐照将硝酸铈中的铈离子还原单质铈。在空气中氧气的作用下,将还原后的铈氧化为二氧化铈,得到粒径约为25 nm的球形CeO2纳米粒子。同时,考察了体系中二甲基甲酰胺含量对纳米粒子形貌和尺寸的影响。在此基础上,将氯金酸引入体系,通过紫外辐照法合成出具有哑铃型结构的Au/CeO2复合纳米粒子。(3)利用PS-b-P2VP自组装形成的胶束为模板,将硝酸铈和氯金酸络合进入胶束后,通过氨水蒸气将硝酸铈转变为氢氧化亚铈,经高温煅烧后将氢氧化亚铈和氯金酸转变为氧化铈和金。通过透射电镜、XRD等表征手段证明实验制得了核壳结构的Au@CeO2纳米粒子。通过对比试验得到制备核壳结构Au@CeO2的最佳煅烧条件,即400℃下2h。
[Abstract]:Cerium oxide (CeO2) as an oxide formed by rare earth elements has many unique characteristics. Cerium mainly exists in two valence states, Ce3 and Ce4.. In the practical study, because cerium can transform between Ce3 and Ce4, it can form vacancies on the solid surface. These vacancies provide a convenient way for oxygen transfer on the surface of cerium dioxide. Therefore, cerium oxide can be used as oxygen donor in a large number of practical applications, such as solid fuel cells, catalysts, biochemical drugs and so on. As a new type of nano-reactor, block copolymer micelles have attracted much attention because of their advantages of controlling the morphology and size of nanoparticles. In this paper, the preparation of cerium oxide and its composite nanoparticles using block copolymers as template was studied. CeO2 nanoparticles and Au/CeO2 composite nanoparticles were prepared by hydrazine reduction and oxidation, UV irradiation and calcination using polystyrene-b- poly (2-vinylpyridine) (PS-b-P2VP) micelle as template. The products were characterized and their photocatalytic properties were studied. (1) CeO2 nanoparticles were prepared by hydrazine reduction-oxidation method using PS-b-P2VP micelle as template. Cerium dioxide nanoparticles were further oxidized by the reduction of cerium ion into cerium monoxide by the reaction of cerium nitrate micelle PS-b-P2VP/ nitrate with hydrazine. The synthesized CeO2 nanoparticles can exist stably in organic solvents. Monodisperse CeO2 nanoparticles or spherical CeO2 aggregates with large size can be prepared by simply changing the solubility of the solvent. After the block copolymers were removed, the experimental CeO2 colloidal particles could self-assemble into porous nanostructures, which could greatly improve the catalytic performance of the samples. The experimental CeO2 nanoparticles have potential applications in photocatalysis and organic-inorganic composite nanomaterials. (2) CeO2 and Au/CeO2 nanoparticles were prepared by UV irradiation. The micelle formed by PS-b-P2VP was used as template, and cerium nitrate was introduced into the micelle by complexation. Cerium ion in cerium nitrate was reduced to cerium by ultraviolet irradiation. Under the action of oxygen in air, the reduced cerium was oxidized to cerium dioxide, and the spherical CeO2 nanoparticles with a particle size of about 25 nm were obtained. At the same time, the effect of dimethylformamide content on the morphology and size of nanoparticles was investigated. On this basis, Au/CeO2 composite nanoparticles with dumbbell-shaped structure were synthesized by ultraviolet irradiation by introducing chlorgold acid into the system. (3) the micelle formed by PS-b-P2VP self-assembly was used as template, and cerium nitrate and chlorauric acid were complexed into micelles. Cerium nitrate was transformed into cerous hydroxide by ammonia vapor and cerous hydroxide and chlorgold acid were transformed into cerium oxide and gold oxide after high temperature calcination. The Au@CeO2 nanoparticles with core-shell structure were obtained by transmission electron microscopy (TEM) and XRD. The optimum calcination conditions for the preparation of core-shell Au@CeO2 were obtained by contrast test, that is, at 400 鈩，
本文编号：2268267
[Abstract]:Cerium oxide (CeO2) as an oxide formed by rare earth elements has many unique characteristics. Cerium mainly exists in two valence states, Ce3 and Ce4.. In the practical study, because cerium can transform between Ce3 and Ce4, it can form vacancies on the solid surface. These vacancies provide a convenient way for oxygen transfer on the surface of cerium dioxide. Therefore, cerium oxide can be used as oxygen donor in a large number of practical applications, such as solid fuel cells, catalysts, biochemical drugs and so on. As a new type of nano-reactor, block copolymer micelles have attracted much attention because of their advantages of controlling the morphology and size of nanoparticles. In this paper, the preparation of cerium oxide and its composite nanoparticles using block copolymers as template was studied. CeO2 nanoparticles and Au/CeO2 composite nanoparticles were prepared by hydrazine reduction and oxidation, UV irradiation and calcination using polystyrene-b- poly (2-vinylpyridine) (PS-b-P2VP) micelle as template. The products were characterized and their photocatalytic properties were studied. (1) CeO2 nanoparticles were prepared by hydrazine reduction-oxidation method using PS-b-P2VP micelle as template. Cerium dioxide nanoparticles were further oxidized by the reduction of cerium ion into cerium monoxide by the reaction of cerium nitrate micelle PS-b-P2VP/ nitrate with hydrazine. The synthesized CeO2 nanoparticles can exist stably in organic solvents. Monodisperse CeO2 nanoparticles or spherical CeO2 aggregates with large size can be prepared by simply changing the solubility of the solvent. After the block copolymers were removed, the experimental CeO2 colloidal particles could self-assemble into porous nanostructures, which could greatly improve the catalytic performance of the samples. The experimental CeO2 nanoparticles have potential applications in photocatalysis and organic-inorganic composite nanomaterials. (2) CeO2 and Au/CeO2 nanoparticles were prepared by UV irradiation. The micelle formed by PS-b-P2VP was used as template, and cerium nitrate was introduced into the micelle by complexation. Cerium ion in cerium nitrate was reduced to cerium by ultraviolet irradiation. Under the action of oxygen in air, the reduced cerium was oxidized to cerium dioxide, and the spherical CeO2 nanoparticles with a particle size of about 25 nm were obtained. At the same time, the effect of dimethylformamide content on the morphology and size of nanoparticles was investigated. On this basis, Au/CeO2 composite nanoparticles with dumbbell-shaped structure were synthesized by ultraviolet irradiation by introducing chlorgold acid into the system. (3) the micelle formed by PS-b-P2VP self-assembly was used as template, and cerium nitrate and chlorauric acid were complexed into micelles. Cerium nitrate was transformed into cerous hydroxide by ammonia vapor and cerous hydroxide and chlorgold acid were transformed into cerium oxide and gold oxide after high temperature calcination. The Au@CeO2 nanoparticles with core-shell structure were obtained by transmission electron microscopy (TEM) and XRD. The optimum calcination conditions for the preparation of core-shell Au@CeO2 were obtained by contrast test, that is, at 400 鈩，
本文编号：2268267
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