【摘要】：二氧化鈰(CeO2)作為一種稀土元素形成的氧化物具有許多獨(dú)特的特點(diǎn)。鈰主要以兩種價(jià)態(tài)存在,即Ce3+和Ce4。在實(shí)際研究中,由于鈰能夠在Ce3+和Ce4之間轉(zhuǎn)變而能夠在固體表面形成空位,這些空位為氧在二氧化鈰表面?zhèn)鬟f提供了便利的途徑。所以氧化鈰可以作為氧的供體而在大量實(shí)際應(yīng)用中受到人們的青睞,例如:固體燃料電池、催化劑、生化藥物等。嵌段共聚物膠束作為一種新型的納米反應(yīng)器,具有能夠控制納米粒子的形貌和尺寸的優(yōu)點(diǎn)而引起廣泛關(guān)注。本論文主要研究了利用嵌段共聚物為模板制備氧化鈰及其復(fù)合納米粒子。利用聚苯乙烯-b-聚(2-乙烯吡啶)(PS-b-P2VP)膠束為模板,通過(guò)肼還原與氧化、紫外輻照、煅燒等方法來(lái)制備CeO2納米粒子和Au/CeO2復(fù)合納米粒子,并對(duì)產(chǎn)物進(jìn)行了表征以及光催化性能研究。(1)利用PS-b-P2VP膠束為模板,通過(guò)肼還原-氧化法制備出CeO2納米粒子。將PS-b-P2VP/硝酸鈰復(fù)合膠束與肼反應(yīng),將鈰離子還原成單質(zhì)鈰,經(jīng)進(jìn)一步氧化生成二氧化鈰納米粒子。實(shí)驗(yàn)合成出的CeO2納米粒子能夠在有機(jī)溶劑中穩(wěn)定存在。通過(guò)簡(jiǎn)單改變?nèi)軇┑娜芙庑钥梢灾苽涑鰡畏稚⒌腃eO2納米粒子或尺寸較大的球形CeO2聚集體。將嵌段共聚物除去后,實(shí)驗(yàn)制得的CeO2膠體粒子能夠自組裝為多孔的納米結(jié)構(gòu),這種結(jié)構(gòu)能夠大幅提升樣品的催化性能。實(shí)驗(yàn)制得的CeO2納米粒子在光催化、有機(jī)—無(wú)機(jī)復(fù)合納米材料等領(lǐng)域有潛在的應(yīng)用價(jià)值。(2)通過(guò)紫外輻照法制備出CeO2及Au/CeO2納米粒子。利用PS-b-P2VP形成的膠束為模板,將硝酸鈰通過(guò)絡(luò)合作用引入到膠束之中。利用紫外光輻照將硝酸鈰中的鈰離子還原單質(zhì)鈰。在空氣中氧氣的作用下,將還原后的鈰氧化為二氧化鈰,得到粒徑約為25 nm的球形CeO2納米粒子。同時(shí),考察了體系中二甲基甲酰胺含量對(duì)納米粒子形貌和尺寸的影響。在此基礎(chǔ)上,將氯金酸引入體系,通過(guò)紫外輻照法合成出具有啞鈴型結(jié)構(gòu)的Au/CeO2復(fù)合納米粒子。(3)利用PS-b-P2VP自組裝形成的膠束為模板,將硝酸鈰和氯金酸絡(luò)合進(jìn)入膠束后,通過(guò)氨水蒸氣將硝酸鈰轉(zhuǎn)變?yōu)闅溲趸瘉嗏?經(jīng)高溫煅燒后將氫氧化亞鈰和氯金酸轉(zhuǎn)變?yōu)檠趸嫼徒�。通過(guò)透射電鏡、XRD等表征手段證明實(shí)驗(yàn)制得了核殼結(jié)構(gòu)的Au@CeO2納米粒子。通過(guò)對(duì)比試驗(yàn)得到制備核殼結(jié)構(gòu)Au@CeO2的最佳煅燒條件,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，

本文編號(hào)：2268267