Controlled assembly of preformed ceria nanocrystals into highly ordered 3D nanostructures
Controlled assembly of preformed ceria nanocrystals into highly ordered 3D nanostructures
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DOI：
10.1002/smll.200400060
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发表时间：
2005-03-01
期刊：
影响因子：
13.3
通讯作者：
Niederberger, M
中科院分区：
文献类型：
--
作者：
Deshpande, AS;Pinna, N;Niederberger, M
[**] 衷心感谢马克斯·普朗克学会的财政支持。我们感谢 Fritz-Haber-Institute 和 R. Schlçgl 教授使用电子显微镜，并感谢 Klaus Weiss 提供的技术援助。我们还感谢 H. Schlaad 博士和 I. Below 提供的嵌段共聚物以及 J. Polleux 提供的低分辨率 TEM 图像。小 2005 年，1，第 3 期，313–316 DOI：10.1002/smll。 200400060 2005 Wiley-VCH Verlag GmbH & Co. KGaA, D-69451 Weinheim 313 颗粒之间的连接性。[16]最近的一份报告提出了使用锐钛矿溶胶的高度有序介孔 TiO2 薄膜，[17]，而功能化二氧化铈纳米粒子用于合成具有六角孔结构的介孔 CeO2 粉末。 [18]后者的工作突出了纳米结构 CeO2 作为潜在太阳能电池材料的新应用。在这项工作中，我们报告了将近单分散和高度结晶的二氧化铈纳米颗粒（直径约为 3 nm）组装成高度有序的 3D 介观结构。与以前的文献研究相比，本方法显示出一些特殊性和新颖性。我们首次展示了使用纯 CeO2 纳米粒子溶胶（即没有任何有机官能化来稳定溶液中的颗粒）作为嵌段共聚物辅助组装过程中的构建块来获得介孔材料。组成为 Ce1ÀxZrxO2(x= 0–1) 的纳米粒子溶胶之前已被合成并充分表征。 [19]此外，中孔特别大，并且在孔形状和 3D 排列方面表现出异常高的有序度。氢化聚丁二烯-聚环氧乙烷嵌段共聚物（PHB-PEO；H [CH2CH2CH2CH (CH2 CH3)] x (OCH2CH2) yOH；PHB 嵌段的 MW= 4400 g molÀ1，PEO 嵌段的 MW= 3920 g molÀ1）用作结构导向剂。这些类型的嵌段共聚物已被用来获得具有大（% 13–14 nm）球形孔的高度有序的立方介孔二氧化硅和二氧化钛结构。 [12, 20] 与市售的 Pluronic 嵌段共聚物系列相比，这些聚合物的胶束在两个嵌段之间具有更高的疏水性对比度，对醇的敏感性较低，并且温度稳定性较高。这些特性使得 PHB-PEO 嵌段共聚物非常适合组装工艺。作为一个重要特征，该聚合物甚至可以在乙醇和 THF 中形成聚集体。这项研究包括通过 SAXS、WAXS、TEM、HRTEM 和物理吸附等各种方法进行完整、彻底的定量结构研究。
[**] Financial support by the Max Planck Society is gratefully acknowledged. We thank the Fritz-Haber-Institute and Prof. R. Schlçgl for the use of the electron microscope and Klaus Weiss for technical assistance. We also thank Dr. H. Schlaad and I. Below for supplying the block copolymers and J. Polleux for the low-resolution TEM images. small 2005, 1, No. 3, 313–316 DOI: 10.1002/smll. 200400060 2005 Wiley-VCH Verlag GmbH & Co. KGaA, D-69451 Weinheim 313 connectivity between the particles.[16] A recent report presented highly ordered mesoporous TiO2 thin films using anatase sols,[17] whereas functionalized ceria nanoparticles were used for the synthesis of mesoporous CeO2 powders with a hexagonal pore structure.[18] The latter work highlights a novel application of nanostructured CeO2 as a potential solar-cell material.In this work, we report the assembly of nearly monodisperse and highly crystalline ceria nanoparticles (with a diameter of about 3 nm) into highly ordered 3D mesostructures. Compared to previous studies in the literature, the present approach shows several particularities and novel aspects. For the first time, we demonstrate the use of sols of pure (that is, without any organic functionalization to stabilize the particles in solution) CeO2 nanoparticles as building blocks in a block-copolymer-assisted assembly process to obtain mesoporous materials. Nanoparticle sols with the composition Ce1ÀxZrxO2(x= 0–1) have been synthesized and fully characterized before.[19] Furthermore, the mesopores are particularly large and show an exceptionally high degree of ordering in terms of pore shape and 3D arrangement. A hydrogenated polybutadiene–poly (ethylene oxide) block copolymer (PHB–PEO; H [CH2CH2CH2CH (CH2 CH3)] x (OCH2CH2) yOH; MW= 4400 g molÀ1 for the PHB block and MW= 3920 g molÀ1 for the PEO block) was used as structure-directing agent. These types of block copolymers have been used to obtain highly ordered cubic mesoporous silica and titania structures with large (% 13–14 nm) spherical pores.[12, 20] In comparison to the commercially available family of Pluronic block copolymers, the micelles of these polymers have higher hydrophobic contrast between the two blocks, low sensitivity towards alcohols, and higher temperature stability. These features make PHB–PEO block copolymers highly suitable for assembly processes. As an important feature, this polymer can form aggregates even in ethanol and THF. This study comprises a complete and thorough quantitative structural investigation by various methods such as SAXS, WAXS, TEM, HRTEM, and physisorption.