Surfactant-assisted solvothermal synthesis of Co3O4 hollow spheres with oriented-aggregation nanostructures and tunable particle size.
Surfactant-assisted solvothermal synthesis of Co3O4 hollow spheres with oriented-aggregation nanostructures and tunable particle size.
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DOI：
10.1021/la0488710
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发表时间：
2004-09
期刊：
影响因子：
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通讯作者：
T. He;Dairong Chen;X. Jiao;Yanyan Xu;Yuanxiang Gu
中科院分区：
文献类型：
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作者：
T. He;Dairong Chen;X. Jiao;Yanyan Xu;Yuanxiang Gu
金属氧化物空心球因其在催化剂、染料或油墨、涂料、填料和微反应器等方面的应用潜力，引起了人们极大的研究兴趣。它们的制备通常采用模板法。模板分为硬核模板(如胶体颗粒1)和软核模板(主要是超分子组件，如囊泡、2个乳液、3个液滴、4个胶束、5和大分子聚集体6)。然而，空心球的模板制备仍然是一个挑战。首先，硬核模板工艺通常需要对核心表面进行修饰，以确保壳层物质的成功涂层。其次，超分子组装对溶液环境(pH值、溶剂、离子强度等)非常敏感，这使得软核模板工艺的应用受到限制。Stucky的Group7使用半胱氨酸-赖氨酸双嵌段共聚肽作为结构导向剂自组装硅金空心球，以及Naik等人。8还用水热法制备了Silicalite-1准晶体自组装空心球。自组装过程非常容易操作，有理由认为各种预制的纳米颗粒可以作为构建块来扩展壳层组成的范围。本文采用溶剂热法制备了Co3O4中空纳米球。溶剂热过程使无机中空纳米球具有溶剂热稳定性和热稳定性。更有趣的是，纳米晶体的定向聚集形成了具有单晶状纳米结构的壳层。定向凝聚作为一种制造具有不同微纳米结构的先进人工材料以及解释晶体生长中缺陷形成的线索而备受关注。9详细研究了几种金属氧化物的定向聚集现象，为控制金属氧化物的微观结构、形貌和粒度提供了潜在的应用。10最近，我们报道了Co3O4纳米晶在长碳链醇中定向聚集成具有中孔的更大的固体纳米聚集体。11在本文中，首次观察到表面活性剂辅助溶剂热过程中形成Co3O4中空纳米球的定向聚集现象。此外，报告还指出，可以通过改变前驱体悬浮液的前驱体处理来调整空心球的粒度。尖晶石Co3O4在多相催化剂、锂离子二次电池负极材料、固态传感器、电致变色器件、太阳能吸收材料、颜料等方面具有巨大的应用潜力。由于颗粒大小和形貌对材料性能的影响，控制制备不同尺寸和形貌的Co3O4颗粒一直是研究人员的目的。到目前为止，已经制备了不同尺寸和形貌的纳米级Co3O4粒子，包括管状、棒状、纤维、薄膜和立方单晶；12这里介绍了其具有定向聚集结构的空心纳米球的合成。用循环伏安法(CV)测试了所制备的Co3O4空心球在锂离子电池中的电化学性能，表现出良好的循环稳定性。13
Metal oxide hollow spheres have attracted great investigative interests because of their various application potentials, such as in catalysts, dyes or inks, coatings, fillers, and microreactors. The template methods are usually adopted for their preparation. The templates are classified as hard-core templates (such as the colloid particles1) and soft-core templates (mainly supermolecular assemblies, such as vesicles, 2 emulsions, 3 droplets, 4 micelles, 5 and large molecule aggregates6). However, the template preparation of hollow spheres still remains a challenge. First, the hard-core template processes usually require a core surface modification to ensure successful coating of shell substances. Second, supramolecular assemblies are sensitive to solution environments (pH value, solvents, ionic strength, etc.), making the application of soft-core template processes limited. Stucky’s group7 used the cysteine-lysine diblock copolypeptides as structure-directing agents to self-assemble silica-gold hollow spheres, and Naik et al. 8 also prepared silicalite-1 hollow spheres by self-assembly of hydrothermal silicalite-1 quasi-crystals. The self-assembly processes are quite easy to manipulate, and it is reasonable to think that various preformed nanoparticles can be used as building blocks to extend the range of shell compositions. Herein, Co3O4 hollow nanospheres are prepared through a solvothermal process. The solvothermal process endows the inorganic hollow nanospheres with a solvothermal and thermal stability. And more interestingly, oriented aggregation of nanocrystals occurs to form the shells with a single-crystal-like nanostructure. Oriented aggregation attracted much attention as a promising method for creating advanced artificial materials with distinct microand nanostructures and as a clue for the explanation of defect formation in crystal growth. 9 The oriented aggregation phenomena of several metal oxides have been investigated in detail, providing their potential application in the control over the microstructures, morphologies, and particle sizes. 10 Recently, we have reported the oriented aggregation of Co3O4 nanocrystals in long-carbon-chain alcohols to larger solid nanoaggregates with mesopores. 11 While in this paper, oriented aggregation in a surfactantassisted solvothermal process to form Co3O4 hollow nanospheres is first observed. Moreover, the note suggests that the particle size of hollow spheres could be adjusted by changing the pretreatments of precursor suspensions. The spinel Co3O4 has great application potential in heterogeneous catalysts, anode materials in Li ion rechargeable batteries, solid-state sensors, electrochromic devices, solar energy absorbers, pigments, and so on. Because of the influence of particle size and morphology on the properties of materials, the controlled preparation of Co3O4 particles of different sizes and morphologies is always the researcher’s purpose. Up to now, Co3O4 particles of different sizes and morphologies including tubes, rods, fibers, films, and cubic single crystals in nanoscale have been prepared; 12 here, the synthesis of its hollow nanospheres with oriented-aggregation structures is introduced. The electrochemical properties of the asprepared Co3O4 hollow spheres as anodes in Li ion cells are tested via cyclic voltammetry (CV) measurements, presenting good cycling stability. 13