Form emerges from formless entities: temperature-induced self-assembly and growth of ZnO nanoparticles into zeptoliter bowls and troughs.
Form emerges from formless entities: temperature-induced self-assembly and growth of ZnO nanoparticles into zeptoliter bowls and troughs.
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DOI：
10.1002/anie.200701771
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发表时间：
2007-08
影响因子：
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通讯作者：
K. S. Krishna;Uzma Mansoori;N. R. Selvi;M. Eswaramoorthy
中科院分区：
文献类型：
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作者：
K. S. Krishna;Uzma Mansoori;N. R. Selvi;M. Eswaramoorthy
通过控制纳米颗粒在多个长度尺度上的生长和组织来构建复杂的形貌是材料合成中具有挑战性的任务之一。[1，2]通过自组装过程，可以很容易地从胶体和配体稳定的纳米颗粒[3-5]构建流行形状如棒、管和球的无机纳米和微观结构。然而，工程复杂的形式来平行自然存在的生物矿物不是一个简单的任务，需要许多新的合成方法。[6-8]在此，我们首次报道了温度诱导的ZnO纳米粒子的自组装和生长成不寻常的碗，槽，和环形结构。ZnO是一种重要的宽带隙半导体，在催化剂，[9]太阳能电池，[10]传感器，[11]紫外激光，[12]和光电子学中有应用。[13]ZnO的性能与其微观结构密切相关，特别是其晶体尺寸、取向和形貌。[14]虽然通过固-汽相生长（SVG）、[15-21]微乳液[22]和水热法[23]已经获得了各种形状的ZnO纳米和微米结构，但据我们所知，迄今为止还没有报道碗状和三角槽状结构。我们还证明，在这里，由此获得的ZnO碗和环可以用作模板，使金属或金属氧化物复制品。这些小碗（体积为齐普托升）不仅可以容纳超低体积的流体，[24]还可以用于生长纳米颗粒，[25]生物分子，[26]和筛选亚微米尺寸的颗粒。[27]在600 ℃下煅烧复合物（硝酸锌/聚（乙烯基吡咯烷酮）（PVP）重量/重量比0.5）5小时后ZnO碗的场发射扫描电子显微镜（FESEM）图像显示在图1a中。以良好的产率获得了外径从300 nm到1 μm的碗。背景图像显示了由尺寸为30至80 nm的ZnO纳米颗粒组成的多孔网络。碗不是完全圆形的，在某些情况下，它们是多面的。边缘的宽度在80至100 nm的范围内（图1b）。由于制造这些碗的颗粒的大小和形状不同，碗的内表面粗糙。图1b所示碗的内核由小颗粒组成，其外缘由大的细长颗粒熔合而成，这类似于纳米级方解石颗粒熔合形成的微结构。[6]原子力显微镜（AFM）图像和300 nm大小的单个碗的高度轮廓分析显示其深度约为90 nm。的
Construction of complex morphologies by controlled growth and organization of nanoparticles at multiple-length scales is one of the challenging tasks in materials synthesis.[1, 2] Inorganic nano-and microstructures of prevalent shapes like rods, tubes, and spheres can be readily built from colloidal and ligand-stabilized nanoparticles [3–5] through self-assembly processes. However, engineering complex forms to parallel naturally existing biominerals is not a simple task and demands many new synthetic approaches.[6–8] Herein, we report for the first time a temperature-induced self-assembly and growth of ZnO nanoparticles into unusual bowl-, trough-, and ring-shaped structures. ZnO, an important wide-band-gap semiconductor, finds applications in catalysis,[9] solar cells,[10] sensors,[11] UV lasing,[12] and photoelectronics.[13] The properties of ZnO are closely related to its microstructures, particularly its crystal size, orientation, and morphology.[14] Though a variety of ZnO nano-and microstructures of various shapes have been obtained by solid–vapor phase growth (SVG),[15–21] microemulsion,[22] and hydrothermal methods,[23] bowl and triangular trough-shaped structures, to the best of our knowledge, have not been reported so far. We also demonstrate herein that the ZnO bowls and rings thus obtained can be used as a template to make metal or metal oxide replicas. The tiny bowls (of zeptoliter volume) are envisaged not only to hold fluids of ultralow volume,[24] but also to be used to grow nanoparticles,[25] immobilize biomolecules,[26] and screen sub-micrometer-sized particles.[27] The field-emission scanning electron microscopy (FESEM) image of the ZnO bowls after calcining the composite (zinc nitrate/poly (vinyl pyrrolidone)(PVP) wt/wt ratio 0.5) at 6008C for 5 h is shown in Figure 1a. The bowls were obtained in good yield with the outer diameter varying from 300 nm to 1 μm. The background image shows a porous network made up of ZnO nanoparticles of size 30 to 80 nm. The bowls are not fully circular and in some cases they are faceted. The widths of the rims are in the range of 80 to 100 nm (Figure 1b). The bowls have a coarse inner surface owing to variation in the sizes and shapes of the particles from which they are made.The inner core of the bowl shown in Figure1b is composed of small particles, and its outer edge is formed by the fusion of large, elongated particles, which resembles the formation of microstructures of cocolith by the fusion of nanometer-scale calcite particles.[6] An atomic force microscopy (AFM) image and the height-profile analysis of a single bowl of size 300 nm show its depth to be around 90 nm. The