Morphological syntheses of ZnO nanostructures under microwave irradiation
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Morphological syntheses of ZnO nanostructures under microwave irradiation Xiaoping Shen • Jiquan Sun • Guoxing Zhu Zhenyuan Ji • Zhixin Chen • Niya Li
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Received: 12 September 2012 / Accepted: 5 November 2012 / Published online: 21 November 2012 Ó Springer Science+Business Media New York 2012
Abstract ZnO nanostructures with flower-, rod-, and flake-like morphologies have been controllably synthesized using Zn(acac)2H2O (acac = acetylacetonate) as a singlesource precursor through a facile and fast microwaveassisted method. The morphologies of ZnO nanostructures can be systematically adjusted by using various surfactants. The ZnO products are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The results show that all ZnO nanostructures are of singlecrystalline nature with hexagonal wurtzite structure. The possible formation mechanism for these ZnO nanostructures is proposed and their photoluminescence properties are also investigated.
Introduction Zinc oxide, as a versatile smart semiconductor with a wide band gap of 3.37 eV and exciton binding energy of 60 meV [1], has been attracting extensive attention because of its unique physical and chemical properties and its wide range of technological applications in many industrial products, such as ceramics [2], rubber additives [3], pigments [4], and so on [5–8]. Because the properties of ZnO are highly dependent on their size, shape, and crystalline structure, many efforts have been devoted to manipulating X. Shen (&) J. Sun G. Zhu Z. Ji N. Li School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013, China e-mail: [email protected] Z. Chen School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522, Australia
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the shape and size of various ZnO nanostructures in a controllable way for their novel or improved properties, such as the ultraviolet laser [9], piezoelectric effect [10], photocatalysis [11], and potential applications in nanoscale electronics and photonics [12]. Well-defined ZnO nanostructures with an abundant variety of shapes, such as nanoparticles [13], nanorods/wires [14, 15], nanoflowers [16], nanoneedles [17], nanotubes [18], nanobelts [19], nanorings [20], nanocombs [21], nanosheets [22], nanowalls [23], tetrapods [24], and hierarchical and complex nanostructures [1], have been synthesized via various physical and chemical routes [25–28]. However, these methods usually require a high reaction temperature and/or a long reaction time with high energy cost. Therefore, the development of a simple and rapid synthetic route that can control the shape of ZnO nanostructures under mild conditions is of great significance and remains an important topic under investigation. Since the microwave-assisted liquid phase organic synthesis was reported in 1986 [29], the application of microwave heating in synthetic chemistry has been a fastgrowing area of research. Microwave-assisted chemica
