Fabrication of 3D rotor-like ZnO nanostructure from 1D ZnO nanorods and their morphology dependent photoluminescence property Prabhakar Rai, Jin-Nyeong Jo, In-Hwan Lee, Yeon-Tae Yu * Division of Advanced Materials Engineering and Research Centre for Advanced Materials Development, College of Engineering, Chonbuk National University, Jeonju 561-756, South Korea article info Article history: Received 1 June 2010 Received in revised form 6 July 2010 Accepted 6 July 2010 Available online 22 July 2010 Keywords: Zinc oxide Sonochemical method Rotor-like structure Photoluminescence abstract A facile and eco-friendly sonochemical route to fabricate well-defined dentritic (rotor-like) ZnO nano- structures from 1D ZnO nanorods without alloying elements, templates and surfactants has been reported. Phase and structural analysis has been carried out by X-ray diffraction (XRD) and Fourier Transform Infra-Red (FTIR) spectroscopy, showed the formation of hexagonal wurtzite structure of ZnO. Scanning electron microscopic (SEM) study showed the formation of rotor-like ZnO nanostructure having a central core which is surrounded by side branches nanocones. Transmission electron microscopic (TEM) study showed that these nanocones grow along [0001] direction on the six {01e10} planes of central core ZnO nanorods. A plausible formation mechanism of rotor-like ZnO nanostructures was studied by SEM which indicates that the size and morphology of side branches can be controlled by adjusting the concentration of OH  ions and time duration of growth. The photoluminescence (PL) spectrum of the synthesized rotor-like ZnO nanostructures exhibited a weak ultraviolet emission at 400 nm and a strong green emission at 532 nm recorded at room temperature. The influence of morphology on the origin of green emission was discussed in detail. The results suggested a positive relationship among polar plane, oxygen vacancy and green emission. Ó 2010 Elsevier Masson SAS. All rights reserved. 1. Introduction It is well known realization that the technologically useful nano- materials depend not only on the quality of the crystal and their surface chemistry, but also on their special orientation and arrange- ment. One-dimensional (1D) nanomaterials, such as nanotubes, nanowires, nanorods, have stimulated intensive research interest owing to their unique applications in mesoscopic physics and the fabrication of nanoscale devices [1,2]. Some recent efforts have focused on the integration of 1D nanoscale building blocks into two- and three-dimensional (2D/3D) ordered superstructures or complex functional architectures, which is a crucial step toward realization of functional nanosystems [3e7]. For example, MnO 2 nanostructures with sea urchin shapes was synthesized by a sodium dodecyl sulfate- assisted hydrothermal process, [8] etc. Among those advanced func- tional materials, ZnO 3D structures may be promising candidates for future micro-electrical-mechanical-system (MEMS)/nano-electrical- mechanical-system (NEMS) devices. It is because of (i) ZnO crystal favors a wurtzite lattice structure. By controlling the growth velocity of the facets, a diverse group of 3D nanostructures may be obtained [9e17]. (ii) ZnO has low friction factor (z0.2) and well chemical stability [16,17]. (iii) ZnO is bio-compatible, makes it to be promising candidate for bio-systems [18]. So, considerable efforts have been directed towards the preparation of ZnO nanostructure material. Qian and co-workers reported the synthesis of urchin-like, flower-like, and hierarchical ZnO 3D architectures and the photoluminescence spectra of the resultant ZnO 3D architectures presented an intensive ultra- violet emission at about 385 nm and weak green emission, which indicated their high structural and optical quality [12]. Zhang et al. synthesize brush like ZnO and investigated their gas sensing and optical property [14]. They found that the polar planes of ZnO are important for the gas sensing activity, because they favor forming more oxygen vacancies which generate more active centre so as to enhance the gas sensing response. Thus, the complex structures of ZnO are expected to have more potential applications in building functional electronics devices with special architectures and distinctive optoelectronic properties. Because the size, morphology and dimensionality of ZnO have great effect on its property and application therefore, development of morphologically controllable synthesis of ZnO nano or microstructures is urgently important to answer the demand for exploring the potentials of ZnO. Owing to their potential application, ZnO nano-/micro-crystals with different morphologies have been prepared by different * Corresponding author. Tel.: þ82 63 270 2288; fax: þ82 63 270 2305. E-mail address: yeontae@chonbuk.ac.kr (Y.-T. Yu). Contents lists available at ScienceDirect Solid State Sciences journal homepage: www.elsevier.com/locate/ssscie 1293-2558/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.solidstatesciences.2010.07.009 Solid State Sciences 12 (2010) 1703e1710