Autogenerated Air Bubbles for the Spontaneous Formation of Nanostructures
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Autogenerated air bubbles for the spontaneous formation of nanostructures Seok Min Yoon and Hee Cheul Choi* Department of Chemistry, Center for the Integrated Molecular Systems Pohang University of Science and Technology, San 31, Pohang, South Korea 790-784 ABSTRACT In this paper, a novel mild synthetic route was tentatively designed to achieve both shape and dimension-defined nanostructure such as nanorods, nanowires and nanocircles which were fully characterized by AFM and TEM. Bubbles, which are automatically generated when water is mixed with ethanol by a simple shaking, act as a nanoreactor to produce these nanostructures. Fe containing nanowire, nanorod and nanocircle are successfully prepared by using this method. Autogenerated bubble-mediated formation of nanostructures has advantages over conventional methods in terms of short reaction time, low energy consumption and absence of complicated experimental equipments. INTRODUCTION Self-assembly has attracted many scientist’s attention due to their simplicity to form various types of nanostructures which play the role as a building block for more complicated meaningful systems, such as nanoscaled electronic components[1] and sensors[2]. In order to fully utilize self-assembly for this purpose, it is fundamentally important to understand and appropriately modify non-covalent chemical interaction forces such as hydrogen bond, van der walls, dipole-dipole, donor-acceptor interaction.[3] Additionally, mass-producing nanomaterials is also necessary to its application. A variety of method to different novel architectures, such as CVD, sonication, solvothermal or room temperature-solution chemistry was tentatively introduced, while the room temperature chemistry hold more advantages such as simplicity, reproducibility, easy mass-production and so on than other methods. As for the functional inorganic nanostructures, many successful mild chemistry routes have been reported to various architectures. For example, Yang et al. has shown the formation of metallic nanowire converted from electrochemically favorable semiconductor nanowires.[4]A core-sheath nanostructure also has been obtained by spontaneous reduction of Au nanoparticles on Cu2S nanowires.[5] In both cases, spontaneous electrochemical redox reaction is the main driving force for the formation of nanostructures. Recently, more facile preparation method has successfully proved the formation of inorganic nanostructures, which utilizes self-assembly
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tendency but free from electrochemical potential issue. Vanadium oxide nanofiber or nanotube has been synthesized at room temperature by simply mixing ammonium metavanadate with acid resin which gradually releases protons.[6] Furthermore, the ability to control dimension is also important for its application on nano-scale devices. Olli Ikkala et al.[7] proposed that it is possible to make from 1-D to 3-D nanostructures by self-assembly polymeric supramolecules. Diederich et al.[8] successfully showed fullerenes patterned on 1-D to 2-D based porphyrin
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