Synthesis of ZnO Nanostructures

MW-HT techniques can shorten the reaction time. For example, Ivanov et al. [38] synthesized ZnO nanocrystals in 10 min with the assistance of microwave hydro-thermal methods. Huang et al. [39] also demonstrated the use of microwave radiation in the hydrothermal synthesis of ZnO complex nanostructures. These nanocrystals showed high photocatalytic activity in a model reaction of Methyl Orange photodegradation. Li et al. [40] synthesized W03 nanorods in 20 min and showed high... 

Straumal B, Baretzky B, Mazilkin A, Protasova S, Myatiev A, Straumal P (2009) Increase of Mn solubUity with decreasing grain size in ZnO. J Eur Ceram Soc 29 1963-1970 Strobel R, Pratsinis SE (2007) Flame aerosol synthesis of smart nanostructured materials. J Mater Chem 17 4743-4756... 

The potential of ZnO nanostructures as nanosized biosensors has also been explored for detecting different biological molecules. Development of 1D ZnO nanostructures as bio sensors is in the state of infancy and only a hmited number of reports are available [226-231]. The ID ZnO biosensors have advantages such as stability in air, nontoxicity, cJiemical stability, electrochemical activity, ease of synthesis, and bio-safe characteristics. As in the case of gas sensors, the principle of operation is that the conductance of ZnO nanorod FETs drastically changes when biomolecules are adsorbed. 

Mishra, P. Yadav, R. S. and Pandey, A. C. (2009). Starch assisted sonochemical synthesis of flower-like ZnO nanostructure. Digest.. Nano. Bios., 4,193-198. 

Pal U, Kim CW, Jadhav NA, Kang YS (2009) Ultrasound-assisted synthesis of mesoporous ZnO nanostructures of different porosities. J Phys Chem C 113(33) 14676-14680... 

Flou X, Zhou F, Sun Y, Liu W (2007) Ultrasound-assisted synthesis of dentritic ZnO nanostructure in ionic liquid. Mater Lett 61 1789-1792... 

Figure 5.3.9 (A) Simplified geometric model [46, 89] for the preparation of industrial Cu/ZnO catalysts comprising subsequent meso- and nanostructuring of the material from [56], In a first micro structure directing step (mesostructuring), the Cu,Zn coprecipitate crystallizes in the form of thin needles of the zincian malachite precursor, (Cu,Zn)2(0H)C03. In a second step, the individual needles are decomposed and demix into CuO and ZnO. The effectiveness of this nanostructuring step depends critically on a high Zn content in the precursor, which in zincian malachite is limited to Cu Zn ca. 70 30 due to solid-state chemical constraints [75]. Finally, interdispersed CuO/ZnO is reduced to yield active Cu/ZnO. (B) Chemical memory Dependence of catalytic activity in methanol synthesis on the conditions of the coprecipitation and aging steps, from [85].

For their rich potential in various applications described in the previous section, the synthesis and assembly of various ZnO micro and nanostructures have been extensively explored using both gas-phase and solution-based approaches. The most commonly used gas-phase growth approaches for synthesizing ZnO structures at the nanometer and micrometer scale include physical vapor deposition (40, 41), pulsed laser deposition (42), chemical vapor deposition (43), metal-organic chemical vapor deposition (44), vapor-liquid-solid epitaxial mechanisms (24, 28, 29, 45), and epitaxial electrodeposition (46). In solution-based synthesis approaches, growth methods such as hydrothermal decomposition processes (47, 48) and homogeneous precipitation of ZnO in aqueous solutions (49-51) were pursued. 

Topnani N, Hamplovi V, Ka par M, Novotnd V, Gorecka E. Synthesis, characterisation and functionalisahon of ZnO and TiOi nanostructures used as dopants in liquid crystal polymers. Liquid Crystals 2013 1-10. 

Carbothermal route provides a general method for preparing crystaUine nanowires of oxides such as ZnO, Al Oj and Ga Oj, nitrides such as AIN and SijN, and carbides such as SiC [3], The set-up employed for the synthesis of oxide nanomaterials is shown in Figure 3.1. The method has enabled the synthesis of crystalhne nanowires of both silica and sihcon. In the case of GaN, it has been possible to dope it with Mn, Mg and Si to bestow useful optical and magnetic properties. Carbothermal reaction involving Ga Oj powder mixed with activated carbon or carbon nanotubes carried out at 1100 °C in flowing Ar yields nanowires, nanorods as well as novel nanostructures... 

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