| One-dimensional (1D) nanostructures are attracting a great deal of attention due to their unique properties and novel applications. Semiconductor oxides are the basis of functional materials that have excellent properties and important technological applications. As an n-type semiconductor oxide with a wide band gap (Eg = 3.6 eV, at 300 K), SnO2 is well-known for its potential applications in transparent conductive electrodes and transistors, Li-ion batteries, dye-sensitized solar cells and ultrasensitive gas sensors. It is well-known that the performance of this material is influenced by morphological and nanostructure features of the SnO2 crystals. Thus, designing SnO2 1D nanorods and nanoarchitectures with well-defined morphologies is of importance for fundamental research. Up to now, using some techniques, SnO2 nanocrystals have been prepared in the forms of SnO2 nanowires, nanotubes, nanobelts, and nanorods. Compared with other synthesis methods, hydrothermal method has the advantages of producing nanomaterials with uniform structure in large scale. It might be a better choice for the fabrication SnO2 nanostructure.1. In the present work, we demonstrate an efficient and a facile approach for the large scale synthesis of flowerlike SnO2 nanorods bundles by a simple hydrothermal method using PEG as a structure directing agent at 200 oC. The as-synthesized products have uniform structures and high pure phase. It is actinomorphic flowerlike particles, which are built by numerous one-dimensional tetragonal prism nanorods. To the best of our knowledge, this is the lowest temperature reported by far for the fabrication of flowerlike SnO2 nanorods bundles by a simple hydrothermal method. The influences of PEG-400 and NaOH concentration on the shape of the SnO2 samples have been studied. Further investigation of experiment reveals the appropriate concentration of PEG-400 and NaOH for growth of flowerlike SnO2 nanorods bundles is 5ml and 0.3 g. The corresponding formation mechanism with/without PEG has been preliminarily discussed. For PEG can absorb on the surface of SnO2 cell. When the surface of SnO2 cell absorbs this type of polymer, the growth kinetics of the SnO2 cell will be modified, which finally leads into the anisotropic growth of the crystals. Ethanol sensor based on the flowerlike SnO2 nanorods bundles is fabricated. And a linear dependence of the sensitivity on the ethanol concentration was observed.2. Novel SnO2 polygon-like and nano-circular structure have been synthesized by CTAB assisted hydrothermal method at 200℃. The influences of ethanol and CTAB concentration on the shape of the SnO2 samples have been studied. When the ethanol and water volume ratio is 3/2, the aggregate we obtained, which was built by numerous one-dimensional tetragonal prism nanorods. When the ethanol and water volume ratio is 3/1, the product with structure of flowerlike SnO2 nanorods bundles can be formed. With other conditions kept constant, the ethanol and water volume ratio is 1/1, the product with structure of polygon-like was obtained, when the concentration of CTAB is 0.4 g. While the concentration rises to 0.5 g, nano-circular structure can be formed. The corresponding formation mechanism of experiment has been preliminarily discussed. Gas sensors fabricated from these polygon-like SnO2 nanorods are very sensitive to ethanol gas, demonstrated that the polygon-like SnO2 nanorods was well potential candidates as sensing materials.
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