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A novel WO 3 ·H 2 O nanostructure assembled by numerous one-dimensional nanorods as building units were synthesized successfully through a facile hydrothermal process. As a comparison, we also prepared the monodispersed WO 3 ·H 2 O nanorods. The crystal structures and morphologies of two products were characterized by X-ray diffraction and scanning electron microscope. Furthermore, gas sensing experiments indicated that a superior gas-sensing property of aligned WO 3 ·H 2 O nanorods occurs over that of the monodispersed WO 3 ·H 2 O nanorods, which is likely attributed to large effective surface areas and abundant accessible diffusion channels provided by this special structure for sufficient gas reactions. [ABSTRACT FROM AUTHOR]

Sparsely and closely flower-like WO 3 ·H 2 O hierarchical architectures were successfully synthesized via a one-step hydrothermal process. The obtained samples are both WO 3 ·H 2 O nanoflowers assembled by ultrathin nanosheets with the thickness less than electron deletion layer. And the possible formation processed was proposed based on the comparative studies. Furthermore, gas sensing experiments demonstrated that the closely WO 3 ·H 2 O nanoflowers which possess numerous semi-closed spaces have a superior gas-sensing performance compared with the sparsely one. We believe this unique structure will critically enhance the gas sensing properties of WO 3 ·H 2 O nanomaterials. [ABSTRACT FROM AUTHOR]

Nanomaterials with hierarchical architectures consisting of two-dimensional nanostructures have attracted considerable attention for their potential applications in recent years. In current work, flake-flower NiO architectures self-assembled by aggregative nanosheets have been successfully synthesized via the hydrothermal route. It is notable that the NiO sensors exhibit excellent gas sensing performances owing to the open and well-defined structure as well as abundant micro reaction rooms built by two-dimensional ultrathin nanosheets, which are thinner than the thickness of electron depletion layer. Moreover, a possible growth mechanism for the interactions between PVP and Ni 2+ ions in the synthesis of the precursors Ni(OH) 2 and the novel morphology evolution of the NiO nanoflowers are proposed in detail. [ABSTRACT FROM AUTHOR]

Novel urchinlike hexagonal WO 3 microspheres have been fabricated by a facile hydrothermal method in the presence of K 2 SO 4 . Morphology analysis reveals that the as-synthesized WO 3 microstructures are assembled by numerous one-dimensional nanorods. Based on comparative studies, a possible formation mechanism is proposed in detail. What’s more, gas-sensing measurement indicates that the well-defined urchinelike WO 3 microspheres exhibit excellent gas sensing properties. [ABSTRACT FROM AUTHOR]

Monodisperse NiO hierarchical nanoflowers fabricated by nanobundles have been successfully synthesized under hydrothermal conditions followed by a calcination treatment. It is amazingly observed that the bundle-like nanoflowers possessed the emanative needle-like ends on the nanoscale, which was different from the previous 3D hierarchical architectures only fabricated by nanosheets, entire solid rod-like and emanative needle-like structures. Furthermore, based on the further experiments, the amount of ethylene glycol (EG, 99.5 wt%) play a key role on the formation of emanative needle-like ends and constructions of the 3D hierarchical flower-like architectures, and the relative formation mechanism was primarily discussed. Such an unexpected morphology may provide a non-trivial behavior driven by the properties of emanative needle-like ends and electron transformation continuity. [ABSTRACT FROM AUTHOR]

Nanomaterials with low-dimensional architectures frequently exhibit novel functional properties. In current work, NiO nanobelts with well-defined morphologies and uniform size have been successfully synthesized via a facile hydrothermal method. Furthermore, a novel growth mechanism of NiO nanobelts has been proposed in detail. Surprisingly, it is worth mentioning that the sodium oxalate is of great benefit to the formation of NiO one-dimensional nanostructures and plays a vital role on tailoring morphologies of nanobelts on the basis of further comparative experiments. Such a synthetic way may open up an avenue to prepare some other oxides. [ABSTRACT FROM AUTHOR]

Molybdenum trioxides (MoO 3 ) with flower-like hierarchical structure and distinct nanobelts have been synthesized via a hydrothermal method. A series of comparative experiments show that cetyltrimethyl ammonium bromide (CTAB) and HNO 3 have evident impact on forming the morphologies of MoO 3 . Interestingly, the add order of CTAB and HNO 3 can be also a determinant factor in the assemble process. This research is of great significance in the preparations, characterizations and applications of various 1D and 3D semiconductor metal oxides. The possible growth mechanism is also proposed. [ABSTRACT FROM AUTHOR]

Abstract: Self-assembly of one-dimensional nanoscale building blocks into functional 2D or 3D complex superstructures has stimulated a great deal of interest. In current work, using the hydrothermal method and reagent of hexamethylenetetramine (HMT), we synthesize the SnO2 3D hierarchical nanostructures with an average diameter of 200–400nm, which exhibit flower-like architectures assembled by numerous one-dimensional tetragonal prism nanorods. Further comparative studies demonstrate that the HMT provides nucleation sites for the assembling of the nanorods, which plays a crucial role in producing such unique flower-like architectures. Meantime, a novel growth mechanism is proposed in detail. In property, the prepared SnO2 nanoflowers show excellent gas-sensing performances to ethanol of 50ppm at an optimal temperature as low as 250°C. Such unique architectures may open up an avenue to further enhance the gas-sensing performances of SnO2 nanostructures for future sensor application. [Copyright &y& Elsevier]

Nanomaterials with three-dimensional architectures, frequently exhibiting novel functional properties, have attracted considerable attention of the researchers. In current work, we have successfully synthesized the NiO flower-like microspheres with abundant nanoparticles adhering to the petals via a facile hydrothermal method. Interestingly, it is found that the excellent gas sensing properties of the samples towards ethanol are likely attributed to the well-aligned porous architectures as well as great amounts of nanoparticles adhering to the petals, considered as active sites. Meanwhile, we also elaborated a distinctive growth mechanism of such a unique architecture and a plausible gas sensing mechanism, respectively. [ABSTRACT FROM AUTHOR]

We report the successful synthesis of novel Sn 2 O 3 with hierarchical 3D nanostructures via a facile hydrothermal method for the first time. The as-prepared Sn 2 O 3 products transform into SnO 2 after calcinations (800 °C) and a simultaneous TGA and DSC analysis of the as-prepared Sn 2 O 3 sample determines that the main increment of mass takes place in the temperature range 534–800 °C. The well-defined nanostructures are composed of thin nanosheets. The growth mechanisms are also discussed by observing the morphology revolution at various reaction times. Furthermore, the oxidation states of the Sn 2 O 3 hierarchical nanostructures are confirmed by the shape analysis of corresponding XPS O 1 s and Sn 3 d peaks using the decomposition procedure. [ABSTRACT FROM AUTHOR]

Abstract: New morphologies often play a critical role in governing properties of nano-materials. Here, using hydrothermal method and reagents of sodium citrate and polyethylene glycol (PEG), we synthesize the ZnO nano-crystals and find that they exhibit hierarchical flower-like architectures assembled by nanosheets. Further comparative studies demonstrate that the sodium citrate assists a uniform growth of the nanosheets, and the PEG provides nucleation sites for the assembling of the nanosheets, both of which play a critical role in producing such unique flower-like architectures. Consequently, this sample is found to show excellent sensing performances to the target ethanol owing to its largest amount of petals, intervals, and pores. Such an unexpected morphology holds substantial promise for rendering ZnO as a potential gas-sensing material for a broad range of future sensor applications. [Copyright &y& Elsevier]

Novel urchin-like SnO 2 nanostructures were prepared by a facile hydrothermal process. The well-defined nanostructures were composed of numerous one-dimensional nanowires with a diameter of ∼8–10 nm. Based on comparative studies, a possible formation mechanism was proposed in detail. It was believed that the nucleation was initiated by formation of ZnSn(OH) 6 . Furthermore, gas-sensing measurement indicated that the urchin-like SnO 2 nanoflowers showed excellent gas-sensing properties. [ABSTRACT FROM AUTHOR]