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The assembly design of nanostructures has taken a dominated position in improving gas sensing properties. In our work, multi-hierarchical (nanoneedles assembled and nanosheets assembled) SnO nanostructures with size-controllable blocking units were synthesized via facile hydrothermal method. As is recorded, the addition of PVP led to the transformation from nanoneedles assembled nanostructures into nanosheets assembled nanostructures, which can be ascribed to linear molecule structures. While the sizes of the blocking units can be controlled by the temperature due to the Ostwald ripening. And seeing from the gas sensing measurement, the thinner ones had higher gas response and quicker gas response and recovery judging from the sizes of blocking units, at the same time, nanoneedles assembled hierarchical structures possessed higher gas response while nanosheets assembled hierarchical structures had shorter gas response and recovery time. [ABSTRACT FROM AUTHOR]

A novel hierarchical flower-like MoO assembled by uniform nanosheets was reported. We propose a possible nucleation-growth mechanism of nanoflower and formation mechanism of MoO. Moreover, a systematic gas sensing measurement reveals that the flower-like MoO shows excellent gas sensing performances toward ethanol. The result shows an advance of hierarchical flower-like nanostructures in further enhancing the functionality of gas sensors, and this facile method could be applicable to many sensing materials. [ABSTRACT FROM AUTHOR]

Monodisperse NiO with hierarchical nanostructures has been successfully synthesized via a surfactant-assisted hydrothermal process followed by subsequent calcination treatment. It is notable that the NiO nanoflowers are self-assembled by abundant ultrathin nanosheets, and polyvinylpyrrolidone (PVP) plays a key role on the constructions of flower-like architectures. In addition, gas sensors based on NiO nanoflowers were developed and demonstrated outstanding functionalities, owing to the open and well-defined structure as well as abundant micro reaction rooms built by nanosheets. Moreover, a feasible formation mechanism was put forward in detail to illuminate the morphology evolution and the interactions between PVP and Ni ions. [ABSTRACT FROM AUTHOR]

The manner how nano building blocks assemble into hierarchical architectures exerts a tremendous influence on gas-sensing property of the metal oxides. Herein, we focus on tuning the 1D SnO rectangular nanorods into 3D hierarchical nanoflowers by manipulating the concentration of surfactant (citric acid) as well as the period of hydrothermal process, and then investigate their gas-sensing performance. Nanostructures assembled by short, unordered and well-ordered rectangular nanorods were successfully fabricated, corresponding to infant, abnormal and blooming SnO nanoflowers, respectively. In comparison, sensor based on blooming SnO nanoflowers exhibited significantly enhanced gas response to ethanol than the other two, not only in terms of the sensitivity but also the response/recovery time, which may be mainly attributed to the sufficient diffusion channel and exposed surface provided by finely dispersed nanorods in the blooming nanoflowers. [ABSTRACT FROM AUTHOR]

SnO semiconductor gas sensor as the most commonly sensors are used to check the main fault characteristic of dissolved gases in transformer oil. In current study, SnO rods and spheres were synthesized by the hydrothermal routes with tin salts under different conditions. We investigated the intermediate reaction on the formation of SnO with different morphologies and proposed their possible formation mechanisms. The structures and morphologies of this hierarchical architecture were characterized in detail by means of powder X-ray diffraction, field-emission scanning electron microscopy. Moreover, the obtained SnO rods are found to show the better sensing performances than the other structure with higher gas response during the response-recovery time, lower working temperature, and more sensitive response in the same concentration to carbon monoxide. Our results also illustrate that gas sensing properties of SnO can be significantly improved by varying the morphologies of the structures. The results may hold substantial promise in power system gas-sensing applications. [ABSTRACT FROM AUTHOR]

In current study, SnO spheres, corals, sheets and octahedrons were synthesized by the hydrothermal routes with tin salts under different conditions. We investigated the intermediate reaction on the formation of SnO with different morphologies and proposed their possible formation mechanisms. Moreover, the obtained SnO sheets are found to show the better sensing performances than that of other structures. Our results also illustrate that gas sensing properties of SnO can be significantly improved by varying the morphologies of the structures. The results may hold substantial promise in multidimensional gas-sensing applications. [ABSTRACT FROM AUTHOR]

In this work, we reported successful synthesis of SnO nanocubes and nanospheres via a facile hydrothermal technique. The as-obtained SnO nanostructures have been characterized by X-ray diffraction and field-emission scanning electron microscopy. The formation mechanism of aforementioned SnO nanostructures has been proposed in detail, especially SnO nanaocubes, which has been systematically investigated by varying the reaction time and the surfactant SDS play a key role in growth process of nanocubes. Furthermore, the gas sensing properties of as-prepared SnO nanostructures have been tested towards ethanol. Interestingly, it is noted that gas sensing performance of nanocubes are superior to nanospheres, which certified that the gas sensing properties can be enhanced by controlling the morphologies and the SnO nanocubes maybe a promising candidate based materials in the fields of gas sensors. [ABSTRACT FROM AUTHOR]

ZnO nanostructures with four different morphologies (nanoparticles, nanorods, mixtures of nanoparticles and nanorods as well as nanoflowers aggregated by nanoparticles and nanorods) were synthesized successfully via simple hydrothermal method. The crystalline structures of ZnO samples were characterized by the X-ray diffraction and the microscopic morphologies of ZnO samples were observed by the scanning electron microscopy. Besides, the probable growth mechanisms of ZnO nanostructures with four different morphologies were proposed. We found that Hexamethylenetetramine (HMT), the halogen ion F and the concentration of OH played a significant role in the morphology of ZnO nanocrystalline. In addition, further gas sensitivity measurements revealed that all the as-synthesized ZnO performed gas-sensing properties towards the ethanol gas with very low concentration. Furthermore, the gas-sensing properties of nanoflowers were much more excellent than the other three low-dimension nanostructures, which indicated that the splendid gas-sensing properties of ZnO nanoflowers were contributed to their large specific area. [ABSTRACT FROM AUTHOR]

We report the microstructures and gas-sensing properties of various low dimensional nano-TiO prepared by hydrothermal method. In particular, we make a comparison of the ethanol sensing properties among TiO nanospheres, nanorods, nanobelts. The obtained nanobelts TiO is found to show best sensing performances owing to the largest surface area and porous structure providing many quick passages to absorb and desorb gas, suggesting that the gas sensing properties of nanocrystals can be significantly improved by tailoring the shapes and morphologies of nanocrystals. [ABSTRACT FROM AUTHOR]

Morphologies frequently play a critical role in determining the properties of nanomaterials. In current researches, we successfully synthesized varieties of SnO nanostructures from 1D to 3D via a facile hydrothermal method. The as-obtained samples were characterized by X-ray diffraction and scanning electron microscopy. Then the plausible growth mechanism are proposed in detail. Furthermore, PEG and CO(NH) may have an effect on the formation of 1D and 2D nanostructures of SnO as aggregation and template, respectively. The gas sensing properties of SnO nanostructures from 1D to 3D toward ethanol were investigated. Surprisingly, we noticed that SnO nanosheets show the highest gas sensing response while the nanospheres is opposite, which provided a substantial promising candidate of gas sensors and further indicated that gas sensing properties can be enhanced by tailoring the morphologies of nanomaterials in practical application. [ABSTRACT FROM AUTHOR]

Octahedral cuprous oxide has been synthesized by a simple hydrothermal method using copper sulphate and sodium hydroxide as raw materials in ethanol amine/distilled water mixed solution. The synthesized cuprous oxide powders were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy. XRD pattern exhibited that the nanocrystalline nature with cubic structure for the synthesized nanostructures. Analysis results reveal that pH value of solution plays an important role in the formation of octahedron shape for cuprous oxide. A probable formation mechanism of octahedral cuprous oxide is also proposed. [ABSTRACT FROM AUTHOR]

In this work, 2D SnO nanosheets were synthesized via a polyvinylpyrrolidone (PVP)-assisted hydrothermal method. X-ray diffraction and scanning electron microscopy were used to examine the chemical composition and nanostructures. It was found that the concentration of PVP played a critical role in governing the assembly process of nanostructures. Further, their gas-sensing performances were investigated comprehensively. The nanosheet-III structures were found to show the most superior gas-sensing properties due to their largest specific surface and fashionable assembly. [ABSTRACT FROM AUTHOR]

A type of titanium precursor, H-exchanged titanate nanobelts, was used to prepare nanosized anatase titanium dioxide (TiO) with various morphologies by hydrothermal method. Nanorods, nanobelts, nano-polyhedrons and nanoparticles were successfully synthesized. We found that CTAB and EDTA-4Na play critical roles in synthesizing the nanorods and nano-polyhedrons. All the samples exhibit rapid response and recovery time to ethanol, but Nanorods, nanobelts and nano-polyhedrons show lager response than nanoparticles. [ABSTRACT FROM AUTHOR]