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Flower-like ZnO microstrucutures (ZMFs) self-assembled by nanosheets were fabricated by a simple template-free hydrothermal method, and the nanosheets were observed with a great many of mesopores. Without adding NaOH, sphere-like ZnO microstrucutures (ZMSs) which were covered by nanosheets were obtained. Subsequently, according to the characterization of SEM and TEM for ZMFs nanosheets, the possible formation mechanisms and simulation of ZMFs were discussed. The novel ZMFs presented numerous mesopores of size around 6 nm and high BET specific area (about 36.886 m/g) which contributed to its high gas-sensing performance. In comparison with the ZMSs-based sensor, the ZMFs-based sensor displayed excellent gas-sensing performance to the ethanol gas with high sensitivity of nearly 35 at the concentration of 250 ppm. [ABSTRACT FROM AUTHOR]

We have successfully reported a new diamond-like morphology of zinc oxide (ZnO) structures via a simple hydrothermal method and discussed its probable growth mechanism. Compared with other morphologies of ZnO structures (microrods and nanosheets), nanodiamonds have excellent gas-sensing property owning to its large specific surface area, holding the perfect promise for ZnO powders as underlying gas-sensing materials. Furthermore, the as-prepared nanosheets assisted with the sodium citrate as an additive were found to show better gas-sensing property due to the smaller size than microrods. We found the positive role of the sodium citrate and reaction time in the growth of nanosheets and nanodiamonds respectively and the corresponding influences on growth mechanism were discussed. [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]

Multi-layered ZnO circular nanodisks were efficiently fabricated using sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) polymer by a controlled hydrothermal method. As-prepared ZnO nanostructures were characterized by X-ray powder diffraction, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. The effect of SDS and PVP polymer on the formation of ZnO multi-layer nanostructures was described in detail. Based on experimental results, a possible mechanism of circular disk formation was proposed. The gas-sensing properties of multi-layered nanodisks were reported for formaldehyde under different concentrations from 5 to 1200 ppm at 300 °C. A higher response toward formaldehyde was observed, rendering the multi-layered nanostructures a promising gas-sensing material for the on-site detection of formaldehyde. [ABSTRACT FROM AUTHOR]

Regular hexagonal embedded ZnO nanorods were successfully prepared by a simple hydrothermal method. The addition of urea as a homogeneous precursor was found to play a vital role in the embedding of secondary nanorods. The nanostructures were characterized by XRD, SEM, and EDS. The gas-sensing properties of secondary grown embedded nanorods were reported for formaldehyde, ethanol, methanol, acetone, and ammonia at different concentrations and temperatures. A higher response and greater selectivity toward formaldehyde than other gases was observed. A sharp response with the best recovery time was achieved at an optimum temperature of 200 °C. [ABSTRACT FROM AUTHOR]

In this article, a sealed nanotube of ZnO was successfully obtained by a simple hydrothermal technique, which employed Hexamethylene tetramine (HMT) and Fluorinion (F−) as the active agents. The rod-like nanotubes structures were observed through field-emission scanning electron microscopy. The high-resolution transmission electron microscope exhibited a shell-enclosed nanotube structures. On the basis of experimental observations, including temperature, pH of the solution and acting agents, a growth mechanism was proposed. The as-prepared nanostructures showed excellent gas sensitivities to different gases (ethanol, ammonia gas, formaldehyde gas) with a quite low concentration respectively. [ABSTRACT FROM AUTHOR]

Abstract: Hexagonal ZnO nanocones were successfully prepared using a controlled hydrothermal method with the assistance of double anionic surfactants. The products were characterized using X-ray powder diffraction. The morphologies of ZnO nanostructures were characterized using field-emission scanning electron microscopy and high-resolution transmission electron microscopy. The effects of the addition of one anionic to another anionic reagent in the crystal structure formation were discussed in detail. The gas sensing properties were measured for formaldehyde. [Copyright &y& Elsevier]

Abstract: Regular hexagonal twinned ZnO nanodisks were successfully prepared from nanodisks using a controlled hydrothermal method with the assistance of double surfactants. The products were characterized using X-ray powder diffraction. The morphologies of ZnO nanostructures were characterized in detail using field-emission scanning electron microscopy and high-resolution transmission electron microscopy. Based on the experimental results, a growth mechanism for hexagonal structure was proposed. [Copyright &y& Elsevier]