Zhongxi Yang

Flower-like In2O3 hierarchical nanostructures: synthesis, characterization, and gas sensing properties

Hierarchical In2O3 nanostructures with flower-like morphology were synthesized by annealing In(OH)3 precursors prepared via a one-step hydrothermal method using the mixed solution of N,N-dimethylformamide (DMF) and deionized water as solvent. The crystal structure and morphology of the obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption–desorption analyses. The results revealed that the synthesized flower-like In2O3 hierarchical nanostructures were constructed from In2O3 nanoplates which connected with each other to form flower-like architecture. On the basis of experimental results, a possible mechanism for the formation of flower-like In2O3 hierarchical nanostructures was considered. Moreover, gas sensing investigation showed that the sensor based on flower-like In2O3 hierarchical nanostructures exhibited a superior response, good selectivity and stability to ethanol gas. The enhancement in gas sensing properties was attributed to their unique structure, large surface areas, and more surface active sites.

Dispersed SnO2 nanoparticles on MoS2 nanosheets for superior gas-sensing performances to ethanol

The unique properties of MoS2 nanosheets make them a promising supporting substrate for preventing the interparticle aggregation of metal–oxide–semiconductor nanomaterials. Novel composites were successfully obtained by a two-step low temperature hydrothermal method for the synthesis of SnO2 nanoparticles dispersing on the surfaces of MoS2 nanosheets. The morphology and structure of the as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Owing to the supporting substrate of specific two-dimensional MoS2 nanosheets and the superior gas-sensing performance offered by ultrasmall SnO2 nanoparticles, the sensor based on SnO2@MoS2 composites exhibits high response and good selectivity to ethanol gas.

Facile fabrication and enhanced gas sensing properties of hierarchical MoO3 nanostructures

Hierarchical nanostructures are very promising gas-sensing materials due to their well-aligned structures with less agglomerated configurations. In this paper, hierarchical MoO3 nanostructures were successfully synthesized through the oxidization conversion of hydrothermally synthesized MoS2 precursors. The morphology and microstructure were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric and differential scanning calorimeter analysis (TG-DSC), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and N2 adsorption–desorption analyses. The results clearly reveal that MoS2 precursors can completely transfer into MoO3 via the annealing process at 400 °C. And the as-prepared hierarchical MoO3 nanostructures are about 500 nm in diameter, which are constructed by relatively densely packed nanosheets with the thickness of around 5–10 nm. Based on the experimental results, a possible mechanism for the formation of hierarchical MoO3 nanostructures was speculated. Furthermore, owing to the well-defined and uniform hierarchical structure, the sensor based on hierarchical MoO3 nanostructures shows superior gas sensing performance towards ethanol and it maybe has potential application in the detection of ethanol vapors.

Tailored products of dealloying as-sintered Al–Cu alloys in sodium hydroxide solutions

In this work, a two-step method of cold-press sintering–dealloying was applied to fabricate nanostructured copper/copper oxide mixtures. As-sintered AlxCu(100−x) (x = 60, 67 and 85 at%) alloy bulks that were prepared using cold-press sintering were dealloyed in 20 wt% NaOH solution under free corrosion conditions. In addition, Al67Cu33 was studied in detail to study the effects of sintering parameters on precursors and products. The XRD and SEM results suggest that a higher temperature and long duration are beneficial to promote atom diffusion and the formation of a single Al2Cu phase and tailored Cu, Cu2O and CuO with various morphologies were obtained after dealloying. During dealloying, the Al2Cu phase could be fully corroded, whereas the AlCu phase obtained from a higher sintering temperature remains after dealloying. Electrochemical studies show that the critical corrosion potential (Ecrit) of the as-sintered alloys, pure Al and pure Cu, are extremely close to the free corrosion potential (Ecorr), the intersection point of potentiodynamic cathodic and anodic polarization curves. Cyclic voltammetry results imply that the formation of oxides may be related to the reaction of dissolved oxygen and copper ions. A group of recommended parameters was identified: a pressure of 312.5 MPa, sintering temperature of 500 °C and holding time of 60 min, from which a mixture of Cu/Cu2O/CuO could be obtained which exhibits an excellent initial (10 min) degradation efficiency of 77.4% to methyl orange when exposed in an ultrasonic environment in ambient atmosphere.

In2O3-functionalized MoO3 heterostructure nanobelts with improved gas-sensing performance

A novel heterostructure of In2O3 nanoparticle-functionalized MoO3 nanobelts was synthesized via a simple solution method. The phase purity, morphology and structure of the as-prepared In2O3-functionalized MoO3 heterostructure nanobelts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). To demonstrate the potential applications of such In2O3/MoO3 composites, the as-prepared products were used to fabricate a gas sensor that was then investigated for gas-sensing performances. Results of the test showed that the response of In2O3 nanoparticle-functionalized MoO3 nanobelts against 10 ppm trimethylamine (TMA) is up to 31.69 at the working temperature of 260 °C, which is higher than that of bare MoO3 nanobelts. Moreover, the In2O3-functionalized MoO3 heterostructure sensor also exhibits excellent selectivity and rapid response and recovery speed. Such behaviors are attributed to the combination of In2O3 nanoparticles and uniformly decorated MoO3 nanobelts endowing a fascinating sensing performance for a novel sensing material, which may provide a new strategy to enhance the performance of sensing materials in the application of gas sensors.