Growth and characterization of sodium–tungsten oxide nanobelts with U-shape cross section

Na0.3WO3 1D nanostructure forms (nanorods and nanobelts) were grown by a solid–liquid–solid mechanism from a 40 nm sputtered tungsten film deposited on a soda-lime substrate and annealed at 700 °C in a tubular furnace in N2 ambient. The morphology, structure, composition and chemical state of the prepared nanostructures were characterized by SEM, XRD, TEM, SAED and XPS measurements. The Na0.3WO3 1D nanostructures were found to have a cubic crystalline structure and grown along the [0 0 1] direction. The nanorods are a few micrometres in length and about 50 nm in diameter. The field-emission application of the prepared samples at different distances between the cathode and the anode was characterized in a UHV chamber at room temperature and a field enhancement factor of 1736 at a distance of 350 µm was found.

Section: Resultssupporting

confidence: 50%

Section: Introductionmentioning

confidence: 99%

Growth of Na_0.3WO₃nanorods for the field emission application

Azimirad¹,

Khademi²,

Akhavan³

et al. 2009

“…Therefore, the study of the variation of the optical properties of the reduced silica films containing copper-based nanoparticles at a possible higher reduction temperature (600 • C) is useful and interesting. It was previously found that the soda lime glass substrates are thermally stable up to 750 • C [27].…”

Section: Hoursmentioning

confidence: 99%

Chemical durability of metallic copper nanoparticles in silica thin films synthesized by sol–gel

Akhavan¹

2008

In this study, chemical durability of metallic copper nanoparticles dispersed in sol–gel silica thin films was investigated by exposing the films to air after a reduction process. At first, heat treatment in air for 1 h produced silica films containing crystalline cupric oxide nanoparticles agglomerated on the film surface. Subsequently, reduction of the oxidized films in a reducing environment of N2–H2 for another 1 h at temperatures of 400, 500 and 600 °C resulted in the formation of crystalline metallic Cu nanoparticles diffused in the silica matrix. The time evolution of the surface plasmon resonance absorption peak of the reduced Cu nanoparticles was studied after the reduction processes at different temperatures. By fitting the optical absorption spectra with the Mie model, the conversion of Cu into CuO in the silica films exposed to air was examined as a function of the elapsing time. It was found that increasing the reducing temperature resulted in greater diffusion of the reduced Cu nanoparticles into the substrate, and also, in a decrease in the water content of the silica film. Diffusion of the nanoparticles decreased the number of particles exposed to air, and further, the decrease in the water content densified the silica film surrounding the diffused nanoparticles. While after the reduction process of the films at 400 °C, the presence of water in the film and considerable copper on the surface resulted in conversion of 94% of the reduced Cu into CuO in just 24 h, by reducing the film at the high temperature of 600 °C, no water and small copper concentration could be detected on the silica film so that only 8% of the Cu nanoparticles converted to CuO in as much as 12 months.

“…There are several methods to grow one-dimensional (1D) nanostructures [149][150][151][152]. These nanostructures include nanowires, nanorods, nanobelts and nanotubes.…”

Section: D Nanostructure Growthmentioning

confidence: 99%

Nanoparticle catalysts

Moshfegh¹

2009

210

124

In this review, the importance of nanoparticles (NPs), with emphasis on their general and specific properties, especially the high surface-to-volume ratio (A/V), in many technological and industrial applications is studied. Some physical and chemical preparation methods for growing several metallic and binary alloy NP catalysts are reviewed. The growth and mechanism of catalytic reactions for synthesis of 1D nanostructures such as ZnO nanowires and multiwall carbon nanotubes (MWCNTs) are discussed. Gas-phase production with emphasis on dependence of catalytic activity and selectivity on size, shape and structure of NPs is also investigated. Application of NP catalysts in several technological processes including H2 production and storage as well as antibacterial effect, gas sensors and fuel cells is discussed. The mechanism of H2 production from catalytic photoelectrochemical and photocatalytic degradation reactions of some organic dyes is discussed. Finally, the future outlook of NP catalysts in various disciplines is presented.