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Formation of tungsten oxide nanostructures by laser pyrolysis: stars, fibres and spheres.

Govender M, Shikwambana L, Mwakikunga BW, Sideras-Haddad E, Erasmus RM, Forbes A - Nanoscale Res Lett (2011)

Bottom Line: In this letter, the production of multi-phase WO3 and WO3-x (where x could vary between 0.1 and 0.3) nanostructures synthesized by CO2-laser pyrolysis technique at varying laser wavelengths (9.22-10.82 mm) and power densities (17-110 W/cm2) is reported.The average spherical particle sizes for the wavelength variation samples ranged between 113 and 560 nm, and the average spherical particle sizes for power density variation samples ranged between 108 and 205 nm.It was found that more concentrated starting precursors result in the growth of hierarchical structures such as stars, whereas dilute starting precursors result in the growth of simpler structures such as wires.

View Article: PubMed Central - HTML - PubMed

Affiliation: CSIR National Laser Centre, P, O, Box 395, Pretoria 0001, South Africa. BMwakikunga@csir.co.za.

ABSTRACT
In this letter, the production of multi-phase WO3 and WO3-x (where x could vary between 0.1 and 0.3) nanostructures synthesized by CO2-laser pyrolysis technique at varying laser wavelengths (9.22-10.82 mm) and power densities (17-110 W/cm2) is reported. The average spherical particle sizes for the wavelength variation samples ranged between 113 and 560 nm, and the average spherical particle sizes for power density variation samples ranged between 108 and 205 nm. Synthesis of W18O49 (= WO2.72) stars by this method is reported for the first time at a power density and wavelength of 2.2 kW/cm2 and 10.6 μm, respectively. It was found that more concentrated starting precursors result in the growth of hierarchical structures such as stars, whereas dilute starting precursors result in the growth of simpler structures such as wires.

No MeSH data available.


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Left: the Raman spectrum of the sample prepared at the 10.6-μm wavelength and 85 W/cm2 power density with a SEM micrograph in the inset showing the morphology. Right: the corresponding XRD spectrum with the histogram of the diameters of a selection of the nanostructures with the corresponding SEM micrograph in the inset. The Raman and XRD suggest a monoclinic phase WO3-x(x~0.1).
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Figure 6: Left: the Raman spectrum of the sample prepared at the 10.6-μm wavelength and 85 W/cm2 power density with a SEM micrograph in the inset showing the morphology. Right: the corresponding XRD spectrum with the histogram of the diameters of a selection of the nanostructures with the corresponding SEM micrograph in the inset. The Raman and XRD suggest a monoclinic phase WO3-x(x~0.1).

Mentions: Unlike the increasing wavelength, the increase in power density led to more ordered and shaped nanostructures, presumably because of the increase in energy rate. The 10.6 μm wavelength appeared to favour the formation of monoclinic phase tungsten oxide Furthermore, it was observed that at high enough power densities, it was more likely for helping nanostructure growth. At such low power densities (17-110 W/cm2) on the 10.6 μm wavelength, the particle sizes did not show a decrease with increasing power density as predicted [27] for the higher power density range (1-100 kW/cm2). The nanosphere diameters of this sample were found to be in the range 150-400 nm as depicted in inset of Figure 6. It was observed that the overall particle sizes were smaller for the power variation experiment, while the wavelength variation experiment showed larger particle sizes. The increase in power density did not always favour the formation of WO3, and since the photon energy was constant, only the number of photons per unit time varied.


Formation of tungsten oxide nanostructures by laser pyrolysis: stars, fibres and spheres.

Govender M, Shikwambana L, Mwakikunga BW, Sideras-Haddad E, Erasmus RM, Forbes A - Nanoscale Res Lett (2011)

Left: the Raman spectrum of the sample prepared at the 10.6-μm wavelength and 85 W/cm2 power density with a SEM micrograph in the inset showing the morphology. Right: the corresponding XRD spectrum with the histogram of the diameters of a selection of the nanostructures with the corresponding SEM micrograph in the inset. The Raman and XRD suggest a monoclinic phase WO3-x(x~0.1).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211218&req=5

Figure 6: Left: the Raman spectrum of the sample prepared at the 10.6-μm wavelength and 85 W/cm2 power density with a SEM micrograph in the inset showing the morphology. Right: the corresponding XRD spectrum with the histogram of the diameters of a selection of the nanostructures with the corresponding SEM micrograph in the inset. The Raman and XRD suggest a monoclinic phase WO3-x(x~0.1).
Mentions: Unlike the increasing wavelength, the increase in power density led to more ordered and shaped nanostructures, presumably because of the increase in energy rate. The 10.6 μm wavelength appeared to favour the formation of monoclinic phase tungsten oxide Furthermore, it was observed that at high enough power densities, it was more likely for helping nanostructure growth. At such low power densities (17-110 W/cm2) on the 10.6 μm wavelength, the particle sizes did not show a decrease with increasing power density as predicted [27] for the higher power density range (1-100 kW/cm2). The nanosphere diameters of this sample were found to be in the range 150-400 nm as depicted in inset of Figure 6. It was observed that the overall particle sizes were smaller for the power variation experiment, while the wavelength variation experiment showed larger particle sizes. The increase in power density did not always favour the formation of WO3, and since the photon energy was constant, only the number of photons per unit time varied.

Bottom Line: In this letter, the production of multi-phase WO3 and WO3-x (where x could vary between 0.1 and 0.3) nanostructures synthesized by CO2-laser pyrolysis technique at varying laser wavelengths (9.22-10.82 mm) and power densities (17-110 W/cm2) is reported.The average spherical particle sizes for the wavelength variation samples ranged between 113 and 560 nm, and the average spherical particle sizes for power density variation samples ranged between 108 and 205 nm.It was found that more concentrated starting precursors result in the growth of hierarchical structures such as stars, whereas dilute starting precursors result in the growth of simpler structures such as wires.

View Article: PubMed Central - HTML - PubMed

Affiliation: CSIR National Laser Centre, P, O, Box 395, Pretoria 0001, South Africa. BMwakikunga@csir.co.za.

ABSTRACT
In this letter, the production of multi-phase WO3 and WO3-x (where x could vary between 0.1 and 0.3) nanostructures synthesized by CO2-laser pyrolysis technique at varying laser wavelengths (9.22-10.82 mm) and power densities (17-110 W/cm2) is reported. The average spherical particle sizes for the wavelength variation samples ranged between 113 and 560 nm, and the average spherical particle sizes for power density variation samples ranged between 108 and 205 nm. Synthesis of W18O49 (= WO2.72) stars by this method is reported for the first time at a power density and wavelength of 2.2 kW/cm2 and 10.6 μm, respectively. It was found that more concentrated starting precursors result in the growth of hierarchical structures such as stars, whereas dilute starting precursors result in the growth of simpler structures such as wires.

No MeSH data available.


Related in: MedlinePlus