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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: Raman spectrum and Right: XRD spectrum of the sample containing the stars.
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Figure 3: Left: Raman spectrum and Right: XRD spectrum of the sample containing the stars.

Mentions: The Raman and XRD spectra of the samples containing the stars are shown in Figure 3. The stars were not visible under the Raman microscope and so various spots were analyzed on the sample. The Raman study shows that the sample is amorphous after annealing, and the lack of a dominant peak at 800 cm-1 suggests the absence of monoclinic phase tungsten trioxide and possibly oxygen deficiency [13,14]. The Raman peaks found near 224 cm-1, 288 cm-1 and 320 cm-1 are indicative of a W-O-W stretching mode of a tungsten oxide. The Raman peak at 700 cm-1 is designated to the bridging O-W-O vibrations in tungsten trioxide, and the asymmetry in this phonon peak shows that there are a number of phonons confined in the tungsten oxide layer of particles. This indicates that the product is composed of particles less than 20 nm in size [15,16]. The peak near 960 cm-1 is assigned to the W6+ = O symmetric stretching mode.


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: Raman spectrum and Right: XRD spectrum of the sample containing the stars.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Left: Raman spectrum and Right: XRD spectrum of the sample containing the stars.
Mentions: The Raman and XRD spectra of the samples containing the stars are shown in Figure 3. The stars were not visible under the Raman microscope and so various spots were analyzed on the sample. The Raman study shows that the sample is amorphous after annealing, and the lack of a dominant peak at 800 cm-1 suggests the absence of monoclinic phase tungsten trioxide and possibly oxygen deficiency [13,14]. The Raman peaks found near 224 cm-1, 288 cm-1 and 320 cm-1 are indicative of a W-O-W stretching mode of a tungsten oxide. The Raman peak at 700 cm-1 is designated to the bridging O-W-O vibrations in tungsten trioxide, and the asymmetry in this phonon peak shows that there are a number of phonons confined in the tungsten oxide layer of particles. This indicates that the product is composed of particles less than 20 nm in size [15,16]. The peak near 960 cm-1 is assigned to the W6+ = O symmetric stretching mode.

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