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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 10.48-μm wavelength and 51.2 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 of the corresponding SEM micrograph in the inset. The Raman and XRD suggest a monoclinic phase WO3.
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Figure 5: Left: the Raman spectrum of the sample prepared at the 10.48-μm wavelength and 51.2 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 of the corresponding SEM micrograph in the inset. The Raman and XRD suggest a monoclinic phase WO3.

Mentions: To determine how the laser wavelength plays a role in laser pyrolysis, it was varied between 9.19 and 10.84 μm at a constant power of 30 W and power density of 51.2 W/cm2. The lower power density was achieved by replacing the focusing mirror with a flat mirror to obtain a beam radius of 6.11 mm. The low power density was chosen such that all the R- and P-branches of the CO2 laser supplied a constant power output for the varying wavelengths. It was also assumed that at such low power density, minimum heating effects are involved in the laser-precursor interaction. It was found that only the 10.48-μm wavelength formed monoclinic phase WO3 according to the Raman and XRD spectra shown in Figure 5 with the corresponding SEM micrograph.


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 10.48-μm wavelength and 51.2 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 of the corresponding SEM micrograph in the inset. The Raman and XRD suggest a monoclinic phase WO3.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Left: the Raman spectrum of the sample prepared at the 10.48-μm wavelength and 51.2 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 of the corresponding SEM micrograph in the inset. The Raman and XRD suggest a monoclinic phase WO3.
Mentions: To determine how the laser wavelength plays a role in laser pyrolysis, it was varied between 9.19 and 10.84 μm at a constant power of 30 W and power density of 51.2 W/cm2. The lower power density was achieved by replacing the focusing mirror with a flat mirror to obtain a beam radius of 6.11 mm. The low power density was chosen such that all the R- and P-branches of the CO2 laser supplied a constant power output for the varying wavelengths. It was also assumed that at such low power density, minimum heating effects are involved in the laser-precursor interaction. It was found that only the 10.48-μm wavelength formed monoclinic phase WO3 according to the Raman and XRD spectra shown in Figure 5 with the corresponding SEM micrograph.

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