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Intense ultraviolet emission from needle-like WO3 nanostructures synthesized by noncatalytic thermal evaporation.

Park S, Kim H, Jin C, Lee C - Nanoscale Res Lett (2011)

Bottom Line: Photoluminescence measurements showed that needle-like tungsten oxide nanostructures synthesized at 590°C to 750°C by the thermal evaporation of WO3 nanopowders without the use of a catalyst had an intense near-ultraviolet (NUV) emission band that was different from that of the tungsten oxide nanostructures obtained in other temperature ranges.The intense NUV emission might be due to the localized states associated with oxygen vacancies and surface states.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, Inha University, 253 Yonghyeon-dong, Nam-gu, Incheon 402-751, Republic of Korea. cmlee@inha.ac.kr.

ABSTRACT
Photoluminescence measurements showed that needle-like tungsten oxide nanostructures synthesized at 590°C to 750°C by the thermal evaporation of WO3 nanopowders without the use of a catalyst had an intense near-ultraviolet (NUV) emission band that was different from that of the tungsten oxide nanostructures obtained in other temperature ranges. The intense NUV emission might be due to the localized states associated with oxygen vacancies and surface states.

No MeSH data available.


SEM images of the tungsten oxide nanostructures. SEM images of the tungsten oxide nanostructures grown in the different substrate temperature zones.
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Figure 2: SEM images of the tungsten oxide nanostructures. SEM images of the tungsten oxide nanostructures grown in the different substrate temperature zones.

Mentions: Figure 2a,b,c,d,e shows SEM images of the tungsten oxide nanostructures synthesized at temperature zones 1 to 5 (Figure 1), respectively. A pad tungsten oxide layer and a very low density of tungsten oxide whiskers oriented in random directions on the pad tungsten oxide layer in zone 1 were observed (Figure 2a), which suggests that the two-dimensional (2D) nanostructures formed first on the Si substrate and subsequently 1D nanostructures formed on the pregrown 2D nanostructures. The diameters and lengths of the whiskers were in the range of a few tens of nanometers and 0.5 to 2 μm, respectively. High-density fine needle-like tungsten oxide nanowires oriented in random directions were observed in zone 2 (Figure 2b). The diameters and lengths of these nanowires were in the range of a few tens to a few hundreds of nanometers and 5 to 10 μm, respectively. The nanowires were oriented randomly, and some appeared to be connected to each other. Larva-like nanostructures were grown in random directions in zone 3 (Figure 2c). They were partially networked by the growth of secondary dendrites. The nanostructures were not uniform in diameter. The diameters of the nanostructures ranged from 0.2 to 1.5 μm, and the lengths were in the range of 3 to 6 μm. Each nanostructure had several nodes like a larva. The nanostructures grown in zone 4 had a very short rod-like morphology with a rectangular or square cross-section (Figure 2d). They were particles with an orthorhombic shape; the edge lengths of which were in the range of 1 to 3 μm. A tungsten oxide film thicker than the pad tungsten oxide grown in zone 1 was grown again in zone 5 (Figure 2e). Based on the SEM images of the nanostructures grown in the different temperature zones, the individual nanostructures appear to change from a longer, thinner needle-like wire morphology to a shorter, thicker rod-like morphology as the substrate temperature was increased.


Intense ultraviolet emission from needle-like WO3 nanostructures synthesized by noncatalytic thermal evaporation.

Park S, Kim H, Jin C, Lee C - Nanoscale Res Lett (2011)

SEM images of the tungsten oxide nanostructures. SEM images of the tungsten oxide nanostructures grown in the different substrate temperature zones.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211871&req=5

Figure 2: SEM images of the tungsten oxide nanostructures. SEM images of the tungsten oxide nanostructures grown in the different substrate temperature zones.
Mentions: Figure 2a,b,c,d,e shows SEM images of the tungsten oxide nanostructures synthesized at temperature zones 1 to 5 (Figure 1), respectively. A pad tungsten oxide layer and a very low density of tungsten oxide whiskers oriented in random directions on the pad tungsten oxide layer in zone 1 were observed (Figure 2a), which suggests that the two-dimensional (2D) nanostructures formed first on the Si substrate and subsequently 1D nanostructures formed on the pregrown 2D nanostructures. The diameters and lengths of the whiskers were in the range of a few tens of nanometers and 0.5 to 2 μm, respectively. High-density fine needle-like tungsten oxide nanowires oriented in random directions were observed in zone 2 (Figure 2b). The diameters and lengths of these nanowires were in the range of a few tens to a few hundreds of nanometers and 5 to 10 μm, respectively. The nanowires were oriented randomly, and some appeared to be connected to each other. Larva-like nanostructures were grown in random directions in zone 3 (Figure 2c). They were partially networked by the growth of secondary dendrites. The nanostructures were not uniform in diameter. The diameters of the nanostructures ranged from 0.2 to 1.5 μm, and the lengths were in the range of 3 to 6 μm. Each nanostructure had several nodes like a larva. The nanostructures grown in zone 4 had a very short rod-like morphology with a rectangular or square cross-section (Figure 2d). They were particles with an orthorhombic shape; the edge lengths of which were in the range of 1 to 3 μm. A tungsten oxide film thicker than the pad tungsten oxide grown in zone 1 was grown again in zone 5 (Figure 2e). Based on the SEM images of the nanostructures grown in the different temperature zones, the individual nanostructures appear to change from a longer, thinner needle-like wire morphology to a shorter, thicker rod-like morphology as the substrate temperature was increased.

Bottom Line: Photoluminescence measurements showed that needle-like tungsten oxide nanostructures synthesized at 590°C to 750°C by the thermal evaporation of WO3 nanopowders without the use of a catalyst had an intense near-ultraviolet (NUV) emission band that was different from that of the tungsten oxide nanostructures obtained in other temperature ranges.The intense NUV emission might be due to the localized states associated with oxygen vacancies and surface states.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Materials Science and Engineering, Inha University, 253 Yonghyeon-dong, Nam-gu, Incheon 402-751, Republic of Korea. cmlee@inha.ac.kr.

ABSTRACT
Photoluminescence measurements showed that needle-like tungsten oxide nanostructures synthesized at 590°C to 750°C by the thermal evaporation of WO3 nanopowders without the use of a catalyst had an intense near-ultraviolet (NUV) emission band that was different from that of the tungsten oxide nanostructures obtained in other temperature ranges. The intense NUV emission might be due to the localized states associated with oxygen vacancies and surface states.

No MeSH data available.