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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.


EDS line scanning profile. TEM-EDX line concentration profiles of W and O along the line drawn across the diameter of a typical tungsten oxide nanowire synthesized by a catalyst-free thermal evaporation method. Cu and C in the inset table are due to TEM grid.
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Figure 4: EDS line scanning profile. TEM-EDX line concentration profiles of W and O along the line drawn across the diameter of a typical tungsten oxide nanowire synthesized by a catalyst-free thermal evaporation method. Cu and C in the inset table are due to TEM grid.

Mentions: 1. Oxygen vacancies: The NUV emission is attributed to the localized states of oxygen vacancies in the conduction band of the needle-like tungsten oxide nanostructures. Luo et al. [8] reported an NUV emission band centered at 395 nm from WO3 - x nanowire networks, even if the emission band was not as sharp and strong as the one from the needle-like tungsten oxide nanostructures synthesized in this work. They attributed the NUV emission to the states of oxygen vacancies in the conduction band of WO3 - x nanowire networks. They also demonstrated using SEM and X-ray photoemission spectroscopy analyses that oxygen vacancies existed in the WO3 - x nanowire network but not in the WO3 nanowire network. Needle-like tungsten oxide nanostructures were grown in zone 2 (590°C to 750°C), i.e., in quite a low-temperature range. The W/O atomic ratio (8.01/2.80) in the needle-like tungsten nanostructures is approximately 2.86 as shown in the energy-dispersive X-ray spectroscopy (EDS) line scanning profile (Figure 4), so that the nanostructures do not have a molecular formula of WO3 but of WO3 - x. This may be due to the relatively low process temperature for the tungsten nanowire synthesis. The tungsten oxide nanostructures grown at low temperatures have been reported to commonly possess more defects such as oxygen vacancies [9]. Therefore, the NUV emission from the needle-like tungsten nanostructures was attributed to the localized states of oxygen vacancies, as Luo et al. [8] suggested.


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)

EDS line scanning profile. TEM-EDX line concentration profiles of W and O along the line drawn across the diameter of a typical tungsten oxide nanowire synthesized by a catalyst-free thermal evaporation method. Cu and C in the inset table are due to TEM grid.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3211871&req=5

Figure 4: EDS line scanning profile. TEM-EDX line concentration profiles of W and O along the line drawn across the diameter of a typical tungsten oxide nanowire synthesized by a catalyst-free thermal evaporation method. Cu and C in the inset table are due to TEM grid.
Mentions: 1. Oxygen vacancies: The NUV emission is attributed to the localized states of oxygen vacancies in the conduction band of the needle-like tungsten oxide nanostructures. Luo et al. [8] reported an NUV emission band centered at 395 nm from WO3 - x nanowire networks, even if the emission band was not as sharp and strong as the one from the needle-like tungsten oxide nanostructures synthesized in this work. They attributed the NUV emission to the states of oxygen vacancies in the conduction band of WO3 - x nanowire networks. They also demonstrated using SEM and X-ray photoemission spectroscopy analyses that oxygen vacancies existed in the WO3 - x nanowire network but not in the WO3 nanowire network. Needle-like tungsten oxide nanostructures were grown in zone 2 (590°C to 750°C), i.e., in quite a low-temperature range. The W/O atomic ratio (8.01/2.80) in the needle-like tungsten nanostructures is approximately 2.86 as shown in the energy-dispersive X-ray spectroscopy (EDS) line scanning profile (Figure 4), so that the nanostructures do not have a molecular formula of WO3 but of WO3 - x. This may be due to the relatively low process temperature for the tungsten nanowire synthesis. The tungsten oxide nanostructures grown at low temperatures have been reported to commonly possess more defects such as oxygen vacancies [9]. Therefore, the NUV emission from the needle-like tungsten nanostructures was attributed to the localized states of oxygen vacancies, as Luo et al. [8] suggested.

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.