Structure and optical properties of tungsten oxide nanomaterials prepared by a modified plasma arc gas condensation technique

Su, Chung-Yen; Lin, Hsuan Ching; Yang, Tsung Kun; Lin, Chung Kwei

doi:10.1007/s11051-009-9730-y

Cited by 18 publications

(4 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In these reports, the synthesis took place mostly in a solution involving other chemical compounds, i.e., the synthesis routes were chemical rather than physical. WO 3 and non-stoichiometric WO 3−x nanorods and nanowires can be fabricated with physical or chemical vapor deposition techniques [ 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. Baek et al [ 51 ] fabricated monoclinic WO 3 nanowires on W substrate by heating WO 3 powder under vacuum conditions.…”

Section: Resultsmentioning

confidence: 99%

Formation Pathways of Lath-Shaped WO3 Nanosheets and Elemental W Nanoparticles from Heating of WO3 Nanocrystals Studied via In Situ TEM

Chen

Huis

2023

Materials

View full text Add to dashboard Cite

WO3 is a versatile material occurring in many polymorphs, and is used in nanostructured form in many applications, including photocatalysis, gas sensing, and energy storage. We investigated the thermal evolution of cubic-phase nanocrystals with a size range of 5–25 nm by means of in situ heating in the transmission electron microscope (TEM), and found distinct pathways for the formation of either 2D WO3 nanosheets or elemental W nanoparticles, depending on the initial concentration of deposited WO3 nanoparticles. These pristine particles were stable up to 600 °C, after which coalescence and fusion of the nanocrystals were observed. Typically, the nanocrystals transformed into faceted nanocrystals of elemental body-centered-cubic W after annealing to 900 °C. However, in areas where the concentration of dropcast WO3 nanoparticles was high, at a temperature of 900 °C, considerably larger lath-shaped nanosheets (extending for hundreds of nanometers in length and up to 100 nm in width) were formed that are concluded to be in monoclinic WO3 or WO2.7 phases. These lath-shaped 2D particles, which often curled up from their sides into folded 2D nanosheets, are most likely formed from the smaller nanoparticles through a solid–vapor–solid growth mechanism. The findings of the in situ experiments were confirmed by ex situ experiments performed in a high-vacuum chamber.

show abstract

Section: Resultsmentioning

confidence: 99%

Formation Pathways of Lath-Shaped WO3 Nanosheets and Elemental W Nanoparticles from Heating of WO3 Nanocrystals Studied via In Situ TEM

Chen

Huis

2023

Materials

View full text Add to dashboard Cite

show abstract

“…In general, two PL emissions have been reported, namely, ultraviolet and blue [14,21]. The former has been attributed to quantum confinement effects (band-to-band transition) and the second one to oxygen vacancies or defects [22,23].…”

Section: Optical and Electronic Propertiesmentioning

confidence: 99%

Physical Properties of Macroporous Tungsten Oxide Thin Films and Their Impact on the Photocurrent Density

Riech

Acosta

Zambrano-Arjona

et al. 2013

International Journal of Photoenergy

View full text Add to dashboard Cite

Tungsten trioxide (WO3) films were prepared using polystyrene spheres of two different diameters as a template in order to create porous layers. X-ray diffraction data and electron microscopy images show that annealed films exhibit polycrystalline structure with monoclinic phase and pore size of approximately hundred nanometers. The optical band gap energies have been determined by photoacoustic spectroscopy as 3.17 eV, and this value was not affected by sample morphology. Low temperature photoluminescence spectra exhibit broad band in the blue region. Deconvolutions of PL spectra show that there are two transitions which intensity depends on thin film pore size. We discuss the possible origin of this emissions associated with oxygen vacancies and surface states. A comparative study of the WO3films used as photoanodes is presented and correlated with PL results.

show abstract

“…In our case, the average size of crystallite is about 5 nm, which is very lower than the Bohr radius for WO 3 system (∼13 nm), so we can assume the presence of weak quantum confinement [76], [77] associated with our WO 3 system which caused the higher band gaps in WO 3 thin films [46], [77]. So this system belongs to oxygen vacancies or defects [78], [79]. Moreover, the behaviour of optical constants (n, k) in the cooling process could be due to self-trapped charge carriers, known as small polaronic and bipolaronic species which will be explained fully in Section 5.4.…”

Section: Refractive Index Film Density and Electronic Polarizabilitymentioning

confidence: 68%

Thermo Optic Coefficients and Electronic Polarizabilities of Tungsten Bronzes Using Ellipsometry

Hussain

2019

IEEE Photonics J.

View full text Add to dashboard Cite

The values of dn/dT for thermally evaporated WO 3 thin films were found to be negative either in the heating cycle (295-373 K) or in the cooling cycle (100-300 K) and were found to be of order of 10 −5 K −1. On the other hand thermo optic coefficients (TOCs: dn/dT and dk/dT values) of tungsten bronzes (H + , Li + , Na +) with different concentrations were found to be positive and negative, respectively in both the heating and cooling cycles and they were found to be in the order of 10 −4 K −1. Heating cycles show hysteresis loops of n and k for tungsten bronzes, which are good for electrochromic devices. On heating the bronzes at temperature higher than 400 K, there might be a reduction in the porosity but an irreversible disordering of hydrogen, lithium or sodium atoms could occur because of anomalous dispersions produced in the optical data. For cooling cycles, the calculated TOCs were again of the order of 10 −4 but there was an increase in dn/dT and a decrease in dk/dT values due to more amorphousness built up in the bronzes during the cooling cycles. This change in the values of TOCs for tungsten bronzes created small decrease in electronic polarizabilities (α e) which were calculated in the range from 8.003 to 8.02 × 10 −24 cm 3 in the cooling cycles.

show abstract

Structure and optical properties of tungsten oxide nanomaterials prepared by a modified plasma arc gas condensation technique

Cited by 18 publications

References 34 publications

Formation Pathways of Lath-Shaped WO3 Nanosheets and Elemental W Nanoparticles from Heating of WO3 Nanocrystals Studied via In Situ TEM

Formation Pathways of Lath-Shaped WO3 Nanosheets and Elemental W Nanoparticles from Heating of WO3 Nanocrystals Studied via In Situ TEM

Physical Properties of Macroporous Tungsten Oxide Thin Films and Their Impact on the Photocurrent Density

Thermo Optic Coefficients and Electronic Polarizabilities of Tungsten Bronzes Using Ellipsometry

Contact Info

Product

Resources

About