https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:38600 xWO₃) are sub-stoichiometric metal oxides with variable Na content described by x. Methods to determine the overall x of a sample are well-known, but variations of composition within a particle have not yet been explored. In this work, electron microscopy techniques are used to determine the crystallinity and chemical composition of individual Na_0.83WO₃ nanocubes. The particles are found to be single crystals, with the top and bottom faces of the nanocubes parallel to the {100} planes. Compositional homogeneity is observed within the particles other than an approximately ≈5 nm Na-depletion layer at the edge of the particle. An O-depleted layer, believed to be the result of beam damage, is observed when the beam is scanned slowly over the edge of the particle. Calculations of the plasmon responses using the boundary element method (BEM) show that this depletion layer has a minor impact on the optical properties of the large (190 nm) particle studied of this work, but is expected to have a dramatic impact for small (20 nm) particles.]]> Wed 17 Nov 2021 12:39:37 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:41001 0.25) NaxWO3 were prepared. The degradation of rhodamine 6G (R6G) under visible and near infrared (NIR) light illumination was observed only when NaxWO3 and TiO2 were both present in the composite. Photocatalytic activity was generally higher in metallic samples than in semiconducting ones, but the sample with the highest activity had a mixture of both. This suggests that a combination of interband transitions and plasmonics-enhanced processes can be used together to catalyse reactions.]]> Thu 21 Jul 2022 10:30:19 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:27940 ISOTROPY. For HTB, there is one obvious tilting pattern, leading to a structure in space group P6₃/mmc. This differs from the space group P6₃/mcm frequently quoted from X-ray studies - these studies have in effect detected only displacements of the W cations from the centres of the WO₆ octahedra. The correct space group, taking account of both W ion displacement and the octahedral tilting, is P6₃22 - structures in this space group and matching this description have been reported. A second acceptable tilting pattern has been found, leading to a structure in P6/mmm but on a larger '2 x 2 x 2' unit cell - however, no observations of this structure have been reported. For TTB, a search at the special points of the Brillouin zones revealed only one comparable tilting pattern, in a structure with space-group symmetry I4/m on a '2^1/2 x 2^1/2 by 2' unit cell. Given several literature reports of larger unit cells for TTB, we conducted a limited search along the lines of symmetry and found structures with acceptable tilt patterns in Bbmm on a '2^1/22 x 2^1/2 x 2' unit cell. A non-centrosymmetric version has been reported in niobates, in Bbm2 on the same unit cell.]]> Sat 24 Mar 2018 07:36:10 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:50604 Mon 31 Jul 2023 12:15:50 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:37526 Mon 23 Aug 2021 12:41:10 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:30437 x WO₃, where 0  ≤  x  ≤  1, and M is a dopant ion, most commonly an alkali metal. In this work, the sodium tungsten bronzes (Na_x WO₃) are investigated as materials for plasmonic applications. The bronzes were fabricated with a solid state reaction, the dielectric function calculated using density functional theory (DFT) and the nanoparticle responses calculated with the boundary element method (BEM). The results were compared to Au and Ag, the materials most widely used in plasmonic applications. It was shown that for x  >  0.5, the solid state fabrication method produces cube-shaped particles of diameter  ≥1 µm, whose bulk optical properties are well described by a free-electron model and a rigid band structure. The addition of Na into the lattice increases the free electron density, increasing the bulk plasma frequency. Nanoparticle plasmon resonances are found to be highly tunable, and generally at a lower frequency than Au or Ag, and so sodium tungsten bronzes are predicted to be well suited to biomedical or chemical sensing applications.]]> Mon 12 Aug 2024 11:38:05 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:43003 Fri 09 Sep 2022 14:10:35 AEST ]]>