http://hdl.handle.net/2173/31835 Sun, 19 May 2013 04:51:30 GMT 2013-05-19T04:51:30Z http://hdl.handle.net/2173/109075 Title: SEM and Raman study of thermally treated TiO2 anatase nanopowders: influence of calcination on photocatalytic activity Authors: Mahdjoub, N.; Allen, Norman S.; Kelly, Peter; Vishnyakov, Vladimir Abstract: Titania (TiO2) nanopowders called PC 500, synthesised by the sulphate process, were annealed in air at temperatures of up to 1022 K for 30 min. The X-ray Diffraction (XRD) indicates that the thermal annealing resulted in coarsening of the average crystallite size from 13 to 72 nm. However, Scanning Electron Microscopy (SEM) reveals persistence of platelet-like structures which survive up to temperatures around 900 K. This implies that the crystals at least partially grow within the plates in 2D confinement. This implies that direct usage of Scherrer equation in this case should be approached with care. Raman spectra peak positions and the Full-Width-at-Half-Maximum (FWHM) values changed considerably after calcinations crystal growth, while, material composition and oxygen content remain unchanged. The Raman peak behaviour can be cautiously attributed to the first order phonon confinement phenomena, but both, 2D and 3D models of confinement should be accounted. The highest photoactivity, as indicated by photoinduced degradation of a mono azo dye methyl-orange (C14H14N3SO3Na), was observed in material treated at 773 K. Description: Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Journal of Photochemistry and Photobiology, A: Chemistry, published by and copyright Elsevier. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2173/109075 2010-01-01T00:00:00Z http://hdl.handle.net/2173/108934 Title: Thermally induced phase and photocatalytic activity evolution of polymorphous titania Authors: Mahdjoub, N.; Allen, Norman S.; Kelly, Peter; Vishnyakov, Vladimir Abstract: TiO2 nano-powders were prepared by hydrolysing titanium tetraisopropoxide at room temperature. The resulting products were dried at 382 K and then annealed at temperatures up to 1172 K for 1 h. Raman analysis showed different titania phase structures depending on the thermal treatment. A mixture of brookite and anatase was observed in the as-prepared sample and after thermal treatment at 472 K and 672 K, a mixture of anatase and rutile was observed at 872 K and 972 K, while a pure rutile phase was identified at 1172 K. Quantitative XRD analysis revealed nano-powders phase composition and crystallite sizes. The photoactivity was assessed by photoinduced degradation of methyl orange. All anatase–brookite compositions have showed high photoactivity while the best values were observed for the sample calcined at 472 K. Description: Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Journal of Photochemistry and Photobiology, A: Chemistry, published by and copyright Elsevier. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2173/108934 2010-01-01T00:00:00Z http://hdl.handle.net/2173/107442 Title: Surface topography and physicochemistry of silver containing titanium nitride nanocomposite coatings Authors: Whitehead, Kathryn A.; Kelly, Peter; Li, Heqing; Verran, Joanna Description: Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Journal of Vacuum Science and Technology. Part B. Microelectronics and Nanometer Structures, published by and copyright American Institute of Physics. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2173/107442 2010-01-01T00:00:00Z http://hdl.handle.net/2173/87514 Title: QLF is not readily suitable for in vivo denture plaque assessment. Authors: Coulthwaite, Lisa; Pretty, Iain A.; Smith, Philip W.; Higham, Susan M.; Verran, Joanna Abstract: OBJECTIVES: Current methods available for denture plaque assessment utilise visual and planimetric techniques. This paper evaluates the use of the Quantitative Light-induced Fluorescence system (QLF) in image capture of denture plaque and the suitability of these images for planimetric plaque measurement. It is proposed that fluorescence imaging could provide a valuable and sensitive standardising method for plaque assessment in clinical trials for denture cleansing products and denture hygiene. Indeed, the detection of red fluorescent plaque using the QLF system is indicative of black-pigmented obligate anaerobes and mature plaque. METHODS: The QLF system was evaluated in a clinical study for use in denture plaque assessment in comparison to white light based image capture. RESULTS: Despite appearing as a promising system for denture plaque quantification, this study revealed numerous problems associated with the QLF system including small focal depth, thus large numbers of images and processing time were required. In addition, differential fluorescence of acrylic made images unsuitable for plaque quantification. CONCLUSION: QLF is unsuitable for in vivo denture plaque assessment. However, the visualisation of red autofluorescence, indicating mature plaque, remains an important clinical use of QLF for denture hygiene assessment. Description: Full-text of this article is not available in this e-prints service. This article was originally published following peer-review in Journal of Dentistry, published by and copyright Elsevier. Sun, 01 Nov 2009 00:00:00 GMT http://hdl.handle.net/2173/87514 2009-11-01T00:00:00Z