Browsing by Author "Wang, XD"

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    Effective gel for gold nanoparticle formation, support and metal oxide templating
    (Royal Society of Chemistry, 2007-08-07) Wang, XD; Egan, CE; Zhou, MF; Prince, KE; Mitchell, DRG; Caruso, RA
    Gold nanoparticles were synthesized using agarose as a reducing agent, which gelled to support the gold nanoparticles, then readily functioned as a template to produce a porous, evenly-distributed Au/TiO2 nano-hybrid. © 2007, Royal Society of Chemistry
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    Gold nanoparticle incorporation into porous titania networks using an agarose gel templating technique for photocatalytic applications
    (American Chemical Society, 2008-05-20) Wang, XD; Mitchell, DRG; Prince, KE; Atanacio, AJ; Caruso, RA
    Porous titania networks containing gold nanoparticles have been synthesized and tested in photocatalytic applications. The porous structure was controlled using a templating technique, while a range of gold concentrations and a variety of routes were investigated to incorporate the gold nanoparticles. The influence of these parameters on the final structure (surface area and pore size), the gold crystal size, distribution, and content, and the photocatalytic activity of the porous materials were investigated. UV−vis diffuse reflectance spectra of the Au/TiO2 materials showed strong absorbance at approximately 580 nm, indicating the successful incorporation of the gold species. X-ray diffraction analysis ascertained that the titania materials were crystalline (anatase phase) with gold peaks observed only when the gold content was greater than 0.25 wt %. Gold distribution and content in the materials were measured using secondary ion mass spectrometry and inductively coupled plasma mass spectrometry. From transmission electron microscopy analysis, the gold particle size and distribution varied with both the material preparation method and the concentration of gold used in the synthesis. Photocatalytic activity was dependent on the gold particle size and gold quantity. The highest photocatalytic activity under UV light irradiation as monitored by the photodecomposition of methylene blue was obtained for the Au/TiO2 sample containing 2.0 wt % gold prepared by the deposition of gold onto prefabricated porous TiO2.© 2008 American Chemical Society
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    Photocatalytic application of porous Au/TiO2 nano-hybrids prepared by a templating technique
    (International Conference on the Photochemical Conversion and Storage of Solar Energy, 2008-07-30) Wang, XD; Mitchell, DRG; Prince, KE; Caruso, RA
    Gold doping or deposition in TiO2 can effectively improve the photocatalytic performance of the titania by either modifying the bandgap and thereby inducing photoactivity under visible light or decreasing the recombination of excited electron and hole. Templating techniques can produce materials with designed morphology and porosity. The objective of this project was to couple controlled porosity allowing faster molecule diffusion through the porous channels with gold deposition to further increase the photocatalytic activity of TiO2. Templating and sol-gel techniques were combined to synthesise Au/TiO2 nano-hybrids with improved photocatalytic activity. The porous structures directed by the agarose gel template were examined by SEM. X-ray diffraction analysis ascertained the materials to be anatase phase, and the gold peaks were observed when the gold content was over 0.25 wt%. TEM further confirmed the highly porous structure of the composites (Figure 1). The gold particle sizes, influenced by both the synthesis methods and initial gold content, ranged from ~ 2 to 40 nm. The gold distribution and content were identified by means of secondary ion mass spectrometer and inductively coupled plasma mass spectrometry, respectively. Finally, the catalytic performance of the Au/TiO2 was assessed by photodecomposition of methylene blue under UV light. The influence of parameters such as synthesis methods, material properties and photocatalytic test conditions (e.g., pH, catalyst and dye concentration) on the photocatalytic efficiency was also investigated. The photocatalytic efficiency improved by a maximum 40% for the Au/TiO2 sample with a gold particle size of 2 nm and 2 wt % gold content.