Browsing by Author "Waterhouse, GIN"

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    Effect of gold loading and TiO2 support composition on the activity of Au/TiO2 photocatalysts for H-2 production from ethanol-water mixtures
    (Elsevier, 2013-09-01) Jovic, V; Chen, WWT; Sun-Waterhouse, D; Blackford, MG; Idriss, H; Waterhouse, GIN
    This paper systematically compares the activity of Au/TiO2 photocatalysts (Au loadings 0–10 wt.%) for H2 production from ethanol–water mixtures under UV excitation. Degussa P25 TiO2 was used as the support phase. TEM analyses revealed that the average Au nanoparticle size at all loadings was 5 ± 2 nm, with the Au nanoparticles preferentially located at the interfacial sites between TiO2 crystallites. XRD, XRF, XPS, and UV–Vis measurements established that metallic Au was the only gold species on the surface of the photocatalysts. The Au/TiO2 photocatalysts showed an intense absorption maximum centred around 560–570 nm due to the localised surface plasmon resonance (LSPR) of the supported gold nanoparticles. Photoluminescence measurements revealed that gold nanoparticles effectively suppress electron–hole pair recombination in TiO2, even at low Au loadings. All of the Au/TiO2 photocatalysts displayed high activity for H2 production from ethanol–water mixtures under UV irradiation, with the highest activities observed in the Au loading range 0.5–2 wt.% (H2 production rate 31–34 mmol g−1 h−1). In order to deconvolute the role of the P25 TiO2 support in promoting H2 production, anatase and rutile nanoparticles were isolated from P25 TiO2 by selective chemical dissolution and then functionalised with gold nanoparticles (3 wt.% loading, size 5 ± 2 nm). The H2 production activity of the resulting Au/anatase and Au/rutile photocatalysts was 22 and 10 mmol g−1 h−1, respectively, and substantially lower than the corresponding Au/P25 TiO2 photocatalyst (32 mmol g−1 h−1). The data provide strong evidence that synergistic electron transfer between the TiO2 polymorphs and supported Au nanoparticles is responsible for the high rates of H2 production observed in the Au/P25 TiO2 system. The interface between anatase and rutile crystallites, where gold nanoparticles preferentially deposit, is identified as a photocatalytic ‘hot spot’ for H2 production. High Au loadings reduce the efficiency of such ‘hot spots’. © 2013, Elsevier Inc.
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    Investigating biomimetic calcium phosphate and carbonate mineral formation within multilayered biopolymer films using small angle neutron scattering
    (International Conference on Neutron Scattering, 2017-07-12) Shahlori, R; Nelson, A; Mata, JP; Waterhouse, GIN; McGillivray, DJ
    We have produced a multilayered template using chitosan and iota-carrageenan as a substrate for mineralised calcium phosphate or calcium carbonate through exposure to a simulated body fluid (SBF) or simulated sea-water (SSW), respectively. A film consisting of 120-bilayers of these alternating charged biopolymers was successfully dip-coated onto microscope slides and mineralised. The films produced showed striking iridescence due to the periodically alternating nanoscale structure, a golden sheen was observed when the unmineralised film was swollen and transitioned to a blue colour upon mineralisation. Cryo-SEM and TEM images showed the nanoscale structure responsible for the observed iridescence can be attributed to the dense interfaces between the chitosan and iota-carrageenan bilayers. Small angle neutron scattering measurements were conducted using QUOKKA at the Australian Nuclear Science and Technology Organisation (ANSTO). These measurements revealed a scattering feature, between 0.002-0.006 A-1, exclusively for mineralised samples. The large structure (150 nm) responsible for this feature was modelled as lamellar objects attributed to the interfaces between the chitosan and iota-carrageenan layers. This feature becomes more prominent as the nSLD contrast against D2O increases with more mineralised samples. The power law slope of low-q scattering is also shown to increase from 2.2 to 3.8, from an unmineralised to the most mineralised film. This result shows that increase is the overall smoothness and rigidity of the biopolymer film is achieved with mineralisation. A high-q scattering features was observed between 0.01-0.05 A-1, arising from spacing between the polymer mesh within the swollen multilayered film. However, this feature was shown to have no significant changes upon mineralisation. These parameters were compared with films mineralised with different heavy metal ion treatments (Cu2+, Zn2+, Pb2+ and Cd2+) to observe the effect on mineral nucleation, which is of concern for shell-fish growth near industrial areas. Additionally the effect of acidic molecules (L-Glutamic acid, Citric acid and poly-acrylic acid) was also measured, to access the mineralisation influence of calcium ion adsorption on carboxylic acid groups.