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Paulauskas I.E.,Bio Nano Consulting Ltd | Paulauskas I.E.,University College London | Modeshia D.R.,Bio Nano Consulting Ltd | Ali T.T.,King Abdulaziz University | And 5 more authors.
Platinum Metals Review | Year: 2013

The photocatalytic activities of a series of titanium dioxide (TiO 2) based nanoparticles, synthesised via flame spray pyrolysis (FSP), have been investigated and compared with the commercially available Evonik Aeroxide® TiO2 P 25 (P 25). The effects of metal ions aluminium, tin and platinum, respectively, on the physical and chemical properties of the TiO2 nanoparticles are reported. The set of six samples were characterised by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma-mass spectrometry (ICP-MS) and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy. Specific surface areas were determined using nitrogen adsorption and desorption measurements. Subsequent photocatalytic studies of the degradation of methyl orange (MO) dye under UV irradiation demonstrated that addition of Al and Sn had a negative effect on catalytic performance, whereas the addition of ≤ 0.7 at% Pt to each sample enhanced photocatalytic activity. Most interestingly, the Pt-doped composite samples (TiO2-Sn/Pt and TiO2-Al/Pt) both showed a significantly higher rate of degradation of MO, when compared to P 25. All Pt-doped samples show an increased visible photon absorption capacity. The relationships between the physical and chemical characteristics are discussed in relation to photocatalytic performance. © 2013 Johnson Matthey. Source

Alotaibi A.M.,University College London | Sathasivam S.,University College London | Sathasivam S.,Bio Nano Consulting Ltd | Parkin I.P.,University College London
RSC Advances | Year: 2015

ZrO2-TiO2 composite thin films were deposited by aerosol assisted chemical vapour deposition onto a glass substrate at 450 °C and then annealed at 600 °C. For comparison ZrO2 thin films and TiO2 thin films were deposited under the same conditions. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), UV-Vis and Raman spectroscopy were used to characterize all films. Photocatalytic activities were tested by degradation of intelligent ink containing resazurin redox dye under UVA irradiation. The formal quantum efficiency (FQE) and yield (FQY) for the ZrO2-TiO2 composite thin films were determined as 2.03 × 10-3 dye molecules per incident photon and 4.91 × 10-3 dye molecules per absorbed photon respectively. Surprisingly the ZrO2-TiO2 composite was a more efficient photocatalyst than the comparable TiO2 coating. This journal is © The Royal Society of Chemistry. Source

Bhachu D.S.,University College London | Sathasivam S.,University College London | Sathasivam S.,Bio Nano Consulting Ltd | Sankar G.,University College London | And 9 more authors.
Advanced Functional Materials | Year: 2014

This paper reports the synthesis of highly conductive niobium doped titanium dioxide (Nb:TiO2) films from the decomposition of Ti(OEt)4 with dopant quantities of Nb(OEt)5 by aerosol-assisted chemical vapor deposition (AACVD). Doping Nb into the Ti sites results in n-type conductivity, as determined by Hall effect measurements. The doped films display significantly improved electrical properties compared to pristine TiO2 films. For 5 at.% Nb in the films, the charge carrier concentration was 2 × 1021 cm-3 with a mobility of 2 cm2 V-1 s-1. The corresponding sheet resistance is as low as 6.5 Ω sq-1 making the films suitable candidates for transparent conducting oxide (TCO) materials. This is, to the best of our knowledge, the lowest reported sheet resistance for Nb:TiO 2 films synthesized by vapour deposition. The doped films are also blue in colour, with the intensity dependent on the Nb concentration in the films. A combination of synchrotron, laboratory and theoretical techniques confirmed niobium doping into the anatase TiO2 lattice. Computational methods also confirmed experimental results of both delocalized (Ti 4+) and localized polaronic states (Ti3+) states. Additionally, the doped films also functioned as photocatalysts. Thus, Nb:TiO2 combines four functional properties (photocatalysis, electrical conductivity, optical transparency and blue colouration) within the same layer, making it a promising alternative to conventional TCO materials. Solution processing of Nb:TiO2 has presented many challenges to the materials community. Nb:TiO2 made by solution processing has been consigned to sensor/catalysis applications. Here, a solution route is presented to highly conductive and photocatalytically active Nb:TiO2 films. A blue color is observed for the niobium doped films with XPS and computational methods showing a stable localized Ti3+ state at the anatase surface compared to the bulk. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Bawaked S.M.,King Abdulaziz University | Sathasivam S.,University College London | Sathasivam S.,Bio Nano Consulting Ltd | Bhachu D.S.,University College London | And 6 more authors.
Journal of Materials Chemistry A | Year: 2014

This paper shows the aerosol assisted chemical vapour deposition of transparent, blue coloured and conductive tantalum doped titanium dioxide films from the CVD reaction of Ti(OEt)4 and Ta(OEt)5. Hall effect measurements showed the doped films to have excellent n-type electrical conductivity showing, to the best of our knowledge, the lowest reported sheet resistance ever recorded for Ta-doped TiO2 of 14 Ω sq -1. The Ta 6 atom% doped TiO2 film also showed the best electrical results with a charge carrier concentration of 1.60 × 10 21 cm-3 and mobility of 1.44 cm2 V-1 s-1 making it a suitable electrode in photovoltaic devices. The doped films were multifunctional, showing good photocatalytic activity under UV-light illumination. XPS and XRD studies gave strong evidence that the Ta was entering the TiO2 lattice as Ta5+ and that a reduction of some Ti4+ to Ti3+ was observed. © 2014 the Partner Organisations. Source

Chadwick N.,University College London | Sathasivam S.,Bio Nano Consulting Ltd | Kafizas A.,University College London | Bawaked S.M.,King Abdulaziz University | And 5 more authors.
Journal of Materials Chemistry A | Year: 2014

Combinatorial Aerosol Assisted Chemical Vapour Deposition (cAACVD) was used to grow a thin film that graduated across its width from tin dioxide to titanium dioxide. This is a relatively new technique that can be used to create a variety of mixed phase and composition thin films on a single substrate. Here cAACVD was used to deposit a mixed phase TiO2 and SnO2 film and composition was related to UV photocatalysis, hydrophobicity and microstructure not inherent to anatase TiO2 or cassiterite SnO 2. Characterisation was achieved using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and UV-Vis spectroscopy. Functional testing to elucidate the differences in functional properties across the film was undertaken by the photo-induced degradation of a resazurin 'intelligent' ink, a photo-induced wettability study and two-point resistivity measurements. Functional properties showed enhanced photocatalysis in comparison to Pilkington Activ™ with similar formal quantum yield (molecules destroyed per absorbed photon) and formal quantum efficiency (molecules destroyed per incident photon) values. This journal is © the Partner Organisations 2014. Source

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