Photo-activity and low resistivity in N/Nb Co-doped TiO2 thin films by combinatorial AACVD

A combinatorial aerosol assisted chemical vapour deposition (cAACVD) cation–anion co-doping study has been undertaken for the first time, which investigates the interplay of nitrogen and niobium co-dopants and the resultant functional properties within TiO2 thin films. This study advantageously creates a single doped TiO2 thin film which incorporates many compositions that transition from nitrogen doped TiO2 to niobium doped TiO2 across the film's width, in a single deposition. The film was split into a grid and the physical properties of each grid position characterised by X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and UV-visible transmission spectroscopy (UV/Vis). Functional properties such as photo-catalytic activity, water contact angles and resistivity were also characterised. The study was successful in creating and identifying the optimum dopant concentration at which these TiO2 films exhibited both a high rate of photo-activity and favourable transparent conducting oxide (TCO) properties. Whilst most co-doping studies report relatively homogenous film, the inhomogeneity of these films allows both functional properties to exist in conjunction. To the authors knowledge this is the first instance cation and anion co-doping has been explored in the combinatorial regime

Ultrasensitive, rapid and inexpensive detection of DNA using paper based lateral flow assay

Sensitive, specific, rapid, inexpensive and easy-to-use nucleic acid tests for use at the point-of-need are critical for the emerging field of personalised medicine for which companion diagnostics are essential, as well as for application in low resource settings. Here we report on the development of a point-of-care nucleic acid lateral flow test for the direct detection of isothermally amplified DNA. The recombinase polymerase amplification method is modified slightly to use tailed primers, resulting in an amplicon with a duplex flanked by two single stranded DNA tails. This tailed amplicon facilitates detection via hybridisation to a surface immobilised oligonucleotide capture probe and a gold nanoparticle labelled reporter probe. A detection limit of 1 7 10−11 M (190 amol), equivalent to 8.67 7 105 copies of DNA was achieved, with the entire assay, both amplification and detection, being completed in less than 15 minutes at a constant temperature of 37 \ub0C. The use of the tailed primers obviates the need for hapten labelling and consequent use of capture and reporter antibodies, whilst also avoiding the need for any post-amplification processing for the generation of single stranded DNA, thus presenting an assay that can facilely find application at the point of need

Tungsten Doped TiO2 with Enhanced Photocatalytic and Optoelectrical Properties via Aerosol Assisted Chemical Vapor Deposition

Tungsten doped titanium dioxide films with both transparent conducting oxide (TCO) and photocatalytic properties were produced via aerosol-assisted chemical vapor deposition of titanium ethoxide and dopant concentrations of tungsten ethoxide at 500 °C from a toluene solution. The films were anatase TiO2, with good n-type electrical conductivities as determined via Hall effect measurements. The film doped with 2.25 at.% W showed the lowest resistivity at 0.034 Ω.cm and respectable charge carrier mobility (14.9 cm(3)/V.s) and concentration (×10(19) cm(-3)). XPS indicated the presence of both W(6+) and W(4+) in the TiO2 matrix, with the substitutional doping of W(4+) inducing an expansion of the anatase unit cell as determined by XRD. The films also showed good photocatalytic activity under UV-light illumination, with degradation of resazurin redox dye at a higher rate than with undoped TiO2

Activation and local structural stability during the thermal decomposition of Mg/Al-hydrotalcite by total neutron scattering

The activation of synthetic hydrotalcite, the carbonated layered double hydroxide (LDH) with ratio Mg2+/Al3+ = 3 and structural formula [Mg6Al2(OH)(16)](2+)center dot CO(3)(2-)n(H2O), has been investigated using neutron and X-ray diffraction. In situ neutron diffraction was used to follow the structural phase transformations during the thermal decomposition (calcination) of hydrotalcite under vacuum in the temperature range 298-723 K, and during which the residual gas evolved by the sample was analysed by mass spectrometry. Detailed structural information of the LDH and mixed metal oxides (MMOs) was extracted from both the Bragg peaks and the total scattering. These two analysis techniques provide complementary insight into the relevant transition mechanisms, since Bragg diffraction originates from long-range periodicities within the samples while total scattering reveals the subtleties of the local atomic environment. This latter information is particularly important for our understanding of catalytic activity since it elucidates the local metal coordination. We find that, during the calcination process, the local environment around the metal centres is robust, as the various stages during the phase transition have identical local structures. The implications of these new results for the nature of the MMOs is discussed in relation to the well-studied, reverse, rehydration reaction, and the high propensity of trivalent Al ions to migrate to tetrahedrally-coordinated lattice sites

Parameters controlling the photocatalytic performance of ZnO/Hombikat TiO <inf>2</inf> composites

Commercial TiO 2 (Hombikat, UV-100) was impregnated with different loadings of zinc nitrate solution and subsequently calcined at different temperatures in order to obtain a stable homogeneous solid composite of ZnO/TiO 2. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), UV-vis and Raman spectroscopy, inductively coupled plasma mass spectroscopy (ICP), X-ray photoelectron spectroscopy (XPS) as well as N 2 adsorption and desorption measurements. Results show that ZnO was incorporated within the TiO 2 crystals and did not form a separate bulky phase or metallic zinc. Moreover, the calcination temperature dramatically modifies the texture properties of the prepared samples compared with original Hombikat TiO 2. The photocatalytic performance of the prepared samples was evaluated by monitoring the degradation of methyl orange dye under black light illumination. Three main parameters were studied; ZnO loading, surface area and initial pH of the methyl orange solution. The variation in ZnO loading appears to have less influence on the catalytic activity than either the surface area or the pH. © 2011 Elsevier B.V. All rights reserved