UV-activated photocatalyst films and inks for cleaning tarnished metals

A simple UV-activated, TiO2-based film or ink for removing thin oxide or sulfide layers from metal surfaces by reductive photocatalysis is described.

UV dosimeter based on dichloroindophenol and tin(IV) oxide

A UVB specific dosimeter is described comprising: a redox dye (2,6-dichloroindophenol, DCIP), a semiconductor ( tin(IV) oxide, SnO2) and a sacrificial electron donor ( glycerol) dispersed in a polymer ( hydroxy ethyl cellulose, HEC) film. The dosimeter is blue in the absence of UVB light but rapidly loses colour on exposure to UVB light. The spectral characteristics of a typical UVB dosimeter film and the mechanism by which the colour change occurs are detailed. DCIP UVB dosimeter films exhibit a response that is related to the irradiance level and duration of UVB exposure, the level of SnO2 present and to a lesser extent the level of glycerol present. The response of the dosimeter appears to be independent of dye concentration and film thickness. Furthermore, DCIP UVB dosimeter films respond to solar simulated light, exhibiting a colour loss that can be simply related to the Minimal Erythemal Dose (MED) exposure for skin type II. As a consequence, such indicators have potential for measuring solar radiation exposure and providing an early warning of erythema for most Caucasian skin (i.e. skin type II).

Atmospheric Pressure Chemical Vapour Deposition of thin Films of Nb2O5 on Glass

A novel route involving atmospheric pressure chemical vapour deposition (APCVD) is reported for coating Nb2O5 onto glass substrates via the reaction of NbCl5 and ethyl acetate at 400-660degreesC. Raman spectroscopy is shown to be a simple diagnostic tool for the analysis of these thin films. The contact angle of water on Nb2O5-coated glass drops on UV irradiation from 60degrees to 5-20degrees. XPS Analysis showed that the Nb:O ratio of the film was 1:2.5. Glancing angle X-ray diffraction showed that all films were crystalline, with only a single phase being observed; this has some preferred orientation in the (201) plane of Nb2O5. The niobium(V) oxide materials show minimal photocatalytic ability to degrade organic material.

Titania and tungsten doped titania thin films on glass; active photocatalysts

Acidification of an isopropanol solution containing mixtures of [Ti(OPri)(4)] and [W(OEt)(5)] produced solutions from which various TiO2, WO3 and TiO2/WO3 thin films could be obtained by dip coating and annealing. The films were analysed by X-ray diffraction, SEM/EDAX, Raman, electronic spectra, contact angle and photoactivity with respect to destruction of an over layer of stearic acid. The TiO2/WO3 films were shown to be mixtures of two phases TiO2 and WO3 rather than a solid solution TixWyO2. The 2% tungsten oxide doped titania films were shown to be the most effective photocatalysts. All of the TiO2 and TiO2/WO3 films showed light induced superhydrophillicity. (C) 2002 Elsevier Science Ltd. All rights reserved.

Novel TiO2 CVD films for semiconductor photocatalysis

A novel CVD film of titanium(IV) oxide has been prepared on glass, via the reaction of titanium(IV) chloride and ethyl acetate, using a CVD technique. The film is clear, very robust mechanically and comprised of a thin (24 nm) layer of nanocrystalline anatase titania that absorbs light of lambda

Growth of SrS thin films by pulsed-laser deposition

High-quality luminescent thin films of strontium sulphide (SrS) with excellent stoichiometry have been grown by pulsed-laser deposition. The crystallinity, stoichiometry and cathodoluminescence (CL) have been investigated for the films deposited onto two differently coated glass substrates. Furthermore the importance of post-deposition annealing has been studied. SrS thin films grown at 450 degrees C onto glass substrates coated with tin-doped indium oxide show good crystallinity, with a preferred orientation along the (200) axis. Cerium-doped SrS (SrS:Ce) gives a strong blue CL output at 400 nm. Energy-dispersive X-ray spectroscopy shows that the films are stoichiometric and that the stoichiometry is controllable by varying deposition parameters.

Phosphine oxide functionalised imidazolium ionic liquids as tuneable ligands for lanthanide complexation

A series of novel, phosphine oxide functionalised ionic liquids have been synthesised and their application as tuneable lanthanide complexing agents is demonstrated.

Solution-based synthesis of cobalt-doped ZnO thin films

Undoped and cobalt-doped (1-4 wt.%) ZnO polycrystalline, thin films have been fabricated on quartz substrates using sequential spin-casting and annealing of simple salt solutions. X-ray diffraction (XRD) reveals a wurzite ZnO crystalline structure with high-resolution transmission electron microscopy showing lattice planes of separation 0.26 nm, characteristic of (002) planes. The Co appears to be tetrahedrally co-ordinated in the lattice on the Zn sites (XRD) and has a charge of + 2 in a high-spin electronic state (X-ray photoelectron spectroscopy). Co-doping does not alter the wurzite structure and there is no evidence of the precipitation of cobalt oxide phases within the limits of detection of Raman and XRD analysis. Lattice defects and chemisorbed oxygen are probed using photoluminescence and Raman spectroscopy - crucially, however, this transparent semiconductor material retains a bandgap in the ultraviolet (3.30-3.48 eV) and high transparency (throughout the visible spectral regime) across the doping range. © 2012 Elsevier B.V.

A computational study of the mechanism of CO oxidation by a ceria supported surface rhodium oxide layer

A mechanism of CO oxidation by a thin surface oxide of Rh supported on ceria is proposed: CO is oxidized by the Rh-oxide film, which is subsequently reoxidized by a ceria surface O atom. The proposed mechanism is supported by in situ Raman spectroscopic investigations.

Effect of post-weld heat-treatment on the oxide film and corrosion behaviour of laser-welded shape memory NiTi wires

Post-weld heat-treatment (PWHT) was applied to NiTi weldments to improve the corrosion behaviour by modifying the microstructure and surface composition. The surface oxide film on the weldments is principally TiO2, together with some Ti, TiO, and Ti2O3. The surface Ti/Ni ratio of the weldments after PWHT is increased. The oxide film formed in Hanks’ solution is thicker on the weldments after PWHT. The pitting resistance of the weldments is increased by PWHT. The galvanic effect in the weldments is very small. The weldment with PWHT at 350 °C shows the best corrosion resistance among other heat-treated weldments in this study.

Low loading platinum nanoparticles on reduced graphene oxide-supported tungsten carbide crystallites as a highly active electrocatalyst for methanol oxidation

In this study, low loading platinum nanoparticles (Pt NPs) have been highly dispersed on reduced graphene oxide-supported WC nanocrystallites (Pt-WC/RGO) via program-controlled reduction-carburization technique and microwave-assisted method. The scanning electron microscopy and transmission electron microscopy results show that WC nanocrystallites are homogeneously decorated on RGO, and Pt NPs with a size of ca. 3 nm are dispersed on both RGO and WC. The prepared Pt-WC/RGO is used as an electrocatalyst for methanol oxidation reaction (MOR). Compared with the Pt/RGO, commercial carbon-supported Pt (Pt/C) and PtRu alloy (PtRu/C) electrocatalysts, the Pt-WC/RGO composites demonstrate higher electrochemical active surface area and excellent electrocatalytic activity toward the methanol oxidation, such as better tolerance toward CO, higher peak current density, lower onset potential and long-term stability, which could be attributed to the characterized RGO support, highly dispersed Pt NPs and WC nanocrystallites and the valid synergistic effect resulted from the increased interface between WC and Pt. The present work proves that Pt-WC/RGO composites could be a promising alternative catalyst for direct methanol fuel cells where WC plays the important role as a functional additive in preparing Pt-based catalysts because of its CO tolerance and lower price. 

Ferroelectric hafnium oxide: A CMOS-compatible and highly scalable approach to future ferroelectric memories

With the ability to engineer ferroelectricity in HfO2 thin films, manufacturable and highly scaled MFM capacitors and MFIS-FETs can be implemented into a CMOS-environment. NVM properties of the resulting devices are discussed and contrasted to existing perovskite based FRAM.

Application of surface plasmon polaritons in the laser ablation and characterisation of thin aluminium films

Surface modification of thin aluminium films is both produced and characterised by exciting surface plasmon polaritons in an attenuated total reflection geometry: silica prism/aluminium/aluminium oxide system. The modification is performed, under ambient conditions, by exposure to a low fluence (

Contrasting damage characteristics in direct incidence and surface plasmon mediated single-shot laser ablation of aluminium films

Thin, oxidised Al films grown an one face of fused silica prisms are exposed. tinder ambient conditions, to single shots from an excimer laser operating at wavelength 248 nm. Preliminary characterisation of the films using attenuated total reflection yields optical and thickness data for the Al and Al oxide layers; this step facilitates the subsequent, accurate tuning of the excimer laser pulse to the: surface plasmon resonance at the Al/(oxide)/air interface and the calculation of the fluence actually absorbed by the thin film system. Ablation damage is characterised using scanning electron, and atomic force microscopy. When the laser pulse is incident, through the prism on the sample at less than critical angle, the damage features are molten in nature with small islands of sub-micrometer dimension much in evidence, a mechanism of film melt-through and subsegment blow-off due to the build up of vapour pressure at the substrate/film interface is appropriate. By contrast, when the optical input is surface plasmon mediated, predominately mechanical damage results with the film fragmenting into large flakes of dimensions on the order of 10 mu m. It is suggested that the ability of surface plasmons to transport energy leads to enhanced, preferential absorption of energy at defect sites causing stress throughout the film which exceeds the ultimate tensile stress for the film: this in turn leads to film break-up before melting can onset. (C) 1998 Elsevier Science B.V.

Sub-nA spatially resolved conductivity profiling of surface and interface defects in ceria films

Spatial variability of conductivity in ceria is explored using scanning probe microscopy (SPM) with galvanostatic control. Ionically blocking electrodes are used to probe the conductivity under opposite polarities to reveal possible differences in the defect structure across a thin film of CeO2. Data suggests the existence of a large spatial inhomogeneity that could give rise to constant phase elements during standard electrochemical characterization, potentially affecting the overall conductivity of films on the macroscale. The approach discussed here can also be utilized for other mixed ionic electronic conductor (MIEC) systems including memristors and electroresistors, as well as physical systems such as ferroelectric tunneling barriers.