BETA Zeolite Thin Films Supported on Honeycomb Monoliths with Tunable Properties as Hydrocarbon Traps under Cold-Start Conditions

A high percentage of hydrocarbon (HC) emissions from gasoline vehicles occur during the cold-start period. Among the alternatives proposed to reduce these HC emissions, the use of zeolites before the three-way catalyst (TWC) is thought to be very effective. Zeolites are the preferred adsorbents for this application; however, to avoid high pressure drops, supported zeolites are needed. In this work, two coating methods (dip-coating and in situ crystallization) are optimized to prepare BETA zeolite thin films supported on honeycomb monoliths with tunable properties. The important effect of the density of the thin film in the final performance as a HC trap is demonstrated. A highly effective HC trap is prepared showing 100 % toluene retention, accomplishing the desired performance as a HC trap, desorbing propene at temperatures close to 300 °C, and remaining stable after cycling. The use of this material before the TWC is very promising, and works towards achieving the sustainability and environmental protection goals.

SERS Active Surface in Two Steps, Patterning and Metallization

Robust and reproducible metallized nano/microstructured surfaces of polymeric surfaces have been successfully prepared by direct laser interference patterning (DLIP) of commercial polymeric films followed by sputtering of metallic thin films. The SERS spectra for 2-thioaniline adsorbed on a structured polycarbonate surfaces covered with a gold or platinum film showed a ca. three order of magnitude enhancement over a flat surface with the same metal film. The method here reported is suitable for mass production of substrates for SERS since large areas (several cm2) can be structured in ca. 1–5 s.

Potentiostatic Reversible Photoelectrochromism: An Effect Appearing in Nanoporous TiO2/Ni(OH)2 Thin Films

In the field of energy saving, finding composite materials with the ability of coloring upon both illumination and change of the applied electrode potential keeps on being an important goal. In this context, chemical bath deposition of Ni(OH)2 into nanoporous TiO2 thin films supported on conducting glass leads to electrodes showing both conventional electrochromic behavior (from colorless to dark brown and vice versa) together with photochromism at constant applied potential. The latter phenomenon, reported here for the first time, is characterized by fast and reversible coloration upon UV illumination. The bleaching kinetics shows first order behavior with respect to the NiIII centers in the film, and an order 1.2 with respect to electrons in the TiO2 film. From a more applied point of view, this study opens up the possibility of having two-mode smart windows showing not only conventional electrochromism but also reversible darkening upon illumination.

Sol–gel copper chromium delafossite thin films as stable oxide photocathodes for water splitting

Significant effort is being devoted to the study of photoactive electrode materials for artificial photosynthesis devices. In this context, photocathodes promoting water reduction, based on earth-abundant elements and possessing stability under illumination, should be developed. Here, the photoelectrochemical behavior of CuCrO2 sol–gel thin film electrodes prepared on conducting glass is presented. The material, whose direct band gap is 3.15 eV, apparently presents a remarkable stability in both alkaline and acidic media. In 0.1 M HClO4 the material is significantly photoactive, with IPCE values at 350 nm and 0.36 V vs. RHE of over 6% for proton reduction and 23% for oxygen reduction. This response was obtained in the absence of charge extraction layers or co-catalysts, suggesting substantial room for optimization. The photocurrent onset potential is equal to 1.06 V vs. RHE in both alkaline and acidic media, which guarantees the combination of the material with different photoanodes such as Fe2O3 or WO3, potentially yielding bias-free water splitting devices.

Water-triggered spontaneous surface patterning in thin films of mexylaminotriazine molecular glasses

Surface patterning that occurs spontaneously during the formation of a thin film is a powerful tool for controlling film morphology at the nanoscale level because it avoids the need for further processing. However, one must first learn under which conditions these patterning phenomena occur or not, and how to achieve control over the surface morphologies that are generated. Mexylaminotriazine-based molecular glasses are small molecules that can readily form amorphous thin films. It was discovered that this class of materials can either form smooth films, or films exhibiting either dome or pore patterns. Depending on the conditions, these patterns can be selectively obtained during film deposition by spin-coating. It was determined that this behavior is controlled by the presence of water or, more generally, of a solvent in which the compounds are insoluble, and that the relative amount and volatility of this poor solvent determines which type of surface relief is obtained. Moreover, AFM and FT-IR spectroscopy have revealed that the thin films are amorphous independently of surface morphology, and no difference was observed at the molecular or supramolecular level. These findings make this class of materials and this patterning approach in general extremely appealing for the control of surface morphology with organic nanostructures.

The blue and gold.

Sometimes published as: The Blue & gold.

Organic Semiconducing Thin Films: Device Applications and Beyond

Thesis (Master's)--University of Washington, 2016-06

Hydrothermal deposition of cerium hydroxycarbonate thin films on glass

The first success in the preparation of rare earth hydroxycarbonate thin films has been achieved. Cerium hydroxycarbonate films were prepared by a hydrothermal deposition method, the sample of a single orthorhombic phase was deposited at a lower temperature while those of orthorhombic and hexagonal phases were obtained at higher temperatures. The crystals in the films could be ellipsoidal, prismatic, or rhombic, depending on the deposition conditions applied. The thin films could be candidates for developing novel optical materials and for advanced ceramics processing. (C) 2003 Elsevier Science B.V. All rights reserved.

The 3-D Structure of Polycrystalline Diamond Film by Electron Backscattering Diffraction (EBSD)

A lithographic method was used to produce polycrystalline diamond films having highly defined surface geometry, showing an array of diamond tips for possible application as a field emitter device. The films grown in this study used microwave plasma assisted chemical vapour deposition (MACVD) on a silicon substrate; the substrate was then dissolved away to reveal the surface features on the diamond film. It is possible to align the crystallite direction and affect the electron emission properties using a voltage bias to enhance the nucleation process and influence the nuclei to a preferred orientation. This study focuses on the identification of the distribution of crystal directions in the film, using electron backscattering diffraction (EBSD) to identify the crystallographic character of the film surface. EBSD allows direct examination of the individual diamond grains, grains boundaries and the crystal orientation of each individual crystallite. The EBSD maps of the bottom (nucleation side) of the films, following which a layer of film is ion-milled away and the mapping process repeated. The method demonstrates experimentally that oriented nucleation occurs and the thin sections allow the crystal texture to be reconstructed in 3-D. (C) 2003 Elsevier B.V. All rights reserved.

Ion beam modification and analysis of metal/polymer bi-layer thin films

A set of varying-thickness Au-films were thermally evaporated onto poly(styrene-co-acrylonitrile) thin film surfaces. The Au/PSA bi-layer targets were then implanted with 50 keV N+ ions to a fluence of 1 × 1016 ions/cm2 to promote metal-to-polymer adhesion and to enhance their mechanical and electrical performance. Electrical conductivity measurements of the implanted Au/PSA thin films showed a sharp percolation behavior versus the pre-implant Au-film thickness with a percolation threshold near the nominal thickness of 44 Å. The electrical conductivity results are discussed along with the film microstructure and the elemental diffusion/mixing within the Au/PSA interface obtained by scanning electron microscopy (SEM) and ion beam analysis techniques (RBS and ERD).

Formation of mesostructured titania thin films using iospropoxide precursors

Mesostructured titania thin films were prepared by an evaporation-induced self-assembly process. The highly acidic sot precursors contained titanium(IV) tetraisopropoxide (TTIP) as a titanium source, a tri-block copolymer Pluronic P123 as a template, and acetylacetonate and HCl as hydrolysis inhibitors. Characteristics of the resultant titania thin films were studied using X-ray diffraction (XRD) analysis, N-2-adsorption/desorption analysis, and transmission electron microscopy (TEM). XRD and TEM investigations on the as-synthesised films revealed the appearance of cubic-like, pseudohexagonal, and lamellar mesophases; depending on the amount of water in the sols of film precursors. Template removal by a calcination process yields high surface area (320-360 m(2)/g) mesoporous materials with crystalline anatase frameworks. Water content also influences the degree of anatase crystallinity of the calcined films. Higher water content resulted in improved anatase crystallinity. These nanostructured materials are of interest for photocatalysts, pbotoelectrochemical solar cells and other photonic devices. (C) 2003 Elsevier B.V. All rights reserved.

Scaling laws for the critical rupture thickness or common thin films

Despite decades of experimental and theoretical investigation on thin films, considerable uncertainty exists in the prediction of their critical rupture thickness. According to the spontaneous rupture mechanism, common thin films become unstable when capillary waves. at the interfaces begin to grow. In a horizontal film with symmetry at the midplane. unstable waves from adjacent interfaces grow towards the center of the film. As the film drains and becomes thinner, unstable waves osculate and cause the film to rupture, Uncertainty sterns from a number of sources including the theories used to predict film drainage and corrugation growth dynamics. In the early studies, (lie linear stability of small amplitude waves was investigated in the Context of the quasi-static approximation in which the dynamics of wave growth and film thinning are separated. The zeroth order wave growth equation of Vrij predicts faster wave growth rates than the first order equation derived by Sharma and Ruckenstein. It has been demonstrated in an accompanying paper that film drainage rates and times measured by numerous investigations are bounded by the predictions of the Reynolds equation and the more recent theory of Manev, Tsekov, and Radoev. Solutions to combinations of these equations yield simple scaling laws which should bound the critical rupture thickness of foam and emulsion films, In this paper, critical thickness measurements reported in the literature are compared to predictions from the bounding scaling equations and it is shown that the retarded Hamaker constants derived from approximate Lifshitz theory underestimate the critical thickness of foam and emulsion films, The non-retarded Hamaker constant more adequately bounds the critical thickness measurements over the entire range of film radii reported in the literature. This result reinforces observations made by other independent researchers that interfacial interactions in flexible liquid films are not adequately represented by the retarded Hamaker constant obtained from Lifshitz theory and that the interactions become significant at much greater separations than previously thought. (c) 2005 Elsevier B.V. All rights reserved.

Application of edge-to-edge matching model to understand the in-plane texture of TiSi2 (C49) thin films on (001)(Si) surface

The edge-to-edge matching model, which was originally developed for predicting crystallographic features in diffusional phase transformations in solids, has been used to understand the formation of in-plane textures in TiSi2 (C49) thin films on Si single crystal (001)si surface. The model predicts all the four previously reported orientation relationships between C49 and Si substrate based on the actual atom matching across the interface and the basic crystallographic data only. The model has strong potential to be used to develop new thin film materials. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Protein film voltammetry of arsenite oxidase from the chemolithoautotrophic arsenite-oxidizing bacterium NT-26

The chemolithoautotrophic bacterium NT-26 (isolated from a gold mine in the Northern Territory of Australia) is unusual in that it acquires energy by oxidizing arsenite to arsenate while most other arsenic-oxidizing organisms perform this reaction as part of a detoxification mechanism against the potentially harmful arsenite [present as As(OH)(3) at neutral pH]. The enzyme that performs this reaction in NT-26 is the molybdoenzyme arsenite oxidase, and it has been previously isolated and characterized. Here we report the direct (unmediated) electrochemistry of NT-26 arsenite oxidase confined to the surface of a pyrolytic graphite working electrode. We have been able to demonstrate that the enzyme functions natively while adsorbed on the electrode where it displays stable and reproducible catalytic electrochemistry in the presence of arsenite. We report a pH dependence of the catalytic electrochemical potential of -33 mV/pH unit that is indicative of proton-coupled electron transfer. We also have performed catalytic voltammetry at a number of temperatures between 5 and 25 degrees C, and the catalytic current (proportional to the turnover number) follows simple Arrhenius behavior.

Tear film lipids:dynamic composition and clinical performance

Purpose: Meibomian-derived lipid secretions are well characterised but their subsequent fate in the ocular environment is less well understood. Phospholipids are thought to facilitate the interface between aqueous and lipid layers of the tear film and to be involved in ocular lubrication processes. We have extended our previous studies on phospholipid levels in the tear film to encompass the fate of polar and non-polar lipids in progressive accumulation and aging processes on both conventional and silicone-modified hydrogel lenses. This is an important aspect of the developing understanding of the role of lipids in the clinical performance of silicone hydrogels. Method: Several techniques were used to identify lipids in the tear film. Mass-spectrometric methods included Agilent 1100-based liquid chromatography coupled to mass spectrometry (LCMS) and Perkin Elmer gas chromatography mass spectrometry (GCMS). Thin layer chromatography (TLC) was used for separation of lipids on the basis of increasing solvent polarity. Routine assay of lipid extractions from patient-worn lenses was carried out using a Hewlett Packard 1090 liquid chromatograph coupled to both uv and Agilent 1100 fluorescence detection. A range of histological together with optical, and electron microscope techniques was used in deposit analysis. Results: Progressive lipid uptake was assessed in various ways, including: composition changes with wear time, differential lipid penetrate into the lens matrix and, particularly, the extent to which lipids become unextractable as a function of wear time. Solvent-based separation and HPLC gave consistent results indicating that the polarity of lipid classes decreased as follows: phospholipids/fatty acids > triglycerides > cholesterol/cholesteryl esters. Tear lipids were found to show autofluorescence—which underpinned the value of fluorescence microscopy and fluorescence detection coupled with HPLC separation. The most fluorescent lipids were found to be cholesteryl esters; histological techniques coupled with fluorescence microscopy indicated that white spots (’’jelly bumps’’) formed on silicone hydrogel lenses contain a high proportion of cholesteryl esters. Lipid profiles averaged for 30 symptomatic and 30 asymptomatic contact lens wearers were compiled. Peak classes were split into: cholesterol (C), cholesteryl esters (CE), glycerides (G), polar fatty acids/phospholipids (PL). The lipid ratio for ymptomatic/symptomatic was 0.6 ± 0.1 for all classes except one—the cholesterol ratio was 0.2 ± 0.05. Significantly the PL ratio was no different from that of any other class except cholesterol. Chromatography indicated that: lipid polarity decreased with depth of penetration and that lipid extractability decreased with wear time. Conclusions: Meibomian lipid composition differs from that in the tear film and on worn lenses. Although the same broad lipid classes were obtained by extraction from all lenses and all patients studied, quantities vary with wear and material. Lipid extractability diminishes with wear time regardless of the use of cleaning regimes. Dry eye symptoms in contact lens wear are frequently linked to lipid layer behaviour but seem to relate more to total lipid than to specific composition. Understanding the detail of lipid related processes is an important element of improving the clinical performance of materials and care solutions.