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  • 2001.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Andersson, Per Ola
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Nikolajeff, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Optical sensor unit for evanescence wave spectroscopy2009Patent (Other (popular science, discussion, etc.))
  • 2002.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Chakarov, D V
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Potassium adsorption on graphite(0001)1999In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 420, no 2-3, p. 174-189Article in journal (Refereed)
    Abstract [en]

    Potassium adsorption on graphite has been studied with emphasis on the two-dimensional K adlayer below one monolayer. Data are presented for the work function versus coverage, high-resolution electron energy loss spectroscopy (HREELS) vibrational spectra of K-adlayers, low energy electron diffraction and ultraviolet photoemission spectroscopy (UPS) spectra at different coverages. The data provide information regarding the vibrational properties of the K-adlayer, the metallization of the adlayer at submonolayer coverages, and the charge transfer from the It adatoms to the graphite substrate. Analysis of the work function, HREELS, and UPS data provides a qualitatively consistent picture of the charge state of the K adatoms, where at low coverages, below a critical coverage theta(c) (theta(c) = 0.2-0.3), the K adatoms are dispersed and (partially) ionized, whereas at theta > theta(c) islands of a metallic 2 x 2 K phase develop that coexist with the dispersed K adatoms up to theta = 1. We show that it is possible to understand the variation of the work function data based on a two-phase model without invoking a depolarization mechanism of adjacent dipoles, as is normally done for alkali-metal adsorption on metal surfaces. Similarly, the intensity variation as a function of coverage of the energy loss peak at 17 meV observed in HREELS, and the photoemission peak at E-b = 0.5 eV seen in UPS can be understood from a two-phase model. A tentative explanation is presented that connects apparent discrepancies in the literature concerning the electronic structure of the K adlayer. In particular, a new assignment of the K-induced states near the Fermi level is proposed. (C) 1999 Elsevier Science B.V. All rights reserved.

  • 2003.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Grant, A. W.
    Chalmers University of Technology.
    Kasemo, B.
    Chalmers University of Technology.
    Lithographic Techniques in Nanocatalysis2007In: NANOCATALYSIS / [ed] U. Heiz, and U. Landman, Springer Berlin/Heidelberg, 2007, p. 269-341Chapter in book (Refereed)
  • 2004.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Karlsson, M.
    Andersson, P. O.
    Nikolaeff, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    EP patent2013Patent (Other (popular science, discussion, etc.))
  • 2005.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kielbassa, S
    Chalmers University of Technology.
    Werdinius, C
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Reactivity of Pt/ceria and Pt/alumina planar model catalysts prepared by colloidal lithography2003In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 215, no 1, p. 94-107Article in journal (Refereed)
    Abstract [en]

    We report on the structure, chemical state, and catalytic activity of nanofabricated, planar Pt/ceria and Pt/alumina model catalysts prepared by colloidal lithography. Employing extended etching times, catalyst particles are fabricated that are much smaller than the size of the polystyrene colloidal particle mask. Using CO oxidation as a probe reaction, the influence of various pretreatments has been studied. We find that the H-2/O-2 pretreatment deteriorates the reactivity on Pt/alumina, which is accompanied by blocking of the high-temperature CO adsorption sites as seen by TPD. After prolonged reactions the Pt/ceria particles show pronounced restructuring, indicating a low-temperature, reaction-induced, strong metal-support interaction, where ceria is decorating the Pt particles. In contrast, after an identical reaction history the Pt/alumina particles become facetted. The nanofabrication approach allows us to attribute the structural changes on individual particles to the integrated, macroscopic catalytic response. (C) 2003 Elsevier Science (USA). All rights reserved.

  • 2006.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kiselev, A.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    New nanomaterials for active decontamination of chemical warfare agents2005In: Second International Conference on Military Technology / [ed] S. Axberg, Stockholm, Sverige: Nyberg&Co , 2005, p. 387-394Chapter in book (Refereed)
  • 2007.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lebrun, Delphine
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kaplakis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sahoo, P. K.
    Anand, S.
    Precise tuning of the photonic band gap using multilayered inverse opals2014In: 12th Russia/CIS/Baltic/Japan Symposium on Ferroelectricity and 9th International conference on Functional Materials and Nanotechnologies – RCBJSF–2014-FM&NT / [ed] A. Sarakovskis, Ulma, Riga , 2014Conference paper (Refereed)
    Abstract [en]

    Inverse opals are photonic band gap (PBG) structures with a periodic arrangement of voids with low refractive index (air) in a high-refractive index dielectric media with sub-wavelength periodicity. In analogy with electronic band gaps in solid state semiconductors these structures form forbidden energy ranges for light, irrespective of the photon’s momentum. Recently, inverse opal structures have been studied for photocatalysis applications. Here the idea is to match the edge of the PBG with the electronic band gap of a semiconductor to allow for efficient light absorption. Here we present a novel approach to tune the position and shape of the PBG by purposefully deposit multilayers of oxides with controlled thicknesses on the inside walls of the inverse opals. This avoids the technical problems of changing the periodicity and materials of the opals. The fabrication involves a three-step process: It consists of self-assembly by convective evaporation of polystyrene beads into close-packed fcc structures; atomic layer deposition (ALD) of metal oxides (Al2O3) to fill the voids between the beads; and subsequent Ar ion etching and calcination to crystallize and develop the inverse opal structure. ALD is then repeated to make multi-layer structures of TiO2 with controlled thickness. The inverse opal structures were characterized by optical spectroscopy, X-ray spectroscopy, electron microscopy, and profilometry. Theoretical modeling was performed to describe the optical properties. The results are analyzed and compared with band structure calculations made by the plane-wave expansion method together with finite-difference time-domain simulations of the transmission spectra (Fig. 1). Our method is versatile and can be used to fabricate reactive nanoparticles with different chemical composition on the inside walls; as well as plasmonic nanoparticles embedded in the layers to efficiently absorb slow light.

  • 2008.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Leideborg, M
    Westin, G
    Highly reactive Photocatalytic material and manufacturing thereof2009Patent (Other (popular science, discussion, etc.))
  • 2009.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Surface characteristics and electronic structure of photocatalytic reactions on TiO2 and doped TiO2 nanoparticles2006In: Solar Hydrogen and Nanotechnology, 2006, p. U5-U19Conference paper (Refereed)
    Abstract [en]

    A molecular approach to understand the photocatalytic degradation of small organic molecules adsorbed from the gas phase on anatase, rutile and doped TiO2 nanoparticles is presented. Using in situ Fourier transform infrared (FTIR) spectroscopy and mass spectrometry the rate determining steps for the photocatalytic degradation of formic acid, acetone and propane are unraveled. Key intermediates are identified and correlated to structural properties of the TiO2 nanoparticles. Specifically, stable bridging bidentate carboxylate (R-CO2) and (bi)carbonate species forms preferentially on rutile particles, and are proposed to inhibit the total photodegradation efficiency. In particular, the concentration of R-CO2 is found to decrease with increasing size of the anatase particles, and may at least partly explain why Degussa P25 is a good photocatalyst. Means to avoid R-CO2 site-blocking is discussed. Improved solar light efficiencies are difficulty to achieve in cation doped TiO2 despite higher visible light absorption and stronger adsorbate-surface interactions.

  • 2010.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Andersson, P. O.
    What makes a good TiO2 photocatalyst?2009In: Ceramic Engineering and Science Proceedings, Wiley & Sons , 2009, 28, Vol. 29, no 8, p. 19-35Chapter in book (Other academic)
    Abstract [en]

    Titanium dioxide pholocatalysis is an area which has witnessed an enormous progress during the past three decades. Applications of TiO2 photocatalysis include environmental remediation, self-cleaning coatings, and is also at the heart of TiO2 based energy production (H-2 and electricity). Despite an enormous literature a comprehensive understanding of the surface reaction steps on TiO2 is still lacking. This reflects both the complex nature of photocatalytic processes and the difficulties of studying nanoparticles. In this paper we present examples from combined in situ molecular spectroscopy studies that highlight the dependence of surface reaction of the structure of TiO2 nanoparticles. We show that for a broad class of organic molecules the reactivity is governed mainly by the bonding and reactivity of a few common intermediate species. The photocatalytic efficiency is correlated with the particle structure and elementary surface reactions steps. We show that p-formate is a common intermediate that control the overall photo-degradation rate of propane, ketones, and carboxylic acid on rutile TiO2 In contrast, on anatase TiO2 photo-oxidation of acetone is rate determining. This shows that the reactivity of TiO2 is sensitive to both surface modification and reactant molecule. Furthermore, the pholo-oxidation rate of formic acid depends on the detailed anatase surface properties. This is attributed to a balance of formate bonded to coordinately unsaturated surface (c.u.s.) Ti atoms and hydrogen bonded molecules due the different bonding strength of formate on c.u.s. sites present oil different crystal facets and defects. Ways to improve the surface reactivity of TiO2, nanoparticles are discussed.

  • 2011.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Andersson, Per Ola
    Functional TiO2 coatings for surface enhanced degradation of CWA and TIC2008Conference paper (Other academic)
  • 2012.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Brischetto, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Johansson Byberg, Joel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Stefanov, Bozhidar I
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu -Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Spectral Selective Solar Light Enhanced Photocatalysis: TiO2/TiAlN Bilayer Films2018In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 61, no 15-17, p. 1607-1614Article in journal (Refereed)
    Abstract [en]

    We demonstrate that spectral selective photocatalytic multilayer films can be tailored such that they can harness the full solar spectrum for enhanced photocatalytic gas-phase oxidation of acetaldehyde. Thin films of anatase TiO2 were deposited on a thin solar absorber TiAlN film to fabricate bilayer TiO2/TiAlN films by dc magnetron sputtering on aluminium substrates. The structural and optical properties of the films were characterized by X-ray diffraction and Raman spectroscopy. The reaction rate and quantum yield for acetaldehyde removal was measured and an almost tenfold enhancement of the quantum yield was observed for the TiO2/TiAlN films compared with the single TiO2 film, on par with enhancements achieved with new heterojunction photocatalysts. The results were interpreted by a temperature-induced change of the reaction kinetics. Absorption of simulated solar light illumination resulted in a temperature increase of the TIAlN film that was estimated to be at most 126 K. We show that a concomitant temperature increase of the top layer TiO2 by 100 K shifts the water gas surface equilibrium from multilayer to submonolayer coverage. We propose that this is the main reason for the observed enhancement of the photocatalytic activity, whereby gas phase molecules may come in direct contact with free surface sites instead of having to diffuse through a thin water film. The implications of the results for judicious control of temperature and relative humidity for efficient gas-phase photocatalysis and exploitation of selective solar absorbing films are discussed.

  • 2013.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu -Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Spectrally selective nanocoatings with synergistically enhanced photocatalytic and solar light modulation properties2019Conference paper (Other academic)
    Abstract [en]

    Spectrally selective nanocoatings that exhibit synergistically enhanced solar light modulation, luminous transmittance and catalytic properties can be made by combining dielectric film stacks with complementary optical and structural properties. Here we show two case studies:

    1)TiO2/VO2 luminous transparent bilayers that exhibits enhanced near-infrared light absorption and heats the TiO2 film by up to ~ 30°C  resulting in ~ 2-fold increase of the photocatalytic reaction rate. The TiO2/VO2 bilayer stack exhibits anti-reflective properties, and enhanced solar light modulation (∼ 9%) compared to VO2, and ∼ 20 times% increased solar absorptance compared to TiO2. In addition the TiO2 chemically protects the VO2 layer avoiding oxidation to vanadium pentoxide. 2)TiO2/TiAlN solar absorber bilayers that yield an almost ~ 10-fold enhancement of the quantum yield for acetaldehyde removal (on par with state-of-the-art, heterojunction photocatalysts), and an associated temperature rise ~120 °C.

  • 2014.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ji, Yu -Xia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Novel multi-functional self-cleaning, air cleaning and thermochromic films for the built environment2018In: FMNT Functional Materials and Nanotechnologies: Book of Abstracts, 2018, p. 63-, article id INV-10Conference paper (Refereed)
    Abstract [en]

    Spectrally selective photocatalytic multilayer films that exhibit dramatically enhanced photochemical reactivity upon solar light activation were fabricated. It is shown that synergistically enhanced physciochemcial properties can be achieved the surpass those of the constituting single-layer films. We present two case studies: TiO2/VO2 and TiO2/TiAlN bilayer films made by reactive dc magnetron sputtering. The TiO2/VO2 bilayer exhibits enhanced near-infrared light absorption, which thereby heats the TiO2 film by more than 15 degrees, resulting in an almost 2-fold increase of the reaction rate for photo-degradation of stearic acid layers. In addition, the TiO2/VO2 bilayer stack exhibited anti-reflective properties, and enhanced solar modulation (∼ 9%) compared to VO2, and ∼ 20% increased solar absorptance compared to TiO2. In the second example, bilayer TiO2/TiAlN films yielded an almost 10-fold enhancement of the quantum yield for acetaldehyde removal (on par with state-of-the-art, heterojunction photocatalysts), and an associated temperature rise larger than 120 degrees. Both findings can be understood by thermal activation to the increase the surface reaction kinetics, where water desorption from the oxide plays and important role. We generalize the results, and discuss their implications for green building technology and possible scenarios for their implementation.

    References

    1. Yu-Xia Ji, Andreas Mattsson, Gunnar A. Niklasson, Claes-Göran Granqvist, Lars Österlund TiO2/VO2 bilayer coatings for glazing: Synergetically enhanced photocatalytic, thermochromic, and luminous properties, submitted to Advanced Functional Materials 2018.

    2. Lars Österlund, Andreas Mattsson, Joel Martin, Spectrally selective heat absorptive bilayer photocatalyst with enhanced reactivity: TiO2/TiAlN, Topics in Catalysis, in press.

  • 2015.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Leideborg, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Westin, G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    PHOTODECOMPOSITION OF ACETONE ON ZrO(x)-TiO(2) THIN FILMS IN O(2) EXCESS AND DEFICIT CONDITIONS2008In: NANOSTRUCTURED MATERIALS AND NANOTECHNOLOGY, 2008, no 6, p. 175-186Conference paper (Refereed)
    Abstract [en]

    We present a molecular spectroscopy study of the photo-induced decomposition of acetone on zirconium oxide (1-5 at.% Zr) modified TiO(2) thin films with anatase modification. A detailed account of the decomposition products and reaction pathways is presented. It is found that surface coordinated acetate, formate, formaldehyde and carbonate form in the course of the photoreaction. The preferred coordination is bridging bidentate (mu-coordination). The ZrO(x) addition leads to a decreased decomposition rate in synthetic air (O(2) excess) and the results in synthetic air are interpreted in terms of an increased recombination rate in the ZrO(x):TiO(2) films, rather than differences in reaction pathways. In contrast, in O(2) free environment employing N(2) gas, the photoreaction involving lattice O leads to a different decomposition pathway than when O(2) is present in excess. A striking result is that the ZrO(x):TiO(2) films exhibit an exceptional stable activity over time and usage; much better than the pure TiO(2) films. Thus despite an inferior activity the sustain activity of the ZrOx-TiO(2) films suggests means to circumvent deactivation of photocatalyst materials.

  • 2016.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lejon, Christian
    FOI.
    Mäkie, Peter
    Umeå Universitet.
    Deactivation mechanisms of transition metal oxide photocatalysts studied by operando surface infrared spectroscopy2011In: Deactivation mechanisms of transition metal oxide photocatalysts studied by operando surface infrared spectroscopy, American Chemical Society (ACS), 2011, p. 324-Conference paper (Refereed)
  • 2017.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mäkie, Peter
    Umeå Universitet.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lejon, Christian
    FOI.
    Deactivation mechanisms of transition metal oxide photocatalysts studied by operando surface infrared spectroscopy2011In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 241, no 1, p. 326-327Article in journal (Refereed)
  • 2018.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pedersen, M O
    University of Aarhus, Aarhus, Denmark.
    Stensgaard, I
    University of Aarhus, Aarhus, Denmark.
    Laegsgaard, E
    University of Aarhus, Aarhus, Denmark.
    Besenbacher, F
    University of Aarhus, Aarhus, Denmark.
    Quantitative determination of adsorbate-adsorbate interactions1999In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 83, no 23, p. 4812-4815Article in journal (Refereed)
    Abstract [en]

    A new concept called configuration distribution analysis is introduced to extract quantitative information on adsorbate-adsorbate interactions from high-resolution scanning tunneling microscopy data. From atom-resolved nitrogen island configurations on an Fe(100) surface we show that the propensity to form small, compact c(2 X 2) nitrogen islands is due to a nearest neighbor repulsion and next-nearest neighbor attraction. We demonstrate the importance of including many-body terms and elastic interactions to account for the detailed description of the island distribution.

  • 2019.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Rasmussen, P B
    University of Aarhus, Aarhus, Denmark.
    Thostrup, P
    University of Aarhus, Aarhus, Denmark.
    Laegsgaard, E
    University of Aarhus, Aarhus, Denmark.
    Stensgaard, I
    University of Aarhus, Aarhus, Denmark.
    Besenbacher, F
    University of Aarhus, Aarhus, Denmark.
    Bridging the pressure gap in surface science at the atomic level: H/Cu(110)2001In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 86, no 3, p. 460-463Article in journal (Refereed)
    Abstract [en]

    The structural response of the Cu(110) surface to H-2 gas pressures ranging from 10(-13) to 1 bar is studied using a novel high-pressure scanning tunneling microscope (HP-STM). We find that at H-2 pressures larger than 2 mbar the Cu(110) surface reconstructs into the (1 X 2) "missing-row" structure. From a quantitative analysis of the pressure dependence of the surface reconstruction, we conclude that Cu(110) responds identically to hydrogen at ultrahigh vacuum conditions and at atmospheric pressures. From the HP-STM data, we extract refined values for the adsorption and desorption rate constants.

  • 2020.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Stefanov, Bozhidar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Topalian, Zareh
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tuning the photocatalytic of TiO2 based films by orientated growth and surfacefunctinalization2014In: 5th International Symposium on Transparent Conductive Materials / [ed] G. Kiriakides, Mitos, Heraklion, Crete , 2014Conference paper (Refereed)
    Abstract [en]

    Anatase TiO2 is by far the most studied photocatalytic material.1 Normally anatase particlesare dominated by the low energy (101) surface planes with small fractions of (001) facets, whichgives the particles their characteristic truncated bi-pyramidal morphology. TiO2 thin films preparedby reactive DC magnetron sputtering in O2 atmosphere are initially amorphous, but after heattreatmentit has been reported that preferential alignment occurs for grains in the <004> direction,which is thought to expose reactive (001) planes at the film surface.2 Here, anatase TiO2 thin filmswere deposited by reactive DC magnetron sputtering in Ar/O2 atmosphere, and were characterizedusing Rietveld refined grazing-incidence XRD, AFM, spectrophotometry and surface profilometry.Upon heat-treatment for 1 h at 500ºC the as-deposited amorphous films crystallized in the anatasephase with grain size between 18 and 26 nm. By varying the partial O2 pressure in the depositionchamber, the degree of orientation of the grains in the film could be systematically varied withpreferred <001> orientation changing between 12 and 38%. Photocatalytic degradation ofmethylene blue dye was measured by in situ absorption spectroscopy in a home-built reactor.3 Aclear relation was found between the amount of preferred orientation and photocatalytic reactivityof the films. The rate increase is non-linear and follows approximately a square dependence on thedegree of <001> orientation.Moreover, we show that modifications of the acid–base properties of TiO2-basedphotocatalysts can be used to improve their sustained photocatalytic activity. Acid surfacefunctionalization was accomplished by a novel method, where SO2 gas molecules are adsorbed onsurface oxygen vacancy sites in a reactive atmosphere, and which subsequently are oxidized tosulphate groups.4 Here we have applied this method to DC magnetron sputtered films with variousdegree of <001> orientation, as well as on Doctor bladed TiO2 film from nanoparticle suspensions.In situ FTIR spectroscopy measurements of the photo-degradation of acetaldehyde shows thepresence of surface sulphate groups weakens bonding of intermediate aldehyde and carboxylatespecies to the surface, and lowers the formation rate of intermediate formate products. Repeatedadsorption/photo-oxidation cycles show that the acetaldehyde adsorption capacity is higher onsulphated TiO2 films, which can be explained by a reduced site-blocking effect of strongly bondedformate species which limit the complete oxidation on TiO2.The presented results point toward new strategies to purposefully improve the photocatalyticactivity of TiO2 films by industrially up-scalable technologies, and also show that appropriatemodification of the acid-base surface properties can help to avoid photocatalyst deactivation

  • 2021.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Stengl, Vaclav
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bakardjieva, Snejana
    Andersson, Per Ola
    Oplustil, Frantisek
    Effect of sample preparation and humidity on the photodegradation rate of CEES on pure and Zn doped anatase TiO2 nanoparticles prepared by homogeneous hydrolysis2009In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 88, no 1-2, p. 194-203Article in journal (Refereed)
  • 2022.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Topalian, Z.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Granqvist, C.-G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Characterization of Oleophobic and Photocatalytic TiO2 Thin Films Prepared by Surface Functionalization with Reactive Sulfur Dioxide Gas2011In: Abstracts 2nd European Symp. Photocatalysis (JEP 2011), 2011Conference paper (Refereed)
  • 2023.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Topalian, Zareh
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Photocatalytic oxide films in the built environment2014In: INERA Workshop: Transition Metal Oxide Thin Films-functional Layers in "Smart windows" and Water Splitting Devices / [ed] Assoc. Prof. Dr.Tatyana Ivanova, Prof. DSc Kostadinka Gesheva, Prof. DSc Hassan Chamatti, Assoc. Prof. Dr. Georgi Popkirov, Institute of Physics (IOP), 2014, p. 012009-Conference paper (Refereed)
    Abstract [en]

    The possibility to increase human comfort in buildings is a powerful driving force for the introduction of new technology. Among other things our sense of comfort depends on air quality, temperature, lighting level, and the possibility of having visual contact between indoors and outdoors. Indeed there is an intimate connection between energy, comfort, and health issues in the built environment, leading to a need for intelligent building materials and green architecture. Photocatalytic materials can be applied as coatings, filters, and be embedded in building materials to provide self-cleaning, antibacterial, air cleaning, deodorizing, and water cleaning functions utilizing either solar light or artificial illumination sources – either already present in buildings, or by purposefully designed luminaries. Huge improvements in indoor comfort can thus be made, and also alleviate negative health effects associated with buildings, such as the sick-house syndrome. At the same time huge cost savings can be made by reducing maintenance costs. Photocatalytic oxides can be chemical modified by changing their acid-base surface properties, which can be used to overcome deactivation problems commonly encountered for TiO2 in air cleaning applications [2, 3]. In addition, the wetting properties oxides can be tailored by surface chemical modifications and made e.g. oleophobic and water repellent [5]. Here we show results of surface acid modified TiO2 coatings on various substrates. In particular, we show that advanced surface treatment of photocatalytic cement yields surfaces with beneficial self-cleaning properties by means of photo-fixation of surface sulfate groups. We propose that such approaches are feasible for a number of applications in the built environment, including windows, tiles, sheet metals, plastics, etc.

  • 2024.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Topalian, Zareh
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Photocatalytic oxide films in the built environment2014In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 559, no 1, p. 012009-Article in journal (Refereed)
  • 2025.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Van der Meulen, Torbjörn
    FOI.
    A comparative study of the photocatalytic oxidation of propane on anatase, rutile, and mixed-phase anatase-rutile TiO2 nanoparticles: Role of surface intermediates2007In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 251, p. 131-144Article in journal (Refereed)
    Abstract [en]

    The photocatalytic oxidation of propane was investigated by simultaneous in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and quadrupole mass spectrometry (QMS) on anatase, rutile, and mixed anatase-rutile TiO2 nanoparticles prepared by hydrothermal treatments of microemulsions. The mixed anatase-rutile sample was compared with a commercial sample (Degussa P25) with similar anatase to rutile mol% ratio. The measured carbon mass balance for the different TiO2 materials reveals that the total oxidation rate (propane --> CO2) over the first 25-min illumination period is highest for samples containing large anatase nanoparticles and that mixed anatase-rutile nanoparticles are superior to single-phase anatase nanoparticles. These findings are correlated with the main intermediate surface species observed on the different nanoparticle systems by DRIFTS. In particular, eta(1)-acetone and bridging bidentate formate (mu-formate) is detected. On both anatase and rutile, it-formate is the final hydrocarbon surface species. Further oxidation yields bicarbonate, carbonate, CO2, and H2O. On all TiO2 samples, the concentration of surface intermediates is found to be proportional to the accumulated carbon concentration, as deduced from the gas-phase carbon mass balance measurements. This shows that the rate-determining step is the oxidation of strongly bound surface intermediates. Furthermore, it is found that the rate-determining step is structure-sensitive. On anatase, photo-oxidation of acetone limits the total oxidation, whereas on rutile, formate does so. The latter is attributed to a combination of thermal dissociation of acetone on defect sites, which aids acetone oxidation, and the strong bonding of mu-formate to the (110) surface facets on rutile. A synergetic effect between anatase and rutile particles is observed, where the measured photo-oxidation rate from either QMS or DRIFT exceeds that for the individual constituent particles. (c) 2007 Elsevier Inc. All rights reserved.

  • 2026.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Zoric, I
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Dissociative sticking of O-2 on Al(111)1997In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 55, no 23, p. 15452-15455Article in journal (Refereed)
    Abstract [en]

    The dissociative sticking probability, S-0, of O-2 on Al(111) has been measured as a function of incident translational and vibrational energy. S-0 rises from approximate to 10(-2) for energies approximate to 30 meV to near unity in the range 0.6-2.0 eV, demonstrating an activated dissociation event. Vibrational excitation enhances the sticking. Surface temperature has no effect on S-0. A peculiar dependence on polar angle is observed. The results are used to discuss possible mechanisms for the recent observation [H. Brune et al. Phys. Rev. Lett. 68, 624 (1992)] of widely separated O atoms after O-2 dissociation on Al(111).

  • 2027.
    Östh, Michael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Hérisson, D
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Exprimental first order reversal curves (FORC) on Ising andHeisenberg spin glasses2006Conference paper (Refereed)
  • 2028.
    Östh, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hérisson, Didier
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Experimental first order reversal curves (FORC) on Ising and Heisenberg spin glasses2007In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 310, no 2, p. E525-E527Article in journal (Refereed)
    Abstract [en]

    The first order reversal curve (FORC) method is employed to analyse the low temperature hysteresis behaviour of two model 3d spin glasses: the Ising system Fe0.5 Mn0.5 TiO3 and the near isotropic Heisenberg like system Ag(11 at% Mn). The hysteresis loops of the two samples are strikingly different (in accord with results from earlier investigations on spin glasses with different anisotropy). The derived FORC distribution of the Ising system is wide, centred around 0-bias field and in parts similar to what has been observed for interacting magnetic nanoparticle systems with wide particle size distributions. The FORC distribution for the Ag(Mn) spin glass on the other hand shows a sharp peak at a weak negative bias field and a coercive field of about - 80 and 200 Oe, respectively.

  • 2029.
    Östh, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hérisson, Didier
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    DeToro, J. A.
    Riveiro, J. M.
    Aging and memory effects in a mechanically alloyed nanoparticle system2007In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 313, no 2, p. 373-377Article in journal (Refereed)
    Abstract [en]

    Ageing and memory experiments have been performed to explore the non-equilibrium dynamics of the mechanically alloyed nanoparticle system Fe30Ag40W30, which comprises a heterogeneous ensemble of magnetic particles with average moment 102 μB dispersed in a metallic non-magnetic matrix. This system has earlier, from critical slowing down analysis, been reported to enter a spin glass like state at low temperatures [J. A. de Toro et al., Phys. Rev. B 69, (2004) 224407]. The wait time dependence of the magnetic relaxation observed after the application of a weak magnetic field and the memory of the thermal history in the low temperature phase recorded on continuous heating in a weak applied field show similar features as observed in corresponding experiments on canonical spin glasses.

  • 2030.
    Östling, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    High Accuracy Speed and Angular Position Detection by Dual Sensor2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    For many decades there has been a need in many industries to measure speed and position of ferrous gears. This is commonly done by converting passing gear teeth from trigger wheels to electrical impulses to calculate speed and angular position.

    By using Hall effect sensors or Giant Magnetoresistance sensors (GMR), a zero speed detection of gear teeth is possible while at the same time be cheap to produce and durable for harsh environments.

    A specially designed trigger-wheel (cogwheel created for measurements) with gear teeth in a specific pattern, exact position can be detected by using a dual sensor, even when no earlier information is available. The new design of trigger-wheel also makes this new method more accurate and universal compared to previous solutions.

    This thesis demonstrates and argues for the advantages of using a dual sensor for speed and angular position detection on gear wheels. Were one sensor do quantitative measurements for pattern detection in the teeth arrangements and the other sensor do qualitative measurements for position detection.

  • 2031.
    Østerberg, F. W.
    et al.
    Dept of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Kongens Lyngby, Danmark.
    Rizzi, G.
    Dept of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Kongens Lyngby, Danmark.
    Zardán Gómez de la Torre, Teresa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hansen, M. F.
    Dept of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, Kongens Lyngby, Danmark.
    Measurements of Brownian relaxation of magnetic nanobeads using planar Hall effect bridge sensors2012In: Biosensors & bioelectronics, ISSN 0956-5663, E-ISSN 1873-4235, Vol. 40, no S1, p. 147-152Article in journal (Refereed)
    Abstract [en]

    We compare measurements of the Brownian relaxation response of magnetic nanobeads in suspension using planar Hall effect sensors of cross geometry and a newly proposed bridge geometry. We find that the bridge sensor yields six times as large signals as the cross sensor, which results in a more accurate determination of the hydrodynamic size of the magnetic nanobeads. Finally, the bridge sensor has successfully been used to measure the change in dynamic magnetic response when rolling circle amplified DNA molecules are bound to the magnetic nanobeads. The change is validated by measurements performed in a commercial AC susceptometer. The presented bridge sensor is, thus, a promising component in future lab-on-a-chip biosensors for detection of clinically relevant analytes, including bacterial genomic DNA and proteins.

38394041 2001 - 2031 of 2031
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