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  • 1.
    Ahlinder, Linnea
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ekstrand-Hammarstrom, Barbro
    Geladi, Paul
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Large Uptake of Titania and Iron Oxide Nanoparticles in the Nucleus of Lung Epithelial Cells as Measured by Raman Imaging and Multivariate Classification2013In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 105, no 2, p. 310-319Article in journal (Refereed)
    Abstract [en]

    It is a challenging task to characterize the biodistribution of nanoparticles in cells and tissue on a subcellular level. Conventional methods to study the interaction of nanoparticles with living cells rely on labeling techniques that either selectively stain the particles or selectively tag them with tracer molecules. In this work, Raman imaging, a label-free technique that requires no extensive sample preparation, was combined with multivariate classification to quantify the spatial distribution of oxide nanoparticles inside living lung epithelial cells (A549). Cells were exposed to TiO2 (titania) and/or alpha-FeO(OH) (goethite) nanoparticles at various incubation times (4 or 48 h). Using multivariate classification of hyperspectral Raman data with partial least-squares discriminant analysis, we show that a surprisingly large fraction of spectra, classified as belonging to the cell nucleus, show Raman bands associated with nanoparticles. Up to 40% of spectra from the cell nucleus show Raman bands associated with nanoparticles. Complementary transmission electron microscopy data for thin cell sections qualitatively support the conclusions.

  • 2.
    Ahlinder, Linnea
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Henych, Jiří
    Wiklund Lindström, Susanne
    Ekstrand-Hammarström, Barbro
    Stengl, Václav
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Graphene oxide nanoparticle attachment and its toxicity on living lung epithelial cells2015In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 73, p. 59447-59457Article in journal (Refereed)
    Abstract [en]

    Since its discovery, graphene and its oxidized form, graphene oxide (GO), have attracted interest in a wide range of technical applications. Concerns about their potential toxicity calls for scrutinized studies, but hitherto conflicting results have been reported which partly may be due to variations of synthesis and exposure procedures. Here we report on the attachment and toxicity of contamination-free graphene oxide nanoparticles (GONP) in living lung epithelial cells. The synthesis of chemically pure GONP was made by an improvement of the Hummer's method based on graphene exfoliated from graphite using high-intensity ultrasonication, resulting in two dimensional sheets with a lateral dimension in the range 200 nm to 3 mu m and thickness of 0.9 nm. Confocal Raman spectroscopy combined with multivariate analysis was used to study the interaction of GONP and living cells. It is shown that overlapping Raman bands due to GONPs and biomolecules in the cells can clearly be separated with this approach. Orthogonal partial least squares discriminant analysis was used to compare spectral data collected from cells exposed to GONP with spectral data collected from non-exposed control cells, and spectral data from cells exposed to a surfactant known to induce apoptosis. Our analyses show that GONP readily attach to the cells, forming sheets which cover a large fraction of the cell surfaces, and induce small chemical changes. In particular, chemical modifications of proteins and lipids in lung epithelial cells are inferred. GONPs do not, however, decrease cell viability. In contrast, enhanced cell proliferation is observed. Our results shed new light on the interactions of GO, and in contrast to some previous reports, suggest that GO is not toxic. The hyperspectral Raman spectroscopy analysis employed here should be applicable for other fields in nanomedicine as a label-free non-perturbing analytical method.

  • 3.
    Ahlinder, Linnea
    et al.
    Swedish Def Res Agcy, FOI, Cementvagen 20, SE-90182 Umea, Sweden..
    Lindstrom, Susanne Wiklund
    Swedish Def Res Agcy, FOI, Cementvagen 20, SE-90182 Umea, Sweden..
    Lejon, Christian
    Swedish Def Res Agcy, FOI, Cementvagen 20, SE-90182 Umea, Sweden..
    Geladi, Paul
    Swedish Univ Agr Sci, Dept Forest Biomat & Technol, SE-90183 Umea, Sweden..
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Noise Removal with Maintained Spatial Resolution in Raman Images of Cells Exposed to Submicron Polystyrene Particles2016In: NANOMATERIALS, ISSN 2079-4991, Vol. 6, no 5, article id UNSP 83Article in journal (Refereed)
    Abstract [en]

    The biodistribution of 300 nm polystyrene particles in A549 lung epithelial cells has been studied with confocal Raman spectroscopy. This is a label-free method in which particles and cells can be imaged without using dyes or fluorescent labels. The main drawback with Raman imaging is the comparatively low spatial resolution, which is aggravated in heterogeneous systems such as biological samples, which in addition often require long measurement times because of their weak Raman signal. Long measurement times may however induce laser-induced damage. In this study we use a super-resolution algorithm with Tikhonov regularization, intended to improve the image quality without demanding an increased number of collected pixels. Images of cells exposed to polystyrene particles have been acquired with two different step lengths, i.e., the distance between pixels, and compared to each other and to corresponding images treated with the super-resolution algorithm. It is shown that the resolution after application of super-resolution algorithms is not significantly improved compared to the theoretical limit for optical microscopy. However, to reduce noise and artefacts in the hyperspectral Raman images while maintaining the spatial resolution, we show that it is advantageous to use short mapping step lengths and super-resolution algorithms with appropriate regularization. The proposed methodology should be generally applicable for Raman imaging of biological samples and other photo-sensitive samples.

  • 4. Ahlinder, Linnea
    et al.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hyperspektral analys av celler och vävnad exponerade för luftburna partiklar2010Report (Refereed)
  • 5.
    Ahlinder, Linnea
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wiklund Lindström, Susanne
    Raman mapping and hyperspectral data analysis2010Report (Refereed)
  • 6.
    Andersson, M.
    et al.
    Chalmers University of Technology.
    Kiselev, A.
    Umeå University.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Palmqvist, A E C
    Chalmers University of Technology.
    Microemulsion-mediated room-temperature synthesis of high-surface-area rutile and its photocatalytic performance2007In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 111, no 18, p. 6789-6797Article in journal (Refereed)
    Abstract [en]

    Nanosized titania having the rutile crystalline structure was synthesized at room temperature using a microemulsion-mediated system. The formed rutile particles had a diameter of 3 nm, which corresponds well with the droplet size of the water-in-oil microemulsion used for their preparation. The crystallinity was monitored by both X-ray diffraction (XRD) and electron diffraction, together with dark-field electron microscopy (TEM) and high-resolution TEM. The rutile had a high specific surface area (similar to 300 m(2)/g) according to N-2 adsorption and the BET equation. To our knowledge, this is the highest specific surface area ever reported for rutile. The rutile crystals aligned in a specific crystallographic direction forming elongated aggregates 200-1000 nm in size, as observed by TEM and high-resolution TEM. The titania formation was followed in situ using dynamic light scattering and UV-vis spectroscopy, and together with TEM and XRD performed on samples collected throughout the duration of the titania synthesis, the results gave support for a formation scheme involving the initial formation of amorphous titania followed by crystallization of rutile. The photocatalytic performance of the formed material was evaluated by in situ Fourier transform infrared spectroscopy and compared to that of a rutile sample having a lower specific surface area (similar to 40 m(2)/g). The TEM and formate adsorption experiments revealed that the high-surface-area rutile had a much higher fraction of (101) facets than the low-surface-area sample, which predominantly exposed (110) facets. In particular, a new bidentate formate (mu-formate) species bridge-bonded to the (101) facet could be identified with characteristic bands at 1547 and 1387 cm(-1). The photodegradation rate of this species was found to be similar to the mu-formate species on the (110) facet. However, the overall formate degradation rate was larger on the high-surface-area rutile sample because of a high concentration of the more readily photodegradable monodentate formate (eta(1)-formate) on that sample.

  • 7.
    Andersson, M
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ljungstrom, S
    Chalmers University of Technology.
    Palmqvist, A E C
    Chalmers University of Technology.
    Preparation of nanosize anatase and rutile TiO2 by hydrothermal treatment of microemulsions and their activity for photocatalytic wet oxidation of phenol2002In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 106, no 41, p. 10674-10679Article in journal (Refereed)
    Abstract [en]

    Titanium dioxide (TiO2) nanoparticles of both anatase and rutile phases were synthesized by hydrothermal treatment of microemulsions, and their photocatalytic activity for wet oxidation of phenol was studied. The only difference between the two syntheses used was that different acids were added to the microemulsions, making direct comparison of the catalytic activity of the two polymorphs possible. If hydrochloric acid was used, the rutile structure formed, and if nitric acid was used, anatase formed. The phase stability of the microemulsion was studied and according to conductivity and turbidity measurements the idea of a direct template effect could be discarded during the hydrothermal treatment. However, an initial size-templating phenomenon is possible during the mixing step. The particles, which were in the size range of a few nanometers were characterized with N-2-adsorption; XRD, SEM, and XPS. The activity of the two polymorphs for the photocatalytic oxidation of phenol in water was examined. It was shown that the rutile phase initially decomposed phenol much faster and follows a first-order process reasonably well (k = 4 x 10(-5) s(-1)). The photodecomposition process using the anatase phase led, however, to a much more rapid overall degradation following an initial slower rate of phenol oxidation. The results indicate that the observed difference of the photodecomposition process for the two TiO2 phases is due to the formation of different intermediates.

  • 8.
    Andersson, Per Ola
    et al.
    FOI, Umeå.
    Lejon, Christian
    FOI, Umeå.
    Ekstrand Hammarström, Barbro
    FOI, Umeå.
    Akfur, Christine
    FOI, Umeå.
    Ahlinder, Linnea
    FOI, Umeå.
    Bucht, Anders
    FOI, Umeå.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Polymorph and size dependent uptake and toxicity of TiO2 nanoparticles in living lung epithelial cells2011In: Small, ISSN 1613-6810, Vol. 7, no 4, p. 514-523Article in journal (Refereed)
    Abstract [en]

    The cellular uptake and distribution of five types of well-characterized anatase and rutile TiO(2) nanoparticles (NPs) in A549 lung epithelial cells is reported. Static light scattering (SLS), in-vitro Raman microspectroscopy (mu-Raman) and transmission electron spectroscopy (TEM) reveal an intimate correlation between the intrinsic physicochemical properties of the NPs, particle agglomeration, and cellular NP uptake. It is shown that mu-Raman facilitates chemical-, polymorph-, and size-specific discrimination of endosomal-particle cell uptake and the retention of particles in the vicinity of organelles, including the cell nucleus, which quantitatively correlates with TEM and SLS data. Depth-profiling mu-Raman coupled with hyperspectral data analysis confirms the location of the NPs in the cells and shows that the NPs induce modifications of the biological matrix. NP uptake is found to be kinetically activated and strongly dependent on the hard agglomeration size-not the primary particle size-which quantitatively agrees with the measured intracellular oxidative stress. Pro-inflammatory responses are also found to be sensitive to primary particle size.

  • 9. Andersson, Per Ola
    et al.
    Lind, Per
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    A novel ATR-FTIR method for functionalised surface characterisation2008In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 40, no 3-4, p. 623-626Article in journal (Refereed)
    Abstract [en]

    We demonstrate a novel method to analyse ex situ prepared chips by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), which circumvents tedious functionalisation steps of internal reflection elements (IREs), and simultaneously allows for complementary measurements by other analytical techniques. This concept is proved by utilising immobilised metal affinity capture (IMAC) chips containing about 10 gm thick films of copolymers coated with nitrilotriacetic acid (NTA) groups. With this so-called 'upside-down' ATR-FTIR technique, each chemical modification step can be followed and optimised with respect to concentration, buffer, pH, ionic strength, and so on, and there are no limitations in variations or numbers of functionalised surfaces that can be generated. We have demonstrated the feasibility of this approach to determine the molecular structure of ligand bonded to immobilised polypeptide, directly observed in the raw ATR-FTIR spectrum. Peptide adsorption in a thick NTA-copolymer matrix yields a high peptide concentration as determined by the analysis of the Langmuir adsorption isotherm. Combined with the 'upside-down' ATR-FTIR approach which samples the outermost region of the exposed NTA-copolymer film, this generates well-resolved amide I and II absorption bands that reduce the necessity of using D2O based buffers, which otherwise is common in mid-IR spectroscopy of proteins. We believe that this new optical surface characterisation method has a great potential as a stand-alone or complementary analytical tool. We emphasise further that with this approach no chemical treatment of IREs is needed; the chips can be regenerated and reused, and analysed by complementary analytical techniques such as mass spectrometry.

  • 10.
    Andersson, Per Ola
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. FOI Swedish Def Res Agcy, CBRN Def & Secur, S-90182 Umea, Sweden.; Mol Fingerprint Sweden AB, Eksatravagen 130, S-75655 Uppsala, Sweden.
    Viberg, Pernilla
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Forsberg, Pontus
    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. Mol Fingerprint Sweden AB, Eksatravagen 130, S-75655 Uppsala, Sweden.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Mol Fingerprint Sweden AB, Eksatravagen 130, S-75655 Uppsala, Sweden.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Mol Fingerprint Sweden AB, Eksatravagen 130, S-75655 Uppsala, Sweden.
    Nanocrystalline diamond sensor targeted for selective CRP detection: An ATR-FTIR spectroscopy study2016In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642, E-ISSN 1618-2650, Vol. 408, no 14, p. 3675-3680Article in journal (Refereed)
    Abstract [en]

    Protein immobilization on functionalized fluorine- terminated nanocrystalline (NCD) films was studied by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy using an immobilization protocol developed to specifically bind C-reactive protein (CRP). Using an ATR- FTIR spectroscopy method employing a force-controlled anvil-type configuration, three critical steps of the ex situ CRP immobilization were analyzed. First, the NCD surface was passivated by deposition of a copolymer layer consisting of polyethylene oxide and polypropylene oxide. Second, a synthetic modified polypeptide binder with high affinity to CRP was covalently attached to the polymeric film. Third, CRP dissolved in aqueous buffer in concentrations of 10–20 μg/ mL was added on the functionalized NCD surface. Both the amide I and II bands, due to the polypeptide binder and CRP, were clearly observed in ATR-FTIR spectra. CRP amide I bands were extracted from difference spectra and yielded bands that agreed well with the reported amide I band of free (non-bonded) CRP in solution. Thus, our results show that CRP retains its secondary structure when it is attached to the polypeptide binders. Compared to previous IR studies of CRP in solution, about 200 times lower concentration was applied in the present study. 

  • 11. Ausen, Dag
    et al.
    Westvik, Rita
    Svagård, Ingrid
    Österlund, Lars
    Gustafson, Inga
    Vikholm-Lundin, Inger
    Winquist, Fredrik
    Lading, Lars
    Gran, Jens
    Foresight Biomedical Sensors2007Report (Other academic)
    Abstract [en]

    The foresight study on biomedical sensors has addressed different approaches with future use of biomedical sensors in the health care sector, like: How will biomedical sensors shape the healthcare systems of the future? How can they impact the quality and cost of healthcare and what are the business opportunities in the Nordic region?

  • 12.
    Cai, Yixao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Almandoz-Gil, Leire
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    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.
    Österund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bergström, Joakim
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    ATR- FTIR spectroscopy study of oxidative modification of the a-synuclein secondary structure2013Conference paper (Refereed)
  • 13.
    Cai, Yixiao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lendel, Christofer
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kasrayan, Alex
    Lannfelt, Lars
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Ingelsson, Martin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Nikolajeff, Fredrik
    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.
    Bergström, Joakim
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Public Health and Caring Sciences, Geriatrics.
    Changes in secondary structure of α-synuclein during oligomerization induced by reactive aldehydes.2015In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 464, no 1, p. 336-341Article in journal (Refereed)
    Abstract [en]

    The oxidative stress-related reactive aldehydes 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) have been shown to promote formation of α-synuclein oligomers in vitro. However, the changes in secondary structure of α-synuclein and the kinetics of the oligomerization process are not known and were the focus of this study. Size exclusion chromatography showed that after 1 h of incubation, HNE induced the formation of an oligomeric α-synuclein peak with a molecular weight of about ∼2000 kDa, which coincided with a decreasing ∼50 kDa monomeric peak. With prolonged incubation (up to 24 h) the oligomeric peak became the dominating molecular species. In contrast, in the presence of ONE, a ∼2000 oligomeric peak was exclusively observed after 15 min of incubation and this peak remained constant with prolonged incubation. Western blot analysis of HNE-induced α-synuclein oligomers showed the presence of monomers (15 kDa), SDS-resistant low molecular (30-160 kDa) and high molecular weight oligomers (≥260 kDa), indicating that the oligomers consisted of both covalent and non-covalent protein. In contrast, ONE-induced α-synuclein oligomers only migrated as covalent cross-linked high molecular-weight material (≥300 kDa). Both circular dichroism (CD) and Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy showed that the formation of HNE- and ONE-induced oligomers coincided with a spectral change from random coil to β-sheet. However, ONE-induced α-synuclein oligomers exhibited a slightly higher degree of β-sheet. Taken together, our results indicate that both HNE and ONE induce a change from random coil to β-sheet structure that coincides with the formation of α-synuclein oligomers. Albeit through different kinetic pathways depending on the degree of cross-linking.

  • 14.
    Carlsson, P A
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thormahlen, P
    Chalmers University of Technology.
    Palmqvist, A E C
    Chalmers University of Technology.
    Fridell, E
    Chalmers University of Technology.
    Jansson, J
    Chalmers University of Technology.
    Skoglundh, M
    Chalmers University of Technology.
    A transient in situ FTIR and XANES study of CO oxidation over Pt/Al2O3 catalysts2004In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 226, no 2, p. 422-434Article in journal (Refereed)
    Abstract [en]

    We report experimental results for the oxidation of CO over supported Pt/Al2O3 catalysts operating in oxygen excess at atmospheric pressure. To study the reaction kinetics under transient conditions we have employed step changes of the O-2 concentration by intermittently switching off the O-2 supply at various temperatures ranging from 523 to 623 K. Detailed in situ FTIR and XANES data for CO coverage and the chemical state of Pt, respectively, are presented together with the CO conversion, which in both cases was monitored by mass spectrometry. A red-shift of the vibrational frequency of linearly bonded CO which correlates with a blue-shift of the Pt L-III binding energy indicates that the Pt catalyst initially is partially oxidised and gradually reduced when the O-2 supply is switched off. Control experiments with a NO2 oxidised Pt/Al2O3 catalyst support these findings. A hysteresis in the catalytic activity due to the different rates whereby Pt is oxidised and reduced as a function of gas-phase composition is observed. The activation energy for the Pt oxide reduction (decomposition) process is estimated to be about 50 kJ/mol. The results further emphasise that the conventional three-step Langmuir-Hinshelwood (LH) scheme used to interpret CO oxidation on Pt surfaces must be complemented by a Pt oxidation and reduction mechanism during transient conditions. Moreover, FTIR data suggest that during the extinction, the partially oxidised platinum surface is reduced by chemisorbed CO which should be explicitly accounted for in the modeling of the reaction mechanism. (C) 2004 Elsevier Inc. All rights reserved.

  • 15.
    Chakarov, D V
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hellsing, B
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Photos induced desorption and intercalation of potassium atoms deposited on graphite(0001)1996In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 106, p. 186-192Article in journal (Refereed)
    Abstract [en]

    In addition to the photodesorption phenomenon previously observed for single K atoms from a graphite surface covered with a monolayer of potassium we present new results related to the photon stimulated interaction of potassium with graphite, which concerns alternative routes for energy relaxation of the photo excited K adatoms: photoinduced intercalation. The desorption yield has a threshold at h omega approximate to 3 eV and a maximum at h omega(max) approximate to 4.9 eV, Polarization measurements indicate a substrate-mediated mechanism. The coverage dependence suggests that only the ionic 2D, K-phase is photo active. The proposed mechanism includes attachment of photo-generated hot electrons to the K 4s adsorbate resonance of energy E(res). Assuming an analogous excitation process we discuss different mechanisms for the K photo intercalation and possible applications of the photon stimulated doping of carboneous materials at low temperature.

  • 16.
    CHAKAROV, DV
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    HELLSING, B
    Chalmers University of Technology.
    ZHDANOV, VP
    Chalmers University of Technology.
    KASEMO, B
    Chalmers University of Technology.
    PHOTOSTIMULATED DESORPTION OF METAL ADATOMS - POTASSIUM ON GRAPHITE1994In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 311, no 3, p. L724-L730Article in journal (Refereed)
    Abstract [en]

    Photodesorption is observed of single K atoms from a graphite surface covered with less than 1 monolayer of potassium. The desorption cross section has a threshold at homegaBAR almost-equal-to 3 eV and a maximum at homega(max)BAR almost-equal-to 4.9 eV. Polarization measurements indicate a substrate-mediated mechanism. The coverage dependence suggests that only the ionic 2D, K-phase is photoactive. The proposed mechanism includes attachment of hot electrons, photoexcited in the bulk, to the K4s adsorbate resonance of energy E(res). The band structure of graphite causes a narrow energy distribution of hot electrons, which yields homega(max)BAR almost-equal-to 2E(res).

  • 17.
    CHAKAROV, DV
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    KASEMO, B
    Chalmers University of Technology.
    INTERACTION OF WATER WITH POTASSIUM ON GRAPHITE - A HREELS STUDY1993In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 64-5, p. 279-285Article in journal (Refereed)
    Abstract [en]

    Water and coadsorbed water + potassium on the basal plane of graphite were studied with high resolution electron energy loss spectroscopy (HREELS) at 85 K and after stepwise annealing up to 500 K. Water adsorbs non-dissociatively on both clean and potassium precovered surface at 85 K. The vibration spectra, together with thermal desorption spectroscopy (TDS) reveal a series of reactions within the coadsorbed layer leading to the formation of KOH, KH, and KOx and volatile products. Eventually a precursor to CO2 formation, of yet unindentified composition and observed also in K + O-2 coadsorption studies on graphite, is observed at approximate to 27 meV.

  • 18.
    CHAKAROV, DV
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    KASEMO, B
    Chalmers University of Technology.
    WATER-ADSORPTION AND COADSORPTION WITH POTASSIUM ON GRAPHITE(0001)1995In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 11, no 4, p. 1201-1214Article in journal (Refereed)
    Abstract [en]

    Water and water coadsorbed with potassium on the basal plane of graphite were studied with thermal desorption spectroscopy (TDS) and high-resolution electron energy loss spectroscopy (HREELS) in the temperature range 85-900 K. Water alone adsorbs nondissociatively on the clean graphite surface at 85 K, forming hydrogen bonded aggregates. Its structure depends both on the coverage and on substrate temperature. With increasing coverage at 85 K(0.5-1.0 monolayer (ML)) the libration mode at similar to 86 meV shows a rapid upward shift, indicating a phase transition from a 2D to a 3D structure. The transition can also be induced by annealing the low coverage structure. Water coadsorption with potassium is nonreactive or reactive, depending on temperature and potassium coverage. The nonreactive coadsorption at T-s = 85 K occurs only below a critical potassium coverage of BK less than or equal to 0.3 ML. It is characterized by substantial symmetry changes of the adsorbed water molecules, compared to the pure water adsorption, and is attributed to formation of hydrated-ion species on the surface. The surface solvation number at the lowest K coverage is three to four H2O molecules per potassium atom. K and H2O react at submonolayer coverages at 120-160 K to form surface KOH, KH, KxOy, and volatile products. The surface species gradually transforms/decomposes at elevated temperatures (200-500 K) to first form potassium-oxygen complexes that then serve as precursors to graphite oxidation to CO2 at similar to 750 K.

  • 19.
    CHAKAROV, DV
    et al.
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    KASEMO, B
    Chalmers University of Technology.
    WATER-ADSORPTION ON GRAPHITE(0001)1995In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 46, no 8-10, p. 1109-1112Article in journal (Refereed)
    Abstract [en]

    Wafer adsorption on the clean graphite (0001) surface has been studied by high-resolution electron-energy-loss spectroscopy (HREELS) and temperature-programmed desorption (TPD). At 85 K H2O adsorbs non-dissociatively forming hydrogen-bonded aggregates. The structure and the growth mode of water clusters depend on the substrate temperature and the coverage. At all coverages, above a few per cent of a monolayer (ML), the desorption is characterized by zero-order kinetics, while the HREEL spectra reveal a threshold coverage approximately 1 ML when the average co-ordination of the H2O molecules changes. Isothermal measurements of the desorption rate and HREELS measurements at elevated temperatures suggest an irreversible phase transition from amorphous to crystalline ice at approximately 135 K.

  • 20.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lansåker, Pia C.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    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.
    Sputter-Deposited Indium-Tin Oxide Thin Films for Acetaldehyde Gas Sensing2016In: Coatings, ISSN 2079-6412, Vol. 6, no 2, article id 19Article in journal (Refereed)
    Abstract [en]

    Reactive dual-target DC magnetron sputtering was used to prepare In-Sn oxide thin films with a wide range of compositions. The films were subjected to annealing post-treatment at 400 degrees C or 500 degrees C for different periods of time. Compositional and structural characterizations were performed by X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, Rutherford backscattering and scanning electron microscopy. Films were investigated for gas sensing at 200 degrees C by measuring their resistance response upon exposure to acetaldehyde mixed with synthetic air. We found that the relative indium-to-tin content was very important and that measurable sensor responses could be recorded at acetaldehyde concentrations down to 200 ppb, with small resistance drift between repeated exposures, for both crystalline SnO2-like films and for amorphous films consisting of about equal amounts of In and Sn. We also demonstrated that it is not possible to prepare crystalline sensors with intermediate indium-to-tin compositions by sputter deposition and post-annealing up to 500 degrees C.

  • 21.
    Cindemir, Umut
    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.
    Österlund, Lars
    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.
    Gunnar, Niklasson
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Porous Nickel Oxide Film Sensor for Formaldehyde2014In: INERA Workshop: Transition Metal Oxides as Functional Layers in Smart windows and Water Splitting Devices / Parallel session of the 18th International School on Condensed Matter Physics, 2014, p. UNSP 012012-Conference paper (Refereed)
    Abstract [en]

    Formaldehyde is a volatile organic compound and a harmful indoor pollutant contributing to the "sick building syndrome". We used advanced gas deposition to fabricate highly porous nickel oxide (NiO) thin films for formaldehyde sensing. The films were deposited on Al2O3 substrates with prefabricated comb-structured electrodes and a resistive heater at the opposite face. The morphology and structure of the films were investigated with scanning electron microscopy and X-ray diffraction. Porosity was determined by nitrogen adsorption isotherms with the Brunauer-Emmett-Teller method. Gas sensing measurements were performed to demonstrate the resistive response of the sensors with respect to different concentrations of formaldehyde at 150 degrees C.

  • 22.
    Cindemir, Umut
    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.
    Österlund, Lars
    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.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Porous Nickel Oxide Sensor for Formaldehyde Detection2014In: European Materials Society (E-MRS) Spring Meeting, Lille, France, May 26-30, 2014.: Symposium B: Advanced functional materials for environmental monitoring and applications., 2014Conference paper (Other academic)
    Abstract [en]

    Formaldehyde is a volatile organic compound, which is a harmful indoor pollutant, causing sick building syndrome (SBS) and is released from household and building materials. Since higher concentrations of formaldehyde are considered to be carcinogenic, monitoring them indoors is of great importance. Advanced gas deposition has here been used to fabricate highly porous nickel oxide (NiO) thin films for formaldehyde sensing. The films were deposited on Al2O3 substrates with prefabricated comb-structured electrodes, and a resistive heater at the opposite face. The morphology of the films was investigated with scanning electron microscopy, and the porosity was determined by nitrogen adsorption isotherms with the Brunauer-Emmett-Teller method. The particle size was found to be less than 10 nm, as determined by x-ray diffraction. X-ray photoelectron spectroscopy of the NiO films was also done. Gas sensing measurements were done using a total gas flow rate of 200 ml/min. Resistivity values of sensors were recorded with formaldehyde diluted in synthetic air. Sensor resistances were recorded at 50 ppm, 25ppm, 10ppm and 5 ppm formaldehyde concentration. NiO films showed promising formaldehyde gas sensing properties implying lower levels of detection limit.

  • 23.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Trawka, Maciej
    Gdansk University of Technology, Gdansk, Poland.
    Smulko, Janusz
    Gdansk University of Technology, Gdansk, poland.
    Granqvist, Claes-Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    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.
    Fluctuation-enhanced and conductometric gas sensing with nanocrystalline NiO thin films: A comparison2017In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 242, p. 132-139Article in journal (Refereed)
    Abstract [en]

    Nanocrystalline thin films of NiO were prepared by advanced reactive gas deposition, and their responses to formaldehyde, ethanol and methane gases were studied via fluctuation-enhanced and conductometric methods Thin films with thicknesses in the 200–1700-nm range were investigated in as-deposited form and after annealing at 400 and 500◦C. Morphological and structural analyses showed porous deposits with NiO nanocrystals having face-centered cubic structure. Quantitative changes in frequency-dependent resistance fluctuations as well as in DC resistance were recorded upon exposure to formaldehyde, ethanol and methane at 200◦C. The response to formaldehyde was higher than that to ethanol while the response to methane was low, which indicates that the NiO films exhibit significant selectivity towards different gaseous species. These results can be reconciled with the fact that formaldehyde has a nucleophilic group, ethanol is an electron scavenger, and methane is hard to either reduce or oxidize. The gas-induced variations in DC resistance and resistance fluctuations were in most cases similar and consistent.

  • 24.
    Cindemir, Umut
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    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 G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Trawka, Maciej
    Gdansk Univ Technol, Fac Elect Telecommun & Informat, Gdansk, Poland.
    Smulko, Janusz M.
    Gdansk Univ Technol, Fac Elect Telecommun & Informat, Gdansk, Poland.
    Nickel oxide thin film sensor for fluctuation-enhanced gas sensing of formaldehyde2015In: 2015 IEEE Sensors, 2015Conference paper (Refereed)
    Abstract [en]

    Nanocrystalline nickel-oxide-based thin films were prepared by advanced reactive gas deposition, and the response of these films to formaldehyde was studied by fluctuation-enhanced sensing. Morphological and structural analyses showed porous deposits of nickel oxide particles with face-centered cubic structure. Resistance fluctuations were measured upon exposure to ethanol, formaldehyde and methane at 200 degrees C. Power density spectra were used to quantify the response. The response to formaldehyde was higher than to ethanol at 200 degrees C, and no significant response was observed for methane thus demonstrating some gas-species selectivity.

  • 25.
    Ekstrand-Hammarström, Barbro
    et al.
    FOI, Umeå.
    Akfur, Christine
    FOI, Umeå.
    Andersson, Per Ola
    FOI, UMEÅ.
    Lejon, Christian
    FOI, Umeå.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Buch, Anders
    FOI, Umeå.
    Human Primary Bronchial Epithelial Cells are more Responsive to Titanium Dioxide Nanoparticles than the Lung Epithelial Cell Lines A549 and BEAS-2B2012In: Nanotoxicology, ISSN 1743-5390, E-ISSN 1743-5404, Vol. 6, no 6, p. 623-634Article in journal (Refereed)
    Abstract [en]

    We have compared the cellular uptake and responses of fivepreparations of nanocrystalline titanium dioxide (TiO2) betweennormal human bronchial epithelial (NHBE) cells and epithelialcell lines (A549 and BEAS-2B). The P25 nanoparticles, containingboth anatase and rutile modifications, induced reactive oxygenspecies (ROS) and secretion of the neutrophil chemoattractantIL-8 in all three cell types used. Pure anatase and rutile particlesprovoked differential IL-8 response in A549 and no response inBEAS-2B cells despite similar formation of ROS. The pure TiO2modifications also provoked release of the inflammatorymediators: IL-6, G-CSF and VEGF, in NHBE cells but not in the twocell lines. We conclude that the responsiveness of lung epithelialcells is strongly dependent on both the physicochemicalproperties of TiO2 nanoparticles and the type of responder cells.The differential pro-inflammatory responsiveness of primarylung epithelial cells compared with immortalized cell linesshould be considered in the assessment of adverse reactions toinhaled nanoparticles.

  • 26.
    Geremariam Welearegay, Tesfalem
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Rovira & Virgili Univ, Dept Elect Elect & Automat Engn, Tarragona 43007, Spain.;Mol Fingerprint Sweden AB, S-75655 Uppsala, Sweden..
    Cindemir, Umut
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Mol Fingerprint Sweden AB, S-75655 Uppsala, Sweden.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Mol Fingerprint Sweden AB, S-75655 Uppsala, Sweden.
    Ionescu, Radu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Rovira & Virgili Univ, Dept Elect Elect & Automat Engn, Tarragona 43007, Spain..
    Fabrication and characterisation of ligand-functionalised ultrapure monodispersed metal nanoparticle nanoassemblies employing advanced gas deposition technique2018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 6, article id 065603Article in journal (Refereed)
    Abstract [en]

    Here, we report for the first time the fabrication of ligand-functionalised ultrapure monodispersed metal nanoparticles (Au, Cu, and Pt) from their pure metal precursors using the advanced gas deposition technique. The experimental conditions during nanoparticle formation were adjusted in order to obtain ultrafine isolated nanoparticles on different substrates. The morphology and surface analysis of the as-deposited metal nanoparticles were investigated using scanning electron microscopy, x-ray diffraction and Fourier transform infra-red spectroscopy, which demonstrated the formation of highly ordered pure crystalline nanoparticles with a relatively uniform size distribution of similar to 10 nm (Au), similar to 4 nm (Cu) and similar to 3 nm (Pt), respectively. A broad range of organic ligands containing thiol or amine functional groups were attached to the nanoparticles to form continuous networks of nanoparticle-ligand nanoassemblies, which were characterised by scanning electron microscopy and x-ray photoelectron spectroscopy. The electrical resistance of the functional nanoassemblies deposited in the gap spacing of two microfabricated parallel Au electrodes patterned on silicon substrates ranged between tens of k Omega and tens of M Omega, which is suitable for use in many applications including (bio)chemical sensors, surface-enhanced Raman spectroscopy and molecular electronic rectifiers.

  • 27.
    Ghaly, Montaser
    et al.
    National Research Centre (NRC), Chemical Engineering and Pilot Plant Department, Cairo, Egypt.
    Ali, Mohamed Eid
    National Research Centre (NRC), Water Pollution Research Department, P.O. 11312, Cairo, Egypt.
    Österlund, Lars
    FOI CBRN Defence and Security, Umeå.
    Khattab, Ibrahim
    National Research Centre (NRC), Chemical Engineering and Pilot Plant Department, Cairo, Egypt.
    Badawy, Mohamed
    National Research Centre (NRC), Water Pollution Research Department, P.O. 11312, Cairo, Egypt.
    Farah, Joseph
    National Research Centre (NRC), Chemical Engineering and Pilot Plant Department, Cairo, Egypt.
    Zaher, Fatama
    National Research Centre (NRC), Chemical Engineering and Pilot Plant Department, Cairo, Egypt.
    Al-Maghrabi, Mohammednoor
    Faculty of Engineering, King Abdul-Aziz University, Jedddah, Saudi Arabia.
    ZnO/spiral-shaped glass for solar photocatalytic oxidation of Reactive Red 1202014In: Arabian Journal of Chemistry, ISSN 1878-5352Article in journal (Refereed)
    Abstract [en]

    ZnO/glass spiral (GS) was prepared by immobilization of ZnO on GS with facilemethod, and was characterized by X-ray diffraction analysis (XRD), scanning electron microscope(SEM) and the crystallite size of ZnO on GS surface was calculated. SEM showed rod-like shape ofZnO particles on GS surface. Photocatalytic activity of prepared immobilized photocatalyst wasinvestigated for decolourization and degradation of C.I. Reactive Red 120 (RR-120) dye under sunlight.The kinetics of decolourization and degradation removal has been investigated. The effect ofpH on decolourization and degradation of dye was studied. The decolourization and degradation ofdye were followed by pseudo-first order reaction. The decolourization and degradation of RR-120dye were enhanced by H2O2 addition to definite dosage beyond that the effect is diminished. Also,the reusability of immobilized ZnO on GS was tested for photocatalytic degradation of dye and itwas worth noting that it has high efficiency with slight decrease (5%) after five successive runs.

  • 28.
    Granqvist, Claes G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Azens, A
    Heszler, P
    Kish, L B
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nanomaterials for benign indoor environments: Electrochromics for “smart windows”, sensors for air quality, and photo-catalysts for air cleaning2007In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 91, no 4, p. 355-365Article in journal (Refereed)
    Abstract [en]

    Nanomaterials can be used in a number of technologies in order to accomplish benign indoor environments. This paper takes a unified view on this problem from a solar-energy-based perspective and specifically considers electrochromics for achieving good day-lighting jointly with energy efficiency, sensors aimed at air quality assessment, and photocatalysis for air cleaning. Recent results, mainly from the authors’ laboratories, are reported for all of these areas.

  • 29.
    Granqvist, Claes G
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Azens, Andris
    Heszler, Peter
    Kish, Laszlo B
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Smart Nano-Materials for Benign Indoor Environments2006Conference paper (Other academic)
  • 30.
    Granqvist, Claes Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Azens, A
    Hezler, P
    Kish, LB
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    New Nanomaterials for Energy Efficient Buildings: Electrochromics for "Smart Windows", Sensors for Air Quality, and Photo-Catalysts for Air Cleaning2008In: Nanomaterials: New Research Developments / [ed] EI Pertsov, Hauppauge, New York, USA: Nova Science Publishers , 2008, p. 295-310Chapter in book (Other academic)
  • 31. Gustafsson, Å.
    et al.
    Bergström, U.
    Ågren, L.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bucht, A.
    Biodistribution of engineered hematite nanoparticles in healthy and asthmatic mice2013In: European Respiratory Journal, ISSN 0903-1936, E-ISSN 1399-3003, Vol. 42, no 1Article in journal (Refereed)
  • 32.
    Gustafsson, Åsa
    et al.
    Swedish Def Res Agcy, Div CBRN Def & Secur, SE-90182 Umea, Sweden.;Umea Univ, Dept Publ Hlth & Clin Med, S-90187 Umea, Sweden..
    Bergström, Ulrika
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Environmental toxicology. Swedish Def Res Agcy, Div CBRN Def & Secur, SE-90182 Umea, Sweden..
    Agren, Lina
    Swedish Def Res Agcy, Div CBRN Def & Secur, SE-90182 Umea, Sweden..
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sandstrom, Thomas
    Umea Univ, Dept Publ Hlth & Clin Med, S-90187 Umea, Sweden..
    Bucht, Anders
    Swedish Def Res Agcy, Div CBRN Def & Secur, SE-90182 Umea, Sweden.;Umea Univ, Dept Publ Hlth & Clin Med, S-90187 Umea, Sweden..
    Differential cellular responses in healthy mice and in mice with established airway inflammation when exposed to hematite nanoparticles2015In: Toxicology and Applied Pharmacology, ISSN 0041-008X, E-ISSN 1096-0333, Vol. 288, no 1, p. 1-11Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the inflammatory and immunological responses in airways and lung-draining lymph nodes (LDLNs), following lung exposure to iron oxide (hematite) nanoparticles (NPs). The responses to the hematite NPs were evaluated in both healthy non-sensitized mice, and in sensitized mice with an established allergic airway disease. The mice were exposed intratracheally to either hematite NPs or to vehicle (PBS) and the cellular responses were evaluated on days 1, 2, and 7, post-exposure. Exposure to hematite NPs increased the numbers of neutrophils, eosinophils, and lymphocytes in the airways of non-sensitized mice on days 1 and 2 post-exposure; at these time points the number of lymphocytes was also elevated in the LDLNs. In contrast, exposing sensitized mice to hematite NPs induced a rapid and unspecific cellular reduction in the alveolar space on day 1 post-exposure; a similar decrease of lymphocytes was also observed in the LDLN. The results indicate that cells in the airways and in the LDLN of individuals with established airway inflammation undergo cell death when exposed to hematite NPs. A possible explanation for this toxic response is the extensive generation of reactive oxygen species (ROS) in the pro-oxidative environment of inflamed airways. This study demonstrates how sensitized and non-sensitized mice respond differently to hematite NP exposure, and it highlights the importance of including individuals with respiratory disorders when evaluating health effects of inhaled nanomaterials.

  • 33.
    Haas, Julian
    et al.
    Ulm University, Germany.
    Vargas Catalan, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Piron, Pierre
    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.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Karlsson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Mizaikoff, Boris
    Ulm University, Germany.
    Polycrystalline diamond thin-film waveguides for mid-infrared evanescent field sensors2018In: ACS Omega, ISSN 2470-1343, Vol. 3, no 6, p. 6190-6198Article in journal (Refereed)
    Abstract [en]

    Photonic design and optimization of thin-film polycrystalline diamond waveguides are shown, serving as advanced evanescent field transducers in the mid-infrared fingerprint regime (2000-909 cm(-1); 5-11 mu m). Design constraints inherent to optical/system considerations and the material were implemented in a finite element method (FEM)-based simulation method that allowed three-dimensional modeling of the overall structure. Thus, lateral mode confinement, attenuation in the direction of radiation propagation, and physical resilience were evaluated. In a final step, the designed structures were fabricated, and their utility in combination with a broadly tunable external cavity quantum cascade laser for chemical sensing of a liquid phase analyte was demonstrated.

  • 34.
    Hagglund, C
    et al.
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    In situ reactivity and FTIR study of the wet and dry photooxidation of propane on anatase TiO22005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 21, p. 10886-10895Article in journal (Refereed)
    Abstract [en]

    The photocatalytic oxidation (PCO) of trace amounts of propane (500 ppm) on nanocrystalline anatase TiO2 has been investigated in situ as a function of temperature (T = 318-473 K), humidity (C-H2O = 0-4%), and time by means of mass spectrometry and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). Propane adsorbs associatively on TiO2 at 318 K in dry air, while at 473 K small amounts of thermal dissociation products appear on the surface. In agreement with previous studies, propane is found primarily to be converted to acetone by reactions with photogenerated oxygen radicals. Various successive reaction paths exist, where the branching depends on the temperature and hydroxylation state of the surface. Under dry conditions at 318 K, acetone oxidation is initially kinetically hindered, while, above 400 K, acetone readily decomposes. The thermally assisted reaction channel leads to detrimental bonding of surface species and inhibition of the catalytic activity. It is manifested by a coloration of the sample and suggested to be coupled to surface reduction. Under humidified conditions, there is an optimum of the PCO in C-H2O and T space, which is estimated to correspond to an equilibrium coverage of one monolayer of H2O (or bilayer). The latter reaction condition also corresponds to sustained high propane conversion and is characterized by rapid establishment of steady state rates. The optimum PCO is discussed in terms of a balance between (i) sustaining enough of a photoactive water monolayer to avoid detrimental bonding of surface species, (ii) allowing reactants to adsorb and access bulk TiO2 photoexcitations, and at the same time (iii) maximizing the thermally assisted decomposition of intermediates.

  • 35.
    Hellsing, B
    et al.
    Chalmers University of Technology.
    Chakarov, D V
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Zhdanov, V P
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Photoinduced desorption of potassium atoms from a two dimensional overlayer on graphite1997In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 106, no 3, p. 982-1002Article in journal (Refereed)
    Abstract [en]

    We present an experimental and theoretical investigation of K atom desorption from the basal plane of graphite at 83 K induced by low energy photons (3-6 eV). The 2D potassium overlayer is characterized by low energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy (HREELS), thermal desorption spectroscopy (TDS), and work function measurements. At monolayer coverage (5.2 x 10(14) atoms cm(-2)), the dependence of the cross section on photon energy has a threshold at (h) over bar omega approximate to 3.0 eV and rises up to a maximum of 1.8 +/- 0.4 x 10(-20) cm(2) at 4.8 eV. The coverage dependence of the photoyield reflects the existence of two phases of adsorbed K, dilute ionized photo-active and close-packed photo-neutral, respectively. The observed photodesorption is a single-photon, nonthermal event, consistent with a substrate-mediated mechanism. The desorption results from attachment of optically excited hot electrons to the empty 4s state of ionized potassium. The theory predicts in this case a Gaussian line shape of the photoyield vs photon energy. Fitting the model parameters to the experimental data, we determine (i) the energy and slope of the excited state potential energy curve, and (ii) the position and width of the potassium-induced 4s resonance. The present findings combined with other available data for potassium on graphite are used to construct 1D potential energy curves along the surface normal for K+ and K-0. The calculated cross sections for s- and p-polarized Light are in qualitative agreement with the measurements. (C) 1997 American Institute of Physics.

  • 36.
    Hellsing, B
    et al.
    Chalmers University of Technology.
    Chakarov, D V
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Zhdanov, V P
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Photoinduced desorption of potassium atoms from graphite1996In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 363, no 1-3, p. 247-251Article in journal (Refereed)
    Abstract [en]

    We present an experimental and theoretical investigation of desorption of potassium atoms from the basal plane of graphite induced by photons with energies from 2 to 6 eV. The intensity of the photon flux employed in the measurements is low, and the observed photodesorption is a single-photon, non-thermal event. At monolayer coverage the photon-energy dependence of the cross section has a maximum at 4.8 eV. The experimental observations are interpreted in terms of a hot carrier mechanism, which involves attachment of optically excited substrate hot electrons to the empty 4s state of ionized potassium, and then desorption. The theory predicts a Gaussian line shape of the photoyield versus photon energy. Fitting the model parameters to the experimental data, we determine: (i) the potential energy for Gr + K+ and Gr + K-0; and (ii) the position (2.4 eV above the Fermi level) and width (0.15 eV) of the potassium 4s resonance, which is in good agreement with independent experimental observations.

  • 37. Henych, Jiri
    et al.
    Stengl, Vaclav
    Kormunda, Martin
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Role of bismuth in nano-structured doped TiO2 photocatalyst prepared by environmentally benign soft synthesis2014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 9, p. 3560-3571Article in journal (Refereed)
    Abstract [en]

    An environmentally benign synthesis method was used to prepare a nearly uniform dispersion of TiO2 nanoparticles modified by bismuth for photocatalytic purposes. The role of bismuth in the catalyst structure was evaluated using numerous methods such as XRPD, HTXRPD, TEM and HRTEM, and XPS, as well as Raman, FTIR, and UV-Vis spectroscopy. The bismuth doping significantly improved the photocatalytic performance of azo dye RB5 discoloration due to the formation of surface Bi3+ species and the abundant hydroxylation of the catalyst surface. The great advantage of this procedure lies in the low temperature preparation under ambient pressure without use of the titanium organometallic precursors. Therefore, this developed synthesis procedure could be easily adapted to the industrial scale.

  • 38. Henych, Jiri
    et al.
    Stengl, Vaclav
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    In Situ FTIR Spectroscopy Study of the Photodegradation of Acetaldehyde and azo Dye Photobleaching on Bismuth-Modified TiO22015In: Photochemistry and Photobiology, ISSN 0031-8655, E-ISSN 1751-1097, Vol. 91, no 1, p. 48-58Article in journal (Refereed)
    Abstract [en]

    The photocatalytic properties of bismuth-modified titania were studied by photobleaching of two aqueous azo dyes solutions (Reactive Black 5 and Acid Orange 7), and by photoinduced decomposition (PID) of acetaldehyde using in situ FTIR spectroscopy. Low bismuth doping concentrations up to 3 at.% is shown to lead to an increased photobleaching rate of both azo dyes solutions. Too high Bi dopant concentrations lead to less developed crystallite nanoparticles and exhibit weaker adsorption capacity. Bismuth doping altered the adsorption kinetics of acetaldehyde resulting in different surface products, and a modified photocatalytic reaction pathway was inferred.

  • 39.
    Hu, Shuanglin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Bopp, Philippe A.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Broqvist, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Herrnansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Formic Acid on TiO2-x (110): Dissociation, Motion, and Vacancy Healing2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 27, p. 14876-14887Article in journal (Refereed)
    Abstract [en]

    The adsorption and dissociation of a formic acid molecule (HCOOH) on a partially reduced rutile TiO2-x (110) surface and the subsequent transformations of the adsorbed fragments are studied via quantum-mechanical molecular dynamics simulations and climbing-image nudged elastic band (CI-NEB) calculations. The electronic structure methods used are self-consistent-charge density functional tight binding (SCC-DFTB) and DFT+U calculations. We address the apparent lack of consensus in the literature regarding the formic acid adsorbate species that heal the O vacancies, where different experiments have suggested the occurrence of one, two, or no such species types. From our calculations, we propose that the formic acid molecule quickly dissociates on the surface into a formate ion and a proton. If no mechanism exists by which the dissociation products can migrate away from each other, three formate species will coexist on the partially reduced TiO2 surface: one majority species bound to the Ti rows and two minority species healing the O vacancies. However, if such a diffusion mechanism does exist, our barrier calculations show that one of the minority species will transform into the other, and only two adsorbate types can be expected on the surface. We also identify a new adsorbate configuration (which we denote C'), where the formate is located on the row of two-coordinated oxygen atoms, healing an O vacancy and accepting an H-bond from the detached H atom.

  • 40.
    Hu, Shuanglin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Wang, Zhuo
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Simulation of IRRAS Spectra for Molecules on Oxide Surfaces: CO on TiO2(110)2015In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 10, p. 5403-5411Article in journal (Refereed)
    Abstract [en]

    We explore a method that cart sirriulate infrared refiection absotption spectroscopy (IRRAS) spectra for molecules adsjorlied on semiconductor surfaces. The method rakes it possible to directly correlate experimental spectra with possible adsorbate structures. Our example in thiS paper is CO adsoihed on rutile TiO2(110). We present simulated IRRAS spectra for coverages in the range from 0.125 to 1.5 Monolayer (ML) An explanation is provided. for the apparent inconsistency in the literature concerning the tilting geometry of 1 ML CO on this surface. We find that a tilted structure (which is also the lowest-energy configuration) generates IRRAS spectra in excellent agreement with the experimental spectra. Furthermore, we predict the adsorption structure for 1.5 ML CO coverage over TiO2 (110), which consists of very weakly bound CO molecules on top of the monolayer. In all cases, our simulation method) which is based On density functioual theory (PFT) vibrational calculations, produces s- and p-polarized IRRAS spectra in excellent agreement with the experimental spectra.

  • 41.
    Jamil, Tarek S.
    et al.
    National Research Center, Water Pollution Control Department, National Research Center, El Buhouth Street, P.O. Box 12311, Dokki, Cairo, Egypt.
    Ghaly, Montaser Y.
    Chemical Engineering and Pilot Plant Department, National Research Centre, Egypt.
    Fathy, Nady A.
    Surface Chemistry and Catalysis Laboratory, National Research Centre, Egypt.
    Abd el-halim, Tarek A.
    Surface Morphology and Elemental Analysis Department, Nuclear Material Authority, Egypt.
    Österlund, Lars
    FOI CBRN Defence and Security, SE-901 82 Umeå, Sweden.
    Enhancement of TiO2 behavior on photocatalytic oxidation of MO dye using TiO2/AC under visible irradiation and sunlight radiation2012In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 98, p. 270-279Article in journal (Refereed)
    Abstract [en]

    The activated carbon loaded TiO2 photocatalyst was prepared and characterized by FT-IR, scanning electron micrograph (SEM) and X-ray diffraction (XRD). The photocatalytic efficiency of activated carbon loaded TiO2 was evaluated by photocatalytic oxidation of Methyl Orange (MO) dye in aqueous medium using visible and solar light. TiO2/AC exhibited higher photocatalytic oxidation efficiency of MO than that of naked TiO2. The various experimental parameters like initial dye concentration, amount of catalyst and solution pH for efficient dye degradation are investigated. Activity measurements performed under visible light and solar irradiation have shown good results for the photo degradation of MO in aqueous solution. The higher efficiency of TiO2/AC is due to synergy effect of activated carbon. Addition of high adsorption capacity activated carbon to photoactive titanium dioxide in photocatalytic degradation of dyes improves the efficiency of dye mineralization. The present catalysts show high adsorptivity and high photoactivity for the degradation of the MO dye and can be very easily separated from the solution by sedimentation or simple filtration and it can be used repeatedly for MO removal with preservation of its photoactivity.

  • 42.
    Jamil, Tarek S.
    et al.
    National Research Center, Egypt.
    Ghaly, Montaser Y.
    National Research Center, Egypt.
    Fathy, Nady A.
    National Research Center, Egypt.
    Abd el-halim, Tarek A.
    Nuclear Material Authority, Egypt.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Enhancement of TiO2 behavior on photocatalytic oxidation of MO dye usingTiO2/AC under visible irradiation and sunlight radiation2012In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 98, p. 270-279Article in journal (Refereed)
    Abstract [en]

    The activated carbon loaded TiO2 photocatalyst was prepared and characterized by FT-IR, scanning electronmicrograph (SEM) and X-ray diffraction (XRD). The photocatalytic efficiency of activated carbonloaded TiO2 was evaluated by photocatalytic oxidation of Methyl Orange (MO) dye in aqueous mediumusing visible and solar light. TiO2/AC exhibited higher photocatalytic oxidation efficiency of MO than thatof naked TiO2. The various experimental parameters like initial dye concentration, amount of catalyst andsolution pH for efficient dye degradation are investigated. Activity measurements performed under visiblelight and solar irradiation have shown good results for the photo degradation of MO in aqueous solution.The higher efficiency of TiO2/AC is due to synergy effect of activated carbon. Addition of highadsorption capacity activated carbon to photoactive titanium dioxide in photocatalytic degradation ofdyes improves the efficiency of dye mineralization. The present catalysts show high adsorptivity and highphotoactivity for the degradation of the MO dye and can be very easily separated from the solution bysedimentation or simple filtration and it can be used repeatedly for MO removal with preservation ofits photoactivity.

  • 43.
    Jansson, J
    et al.
    Chalmers University of Technology.
    Palmqvist, A E C
    Chalmers University of Technology.
    Fridell, E
    Chalmers University of Technology.
    Skoglundh, M
    Chalmers University of Technology.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thormahlen, P
    Chalmers University of Technology.
    Langer, V
    Chalmers University of Technology.
    On the catalytic activity of Co3O4 in low-temperature CO oxidation2002In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 211, no 2, p. 387-397Article in journal (Refereed)
    Abstract [en]

    Oxidation of CO over Co3O4 at ambient temperature was studied with flow reactor experiments, and in-situ spectroscopic and structural methods. The catalyst deactivates during the reaction. The rate of deactivation increased with increasing CO or CO2 gas-phase concentration but decreased with increased 02 concentration or increased temperature. Regeneration of the catalyst in 10% O-2/Ar was more efficient than regeneration in Ar alone. The presence of carbonates and surface carbon on the deactivated catalyst was concluded from TPO experiments. None of these species could, however, be correlated with the deactivation of the catalyst. In-situ FTIR showed the presence of surface carbonates, carbonyl, and oxygen species. The change in structure and oxidation state of the catalyst was studied by in-situ XRD, in-situ XANES, XPS, and flow reactor experiments. One possible explanation for the deactivation of the catalyst is a surface reconstruction hindering the redox cycle of the reaction. (C) 2002 Elsevier Science (USA).

  • 44.
    Johansson, Malin B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Baldissera, Gustavo
    Kungliga Tekniska Högskolan.
    Valyukh, Iryna
    Linköpings Universitet.
    Persson, Clas
    Kungliga Tekniska Högskolan.
    Arwin, Hans
    Linköpings Universitet.
    Niklasson, Gunnar A.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Electronic and optical properties of nanocrystalline WO3 thin films studied by optical spectroscopy and density functional calculations2013In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 25, no 20, p. 205502-Article in journal (Refereed)
    Abstract [en]

    The optical and electronic properties of nanocrystalline WO3 thin films prepared by reactive dc magnetron sputtering at different total pressures (Ptot) were studied by optical spectroscopy and density functional theory (DFT) calculations. Monoclinic films prepared at low Ptot show absorption in the near infrared due to polarons, which is attributed to a strained film structure. Analysis of the optical data yields band-gap energies Eg ≈ 3.1 eV, which increase with increasing Ptot by 0.1 eV, and correlate with the structural modifications of the films. The electronic structures of triclinic δ-WO3, and monoclinic γ- and ε-WO3 were calculated using the Green function with screened Coulomb interaction (GW approach), and the local density approximation. The δ-WO3 and γ-WO3 phases are found to have very similar electronic properties, with weak dispersion of the valence and conduction bands, consistent with a direct band-gap. Analysis of the joint density of states shows that the optical absorption around the band edge is composed of contributions from forbidden transitions (>3 eV) and allowed transitions (>3.8 eV). The calculations show that Eg in ε-WO3 is higher than in the δ-WO3 and γ-WO3 phases, which provides an explanation for the Ptot dependence of the optical data.

  • 45.
    Johansson, Malin B
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kristiansen, Paw
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Baldissera, G
    Duda, Laurent C
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Persson, C
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Band gap states in nanocrystalline WO3 thin films studied by soft x-ray spectroscopy, optical absorption spectroscopy and density functional calculationsManuscript (preprint) (Other academic)
  • 46. Johansson, Malin B
    et al.
    Kristiansen, Paw
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Baldissera, G
    Duda, Laurent C
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Persson, C
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sub-band gap electronic states in nanocrystalline WO3 thin films studied by soft x-ray spectroscopy, optical absorption spectroscopy and density functional calculationsManuscript (preprint) (Other academic)
  • 47.
    Johansson, Malin B.
    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.
    Lindquist, Sten-Eric
    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.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    The Importance of Oxygen Vacancies in Nanocrystalline WO3−x ThinFilms Prepared by DC Magnetron Sputtering for Achieving High Photoelectrochemical Efficiency2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 13, p. 7412-7420Article in journal (Refereed)
    Abstract [en]

    The photoelectrochemical properties of tungsten oxide thinfilms with different stoichiometry (WO3−x) and thickness were investigated.The films were sputtered in O2/Ar gas (ratio 0.43) on glass substrates coatedwith fluorine-doped tin dioxide at two sputter pressures, Ptot = 10 and 30mTorr, yielding O/W ratios of the films, averaged over three samples, of 2.995and 2.999 (x ∼ 0.005 and x ∼ 0.001), respectively. The films were characterizedby X-ray diffraction, scanning electron microscopy, and spectrophotometry.The 10 mTorr samples showed large absorption in the near-infrared (NIR)range, whereas the 30 mTorr samples had a small absorption in this region. Theconcentration of oxygen vacancy band gap states was estimated from cyclicvoltammetry and was found to correlate with the optical absorption in the NIRregion. The incident photon to current efficiency for illumination from theelectrolyte side (IPCEEE) and substrate electrode side (IPCESE) showed higherefficiency for the more stoichiometric films, indicating that oxygen vacancies in the band gap act as recombination centers.Surprisingly high values of IPCEEE and IPCESE were found, and it was concluded that efficient charge separation and transporttake place almost throughout the entire film even for film electrodes as thick as 2 μm. Analysis of the spectral distribution of thephotoresponse (action spectra) using an extended Gärtner−Butler model to calculate the IPCE for front-side and back-sideillumination was performed and showed that the diffusion length is large, of the order of the depletion layer thickness.

  • 48.
    Johansson, Malin B
    et al.
    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.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Structural and optical properties of visible active photocatalytic WO3 thin films prepared by reactive dc magnetron sputtering2012In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 27, no 24, p. 3130-3140Article in journal (Refereed)
    Abstract [en]

    Nanostructured tungsten trioxide films were prepared by reactive dc magnetron sputteringat different working pressures P-tot = 1-4 Pa. The films were characterized by scanning electron microscopy, x-ray diffraction, Rutherford backscattering spectroscopy, Raman spectroscopy, and ultraviolet-visible spectrophotometry. The films were found to exhibit predominantly monoclinic structures and have similar band gap, E-g approximate to 2.8 eV, with a pronounced Urbach tail extending down to 2.5 eV. At low P-tot, strained film structures formed, which were slightly reduced and showed polaron absorption in the near-infrared region. The photodegradation rate of stearic acid was found to correlate with the stoichiometry and polaron absorption. This is explained by a recombination mechanism, whereby photoexcited electron-hole pairs recombine with polaron states in the band gap. The quantum yield decreased by 50% for photon energies close to E-g due to photoexcitations to band gap states lying below the O-2 affinity level.

  • 49.
    Johansson, Malin B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zietz, Burkhard
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Niklasson, Gunnar A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optical properties of nanocrystalline WO3 and WO3-x thin films prepared by DC magnetron sputtering2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 21, p. 213510-Article in journal (Refereed)
    Abstract [en]

    The optical properties of tungsten trioxide thin films prepared by DC magnetron sputtering, withdifferent oxygen vacancy (Vo) concentration, have been studied by spectrophotometry andphotoluminescence (PL) emission spectroscopy. Absorption and PL spectra show that the filmsexhibit similar band gap energies, Eg 2.9 eV. The absorption spectra of the films show twopronounced absorption bands in the near-infrared region. One peak (P1) is located atapproximately 0.7 eV, independent of Vo concentration. A second peak (P2) shifts from 0.96 eV to1.16 eV with decreasing Vo concentration. Peak P1 is assigned to polaron absorption due totransitions between tungsten sites (W5þ!W6þ), or an optical transition from a neutral vacancystate to the conduction band, Vo0!W6þ. The origin of peak P2 is more uncertain but may involveþ1 and þ2 charged vacancy sites. The PL spectra show several emission bands in the range 2.07 to3.10 eV in the more sub-stoichiometric and 2.40 to 3.02 eV in the less sub-stoichiometric films.The low energy emission bands agree well with calculated optical transition energies of oxygenvacancy sites, with dominant contribution from neutral and singly charged vacancies in the lesssub-stoichiometric films, and additional contributions from doubly charged vacancy sites in themore sub-stoichiometric films.

  • 50. Johansson, Malin
    et al.
    Niklasson, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Determination of structures and properties of WO3 thin films deposited by DC magnetron sputtering2009Conference paper (Refereed)
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