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  • 1. 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.

  • 2. 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.

  • 3. 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.

  • 4.
    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.

  • 5.
    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.

  • 6.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Formic acid adsorption and photodecomposition on rutile TiO2 (110): An in situ infrared reflection absorption spectroscopy study2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    TiO2 based photocatalysis is an emerging green nanotechnology that can be used forremoval of pollutants from water and air. It has had an increased research interest, bothfrom an application and fundamental point of view, during the last decades. Despite thismany elementary processes that occur on the photocatalyst surface are not fullyunderstood and are thus limiting our ability to purposefully manufacture more efficientphotocatalytic materials.In this licentiate thesis, the adsorption geometry and photodecomposition of formicacid on differently prepared rutile TiO2 (110) surfaces were investigated. The surface wasprepared by repeated cycles of Argon ion sputtering and annealing. By modifying thisprocedure either reduced, stoichiometric or oxylated surfaces have been obtained. Thesedifferent surfaces are all well-ordered as evident from the obtained low energy electrondiffraction pattern. In addition, a totally disordered surface was also prepared by Argonsputtering alone. Grazing incidence infrared reflection-absorption spectroscopy (IRRAS)employing polarized light with different azimuthal orientations of the TiO2 single crystalwas used to investigate the binding geometry of formic acid (HCOOH) on the surface.Upon adsorption of formic acid on the TiO2 surface, the molecule is deprotonatedresulting in a formate (HCOO-) and a hydrogen (H+) molecule on the surface. The formatemolecules are mainly bridge-bonded to the Ti5c surface atoms with their molecular axisalong the [001] direction. A minority of the formate species was found to adsorb throughhydroxylated oxygen vacancies (or protonated oxygen atoms) and therefore have differentorientations on the surface. For the disordered surface, it was found that the orientation ofthe formate adsorbates are more or less random since no changes in the IRRAS spectraare seen for the different directions of the single crystal. The adsorption geometry for thedisordered surface is also changed, as seen in the shift of the peak positions in the IRRASspectra. This changed adsorption geometry is attributed to exposures of Ti3+ atoms on thesurface, and is a result of the Ar ion sputtering.Irradiation of the HCOO/TiO2 systems by UV light (365 nm, 2 mW/cm2) showed onlya small change in formate coverage after 100 minutes of illumination. The decrease waslargest on the disordered surface and miniscule on the ordered surface. These results werecompared with those obtained on rutile nanoparticles at ambient conditions. Thecomparison shows that the adsorption geometry for the nanoparticles is similar to that ofthe ordered single crystal surfaces and that the photodecomposition rate is about a factorof 30 higher on the nanoparticles than on the disordered surface. This difference isexpected as the single crystal experiments were performed in vacuum, where the supplyof O2 electron acceptors and OH/H2O donors from the gas phase is limited.These results shows that the rutile TiO2 (110) surface is a good model system forfundamental studies of nanoparticle systems and that the presence of hydroxylated oxygenvacancies and protonated oxygen atoms are important for the reactivity of the TiO2surface and must be included in the description of surface reactions on rutile surfaces.

    List of papers
    1. Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study
    Open this publication in new window or tab >>Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study
    2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 3, p. 034705-Article in journal (Refereed) Published
    Abstract [en]

    Formic acid (HCOOH) adsorption on rutile TiO2 (110) has been studied by s- and p-polarized infrared reflection-absorption spectroscopy (IRRAS) and spin-polarized density functional theory together with Hubbard U contributions (DFT+U) calculations. To compare with IRRAS spectra, the results from the DFT+U calculations were used to simulate IR spectra by employing a three-layer model, where the adsorbate layer was modelled using Lorentz oscillators with calculated dielectric constants. To account for the experimental observations, four possible formate adsorption geometries were calculated, describing both the perfect (110) surface, and surfaces with defects; either O vacancies or hydroxyls. The majority species seen in IRRAS was confirmed to be the bridging bidentate formate species with associated symmetric and asymmetric frequencies of the nu(OCO) modes measured to be at 1359 cm(-1) and 1534 cm(-1), respectively. The in-plane delta(C-H) wagging mode of this species couples to both the tangential and the normal component of the incident p-polarized light, which results in absorption and emission bands at 1374 cm(-1) and 1388 cm(-1). IRRAS spectra measured on surfaces prepared to be either reduced, stoichiometric, or to contain surplus O adatoms, were found to be very similar. By comparisons with computed spectra, it is proposed that in our experiments, formate binds as a minority species to an in-plane Ti-5c atom and a hydroxyl, rather than to O vacancy sites, the latter to a large extent being healed even at our UHV conditions. Excellent agreement between calculated and experimental IRRAS spectra is obtained. The results emphasize the importance of protonation and reactive surface hydroxyls - even under UHV conditions - as reactive sites in e. g., catalytic applications. (C) 2014 AIP Publishing LLC.

    National Category
    Natural Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-220815 (URN)10.1063/1.4855176 (DOI)000330614400051 ()
    Available from: 2014-03-21 Created: 2014-03-20 Last updated: 2018-10-03Bibliographically approved
    2. Infrared spectroscopy study of adsorption and photodecomposition of formic acid on reduced and defective rutile TiO2 (110) surfaces
    Open this publication in new window or tab >>Infrared spectroscopy study of adsorption and photodecomposition of formic acid on reduced and defective rutile TiO2 (110) surfaces
    2014 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 32, no 6, article id 061402Article in journal (Refereed) Published
    Abstract [en]

    Adsorption and photodecomposition of formic acid on rutile TiO2 (110) have been investigated with infrared reflection–absorption spectroscopy (IRRAS) employing p- and s-polarized light along the [001] and [ 11⎯⎯0 ] crystal directions. The single crystal surfaces were prepared either by sputtering and annealing in ultrahigh vacuum (UHV) to obtain a reduced surface (r-TiO2), or by sputtering without annealing to create a rough, highly defective surface (sp-TiO2). Results are compared with corresponding measurements on rutile nanocrystals performed in synthetic air. IRRAS spectra obtained on r-TiO2 and rutile nanocrystals are very similar, and show that in both cases formic acid dissociates and is predominately adsorbed as a bridging bidentate formate species, and that the formate adsorption structure on the nanocrystals is dominated by interactions with majority (110) surfaces. In contrast, the IRRAS spectra on sp-TiO2 are different, with only minor spectral features associated with (110) surfaces and lost azimuthal symmetry, both of which imply changed adsorption geometry due to bonding to low-coordinated Ti atoms with lower valences. The UV-induced rate of formate photodecomposition is about 30 times higher on rutile nanocrystals in synthetic air compared with sp-TiO2 under UHV conditions, and even larger than on r-TiO2. These differences are explained by the lack of oxygen and limited hydroxyl coverage under UHV conditions. The difference in reactivity between the r-TiO2 and sp-TiO2 surfaces is attributed to a high concentration of strongly bonded bridging bidentate formate species on the (110) surface, which lowers its reactivity. The results point to a pressure gap where the availability of molecular oxygen and the hydroxyl concentration limit the photoreactivity in UHV leading to an almost 20-fold decrease of the formate degradation rate in UHV. In contrast, the structure represented by the single crystal (110) surface is shown to capture the essential structural properties, which dictates the formic acid adsorption and adsorption structure of rutile nanocrystals.

    National Category
    Condensed Matter Physics Engineering and Technology
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-227100 (URN)10.1116/1.4898568 (DOI)000345215500012 ()
    Funder
    Swedish Research Council, 2010-3514eSSENCE - An eScience CollaborationThe Swedish Foundation for International Cooperation in Research and Higher Education (STINT)
    Available from: 2014-06-24 Created: 2014-06-24 Last updated: 2018-10-03Bibliographically approved
  • 7.
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Infrared spectroscopy studies of adsorption and photochemistry on TiO2 surfaces: From single crystals to nanostructured materials2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    TiO2 based photocatalysis is a green nanotechnology that can be used for removal of pollutants from water and air, as well as making synthetic fuels from water and carbon dioxide. Said photocatalysis has received major research interests during the last decades. Despite these efforts, many elementary processes that occur on the photocatalyst surface are not fully understood and, therefore, limit our ability to purposefully manufacture more efficient photocatalytic materials. The objective of this thesis is to provide new understanding at a molecular level of important adsorbate species on the TiO2 surfaces.

    Fundamental properties of adsorption and photochemistry of primarily formic acid on different TiO2 surfaces, ranging from single crystals to nanoparticles, have been studied using infrared spectroscopy. A method to simulate IR spectra have been developed and, combined with experimental data, has been proven to be a powerful tool to identify different adsorbate geometries on the surface. In the presence of oxygen, a thermally activated and irreversible reaction between formate and oxygen adatoms takes place on the single crystal rutile (110) surface to yield hydrogen bicarbonate surface complexes. For disordered single crystal surfaces, the adsorption geometry of formate changes due to exposure of Ti3+ atoms on the surface, and the adsorption spectra shows resemblances with that observed for formate adsorption on nanocrystalline surfaces.

    Illumination with UV light results in small changes of the formate coverage on the disordered single crystal and nanocrystalline rutile surfaces, whereas on the rutile (110) surface only miniscule changes in formate coverages are seen. This is due to the lack of oxygen electron acceptors and OH/H2O electron donors in the vacuum environment, which results in a much lower degradation rate compared to measurements made at ambient conditions. Furthermore, it is shown that the coordination of the formate molecule on various TiO2 surfaces has a profound effect on the photocatalytic degradation rate, with bidentate coordinated formate molecules being most resilient towards oxidation.

    The results presented here shows that additional insight in the processes on the TiO2 photocatalyst surface can be obtained by combining spectroscopic studies of single crystals and nanocrystalline films and that it is possible to unravel adsorption geometries on surfaces by combining experimental and simulated IR spectra.

    List of papers
    1. Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study
    Open this publication in new window or tab >>Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study
    2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 3, p. 034705-Article in journal (Refereed) Published
    Abstract [en]

    Formic acid (HCOOH) adsorption on rutile TiO2 (110) has been studied by s- and p-polarized infrared reflection-absorption spectroscopy (IRRAS) and spin-polarized density functional theory together with Hubbard U contributions (DFT+U) calculations. To compare with IRRAS spectra, the results from the DFT+U calculations were used to simulate IR spectra by employing a three-layer model, where the adsorbate layer was modelled using Lorentz oscillators with calculated dielectric constants. To account for the experimental observations, four possible formate adsorption geometries were calculated, describing both the perfect (110) surface, and surfaces with defects; either O vacancies or hydroxyls. The majority species seen in IRRAS was confirmed to be the bridging bidentate formate species with associated symmetric and asymmetric frequencies of the nu(OCO) modes measured to be at 1359 cm(-1) and 1534 cm(-1), respectively. The in-plane delta(C-H) wagging mode of this species couples to both the tangential and the normal component of the incident p-polarized light, which results in absorption and emission bands at 1374 cm(-1) and 1388 cm(-1). IRRAS spectra measured on surfaces prepared to be either reduced, stoichiometric, or to contain surplus O adatoms, were found to be very similar. By comparisons with computed spectra, it is proposed that in our experiments, formate binds as a minority species to an in-plane Ti-5c atom and a hydroxyl, rather than to O vacancy sites, the latter to a large extent being healed even at our UHV conditions. Excellent agreement between calculated and experimental IRRAS spectra is obtained. The results emphasize the importance of protonation and reactive surface hydroxyls - even under UHV conditions - as reactive sites in e. g., catalytic applications. (C) 2014 AIP Publishing LLC.

    National Category
    Natural Sciences Engineering and Technology
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-220815 (URN)10.1063/1.4855176 (DOI)000330614400051 ()
    Available from: 2014-03-21 Created: 2014-03-20 Last updated: 2018-10-03Bibliographically approved
    2. Infrared spectroscopy study of adsorption and photodecomposition of formic acid on reduced and defective rutile TiO2 (110) surfaces
    Open this publication in new window or tab >>Infrared spectroscopy study of adsorption and photodecomposition of formic acid on reduced and defective rutile TiO2 (110) surfaces
    2014 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 32, no 6, article id 061402Article in journal (Refereed) Published
    Abstract [en]

    Adsorption and photodecomposition of formic acid on rutile TiO2 (110) have been investigated with infrared reflection–absorption spectroscopy (IRRAS) employing p- and s-polarized light along the [001] and [ 11⎯⎯0 ] crystal directions. The single crystal surfaces were prepared either by sputtering and annealing in ultrahigh vacuum (UHV) to obtain a reduced surface (r-TiO2), or by sputtering without annealing to create a rough, highly defective surface (sp-TiO2). Results are compared with corresponding measurements on rutile nanocrystals performed in synthetic air. IRRAS spectra obtained on r-TiO2 and rutile nanocrystals are very similar, and show that in both cases formic acid dissociates and is predominately adsorbed as a bridging bidentate formate species, and that the formate adsorption structure on the nanocrystals is dominated by interactions with majority (110) surfaces. In contrast, the IRRAS spectra on sp-TiO2 are different, with only minor spectral features associated with (110) surfaces and lost azimuthal symmetry, both of which imply changed adsorption geometry due to bonding to low-coordinated Ti atoms with lower valences. The UV-induced rate of formate photodecomposition is about 30 times higher on rutile nanocrystals in synthetic air compared with sp-TiO2 under UHV conditions, and even larger than on r-TiO2. These differences are explained by the lack of oxygen and limited hydroxyl coverage under UHV conditions. The difference in reactivity between the r-TiO2 and sp-TiO2 surfaces is attributed to a high concentration of strongly bonded bridging bidentate formate species on the (110) surface, which lowers its reactivity. The results point to a pressure gap where the availability of molecular oxygen and the hydroxyl concentration limit the photoreactivity in UHV leading to an almost 20-fold decrease of the formate degradation rate in UHV. In contrast, the structure represented by the single crystal (110) surface is shown to capture the essential structural properties, which dictates the formic acid adsorption and adsorption structure of rutile nanocrystals.

    National Category
    Condensed Matter Physics Engineering and Technology
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-227100 (URN)10.1116/1.4898568 (DOI)000345215500012 ()
    Funder
    Swedish Research Council, 2010-3514eSSENCE - An eScience CollaborationThe Swedish Foundation for International Cooperation in Research and Higher Education (STINT)
    Available from: 2014-06-24 Created: 2014-06-24 Last updated: 2018-10-03Bibliographically approved
    3. Simulation of IRRAS Spectra for Molecules on Oxide Surfaces: CO on TiO2(110)
    Open this publication in new window or tab >>Simulation of IRRAS Spectra for Molecules on Oxide Surfaces: CO on TiO2(110)
    Show others...
    2015 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 10, p. 5403-5411Article in journal (Refereed) Published
    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.

    National Category
    Physical Chemistry Other Engineering and Technologies
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-251804 (URN)10.1021/jp5094096 (DOI)000351189100017 ()
    Available from: 2015-04-28 Created: 2015-04-24 Last updated: 2018-10-03
    4. Co-adsorption of oxygen and formic acid on rutile TiO2 (110) studied by infrared reflection-absorption spectroscopy
    Open this publication in new window or tab >>Co-adsorption of oxygen and formic acid on rutile TiO2 (110) studied by infrared reflection-absorption spectroscopy
    2017 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 663, p. 47-55Article in journal (Refereed) Published
    Abstract [en]

    Adsorption of formic acid and co-adsorption with oxygen have been investigated on the rutile TiO2(110) surface using p- and s-polarized infrared reflection-absorption spectroscopy (IRRAS) at O2 exposures between 45 L to 8100 L and at temperatures between 273 K and 343 K. On the clean surface formic acid dissociates into a formate ion (formate) and a proton. Formate binds to two five-fold coordinated Ti atoms in the troughs along the [001] direction, and the proton binds to neighboring bridging O atoms. Exposure of adsorbed formate to O2 leads to a decrease in the asymmetric νas(OCO) band at 1532 cm−1 and to the concomitant formation of a new vibration band at 1516 cm−1. From the s-and p-polarized IRRAS measurements performed at different O2 exposures, surface pre-treatments and substrate temperatures, and by comparisons with previous reports, we conclude that the new species is a bidentate surface hydrogen carbonate, which is formed by reaction between formate and oxygen adatoms on the surface. The σv reflection plane of the surface hydrogen carbonate molecule is oriented along the [001] direction, i.e. the same direction as the adsorbed formate molecule. On the clean TiO2(110) surface exposed to O2 prior to formic acid adsorption, similar results are obtained. The reaction rate to form surface hydrogen carbonate from formate is found to follow first-order kinetics, with an apparent activation energy of Er=0.25 eV.

    National Category
    Engineering and Technology Condensed Matter Physics
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-332994 (URN)10.1016/j.susc.2017.04.012 (DOI)000405043300007 ()
    Funder
    Swedish Research Council, 2010-3514
    Available from: 2017-12-01 Created: 2017-12-01 Last updated: 2018-10-03Bibliographically approved
    5. Formic acid adsorption and photo-induced decomposition on TiO2: A comparative study of rutile single crystals, sputtered and sol-gel synthesized anatase, brookite and rutile thin films
    Open this publication in new window or tab >>Formic acid adsorption and photo-induced decomposition on TiO2: A comparative study of rutile single crystals, sputtered and sol-gel synthesized anatase, brookite and rutile thin films
    (English)Manuscript (preprint) (Other academic)
    National Category
    Nano Technology
    Research subject
    Engineering Science with specialization in Solid State Physics
    Identifiers
    urn:nbn:se:uu:diva-361326 (URN)
    Available from: 2018-09-29 Created: 2018-09-29 Last updated: 2018-10-03
  • 8.
    Mattsson, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hu, Shuanglin
    Hermansson, Kersti
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Adsorbtion and photodecomposition of formic acid on stoichiometric and defective rutile TiO2 (110) surfaces2014In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 32, no 061402-1Article in journal (Refereed)
  • 9.
    Mattsson, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hu, Shuanglin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Adsorption and photodecomposition of formic acid on rutile TiO2 (110) surfaces2013Conference paper (Other academic)
  • 10.
    Mattsson, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hu, Shuanglin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Adsorption of formic acid on rutile TiO2 (110) revisited: An infrared reflection-absorption spectroscopy and density functional theory study2014In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 3, p. 034705-Article in journal (Refereed)
    Abstract [en]

    Formic acid (HCOOH) adsorption on rutile TiO2 (110) has been studied by s- and p-polarized infrared reflection-absorption spectroscopy (IRRAS) and spin-polarized density functional theory together with Hubbard U contributions (DFT+U) calculations. To compare with IRRAS spectra, the results from the DFT+U calculations were used to simulate IR spectra by employing a three-layer model, where the adsorbate layer was modelled using Lorentz oscillators with calculated dielectric constants. To account for the experimental observations, four possible formate adsorption geometries were calculated, describing both the perfect (110) surface, and surfaces with defects; either O vacancies or hydroxyls. The majority species seen in IRRAS was confirmed to be the bridging bidentate formate species with associated symmetric and asymmetric frequencies of the nu(OCO) modes measured to be at 1359 cm(-1) and 1534 cm(-1), respectively. The in-plane delta(C-H) wagging mode of this species couples to both the tangential and the normal component of the incident p-polarized light, which results in absorption and emission bands at 1374 cm(-1) and 1388 cm(-1). IRRAS spectra measured on surfaces prepared to be either reduced, stoichiometric, or to contain surplus O adatoms, were found to be very similar. By comparisons with computed spectra, it is proposed that in our experiments, formate binds as a minority species to an in-plane Ti-5c atom and a hydroxyl, rather than to O vacancy sites, the latter to a large extent being healed even at our UHV conditions. Excellent agreement between calculated and experimental IRRAS spectra is obtained. The results emphasize the importance of protonation and reactive surface hydroxyls - even under UHV conditions - as reactive sites in e. g., catalytic applications. (C) 2014 AIP Publishing LLC.

  • 11.
    Mattsson, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hu, Shuang-Lin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Infrared spectroscopy study of adsorption and photodecomposition of formic acid on reduced and defective rutile TiO2 (110) surfaces2014In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 32, no 6, article id 061402Article in journal (Refereed)
    Abstract [en]

    Adsorption and photodecomposition of formic acid on rutile TiO2 (110) have been investigated with infrared reflection–absorption spectroscopy (IRRAS) employing p- and s-polarized light along the [001] and [ 11⎯⎯0 ] crystal directions. The single crystal surfaces were prepared either by sputtering and annealing in ultrahigh vacuum (UHV) to obtain a reduced surface (r-TiO2), or by sputtering without annealing to create a rough, highly defective surface (sp-TiO2). Results are compared with corresponding measurements on rutile nanocrystals performed in synthetic air. IRRAS spectra obtained on r-TiO2 and rutile nanocrystals are very similar, and show that in both cases formic acid dissociates and is predominately adsorbed as a bridging bidentate formate species, and that the formate adsorption structure on the nanocrystals is dominated by interactions with majority (110) surfaces. In contrast, the IRRAS spectra on sp-TiO2 are different, with only minor spectral features associated with (110) surfaces and lost azimuthal symmetry, both of which imply changed adsorption geometry due to bonding to low-coordinated Ti atoms with lower valences. The UV-induced rate of formate photodecomposition is about 30 times higher on rutile nanocrystals in synthetic air compared with sp-TiO2 under UHV conditions, and even larger than on r-TiO2. These differences are explained by the lack of oxygen and limited hydroxyl coverage under UHV conditions. The difference in reactivity between the r-TiO2 and sp-TiO2 surfaces is attributed to a high concentration of strongly bonded bridging bidentate formate species on the (110) surface, which lowers its reactivity. The results point to a pressure gap where the availability of molecular oxygen and the hydroxyl concentration limit the photoreactivity in UHV leading to an almost 20-fold decrease of the formate degradation rate in UHV. In contrast, the structure represented by the single crystal (110) surface is shown to capture the essential structural properties, which dictates the formic acid adsorption and adsorption structure of rutile nanocrystals.

  • 12.
    Mattsson, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Leideborg, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Persson, Leif
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Oxygen Diffusion and Photon-Induced Decomposition of Acetone on Zr- and Nb-Doped TiO2 Nanoparticles2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 9, p. 3810-3818Article in journal (Refereed)
    Abstract [en]

    We report on the photoinduced decomposition of acetone on Zr- and Nb-doped anatase TiO2 nanoparticles prepared by the sol−gel method in oxygen-free environment (N2) and synthetic air, respectively. Physical properties of the nanoparticles were determined by TEM, SEM, AFM, XRD, and UV−vis spectroscopy. Photoinduced surface reactions were monitored by in situ Fourier transform infrared (FTIR) spectroscopy. Acetone photo-oxidation occurs in the absence of O2 in the reaction gas and is proposed to be due to reactions with photoactivated surface oxygen. In N2 atmosphere a new parallel reaction pathway is found that stimulates surface carbonate formation. A coupled diffusion-reaction model was developed to quantitatively determine the role of O diffusion. The results yield quantitative support to an oxygen surface diffusion mechanism, which depletes the surface from oxygen and gradually deactivates the particles in the absence of external oxygen supply. The diffusion reaction pathway is significant on the doped TiO2 particles. The contribution of this reaction pathway amounts to up to 65% of the total PID rate on Nb- and Zr-doped TiO2 in synthetic air environment, while it gives only a minor contribution on pure TiO2.

  • 13.
    Mattsson, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lejon, Christian
    Bakardjieva, Snejana
    Stengl, Vaclav
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Characterisation, phase-stability and surface chemical properties of photocatalytic active Zr and Y co-doped anatase TiO2 nanoparticles2013In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 199, p. 212-223Article in journal (Refereed)
    Abstract [en]

    We report on the characterization, phase stability, surface chemical andphotocatalytic properties of Zr and Y co-doped anatase TiO2 nanoparticles prepared by homogenous hydrolysis methods using urea as precipitating agent. The materials were analyzed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, BET isotherm and BJH pore size distribution measurements. It is shown that Y and Zr ions replace Ti ions in the anatase TiO2 structures up to a critical total dopant concentration of approximately 13 wt%. The co-doped particles show increased phase stability compared to pure anatase TiO2nanoparticles. The anatase to rutile phase transformation is shown to be preceded by cation segregation and dissolution with concomitant precipitation of Y2Ti2-xZrxO7 and ZrTiO4. Co-doping modifies the optical absorption edge with a resulting attenuation of the Urbach tail. The band gap is slightly blue-shifted at high doping concentrations, and red shifted at lower doping concentrations. Formic acid adsorption was used as a probe molecule to investigate surfacechemical properties and adsorbate structures. It was found that the relative abundance ofmonodentate formate compared to bidentate coordinated formate decreases with increasing doping concentration. This is attributed to an increased surface acidity with increasing dopant concentration. Photodegradation of formic acid occurred on all samples. With mode-resolved in situ FTIR spectroscopy it is shown that the rate of photodegradation of monodentate formate species are higher than for bidentate formate species. Thus our results show that the trend ofdecreasing photo-degradation rate with increasing dopant concentration can be explained by the adsorbate structure, which is controlled by the acidity of the surface. 

  • 14.
    Mattsson, Andreas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lejon, Christian
    Stengl, Vaclav
    Bakardjieva, Snejana
    Oplustil, Frantisek
    Andersson, Ola
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Photodegradation of DMMP and CEES on zirconium doped titania nanoparticles2009In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 92, no 3-4, p. 401-410Article in journal (Refereed)
    Abstract [en]

    The structure and photocatalytic activity of Zr doped TiO2 nanocrystallites with a varying Zr content between 0 and 15 wt% prepared by an efficient and environmentally benign method has been Studied by vibrational spectroscopy, TEM and XRD. It is shown that the presence of Zr4+ ions stabilizes the anatase structure and delays phase transformation to rutile upon annealing as well as retarding grain coarsening. All TiO2 samples up to 13 wt% Zr doping concentration show better or similar photoreactivity compared to P25 (Degussa) for decomposition of adsorbed 2-chloroethyl ethyl sulphide (CEES) and dimethyl methylphosphonate (DMMP) in synthetic air at room temperature. The most efficient sample for photodegradation of both CEES and DMMP is shown to be titania doped with 6.8 wt% Zr. The photodegradation of CEES is faster than DMMP under the same experimental conditions. On the undoped TiO2 sample urea residues are detected spectroscopically. Much less is detected on the Zr doped samples. Mode resolved in situ FTIR surface spectroscopy enables distinction of CEES or DMMP, decomposition products as well as the influence of residues from the particle synthesis. This facilitates extraction of intra-comparable reaction rates. Possible explanations for the improved reactivity of the Zr doped titania are discussed.

  • 15.
    Mattsson, Andreas
    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.
    Adsorption and Photoinduced Decomposition of Acetone and Acetic Acid on Anatase, Brookite, and Rutile TiO2 Nanoparticles2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 33, p. 14121-14132Article in journal (Refereed)
    Abstract [en]

    A comparative study of the adsorption and photoinduced degradation (PID) of acetone and acetic acid on thin films of anatase, brookite, and rutile TiO2 nanoparticles is presented. The materials were thoroughly characterized by a wide range of methods, including X-ray diffraction, transmission electron microscopy, and Raman and UV-vis spectroscopies. In situ FTIR transmission spectroscopy was used to follow adsorption and PID reactions. Molecular adsorption of acetone and acetic acid is observed on anatase and brookite, whereas significant dissociation occurs on rutile. It is inferred that adsorbate surface interaction increases in the order anatase < brookite < rutile, favoring formation of bridge-bonded species on rutile (acetate and formate). Illumination with simulated solar light readily dissociates acetic acid and acetone on all TiO2 samples and produces polymorph-specific intermediate surface species, including acetate, formate, carbonate, and water. PID of surface coordinated acetate is rate determining for complete mineralization of acetic acid and prevents further photooxidation on rutile. On anatase and brookite surfaces, acetate formation is suppressed upon photooxidation of acetone, whereas on rutile, acetate readily forms. On anatase, intermediate species form, which are not observed on either brookite or rutile, suggesting different reaction pathways for the different TiO2 polymorphs. Accurate quantum yield measurements were performed. The quantum yield for PID of acetone is larger for brookite than for anatase and much larger than for rutile. In contrast, the quantum yield for PID of acetate is lower for brookite than for anatase, whereas PID of acetate does not occur on rutile under our experimental conditions. The results are discussed in terms of a balance of strong adsorbate surface interactions, moderate bonding of intermediate PID surface species, and efficient surface adsorbate charge transfer of photogenerated electrons and holes.

  • 16.
    Mattsson, Andreas
    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.
    Infrared reflection-absorption spectroscopy study of HCOOH/TiO2 (110): Photo-reactions on stoichiometric and defective surfaces2014Conference paper (Other academic)
  • 17.
    Mattsson, Andreas
    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.
    Infrared Reflection-Absorption Spectroscopy Study of the Interaction between O2 and Formic Acid on Rutile TiO2 (110) Surfaces2016Conference paper (Refereed)
    Abstract [en]

    Formic acid adsorption on rutile TiO2(110) single crystals exposed to different oxygen partial pressures have been investigated with infrared reflection-absorption spectroscopy (IRRAS) employing p- and s-polarized light incident along the [001] crystal direction at a temperatures between 273K and 303K. IRRAS spectra, prior to oxygen exposure, shows that formic acid dissociates upon adsorption and binds to the surface as bridging formate species with the symmetric νs(OCO) and asymmetric νas(OCO) peak at 1360 and 1531 cm-1, respectively. A new asymmetric νas(OCO) band at 1517 cm-1develops in the presence of O2, which is correlated with the O2 partial pressure, whereas no changes is seen in the symmetric νs(OCO) band. At low O2 pressures(<1 ×10-7mbar), this band is not detectable within 3 h of O2 exposure. At higher O2pressures, 5 ×10-7 mbar, the band starts to develop, and at 1 ×10-6 mbar, a pronounced band develops after 30 min exposure. The O2 induced band at 1517 cm-1 does not disappear as the O2 gas is removed, suggesting that a stable chemical modification of adsorbed formate molecules. No changes were observed in the s-polarized IRRAS spectra with O2 exposure, showing that there is no rotation of the formate molecules in the plane of the surface. The appearance of the new νas(OCO) band are consistent with a model where O2 dissociated to form O adatoms bonded to the Ti5c atoms, which interact with bridging formate molecules bonded along the [001] direction. The relationship between the oxygen partial pressure and the formation of this new band is due to the increased larger interaction between the surface and the oxygen with increase pressure or an increased oxygenation of formate. Our results provide new insight into the interaction between O2and TiO2surfaceat elevated pressures relevant for practical applications.

  • 18.
    Mattsson, Andreas
    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.
    Photocatalytic degradation of acetone and acetic acid on anatase, brookite and rutile TiO2In: Russian Journal of Physical Chemistry, ISSN 0036-0244, E-ISSN 1531-863XArticle in journal (Refereed)
  • 19.
    Mattsson, Andreas
    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.
    Photodegradation of DMMP and CEES on ZnS:TiO2 nanoparticles2007Report (Refereed)
  • 20.
    Mattsson, Andreas
    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.
    Photodegradation of DMMP and CEES on Zr:TiO2 nanoparticles2007Report (Refereed)
  • 21.
    Stefanov, Bozhidar I.
    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.
    Mattsson, Andreas
    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.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Demonstrating Online Monitoring of Air Pollutant Photodegradation in a 3D Printed Gas-Phase Photocatalysis Reactor2015In: Journal of Chemical Education, ISSN 0021-9584, E-ISSN 1938-1328, Vol. 92, no 4, p. 678-682Article in journal (Refereed)
    Abstract [en]

    We present a demonstration of online monitoring of gas-phase photocatalytic reactions. A cotton cloth impregnated with commercial titanium dioxide nanoparticles is used as a photocatalytic filter to clean air contaminated with a model pollutant. A fan forces air through the filter while it is irradiated by UV diodes. The concentration of the air pollutant is measured online by an inexpensive, commercially available semiconductor air quality sensor. The structural parts of the reactor were 3D printed in polylactide bioplastic. We provide all schematics, 3D printed model parts, hardware, firmware, and computer code of the reactor and control units. The device can be used for interactive learning of both gas phase photocatalysis and gas sensing, as well as in student laboratory classes for measuring air pollutants and their photodegradation. The experimental setup can also form the basis for a project work for chemical engineering university students, and it can be employed as a building block for development of other gas phase chemical reaction demonstrations.

  • 22.
    Stefanov, Bozhidar
    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.
    Mattsson, Andreas
    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.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Demonstration of a 3D printed gas-phase photocatalysis reactor and its use for on-line monitoring of degradation of air pollutants.2014In: Journal of Chemical Education, ISSN 0021-9584, E-ISSN 1938-1328Article in journal (Refereed)
  • 23.
    Stengl, Vaclav
    et al.
    Institute of Inorganic Chemistry AS CR v.v.i., Czech Republic .
    Bakardjieva, Snejana
    Institute of Inorganic Chemistry AS CR v.v.i., Czech Republic .
    Murafa, N.
    Institute of Inorganic Chemistry AS CR v.v.i., Czech Republic .
    Opluštil, F.
    Military Technical Institute of Protection Brno, Czech Republic .
    Österlund, Lars
    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
    FOI - Swedish Defence Research Agency.
    Warfare Agents Degradation on Zirconium Doped Titania2009In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 15, no S2, p. 1038-1039Article in journal (Refereed)
  • 24.
    Wäckelgård, Ewa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Bartali, Ruben
    Fondazione Bruno Kessler.
    Gerosa, Riccardo
    Laidani, Nadhira
    Mattsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Micheli, Victor
    Rivolta, Barbara
    New Cermet Coatings for Mid-temperature Applications for Solar Concentrated Combine Heat and Power System2014In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 48, p. 242-249Article in journal (Refereed)
  • 25.
    Wäckelgård, Ewa
    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.
    Bartali, Ruben
    Center for Materials and Microsystems, Fondazione Bruno Kessler, Trento, Italy.
    Gerosa, Riccardo
    Dipartimento di Meccanica, Politecnico di Milano, Milan, Italy.
    Gloria, Gottardi
    Center for Materials and Microsystems, Fondazione Bruno Kessler, Trento, Italy.
    Gustavsson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Laidani, Nadhira
    Center for Materials and Microsystems, Fondazione Bruno Kessler, Trento, Italy.
    Micheli, Victor
    Center for Materials and Microsystems, Fondazione Bruno Kessler, Trento, Italy.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Rivolta, Barbara
    Dipartimento di Meccanica, Politecnico di Milano, Milan, Italy.
    Development of W–SiO2 and Nb–TiO2 solar absorber coatings for combined heat and power systems at intermediate operation temperatures2015In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 133, p. 180-193Article in journal (Refereed)
    Abstract [en]

    Two new absorber coatings for mid-temperature operation (300–350 1C) in collectors for solar thermal electricity plants are presented in this study. The absorbers consist of two cermet layers of either W–SiO2 or Nb–TiO2, deposited on a molybdenum infrared reflector and coated with an antireflection layer of silicon oxide. The optimization of the optical performance was made in two steps. First, the layer structure was optimized in model calculations. The optical constants used in this modelling were derived directly from sputtered films of the cermet constituents using reflectance and transmittance measure- ments. The absorber coatings were then sputter-deposited using parameters from the modelling. The results show good agreement between modelled and sputtered optical performance evaluated as solar absorptance and thermal emittance at 350 1C. The optimal values reached for W–SiO2 was 0.91 in combination with 0.08 and 0.93 in combination with 0.09 for Nb–TiO2. The materials characterization from XRD, AES and TEM shows that the composite coatings contain nano-metal inclusions, meaning that they are cermet coatings. Scratch tests show that the coatings adhere well to the substrate of stainless steel. Temperature testing at 350 1C in vacuum for up to 1500 h shows that both coatings are stable under such conditions. Only a slight change occurs during the first 72 h that decreases the emittance but does not change the solar absorptance. ERDA confirms that there is no detectable level of ion migration between layers, only a small decrease in hydrogen content was observed, which indicates outgassing.

  • 26.
    Wäckelgård, Ewa
    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.
    Bartali, Ruben
    Gerosa, Riccardo
    Gottardi, Gloria
    Gustavsson, Fredrik
    Laidani, Nadhira
    Micheli, Victor
    Primetzhofer, Daniel
    Rivolta, Barbara
    Development of W-SiO2 and Nb-TiO2 solar absorber coatings for combined heat and power systems at intermediate operation temperatures2014In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 133Article in journal (Refereed)
  • 27.
    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)
  • 28.
    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.

  • 29.
    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)
  • 30.
    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.

  • 31.
    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)
  • 32.
    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)
  • 33.
    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)
1 - 33 of 33
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