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  • 1.
    Ahrén, Maria
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Olsson, Petter
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Söderlind, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Klasson, Anna
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Health Sciences, Radiology . Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Petoral, Rodrigo Jr
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Engström, Maria
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Uvdal, Kajsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Rare earth nanoparticles as contrast agent in MRI: Nanomaterial design and biofunctionalization2007In: IVC-17/ICSS-13 ICNT,2007, 2007Conference paper (Other academic)
  • 2.
    Ahrén, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Selegård, Linnéa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Kauczor, Joanna
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    A simple polyol-free synthesis route to Gd2O3 nanoparticles for MRI applications: an experimental and theoretical study2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 8Article in journal (Refereed)
    Abstract [en]

    Chelated gadolinium ions, e. g., GdDTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd2O3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r(1) and r(2) values almost as high as those for free Gd3+ ions in water. The Gd2O3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI.

  • 3.
    Brena, B.
    et al.
    Department of Physics, Uppsala University, Box 518, SE-751 20 Uppsala, Sweden.
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Surface effects and quantum confinement in nanosized GaN clusters: Theoretical predictions2008In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, no 35, p. 13516-13523Article in journal (Refereed)
    Abstract [en]

    The structure and the electronic properties of stoichiometric (GaN) n clusters (with 6 = n = 48) were investigated by means of quantum-chemical hybrid density functional theory (DFT) using the B3LYP functional. Particular emphasis was put on the investigation of the evolution of the physical properties of the clusters as a function of their size. Two types of model clusters were studied. Cage-type structures were found to be the most stable for smaller cluster sizes, whereas for larger sizes conformations cut out from the GaN wurtzite crystal were favorable. The study of the electronic structure shows that the energy gap of the clusters tends to become larger as the dimensions of the clusters increase. The vertical electronic absorption energies were calculated by means of time-dependent (TD) DFT. For such small clusters, probably due to the predominant amount of surface atoms, well-defined quantum confinement effects, as commonly observed in crystalline quantum dots, are not apparent. © 2008 American Chemical Society.

  • 4.
    Buchholt, Kristina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ieva, E.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Torsi, L
    Universita degli Studi di Bari, Italy.
    Lutic, D.
    Växjö universitet.
    Strand, M
    Växjö universitet.
    Sanati, M.
    Växjö universitet.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    FET devices with gold nanoparticle gate material as nitrogen oxide gas sensors2006In: Proceedings from E-MRS 2006, Nice France, May 29- June 1, 2006, 2006, p. 87-92Conference paper (Refereed)
    Abstract [en]

       

  • 5.
    Buchholt, Kristina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ieva, Eliana
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Torsi, L
    Dipartimento di Chimica, Universita degli Studi di Bari, Italy.
    Cioffi, N
    Dipartimento di Chimica, Universita degli Studi di Bari, Italy.
    Colaianni, L
    Dipartimento di Chimica, Universita degli Studi di Bari, Italy.
    Söderlind, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics.
    A comparison between the use of Pd- and Au-nanoparticles as sensing layers in a field effect NOx-sensitive sensor2007In: The 2nd Conference on Sensing Technology ICST,2007, 2007, p. 87-92Conference paper (Refereed)
  • 6.
    Buchholt, Kristina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Leva, E
    Dipartimento di Chimica, Università degli Studi di Bari, Bari, Italy.
    Torsi, L
    Dipartimento di Chimica, Università degli Studi di Bari, Bari, Italy.
    Cioffi, N
    Dipartimento di Chimica, Università degli Studi di Bari, Bari, Italy.
    Colaianni, L
    Dipartimento di Chimica, Università degli Studi di Bari, Bari, Italy.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Electrochemically Synthesised Pd- and Au-nanoparticles as sensing layers in NOx-sensitive field effect devices2008In: Smart Sensors and Sensing Technology / [ed] Subhas Chandra Mukhopadhyay and Gourab Sen Gupta, Berlin, Heidelberg: Springer , 2008, p. 63-75Conference paper (Other academic)
    Abstract [en]

    An environmental pollutant of great concern is NOx (nitrogen monoxide and nitrogen dioxide). Here we report the utilisation of electrochemically synthesised gold and palladium nanoparticles as catalytically active gate material on gas sensitive field effect sensor devices. The synthesised nanoparticles have been characterised by TEM and XPS, and the morphology of the thermally treated nanostructured sensing layers has been investigated using SEM and XPS. Measurements on the gas response of the palladium as well as the gold nanoparticle sensors towards a number of analytes found in automotive gas exhausts were performed and their response patterns were compared. The initial gas response measurements show interesting sensing properties for both the gold and the palladium nanoparticle sensors towards NOx detection.

  • 7. Cavalleri, M
    et al.
    Näslund, LÅ
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Edwards, DC
    Wernet, Ph
    Ogasawara, H
    Myneni, S
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry.
    Odelius, M
    Nilsson, A
    Pettersson, LGM
    The local structure of protonated water from x-ray absorption and density functional theory2006In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 124, p. 194508-194508Article in journal (Refereed)
    Abstract [en]

      

  • 8.
    Danielsson, Örjan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Sukkaew, Pitsiri
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Kordina, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Shortcomings of CVD modeling of SiC today2013In: Theoretical Chemistry accounts, ISSN 1432-881X, E-ISSN 1432-2234, Vol. 132, no 11, p. 1398-Article in journal (Refereed)
    Abstract [en]

    The active, epitaxial layers of silicon carbide (SiC) devices are grown by chemical vapor deposition (CVD), at temperatures above 1,600 °C, using silane and light hydrocarbons as precursors, diluted in hydrogen. A better understanding of the epitaxial growth process of SiC by CVD is crucial to improve CVD tools and optimize growth conditions. Through computational fluid dynamic (CFD) simulations, the process may be studied in great detail, giving insight to both flow characteristics, temperature gradients and distributions, and gas mixture composition and species concentrations throughout the whole CVD reactor. In this paper, some of the important parts where improvements are very much needed for accurate CFD simulations of the SiC CVD process to be accomplished are pointed out. First, the thermochemical properties of 30 species that are thought to be part of the gas-phase chemistry in the SiC CVD process are calculated by means of quantum-chemical computations based on ab initio theory and density functional theory. It is shown that completely different results are obtained in the CFD simulations, depending on which data are used for some molecules, and that this may lead to erroneous conclusions of the importance of certain species. Second, three different models for the gas-phase chemistry are compared, using three different hydrocarbon precursors. It is shown that the predicted gas-phase composition varies largely, depending on which model is used. Third, the surface reactions leading to the actual deposition are discussed. We suggest that hydrocarbon molecules in fact have a much higher surface reactivity with the SiC surface than previously accepted values.

  • 9.
    Darmastuti, Zhafira
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Larsson, Mikael
    Alstom Power, Sweden.
    Lindqvist, Niclas
    Alstom Power, Sweden.
    SiC based field effect transistor for H2S detection2011In: Proc. IEEE Sensors 2011, Limerick, Ireland, October 28-31, IEEE , 2011, p. 770-773Conference paper (Refereed)
    Abstract [en]

    Experimental characterization and quantum chemical calculations were performed to evaluate the performance of a SiC based Field Effect Transistors with Pt and Ir gates as H2S sensors. The sensors were tested against various concentrations of H2S gas at the operating temperature between 150 and 350 °C. It was observed that Ir was very sensitive and selective to H2S at 350 °C. This phenomenon was studied further by comparing the reaction energy when H2S is exposed to Pt and Ir with density functional theory (DFT) calculations.

  • 10.
    Engström, Maria
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Klasson, Anna
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vahlberg, Cecillia
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    High Proton Relaxivity for Gadolinium Oxide Nanoparticles2006In: Magnetic Resonance Materials in Physics, Biology and Medicine, ISSN 0968-5243, E-ISSN 1352-8661, Vol. 19, no 4, p. 180-186Article in journal (Refereed)
    Abstract [en]

    Objective: Nanosized materials of gadolinium oxide can provide high-contrast enhancement in magnetic resonance imaging (MRI). The objective of the present study was to investigate proton relaxation enhancement by ultrasmall (5 to 10 nm) Gd2O3 nanocrystals.

    Materials and methods: Gd2O3 nanocrystals were synthesized by a colloidal method and capped with diethylene glycol (DEG). The oxidation state of Gd2O3 was confirmed by X-ray photoelectron spectroscopy. Proton relaxation times were measured with a 1.5-T MRI scanner. The measurements were performed in aqueous solutions and cell culture medium (RPMI).

    Results: Results showed a considerable relaxivity increase for the Gd2O3–DEG particles compared to Gd-DTPA. Both T 1 and T 2 relaxivities in the presence of Gd2O3–DEG particles were approximately twice the corresponding values for Gd–DTPA in aqueous solution and even larger in RPMI. Higher signal intensity at low concentrations was predicted for the nanoparticle solutions, using experimental data to simulate a T1-weighted spin echo sequence.

    Conclusion: The study indicates the possibility of obtaining at least doubled relaxivity compared to Gd–DTPA using Gd2O3–DEG nanocrystals as contrast agent. The high T 1 relaxation rate at low concentrations of Gd2O3 nanoparticles is very promising for future studies of contrast agents based on gadolinium-containing nanocrystals.

  • 11.
    Eriksson, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Khranovskyy, Volodymyr
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lloyd-Spets, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    ZnO nanoparticles or ZnO films: A comparison of the gas sensing capabilities2009In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 137, no 1, p. 94-102Article in journal (Refereed)
    Abstract [en]

    Zinc oxide is an interesting material for bio and chemical sensors. it is a semiconducting metal oxide with potential as an integrated multisensing sensor platform, which simultaneously detects Parameters like change in field effect, mass and Surface resistivity. in this investigation we have used resistive sensor measurements regarding the oxygen gas sensitivity in order to characterize sensing layers based on electrochemically produced ZnO nanoparticles and PE-MOCVD grown ZnO films. Proper annealing procedures were developed in order to get stable sensing properties and the oxygen sensitivity towards operation temperature was investigated. The ZnO nanoparticles showed a considerably increased response to oxygen as compared to the films. Preliminary investigations were also performed regarding the selectivity to other gases present in car exhausts or flue gases.

  • 12.
    Flemström, A.
    et al.
    Department of Inorganic, Structural and Physical Chemistry, Arrhenius Laboratory, Stockholm University, S-10691, Stockholm, Sweden.
    Hirsch, T. K.
    Department of Inorganic, Structural and Physical Chemistry, Arrhenius Laboratory, Stockholm University, S-10691, Stockholm, Sweden.
    Sehlstedt, L.
    Department of Inorganic, Structural and Physical Chemistry, Arrhenius Laboratory, Stockholm University, S-10691, Stockholm, Sweden.
    Lidin, S.
    Department of Inorganic, Structural and Physical Chemistry, Arrhenius Laboratory, Stockholm University, S-10691, Stockholm, Sweden.
    Ojamäe, L.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Effects from hydrogen bonds on water structure in (H3O)2[Mo6Cl8X6yH2O X=Cl (y=7), Br (y=6), or I (y=6)2002In: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 4, no 8, p. 1017-1022Article in journal (Refereed)
    Abstract [en]

    The compounds (a) (H3O)2[Mo6Cl8Cl6]·7H2O, (b) (H3O)2[Mo6Cl8Br6]·6H2O and (c) (H3O)2[Mo6Cl8I6]·6H2O were synthesized from MoCl2 and the corresponding halide acid. The structures were determined by X-ray diffraction and refined in the monoclinic space groups, (a) C2/c and for (b) and (c) P21/a. The cell parameters were for (a), a=17.3607(2), b=9.1351(7), c=18.6300(2) Å and β=98.13(1)°, (b) a=17.4295(2), b=9.3803(10), c=9.3769(12) Å and β=101.04(1)° and (c) a=18.0083(10), b=9.7612(10), c=9.8139(12) Å and β=100.20(2)°. The positions of the hydrogen atoms were determined by theoretical energy optimization. The structures are compared with respect to the effect of hydrogen bonding on the water structure.

  • 13.
    Fortin, Marc-Andre
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Petoral, Rodrigo Jr
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Söderlind, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Engström, Maria
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Uvdal, Kajsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Synthesis of gadolinium oxide nanoparticles as a contrast agent in MRI2006In: Trends in Nanotechnology,2006, 2006Conference paper (Other academic)
    Abstract [en]

           

  • 14.
    Fortin, Marc-André
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Petoral Jr, Rodrigo M.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, Faculty of Science & Engineering.
    Klasson, Anna
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Engström, Maria
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences.
    Veres, Teodor
    National Research Council of Canada (CNRC-IMI) 75, Boucherville, QC, Canada.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Polyethylene glycol-cover ultra-small Gd2O3 nanoparticles for positive contras at 1.5 T magnetic resonance clinical scanning2007In: Nanotechnology, ISSN 0957-4484, Vol. 18, no 39, p. 395501-Article in journal (Refereed)
    Abstract [en]

    The size distribution and magnetic properties of ultra-small gadolinium oxide crystals (US-Gd2O3) were studied, and the impact of polyethylene glycol capping on the relaxivity constants (r1, r2) and signal intensity with this contrast agent was investigated. Size distribution and magnetic properties of US-Gd2O3 nanocrystals were measured with a TEM and PPMS magnetometer. For relaxation studies, diethylene glycol (DEG)-capped US-Gd2O3 nanocrystals were reacted with PEG-silane (MW 5000). Suspensions were adequately dialyzed in water to eliminate traces of Gd3+ and surfactants. The particle hydrodynamic radius was measured with dynamic light scattering (DLS) and the proton relaxation times were measured with a 1.5 T MRI scanner. Parallel studies were performed with DEG–Gd2O3 and PEG-silane–SPGO (Gd2O3,< 40 nm diameter). The small and narrow size distribution of US-Gd2O3 was confirmed with TEM (~3 nm) and DLS. PEG-silane–US-Gd2O3 relaxation parameters were twice as high as for Gd–DTPA and the r2/r1 ratio was 1.4. PEG-silane–SPGO gave low r1 relaxivities and high r2/r1 ratios, less compatible with positive contrast agent requirements. Higher r1 were obtained with PEG-silane in comparison to DEG–Gd2O3. Treatment of DEG–US-Gd2O3 with PEG-silane provides enhanced relaxivity while preventing aggregation of the oxide cores. This study confirms that PEG-covered Gd2O3 nanoparticles can be used for positively contrasted MR applications requiring stability, biocompatible coatings and nanocrystal functionalization.

  • 15.
    Gustafsson, Håkan
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ahrén, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Córdoba Gallego, José M.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, Faculty of Science & Engineering.
    Nordblad, Per
    Uppsala Universitet.
    Westlund, Per-Olof
    Umeå Universitet.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Faculty of Health Sciences.
    Magnetic and Electron Spin Relaxation Properties of (GdxY1-x)2O3 (0 ≤ x ≤ 1) Nanoparticles Synthesized by the Combustion Method. Increased Electron Spin Relaxation Times with Increasing Yttrium Content2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 13, p. 5469-5477Article in journal (Refereed)
    Abstract [en]

    The performance of a magnetic resonance imaging contrast agent (CA) depends on several factors, including the relaxation times of the unpaired electrons in the CA. The electron spin relaxation time may be a key factor for the performance of new CAs, such as nanosized Gd2O3 particles. The aim of this work is, therefore, to study changes in the magnetic susceptibility and the electron spin relaxation time of paramagnetic Gd2O3 nanoparticles diluted with increasing amounts of diamagnetic Y2O3. Nanoparticles of (GdxY1-x)2O3 (0 e x e 1) were prepared by the combustion method and thoroughly characterized (by X-ray di.raction, transmission electron microscopy, thermogravimetry coupled with mass spectroscopy, photoelectron spectroscopy, Fourier transform infrared spectroscopy, and magnetic susceptibility measurements). Changes in the electron spin relaxation time were estimated by observations of the signal line width in electron paramagnetic resonance spectroscopy, and it was found that the line width was dependent on the concentration of yttrium, indicating that diamagnetic Y2O3 may increase the electron spin relaxation time of Gd2O3 nanoparticles.

  • 16.
    Hirsch, T.K.
    et al.
    Department of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden.
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    An investigation of H-atom positions in sulfuric acid crystal structures2004In: Acta Crystallographica Section B: Structural Science, ISSN 0108-7681, E-ISSN 1600-5740, Vol. 60, no 2, p. 179-183Article in journal (Refereed)
    Abstract [en]

    Hydrogen conformations in crystalline H2SO4· 8H2O and H2SO4·6.5H2O have been studied using a system developed by Hirsch [(2003), Z. Anorg. Allg. Chem. 629, 666-672]. New H-atom coordinates, as estimated from DFT calculations, are given for these structures. © 2004 International Union of Crystallography Printed in Great Britain - all rights reserved.

  • 17.
    Hirsch, T.K.
    et al.
    Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden.
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Quantum-chemical and force-field investigations of ice Ih: Computation of proton-ordered structures and prediction of their lattice energies2004In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, no 40, p. 15856-15864Article in journal (Refereed)
    Abstract [en]

    The different possible proton-ordered structures of ice Ih for an orthorombic unit cell with 8 water molecules were derived. The number of unique structures was found to be 16. The crystallographic coordinates of these are reported. The energetics of the different polymorphs were investigated by quantum-mechanical density-functional theory calculations and for comparison by molecular-mechanics analytical potential models. The polymorphs were found to be close in energy, i.e., within approximately 0.25 kcal/mol H2O, on the basis of the quantum-chemical DFT methods. At 277 K, the different energy levels are about evenly populated, but at a lower temperature, a transition to an ordered form is expected. This form was found to agree with the ice phase XI. The difference in lattice energies among the polymorphs was rationalized in terms of structural characteristics. The most important parameters to determine the lattice energies were found to be the distributions of water dimer H-bonded pair conformations, in an intricate manner.

  • 18.
    Huang, C
    et al.
    Stanford Synchrotron Radiat Lightsource.
    Wikfeldt, K T
    Stockholm University.
    Tokushima, T
    RIKEN SPring 8, Mikazuki, Hyogo, Japan .
    Nordlund, D
    Stanford Synchrotron Radiat Lightsource.
    Harada, Y
    RIKEN SPring 8, Mikazuki, Hyogo Japan .
    Bergmann, U
    Stanford Synchrotron Radiat Lightsource.
    Niebuhr, M
    Stanford Synchrotron Radiat Lightsource.
    Weiss, T M
    Stanford Synchrotron Radiat Lightsource.
    Horikawa, Y
    RIKEN SPring 8, Mikazuki, Hyogo Japan .
    Leetmaa, M
    Stockholm University.
    Ljungberg, M P
    Stockholm University.
    Takahashi, O
    Hiroshima University.
    Lenz, Annika
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Lyubartsev, A P
    Stockholm University.
    Shin, S
    RIKEN SPring 8, Mikazuki, Hyogo Japan .
    Pettersson, L G M
    Stockholm University.
    Nilsson, A
    Stanford Synchrotron Radiat Lightsource.
    Letter: Reply to Soper et al.: Fluctuations in water around a bimodal distribution of local hydrogen-bonded structural motifs2010In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 107, no 12, p. E45-E45Article in journal (Other academic)
    Abstract [en]

    n/a

  • 19.
    Huang, C
    et al.
    Stanford Synchrotron Radiat Lightsource.
    Wikfeldt, K T
    AlbaNova.
    Tokushima, T
    RIKEN.
    Nordlund, D
    Stanford Synchrotron Radiat Lightsource.
    Harada, Y
    RIKEN.
    Bergmann, U
    Stanford Synchrotron Radiat Lightsource.
    Niebuhr, M
    Stanford Synchrotron Radiat Lightsource.
    Weiss, T M
    Stanford Synchrotron Radiat Lightsource.
    Horikawa, Y
    RIKEN.
    Leetmaa, M
    AlbaNova.
    Ljungberg, M P
    AlbaNova.
    Takahashi, O
    Hiroshima University.
    Lenz, Annika
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Lyubartsev, A P
    Stockholm University.
    Shin, S
    RIKEN.
    Pettersson, L G M
    AlbaNova.
    Nilsson, A
    Stanford Synchrotron Radiat Lightsource.
    The inhomogeneous structure of water at ambient conditions2009In: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, ISSN 0027-8424, Vol. 106, no 36, p. 15214-15218Article in journal (Refereed)
    Abstract [en]

    Small-angle X-ray scattering (SAXS) is used to demonstrate the presence of density fluctuations in ambient water on a physical length-scale of approximate to 1 nm; this is retained with decreasing temperature while the magnitude is enhanced. In contrast, the magnitude of fluctuations in a normal liquid, such as CCl4, exhibits no enhancement with decreasing temperature, as is also the case for water from molecular dynamics simulations under ambient conditions. Based on X-ray emission spectroscopy and X-ray Raman scattering data we propose that the density difference contrast in SAXS is due to fluctuations between tetrahedral-like and hydrogen-bond distorted structures related to, respectively, low and high density water. We combine our experimental observations to propose a model of water as a temperature-dependent, fluctuating equilibrium between the two types of local structures driven by incommensurate requirements for minimizing enthalpy (strong near-tetrahedral hydrogen-bonds) and maximizing entropy (non-directional H-bonds and disorder). The present results provide experimental evidence that the extreme differences anticipated in the hydrogen-bonding environment in the deeply supercooled regime surprisingly remain in bulk water even at conditions ranging from ambient up to close to the boiling point.

  • 20.
    Huang, X.
    et al.
    Cherry L. Emerson Ctr. of Sci. Comp., Department of Chemistry, Emory University, Atlanta, GA 30322, United States.
    Cho, H.M.
    Department of Chemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, OH 43210, United States.
    Carter, S.
    Cherry L. Emerson Ctr. of Sci. Comp., Department of Chemistry, Emory University, Atlanta, GA 30322, United States, Department of Chemistry, University of Reading, Reading, United Kingdom.
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Bowman, J.M.
    Cherry L. Emerson Ctr. of Sci. Comp., Department of Chemistry, Emory University, Atlanta, GA 30322, United States.
    Singer, S.J.
    Department of Chemistry, The Ohio State University, 100 W. 18th Avenue, Columbus, OH 43210, United States.
    Full dimensional quantum calculations of vibrational energies of H5O2+2003In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 107, no 37, p. 7142-7151Article in journal (Refereed)
    Abstract [en]

    The full dimensional (15 degrees-of-freedom) quantum calculations of vibrational energies of H5O2+ are reported using the global potential energy surface (OSS) of Ojamäe et al. (J. Chem. Phys. 1998, 109, 5547). One set of calculations uses the diffusion Monte Carlo (DMC) method with a highly flexible initial trial wave function. This method is limited to the ground vibrational state, but produces what we believe is a highly accurate, benchmark energy and wave function for that state. The DMC wave function is analyzed to identify coordinates that are strongly correlated in zero-point fluctuations. A simple harmonic model is developed to elucidate the energetic consequences of these correlations. The other set of calculations is based on the code MULTIMODE, which does configuration interaction (CI) calculations using a basis determined from a vibrational self-consistent field (VSCF) Hamiltonian, but which uses a representation of the potential with mode coupling limited to a maximum of four modes. Good agreement is obtained between the DMC and the CI MULTIMODE energies for the ground vibrational state. When less sophisticated theoretical treatments are applied, either variational Monte Carlo or vibrational self-consistent field, fairly large errors are found. Vibrationally excited-state energies obtained with MULTIMODE are also reported.

  • 21.
    Ieva, Eliana
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Buchholt, Kristina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Colaianni, L
    University of Bari.
    Cioffi, N
    University of Bari.
    Sabbatini, L
    University of Bari.
    Capitani, G C
    University of Bari.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry.
    Torsi, L
    University of Bari.
    Au Nanoparticles as Gate Material for NOx Field Effect Capacitive Sensors2008In: Sensor letters, ISSN 1546-198X, Vol. 6, no 4, p. 577-584Article in journal (Refereed)
    Abstract [en]

    Gold nanoparticles (Au-NPs) are electrochemically synthesized in the presence of tetra-alkylammonium stabilizers and used as active element in Field Effect capacitive gas sensors. Before use, the sensing area is treated by a relatively mild annealing procedure aimed to partially remove the organic stabilizer without loosing the nano-structured character of the particles. Both pristine and annealed materials have been subjected to a spectroscopic and morphological characterization (by means of UV-Vis, XPS, TEM, SEM techniques). Preliminary results on the application of AuNPs as gate material for NO, sensing are reported. The sensor is able to detect NO, with appreciable selectivity and low response towards the other tested gases (C3H6, CO, H-2, NH3).

  • 22.
    Ieva, Eliana
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Buchholt, Kristina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Colaianni, L
    Dipartimento di Chimica, Università degli Studi di Bari, Italy .
    van der Werf, I.D.
    Dipartimento di Chimica, Università degli Studi di Bari, Italy .
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Torsi, L
    Dipartimento di Chimica, Università degli Studi di Bari, Bari, Italy .
    Gold Nanoparticle Sensors For Environmental Pollutant Monitoring2007In: Proceedings of the 2007 2nd IEEE International Workshop on Advances in Sensors and Interfaces, June 26-27, 2007 Bari, Italy, IEEE , 2007, p. 1-4Conference paper (Other academic)
    Abstract [en]

         Gold nanoparticles (Au-NPs) have been synthesised using a sacrificial anode electrolysis in the presence of tetra-alkyl-ammonium halides, employed as cationic stabilizers. Catalytic NPs have been then deposited on top of Field Effect (FE) gas sensing devices and subjected to mild annealing procedures. Transmission Electron Microscopy (TEM) shows that the NP average core diameter is around 5 nm. X-Ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) have been applied to the surface characterization of the annealed NP films used as active sensing layers. Morphological and spectroscopic results demonstrate that the annealed inorganic nano-clusters are finely dispersed and maintain a metallic oxidation state. Au-NPs can be proficiently employed as gate material in Si-Field Effect Gas Sensors. Preliminary results show interesting selectivity and sensitivity sensing features towards NOx detection.

  • 23.
    Kanungo, Jayita
    et al.
    IC Design & Fabrication Centre, Dept. of Electronics & Telecommunications Engineering, Jadavpur University, Kolkata, India.
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Darmastuti, Zhafira
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Basu, Sukumar
    IC Design & Fabrication Centre, Dept. of Electronics & Telecommunications Engineering, Jadavpur University, Kolkata, India.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Lloyd Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Development of SiC-FET methanol sensor2011In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 160, no 1, p. 72-78Article in journal (Refereed)
    Abstract [en]

    A silicon carbide based field effect transistor (SiC-FET) structure was used for methanol sensing. Due to the chemical stability and wide band gap of SiC, these sensors are suitable for applications over a wide temperature range. Two different catalytic metals, Pt and Ir, were tested as gate contacts for detection of methanol. The sensing properties of both Ir gate and Pt gate SiC-FET sensors were investigated in the concentration range 0.3–5% of methanol in air and in the temperature range 150–350 °C. It was observed that compared to the Ir gate sensor, the Pt gate sensor showed higher sensitivity, faster response and recovery to methanol vapour at comparatively lower temperature, with an optimum around 200 °C. Quantum-chemical calculations were used to investigate the MeOH adsorption and to rationalize the observed non-Langmuir behavior of the response functions. The methanol sensing mechanism of the SiC-FET is discussed.

  • 24.
    Khan, Yagoob
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Tajammul Hussain, Syed
    National Centre for Physics, Quaid-e-Azam University Campus, Islamabad, Pakistan.
    Abbasi, Mazhar Ali
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    On the decoration of 3D nickel foam with single crystal ZnO nanorod arrays and their cathodoluminescence study2013In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 90, p. 126-130Article in journal (Refereed)
    Abstract [en]

    Starting with an ammonical solution of zinc acetate, dense single crystal ZnO nanorod arrays were grown directly on high surface area porous 3D nickel foam substrates using a low temperature hydrothermal route. Heterogeneous nucleation of the nanorods with diameters around 100 nm can be conveniently and reproducibly Controlled by adjusting the amount of ammonia added to the growth solution. X-ray diffraction and HRTEM analysis confirmed the single phase wurtzite structure and c-axis orientation of the as grown ZnO nanorod arrays. Cathodoluminescence measurements indicate that the as-grown nanorod arrays were rich in atomic defects and gave strong orange emissions in the visible region. The nanorod arrays on unique 3D substrate are expected to improve the sensitivity and efficiency of ZnO based electrochemical sensors and heterogeneous catalysts.

  • 25.
    Klasson, Anna
    et al.
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Ahrén, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Hellqvist, Eva
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, Faculty of Science & Engineering.
    Rosén, Anders
    Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Radiology. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Positive MRI Enhancement in THP-1 Cells with Gd2O3 Nanoparticles2008In: Contrast Media and Molecular Imaging, ISSN 1555-4309, Vol. 3, no 3, p. 106-111Article in journal (Refereed)
    Abstract [en]

    There is a demand for more efficient and tissue-specific MRI contrast agents and recent developments involve the design of substances useful as molecular markers and magnetic tracers. In this study, nanoparticles of gadolinium oxide (Gd2O3) have been investigated for cell labeling and capacity to generate a positive contrast. THP-1, a monocytic cell line that is phagocytic, was used and results were compared with relaxivity of particles in cell culture medium (RPMI 1640). The results showed that Gd2O3-labeled cells have shorter T1 and T2 relaxation times compared with untreated cells. A prominent difference in signal intensity was observed, indicating that Gd2O3 nanoparticles can be used as a positive contrast agent for cell labeling. The r1 for cell samples was 4.1 and 3.6 s-1 mm-1 for cell culture medium. The r2 was 17.4 and 12.9 s-1 mm-1, respectively. For r1, there was no significant difference in relaxivity between particles in cells compared to particles in cell culture medium, (pr1 = 0.36), but r2 was significantly different for the two different series (pr2 = 0.02). Viability results indicate that THP-1 cells endure treatment with Gd2O3 nanoparticles for an extended period of time and it is therefore concluded that results in this study are based on viable cells.

  • 26.
    Klasson, Anna
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Engström, Maria
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology.
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Uvdal, Kajsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Cell tracking with novel contrast agents fromed by gadolinium oxide nanoparticels2005In: ESMRMB,2005, 2005Conference paper (Refereed)
  • 27.
    Klasson, Anna
    et al.
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Hellqvist, Eva
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Biomedicine and Surgery, Division of cell biology.
    Rosén, Anders
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Biomedicine and Surgery, Division of cell biology.
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Uvdal, Kajsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Engström, Maria
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Linköping University, Center for Medical Image Science and Visualization, CMIV.
    Cell tracking with positive contrast using Gd2O3 nanoparticles2006In: ESMRMB,2006, 2006Conference paper (Other academic)
  • 28.
    Knight, C
    et al.
    Ohio State University.
    Singer, SJ
    Ohio State University.
    Kuo, J-L
    Nanyang Technological University.
    Hirsch, TK
    Stockholm University.
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Klein, ML
    University of Pennsylvania.
    Hydrogen bond topology and the ice VII/VIII and Ih/XI proton ordering phase transitions2006In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 73, p. 056113-056113Article in journal (Refereed)
    Abstract [en]

      Ice Ih, ordinary ice at atmospheric pressure, is a proton-disordered crystal that when cooled under special conditions is believed to transform to ferroelectric proton-ordered ice XI, but this transformation is still subject to controversy. Ice VII, also proton disordered throughout its region of stability, transforms to proton-ordered ice VIII upon cooling. In contrast to the ice Ih/XI transition, the VII/VIII transition and the crystal structure of ice VIII are well characterized. In order to shed some light on the ice Ih proton ordering transition, we present the results of periodic electronic density functional theory calculations and statistical simulations. We are able to describe the small energy differences among the innumerable H-bond configurations possible in a large simulation cell by using an analytic theory to extrapolate from electronic DFT calculations on small unit cells to cells large enough to approximate the thermodynamic limit. We first validate our methods by comparing our predictions to the well-characterized ice VII/VIII proton ordering transition, finding agreement with respect to both the transition temperature and structure of the low-temperature phase. For ice Ih, our results indicate that a proton-ordered phase is attainable at low temperatures, the structure of which is in agreement with the experimentally proposed ferroelectric Cmc21 structure. The predicted transition temperature of 98  K is in qualitative agreement with the observed transition at 72  K on KOH-doped ice samples.

  • 29.
    Kula, Mathias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    A theoretical study of the electronic structure of GaN nanorods2012In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 112, no 7, p. 1796-1802Article in journal (Refereed)
    Abstract [en]

    We present a theoretical study of the evolution of the electronic structure of wurtzite GaN nanorods for different lengths (2.415.4 nm) in the [0001] direction and different diameters (0.972.25 nm). This study includes both a hybrid density functional theory study and a comparison with the k.p empirical band structure method. From the quantum chemical calculations, surface effects are found to be important. When these have been compensated for the electronic structure properties as a function of rod length or diameter approximately follow the trend expected from the quantum confinement effect. The k.p method predicts a similar behavior although deviations are apparent for smaller sizes.

  • 30.
    Kuo, J. L.
    et al.
    Univ Penn, Dept Chem, Ctr Mol Modeling, Philadelphia, PA 19104 USA.
    Klein, M. L.
    Univ Penn, Dept Chem, Ctr Mol Modeling, Philadelphia, PA 19104 USA.
    Singer, S. J.
    Ohio State Univ, Dept Chem, Columbus, OH 43210 USA.
    Ojamäe, L.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Ice lh-Ice XI phase transition: A quantum mechanical study2004Conference paper (Other academic)
  • 31.
    Kuo, Jer-Lai
    et al.
    Department of Chemistry, Ohio State University, Columbus, Ohio 43214.
    Coe, James V.
    Department of Chemistry, Ohio State University, Columbus, Ohio 43214.
    Singer, Sherwin J.
    Department of Chemistry, Ohio State University, Columbus, Ohio 43214.
    Band, Yehuda B.
    Departments of Chemistry and Physics, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    On the use of graph invariants for efficiently generating hydrogen bond topologies and predicting physical properties of water clusters and ice2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 114, no 6, p. 2527-2540Article in journal (Refereed)
    Abstract [en]

    Water clusters and some phases of ice are characterized by many isomers with similar oxygen positions, but which differ in direction of hydrogen bonds. A relationship between physical properties, like energy or magnitude of the dipole moment, and hydrogen bond arrangements has long been conjectured. The topology of the hydrogen bond network can be summarized by oriented graphs. Since scalar physical properties like the energy are invariant to symmetry operations, graphical invariants are the proper features of the hydrogen bond network which can be used to discover the correlation with physical properties. We demonstrate how graph invariants are generated and illustrate some of their formal properties. It is shown that invariants can be used to change the enumeration of symmetry-distinct hydrogen bond topologies, nominally a task whose computational cost scales like N2, where N is the number of configurations, into an N ln N process. The utility of graph invariants is confirmed by considering two water clusters, the (H2O)6 cage and (H2O)20 dodecahedron, which, respectively, possess 27 and 30 026 symmetry-distinct hydrogen bond topologies associated with roughly the same oxygen atom arrangements. Physical properties of these clusters are successfully fit to a handful of graph invariants. Using a small number of isomers as a training set, the energy of other isomers of the (H2O)20 dodecahedron can even be estimated well enough to locate phase transitions. Some preliminary results for unit cells of ice-Ih are given to illustrate the application of our results to periodic systems.

     

  • 32.
    Kuo, J.-L.
    et al.
    Department of Chemistry, Ohio State University, Columbus, OH 43210, United States.
    Ciobanu, C.V.
    Department of Physics, Ohio State University, Columbus, OH 43210, United States.
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Shavitt, I.
    Department of Chemistry, University of Illinois, Urbana, IL 61801, United States.
    Singer, S.J.
    Department of Chemistry, Ohio State University, Columbus, OH 43210, United States.
    Short H-bonds and spontaneous self-dissociation in (H2O)20: Effects of H-bond topology2003In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 118, no 8, p. 3583-3588Article in journal (Refereed)
    Abstract [en]

    The affects of H-bond topology and spontaneous self-dissociation in (H2O)20 was discussed. The enthalpy of dissociation of water to H+ and OH- in bulk water was found to be 13.5 kcal/mol. The surface of ice was characterized by dangling hydrogens and variable H-bond topology.

  • 33.
    Käll, Per-Olov
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Grins, J.
    Department of Inorganic Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Söderlind, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Synthesis, structure determination and X-ray photoelectron spectroscopy characterisation of a novel polymeric silver(I) nicotinic acid complex, H[Ag(py-3-CO2)2]2001In: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 20, no 21, p. 2747-2753Article in journal (Refereed)
    Abstract [en]

    Polymeric inorganic or organometallic coordination compounds represent an interesting class of materials where novel (combinations of) electrical, optical, magnetic, catalytic, or other properties are expected to occur. It has recently been shown that Ag1 complexes formed by organic N,N'-bidentate type ligands exhibit a rich structural variety encompassing ID, 2D and 3D polymers. Previous investigations of the silver(I) nicotinic acid system have revealed two different structural types, in both of which Ag1 is three-coordinated. We have investigated the system nicotinic acid (C6H5NO2/AgA in water (A = NO3-, CH3COO- and F-). In all the cases the same product precipitated, catena-{hydrogen bis[pyridine-3-carboxylato-(N,N')]silver(I)}, H[Ag(py-3-CO2)2] (M = 353.1 g mol-1). The structure can be described as a 1D polymer consisting of [Ag(C6H4NO2)2]- monomers linked via C21(12)[R21(4)] hydrogen bonds, where the connecting H+ ion is located at the same distance (1.24 Å) to the carboxyl oxygens of consecutive monomers. The measured X-ray photoelectron spectrum shows an excellent agreement with the proposed structure. FTIR measurements of the complex were also performed. © 2001 Elsevier Science Ltd. All rights reserved.

  • 34.
    Käll, Per-Olov
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Ojamäe, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Pedersen, Henrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Söderlind, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Petoral, Rodrigo Jr
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Uvdal, Kajsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics .
    Zhang, H.
    Zouc, X.
    Synthesis, Characterisation and Molecular Functionalisation of Gd2O3 Nanocrystals2004In: NAN:-8,2004, 2004Conference paper (Other academic)
    Abstract [en]

      

  • 35.
    Lenz, Annika
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Theoretical Investigations of Water Clusters, Ice Clathrates and Functionalized Nanoparticles2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nanosized structures are of intermediate size between individual molecules and bulkmaterials which gives them several unique properties. At the same time their relative limitedsizes make them suitable for studies by the methods of computational chemistry. In this thesiswater clusters, ice clathrates and functionalized metal-oxide nanoparticles have been studiedby quantum-chemical calculations and statistical thermodynamics.

    The stabilities of water clusters composed of up to 100 molecules have been investigated. Themultitude of possible H-bonded topologies and their importance for determining theproperties of the clusters have been highlighted. Several structural characteristics of thehydrogen bonded network have been examined and the structural factors that determine thestability of an H-bonded network have been identified. The stability of two kinds of oxygenframeworks for water clusters have been analyzed, taking into account thermal energy andentropy corrections. Clusters with many 4-coordinated molecules have been found to be lowerin energy at low temperatures whereas the clusters with less-coordinated molecules dominateat higher temperatures. The equilibrium size distribution of water clusters as a function oftemperature and pressure has been computed using statistical thermodynamics. Themicroscopic local structure of liquid water has been probed by utilizing information from thestudied water clusters. The average number of H-bonds in liquid water has been predicted byfitting calculated average IR spectra for different coordination types in water clusters toexperimental IR spectra.

    Water can form an ice-like structure that encloses various molecules such as methane. Thesemethane hydrates are found naturally at the ocean floor and in permafrost regions and canconstitute a large unemployed energy resource as well as a source of an effective green-housegas. The pressure dependencies of the crystal structures, lattice energies and phase transitionsfor the three methane hydrates with the clathrate structures I, II and H have been mapped out.

    Zinc oxide is a semiconducting material with interesting luminescence properties that can beutilized in optical devices, such as photodetectors, light emitting devices and biomarkers. Theeffect of water molecules adsorbed on the ZnO surface when adsorbing organic acids havebeen investigated. Changes in optical properties by the adsorption of carboxylic acids havebeen studied and compared with experimental results. Aromatic alcohols at TiO2 metal-oxidenanoparticles have been studied as model systems for dye-sensitizied solar cells. Adsorptiongeometries are predicted and the influence from the adsorbed molecules on the electronicproperties has been studied.

    List of papers
    1. A theoretical study of water clusters: the relation between hydrogen-bond topology and interaction energy from quantum-chemical computations for clusters with up to 22 molecules
    Open this publication in new window or tab >>A theoretical study of water clusters: the relation between hydrogen-bond topology and interaction energy from quantum-chemical computations for clusters with up to 22 molecules
    2005 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 7, p. 1905-1911Article in journal (Refereed) Published
    Abstract [en]

    Quantum-chemical calculations of a variety of water clusters with eight, ten and twelve molecules were performed, as well as for selected clusters with up to 22 water molecules. Geometry optimizations were carried out at the B3LYP/cc-pVDZ level and single-point energies were calculated at the B3LYP/aug-cc-pVDZ level for selected clusters. The electronic energies were studied with respect to the geometry of the oxygen arrangement and six different characteristics of the hydrogen-bond arrangement in the cluster. Especially the effect of the placement of the non-hydrogen bonding hydrogens on the interaction energy was studied. Models for the interaction energy with respect to different characteristics of the hydrogen-bond arrangement were derived through least-square fits. The results from the study of the clusters with eight, ten and twelve molecules are used to predict possible low-energy structures for various shapes of clusters with up to 22 molecules.

    Place, publisher, year, edition, pages
    RCS Publishing, 2005
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-30387 (URN)10.1039/b502109j (DOI)15935 (Local ID)15935 (Archive number)15935 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
    2. On the stability of dense versus cage-shaped water clusters: quantum-chemical investigations of zero-point energies, free energies, basis-set effects and IR spectra of (H2O)12 and (H2O)20
    Open this publication in new window or tab >>On the stability of dense versus cage-shaped water clusters: quantum-chemical investigations of zero-point energies, free energies, basis-set effects and IR spectra of (H2O)12 and (H2O)20
    2006 (English)In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 418, p. 361-367Article in journal (Refereed) Published
    Abstract [en]

    The energetics of water clusters with 12 and 20 molecules are studied by quantum-chemical computations using the B3LYP, MP2, MP4 and CCSD methods. The effect of electron-correlation method, basis set, zero-point energy, thermal energy and Gibbs free energy on the relative stability of fused clusters (structures consisting of cubic- or prismatic-shaped subparts) versus cage-shaped clusters (more open structures with only three-coordinated molecules) are investigated. The O–H stretching IR vibrational spectra are studied. The contribution of zero-point and Gibbs free energy will diminish the energy difference between fused- and cage-shaped clusters, but the fused structures are still slightly more favorable.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-36194 (URN)10.1016/j.cplett.2005.11.013 (DOI)30469 (Local ID)30469 (Archive number)30469 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
    3. Theoretical IR spectra for water clusters (H2O)n (n = 6-22, 28, 30) and identification of spectral contributions from different H-Bond conformations in gaseous and liquid water
    Open this publication in new window or tab >>Theoretical IR spectra for water clusters (H2O)n (n = 6-22, 28, 30) and identification of spectral contributions from different H-Bond conformations in gaseous and liquid water
    2006 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 110, no 50, p. 13388-13393Article in journal (Refereed) Published
    Abstract [en]

    The vibrational IR spectra in the O-H stretching region are computed for water clusters containing 6-22, 28, and 30 molecules using quantum-chemical calculations (B3LYP and an augmented basis set). For the cluster with 20 molecules, several different structures were studied. The vibrational spectrum was partitioned into contributions from different molecules according to their coordination properties. The frequency shifts depend on the number of donated/accepted H-bonds primarily of the two molecules participating in the H-bond, but also of the surrounding molecules H-bonding to these molecules. The frequencies of H-bonds between two molecules of the same coordination type are spread over a broad interval. The most downshifted hydrogen-bond vibrations are those donated by a single-donor 3-coordinated molecule where the H-bond is accepted by a single-acceptor molecule. The H-bonded neighbors influence the downshift, and their contribution can be rationalized in the same way as for the central dimer. Single donors/acceptors cause larger downshifts than 4-coordinated molecules, and the least downshift is obtained for double donors/acceptors. This result is at variance with the conception that experimental liquid water spectra may be divided into components for which larger downshifts imply higher H-bond coordination. A mean spectral contribution for each coordination type for the donor molecule was derived and fitted to the experimental liquid water IR spectrum, which enabled an estimation of the distribution of H-bond types and average number of H-bonds (3.0 ± 0.2) in the liquid. © 2006 American Chemical Society.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-36614 (URN)10.1021/jp066372x (DOI)31825 (Local ID)31825 (Archive number)31825 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
    4. A theoretical study of water equilibria: The cluster distribution versus temperature and pressure for (H2O)n, n=1–60, and ice
    Open this publication in new window or tab >>A theoretical study of water equilibria: The cluster distribution versus temperature and pressure for (H2O)n, n=1–60, and ice
    2009 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, no 13, p. 134302-134302-13Article in journal (Refereed) Published
    Abstract [en]

    The size distribution of water clusters at equilibrium is studied using quantum-chemical calculations in combination with statistical thermodynamics. The necessary energetic data is obtained by quantum-chemical B3LYP computations and through extrapolations from the B3LYP results for the larger clusters. Clusters with up to 60 molecules are included in the equilibrium computations. Populations of different cluster sizes are calculated using both an ideal gas model with noninteracting clusters and a model where a correction for the interaction energy is included analogous to the van der Waals law. In standard vapor the majority of the water molecules are monomers. For the ideal gas model at 1 atm large clusters [56-mer (0–120 K) and 28-mer (100–260 K)] dominate at low temperatures and separate to smaller clusters [21–22-mer (170–280 K) and 4–6-mer (270–320 K) and to monomers (300–350 K)] when the temperature is increased. At lower pressure the transition from clusters to monomers lies at lower temperatures and fewer cluster sizes are formed. The computed size distribution exhibits enhanced peaks for the clusters consisting of 21 and 28 water molecules; these sizes are for protonated water clusters often referred to as magic numbers. If cluster-cluster interactions are included in the model the transition from clusters to monomers is sharper (i.e., occurs over a smaller temperature interval) than when the ideal-gas model is used. Clusters with 20–22 molecules dominate in the liquid region. When a large icelike cluster is included it will dominate for temperatures up to 325 K for the noninteracting clusters model. Thermodynamic properties (Cp, H) were calculated with in general good agreement with experimental values for the solid and gas phase. A formula for the number of H-bond topologies in a given cluster structure is derived. For the 20-mer it is shown that the number of topologies contributes to making the population of dodecahedron-shaped cluster larger than that of a lower-energy fused prism cluster at high temperatures.

    Keywords
    water, vapour, ice, quantum chemistry, statistical thermodynamics, hydrogen bonding
    National Category
    Theoretical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-50778 (URN)10.1063/1.3239474 (DOI)
    Available from: 2009-10-14 Created: 2009-10-14 Last updated: 2017-12-12
    5. Computational studies of the stability of the (H2O)100 nanodrop
    Open this publication in new window or tab >>Computational studies of the stability of the (H2O)100 nanodrop
    2010 (English)In: Journal of Molecular Structure: THEOCHEM, ISSN 0166-1280, Vol. 944, no 1-3, p. 163-167Article in journal (Refereed) Published
    Abstract [en]

    The stability of the (H2O)100 nanodrop, experimentally known from a polyoxomolybdatecrystal structure (Müller et al. Inorg. Chem. Commun., 2003, 6, 52) and other structuresinferred from clathrate structures, are studied by quantum-chemical B3LYP computations.The free energies are compared to the trends for smaller clusters with 15-30 molecules. Forthe small clusters both cage-based structures and denser structures with a larger number of Hbondsobtained by an evolutionary algorithm (Bandow and Hartke, J. Phys. Chem. A, 2006,110, 5809) are used. The dense structures are most often found to be lower in electronicenergy. The cage-based structures, to which the structure of the experimentally found(H2O)100 cluster can be categorized, become more stable when Gibbs free energy is calculatedat 298 K. Additional cage-based clusters in the 35-81 molecular range were constructed forcomparison. The experimental cluster with 100 molecules (C2h/Ci-symmetry for oxygens/allatoms) and the constructed cluster with 42 molecules are found to be lower in energy than aplausible overall trend. The (H2O)42 cluster has an extraordinary high symmetry (S6), evenwhen the hydrogens are considered. The (H2O)100 cluster is the only of the studied clusters forwhich ΔG is negative at 298 K.

    Keywords
    Water clusters, Quantum-chemical computations, Hydrogen bonding, B3LYP calculations, Gibbs free energy
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-53176 (URN)10.1016/j.theochem.2009.12.033 (DOI)000275688200022 ()
    Note
    Original Publication: Annika Lenz and Lars Ojamäe, Computational studies of the stability of the (H2O)100 nanodrop, 2010, Journal of Molecular Structure: THEOCHEM, (944), 1-3, 163-167. http://dx.doi.org/10.1016/j.theochem.2009.12.033 Copyright: Elsevier Science B.V., Amsterdam http://www.elsevier.com/ Available from: 2010-01-18 Created: 2010-01-18 Last updated: 2017-12-12
    6. Structures of the I-, II- and H-Methane Clathrates and the Ice−Methane Clathrate Phase Transition from Quantum-Chemical Modeling with Force-Field Thermal Corrections
    Open this publication in new window or tab >>Structures of the I-, II- and H-Methane Clathrates and the Ice−Methane Clathrate Phase Transition from Quantum-Chemical Modeling with Force-Field Thermal Corrections
    2011 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 115, no 23, p. 6169-6176Article in journal (Refereed) Published
    Abstract [en]

    Methane hydrates with the three clathrate structures I, II and H are studied by quantumchemicalmethods. The periodic B3LYP computations are combined with force-field methodsfor the thermal energy corrections. The pressure dependencies for the crystal structures, latticeenergies and guest molecule interactions are derived. Quantum-chemical geometryoptimizations predict too small cell volumes compared to experimental data, but includingzero-point energy and thermal energy the cell volume increases and the correct densities areobtained. Phase diagram for the three structures are investigated, and phase transitions werefound at 5 GPa for the MH-I–MH-II transition and at 10 GPa for the MH-II–MH-H transition.

    Place, publisher, year, edition, pages
    ACS Publications, 2011
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-53177 (URN)10.1021/jp111328v (DOI)
    Note
    The original title of this article was: "Structure and phase transitions of I-, II- and H- methane clathrates and ice from quantum-chemical B3LYP computations with corrections for thermal effects".Available from: 2010-01-18 Created: 2010-01-18 Last updated: 2017-12-12Bibliographically approved
    7. ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study
    Open this publication in new window or tab >>ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study
    Show others...
    2009 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 40, p. 17332-17341Article in journal (Refereed) Published
    Abstract [en]

    Electrochemical synthesis and physical characterization of ZnO nanoparticles functionalized with four different organic acids, three aromatic (benzoic, nicotinic, and trans-cinnamic acid) and one nonaromatic (formic acid), are reported. The functionalized nanoparticles have been characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV−vis, and photoluminescence spectroscopy. The adsorption of the organic acids at ZnO nanoparticles was further analyzed and interpreted using quantum-chemical density-functional theory computations. Successful functionalization of the nanoparticles was confirmed experimentally by the measured splitting of the carboxylic group stretching vibrations as well as by the N(1s) and C(1s) peaks from XPS. From a comparison between computed and experimental IR spectra, a bridging mode adsorption geometry was inferred. PL spectra exhibited a remarkably stronger near band edge emission for nanoparticles functionalized with formic acid as compared to the larger aromatic acids. From the quantum-chemical computations, this was interpreted to be due to the absence of aromatic adsorbate or surface states in the band gap of ZnO, caused by the formation of a complete monolayer of HCOOH. In the UV−vis spectra, strong charge-transfer transitions were observed.

    Keywords
    nanoparticles, ZnO, organic acids, adsorption, synthesis, XPS, UV-vis, quantum chemical calculations
    National Category
    Physical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-50783 (URN)10.1021/jp905481v (DOI)
    Available from: 2009-10-14 Created: 2009-10-14 Last updated: 2017-12-12
    8. Quantum-chemical investigations of phenol and larger aromatic molecules at the TiO2 anatase (101) surface
    Open this publication in new window or tab >>Quantum-chemical investigations of phenol and larger aromatic molecules at the TiO2 anatase (101) surface
    2008 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 117, p. 012020-(8 pp)Article in journal (Refereed) Published
    Abstract [en]

    Adsorption of aromatic molecules at the (101) surface of titanium dioxide anatase is studied by quantum-chemical B3LYP computations, where both cluster and periodic calculations were performed and compared. For phenol different adsorption modes at a TiO2 cluster were mapped out and the energetically most favourable conformation was used for investigation of the electronic structure, for periodic calculations, and as a mould for the adsorption modes of phenylmethanol, phenylethanol, naphthalen-2-ol, phenanthren-2-ol, pyren-2-ol and perylen-2-ol. The alcohols form a H-bond to a surface O and a O(molecule)-Ti bond. For the larger aromatic molecules their increasingly higher HOMO levels decrease the effective bad gap of the system. Inclusion of spacer groups as in phenylmethanol and phenylethanol results in higher adsorption energies and larger band gaps. The LUMOs for the adsorbates help visualize the electronic coupling to the surface. Comparison of the cluster with the periodic model indicates that the former describes the electronic coupling in a similar manner as the latter, although the former lacks in the description of the anatase substrate.

    Keywords
    TiO2, anatase, phenol, adsorption, nanoparticles
    National Category
    Theoretical Chemistry
    Identifiers
    urn:nbn:se:liu:diva-50664 (URN)10.1088/1742-6596/117/1/012020 (DOI)
    Available from: 2009-10-13 Created: 2009-10-13 Last updated: 2017-12-12
  • 36.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Kariis, Hans
    Swedish Defence Research Agency.
    Pohl, Anna
    Swedish Defence Research Agency.
    Persson, Petter
    Lund University.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    The electronic structure and reflectivity of PEDOT:PSS from density functional theory2011In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 384, no 03-jan, p. 44-51Article in journal (Refereed)
    Abstract [en]

    The geometric and electronic structure of condensed phase organic conducting polymer PEDOT:PSS blends has been investigated by periodic density functional theory (DFT) calculations with a generalized-gradient approximation (GGA) functional, and a plane wave basis set. The influence of the degree of doping of the PEDOT polymer on structural and optical parameters such as the reflectivity, absorbance, conductivity, dielectric function, refractive index and the energy-loss function is studied. A flip from the benzoid to the quinoid structure is observed in the calculations when the neutral PEDOT is doped by negatively charged PSS. Also the optical properties are affected by the doping. In particular, the reflectivity was found to be very sensitive to the degree of doping, where higher doping implies higher reflectivity. The reflectivity is highly anisotropic, with the dominant contribution stemming from the direction parallel to the PEDOT polymer chain.

  • 37.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Karlsson, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Quantum-chemical investigations of phenol and larger aromatic molecules at the TiO2 anatase (101) surface2008In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, Vol. 117, p. 012020-(8 pp)Article in journal (Refereed)
    Abstract [en]

    Adsorption of aromatic molecules at the (101) surface of titanium dioxide anatase is studied by quantum-chemical B3LYP computations, where both cluster and periodic calculations were performed and compared. For phenol different adsorption modes at a TiO2 cluster were mapped out and the energetically most favourable conformation was used for investigation of the electronic structure, for periodic calculations, and as a mould for the adsorption modes of phenylmethanol, phenylethanol, naphthalen-2-ol, phenanthren-2-ol, pyren-2-ol and perylen-2-ol. The alcohols form a H-bond to a surface O and a O(molecule)-Ti bond. For the larger aromatic molecules their increasingly higher HOMO levels decrease the effective bad gap of the system. Inclusion of spacer groups as in phenylmethanol and phenylethanol results in higher adsorption energies and larger band gaps. The LUMOs for the adsorbates help visualize the electronic coupling to the surface. Comparison of the cluster with the periodic model indicates that the former describes the electronic coupling in a similar manner as the latter, although the former lacks in the description of the anatase substrate.

  • 38.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    A theoretical study of water clusters: the relation between hydrogen-bond topology and interaction energy from quantum-chemical computations for clusters with up to 22 molecules2005In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 7, p. 1905-1911Article in journal (Refereed)
    Abstract [en]

    Quantum-chemical calculations of a variety of water clusters with eight, ten and twelve molecules were performed, as well as for selected clusters with up to 22 water molecules. Geometry optimizations were carried out at the B3LYP/cc-pVDZ level and single-point energies were calculated at the B3LYP/aug-cc-pVDZ level for selected clusters. The electronic energies were studied with respect to the geometry of the oxygen arrangement and six different characteristics of the hydrogen-bond arrangement in the cluster. Especially the effect of the placement of the non-hydrogen bonding hydrogens on the interaction energy was studied. Models for the interaction energy with respect to different characteristics of the hydrogen-bond arrangement were derived through least-square fits. The results from the study of the clusters with eight, ten and twelve molecules are used to predict possible low-energy structures for various shapes of clusters with up to 22 molecules.

  • 39.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    A theoretical study of water equilibria: The cluster distribution versus temperature and pressure for (H2O)n, n=1–60, and ice2009In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, no 13, p. 134302-134302-13Article in journal (Refereed)
    Abstract [en]

    The size distribution of water clusters at equilibrium is studied using quantum-chemical calculations in combination with statistical thermodynamics. The necessary energetic data is obtained by quantum-chemical B3LYP computations and through extrapolations from the B3LYP results for the larger clusters. Clusters with up to 60 molecules are included in the equilibrium computations. Populations of different cluster sizes are calculated using both an ideal gas model with noninteracting clusters and a model where a correction for the interaction energy is included analogous to the van der Waals law. In standard vapor the majority of the water molecules are monomers. For the ideal gas model at 1 atm large clusters [56-mer (0–120 K) and 28-mer (100–260 K)] dominate at low temperatures and separate to smaller clusters [21–22-mer (170–280 K) and 4–6-mer (270–320 K) and to monomers (300–350 K)] when the temperature is increased. At lower pressure the transition from clusters to monomers lies at lower temperatures and fewer cluster sizes are formed. The computed size distribution exhibits enhanced peaks for the clusters consisting of 21 and 28 water molecules; these sizes are for protonated water clusters often referred to as magic numbers. If cluster-cluster interactions are included in the model the transition from clusters to monomers is sharper (i.e., occurs over a smaller temperature interval) than when the ideal-gas model is used. Clusters with 20–22 molecules dominate in the liquid region. When a large icelike cluster is included it will dominate for temperatures up to 325 K for the noninteracting clusters model. Thermodynamic properties (Cp, H) were calculated with in general good agreement with experimental values for the solid and gas phase. A formula for the number of H-bond topologies in a given cluster structure is derived. For the 20-mer it is shown that the number of topologies contributes to making the population of dodecahedron-shaped cluster larger than that of a lower-energy fused prism cluster at high temperatures.

  • 40.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Computational studies of the stability of the (H2O)100 nanodrop2010In: Journal of Molecular Structure: THEOCHEM, ISSN 0166-1280, Vol. 944, no 1-3, p. 163-167Article in journal (Refereed)
    Abstract [en]

    The stability of the (H2O)100 nanodrop, experimentally known from a polyoxomolybdatecrystal structure (Müller et al. Inorg. Chem. Commun., 2003, 6, 52) and other structuresinferred from clathrate structures, are studied by quantum-chemical B3LYP computations.The free energies are compared to the trends for smaller clusters with 15-30 molecules. Forthe small clusters both cage-based structures and denser structures with a larger number of Hbondsobtained by an evolutionary algorithm (Bandow and Hartke, J. Phys. Chem. A, 2006,110, 5809) are used. The dense structures are most often found to be lower in electronicenergy. The cage-based structures, to which the structure of the experimentally found(H2O)100 cluster can be categorized, become more stable when Gibbs free energy is calculatedat 298 K. Additional cage-based clusters in the 35-81 molecular range were constructed forcomparison. The experimental cluster with 100 molecules (C2h/Ci-symmetry for oxygens/allatoms) and the constructed cluster with 42 molecules are found to be lower in energy than aplausible overall trend. The (H2O)42 cluster has an extraordinary high symmetry (S6), evenwhen the hydrogens are considered. The (H2O)100 cluster is the only of the studied clusters forwhich ΔG is negative at 298 K.

  • 41.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    On the stability of dense versus cage-shaped water clusters: quantum-chemical investigations of zero-point energies, free energies, basis-set effects and IR spectra of (H2O)12 and (H2O)202006In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 418, p. 361-367Article in journal (Refereed)
    Abstract [en]

    The energetics of water clusters with 12 and 20 molecules are studied by quantum-chemical computations using the B3LYP, MP2, MP4 and CCSD methods. The effect of electron-correlation method, basis set, zero-point energy, thermal energy and Gibbs free energy on the relative stability of fused clusters (structures consisting of cubic- or prismatic-shaped subparts) versus cage-shaped clusters (more open structures with only three-coordinated molecules) are investigated. The O–H stretching IR vibrational spectra are studied. The contribution of zero-point and Gibbs free energy will diminish the energy difference between fused- and cage-shaped clusters, but the fused structures are still slightly more favorable.

  • 42.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Structures of the I-, II- and H-Methane Clathrates and the Ice−Methane Clathrate Phase Transition from Quantum-Chemical Modeling with Force-Field Thermal Corrections2011In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 115, no 23, p. 6169-6176Article in journal (Refereed)
    Abstract [en]

    Methane hydrates with the three clathrate structures I, II and H are studied by quantumchemicalmethods. The periodic B3LYP computations are combined with force-field methodsfor the thermal energy corrections. The pressure dependencies for the crystal structures, latticeenergies and guest molecule interactions are derived. Quantum-chemical geometryoptimizations predict too small cell volumes compared to experimental data, but includingzero-point energy and thermal energy the cell volume increases and the correct densities areobtained. Phase diagram for the three structures are investigated, and phase transitions werefound at 5 GPa for the MH-I–MH-II transition and at 10 GPa for the MH-II–MH-H transition.

  • 43.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry . Linköping University, The Institute of Technology.
    Theoretical IR spectra for water clusters (H2O)n (n = 6-22, 28, 30) and identification of spectral contributions from different H-Bond conformations in gaseous and liquid water2006In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 110, no 50, p. 13388-13393Article in journal (Refereed)
    Abstract [en]

    The vibrational IR spectra in the O-H stretching region are computed for water clusters containing 6-22, 28, and 30 molecules using quantum-chemical calculations (B3LYP and an augmented basis set). For the cluster with 20 molecules, several different structures were studied. The vibrational spectrum was partitioned into contributions from different molecules according to their coordination properties. The frequency shifts depend on the number of donated/accepted H-bonds primarily of the two molecules participating in the H-bond, but also of the surrounding molecules H-bonding to these molecules. The frequencies of H-bonds between two molecules of the same coordination type are spread over a broad interval. The most downshifted hydrogen-bond vibrations are those donated by a single-donor 3-coordinated molecule where the H-bond is accepted by a single-acceptor molecule. The H-bonded neighbors influence the downshift, and their contribution can be rationalized in the same way as for the central dimer. Single donors/acceptors cause larger downshifts than 4-coordinated molecules, and the least downshift is obtained for double donors/acceptors. This result is at variance with the conception that experimental liquid water spectra may be divided into components for which larger downshifts imply higher H-bond coordination. A mean spectral contribution for each coordination type for the donor molecule was derived and fitted to the experimental liquid water IR spectrum, which enabled an estimation of the distribution of H-bond types and average number of H-bonds (3.0 ± 0.2) in the liquid. © 2006 American Chemical Society.

  • 44.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Pohl, Anna
    Swedish Defence Research Agency.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Persson, Petter
    Lund University.
    Computational study of the catalytic effect of platinum on the decomposition of DNT2012In: International Journal of Quantum Chemistry, ISSN 0020-7608, E-ISSN 1097-461X, Vol. 112, no 7, p. 1852-1858Article in journal (Refereed)
    Abstract [en]

    The catalytic decomposition of dinitrotoluene (DNT; 3-4-DNT), a by-product of the explosive trinitrotoluene (trotyl), on a platinum surface is investigated computationally. Reaction paths have been computed for a DNT molecule interacting with a Pt-cluster under varying temperatures using quantum-chemical density functional theory. Two possible initiation steps where DNT split either into nitro-tolyl and NO2, or in nitro-tolyl-oxidanyl and NO, are considered. The energy barrier for the catalytic process is found to decrease significantly for the Pt catalyzed reaction compared with the uncatalyzed reaction.

  • 45.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Selegård, Linnea
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Inorganic Chemistry. Linköping University, Faculty of Science & Engineering.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Inorganic Chemistry. Linköping University, The Institute of Technology.
    ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 40, p. 17332-17341Article in journal (Refereed)
    Abstract [en]

    Electrochemical synthesis and physical characterization of ZnO nanoparticles functionalized with four different organic acids, three aromatic (benzoic, nicotinic, and trans-cinnamic acid) and one nonaromatic (formic acid), are reported. The functionalized nanoparticles have been characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV−vis, and photoluminescence spectroscopy. The adsorption of the organic acids at ZnO nanoparticles was further analyzed and interpreted using quantum-chemical density-functional theory computations. Successful functionalization of the nanoparticles was confirmed experimentally by the measured splitting of the carboxylic group stretching vibrations as well as by the N(1s) and C(1s) peaks from XPS. From a comparison between computed and experimental IR spectra, a bridging mode adsorption geometry was inferred. PL spectra exhibited a remarkably stronger near band edge emission for nanoparticles functionalized with formic acid as compared to the larger aromatic acids. From the quantum-chemical computations, this was interpreted to be due to the absence of aromatic adsorbate or surface states in the band gap of ZnO, caused by the formation of a complete monolayer of HCOOH. In the UV−vis spectra, strong charge-transfer transitions were observed.

  • 46.
    Lloyd Spetz, Anita
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Buchholt, Kristina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lutic, Doina
    Lunds universitet.
    Strand, M
    Växjö universitet.
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Sanati, Mehri
    Lunds universitet.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Multifunctional chemical sensors based on wide band gap materials2007In: MRS Spring Meeting,2007, 2007Conference paper (Refereed)
    Abstract [en]

       

  • 47.
    Lloyd Spetz, Anita
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Eriksson, Jens
    Ehrler, S
    Khranovskyy, Volodymyr
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Gas sensors based on ZnO nanopraticels or film: A comparison2008In: IMCS 12,2008, 2008, p. 89-Conference paper (Refereed)
    Abstract [en]

       

  • 48.
    Lloyd Spetz, Anita
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Pearce, Ruth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Hedin, Linnea
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Khranovskyy, Volodymyr
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    New transducer material concepts for biosensors and surface functionalization2009In: Smart Sensors, Actuators,and MEMS IV / [ed] Ulrich Schmid, Carles Cané, Herbert Shea, Bellingham, WA United States: SPIE - International Society for Optical Engineering, 2009, Vol. 7362, p. 736206-Conference paper (Refereed)
    Abstract [en]

    Wide bandgap materials like SiC, ZnO, AlN form a strong platform as transducers for biosensors realized as e.g. ISFET (ion selective field effect transistor) devices or resonators. We have taken two main steps towards a multifunctional biosensor transducer. First we have successfully functionalized ZnO and SiC surfaces with e.g. APTES. For example ZnO is interesting since it may be functionalized with biomolecules without any oxidation of the surface and several sensing principles are possible. Second, ISFET devises with a porous metal gate as a semi-reference electrode are being developed. Nitric oxide, NO, is a gas which participates in the metabolism. Resistivity changes in Ga doped ZnO was demonstrated as promising for NO sensing also in humid atmosphere, in order to simulate breath.

  • 49.
    Lloyd Spetz, Anita
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Skoglundh, Magnus
    Applied Surface Chemistry, Chalmers University, Sweden.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    FET sensors gas sensing mechanism, experimental and theoretical studies2009In: Solid State Gas Sensing: Fundamentals and new trends in gas sensing, US: Springer , 2009, XV, p. 153-(27pp)Chapter in book (Other academic)
    Abstract [en]

    The chemical gas sensor area has gained large improvements from the

    nanoscience technology, e.g., more reproducible processing including control

    on the nanoscale of annealing procedures, which implies improved long-term

    stability. Analytical tools have developed towards detection and investigation

    of ever smaller size phenomena. This has been of importance for the key

    problem of chemical gas sensors, the detailed understanding on the nanoscale

    level of the gas-sensing mechanism. In this chapter, which deals with FET (field

    effect transistor) gas sensor devices, we will review analytical tools that provide

    information about the detection mechanism with special emphasise on the FET

    sensor area. The DRIFT, diffuse reflection infrared Fourier transform, spectroscopy

    as a rather new and very important tool is reviewed. Theoretical modelling

    will speed up the process to provide further details in the mechanistic

    studies. Examples will be given in this chapter. A number of other important

    analytical tools will be briefly described.

  • 50.
    Lloyd-Spets, Anita
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Ieva, Eliana
    IFM .
    Cioffi, N.
    Torsi, L.
    Sabbatini, L.
    Zambonin, P.G.
    Käll, Per-Olov
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Nanoparticelle di oro come materiali attivi in capacitori impiegati come sensori di gas2006In: Conf. on Chemical Sensors,2006, 2006Conference paper (Refereed)
12 1 - 50 of 89
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