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1.	Gustafsson, Håkan, et al. (författare) Magnetic and Electron Spin Relaxation Properties of (GdxY1-x)(2)O-3 (0 <= x <= 1) Nanoparticles Synthesized by the Combustion Method. Increased Electron Spin Relaxation Times with Increasing Yttrium Content 2011 Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:13, s. 5469-5477 Tidskriftsartikel (refereegranskat)abstract 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)(2)O-3 (0 <= x <= 1) were prepared by the combustion method and thoroughly characterized (by X-ray diffraction, 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.
2.	Gustafsson, Håkan, 1976-, et al. (författare) 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 Content 2011 Ingår i: The Journal of Physical Chemistry C. - United States : American Chemical Society. - 1932-7447 .- 1932-7455. ; 115:13, s. 5469-5477 Tidskriftsartikel (refereegranskat)abstract 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.
3.	Lindgren, Johan, et al. (författare) Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur 2018 Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 564:7736 Tidskriftsartikel (refereegranskat)abstract Ichthyosaurs are extinct marine reptiles that display a notable external similarity to modern toothed whales. Here we show that this resemblance is more than skin deep. We apply a multidisciplinary experimental approach to characterize the cellular and molecular composition of integumental tissues in an exceptionally preserved specimen of the Early Jurassic ichthyosaur Stenopterygius. Our analyses recovered still-flexible remnants of the original scaleless skin, which comprises morphologically distinct epidermal and dermal layers. These are underlain by insulating blubber that would have augmented streamlining, buoyancy and homeothermy. Additionally, we identify endogenous proteinaceous and lipid constituents, together with keratinocytes and branched melanophores that contain eumelanin pigment. Distributional variation of melanophores across the body suggests countershading, possibly enhanced by physiological adjustments of colour to enable photoprotection, concealment and/or thermoregulation. Convergence of ichthyosaurs with extant marine amniotes thus extends to the ultrastructural and molecular levels, reflecting the omnipresent constraints of their shared adaptation to pelagic life.
4.	Lenz, Annika, et al. (författare) ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study 2009 Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:40, s. 17332-17341 Tidskriftsartikel (refereegranskat)abstract 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.
5.	Lindgren, Johan, et al. (författare) Interpreting melanin-based coloration through deep time : A critical Review 2015 Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : Royal Society of London. - 0962-8452 .- 1471-2954. ; 282:1813 Forskningsöversikt (refereegranskat)abstract Colour, derived primarily from melanin and/or carotenoid pigments, is integral to many aspects of behaviour in living vertebrates, including social signalling, sexual display and crypsis. Thus, identifying biochromes in extinct animals can shed light on the acquisition and evolution of these biological traits. Both eumelanin and melanin-containing cellular organelles (melanosomes) are preserved in fossils, but recognizing traces of ancient melanin-based coloration is fraught with interpretative ambiguity, especially when observations are based on morphological evidence alone. Assigning microbodies (or, more often reported, their ‘mouldic impressions’) as melanosome traces without adequately excluding a bacterial origin is also problematic because microbes are pervasive and intimately involved in organismal degradation. Additionally, some forms synthesize melanin. In this review, we survey both vertebrate and microbial melanization, and explore the conflicts influencing assessment of microbodies preserved in association with ancient animal soft tissues.We discuss the types of data used to interpret fossil melanosomes and evaluate whether these are sufficient for definitive diagnosis. Finally, we outline an integrated morphological and geochemical approach for detecting endogenous pigment remains and associated microstructures in multimillion-year-old fossils.
6.	Söderlind, Fredrik, et al. (författare) Sol-gel synthesis and characterization of polycrystalline GdFeO3 and Gd3Fe5O12 thin films 2009 Ingår i: Journal of Sol-Gel Science and Technology. - : Springer Science and Business Media LLC. - 0928-0707 .- 1573-4846. ; 49:2, s. 253-259 Tidskriftsartikel (refereegranskat)abstract Thin films of the perovskite and garnet structured gadolinium ferrites GdFeO3 and Gd3Fe5O12 have been synthesized by a sol-gel method, based on stoichiometric mixtures of acetyl acetone chelated Gd3+ and Fe3+ dissolved in 2-methoxy ethanol. After spin coating onto Si wafers, and heating in air at 700 degrees C for 20 h, neatly grown essentially single phase films were obtained. From X-ray photoelectron spectroscopy an iron deficiency is observed in the uppermost layer of both films, implying that the crystallites preferably end in planes rich in Gd and O but not in Fe. The films were also characterized by X-ray powder diffraction, scanning electron microscopy, infrared spectroscopy, and magnetic measurements.
7.	Ahrén, Maria, et al. (författare) A simple polyol-free synthesis route to Gd 2O 3 nanoparticles for MRI applications : An experimental and theoretical study 2012 Ingår i: Journal of nanoparticle research. - : Springer. - 1388-0764 .- 1572-896X. ; 14:8 Tidskriftsartikel (refereegranskat)abstract Chelated gadolinium ions, e.g., Gd-DTPA, 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 Gd 2O 3 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 Gd 3+ ions in water. The Gd 2O 3 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.
8.	Ahrén, Maria, et al. (författare) One-step synthesis of sub 5 nm sized manganese oxide based nanoparticles 2013 Annan publikation (övrigt vetenskapligt/konstnärligt)abstract Sub 5 nm sized manganese oxide nanoparticles; MnOx (1 ≤ x ≤ 2), were synthesized via a short time room temperature synthesis route. The nanoparticles are crystalline, spherically shaped and in the size range of 2-4 nm as shown by transmission electron microscopy studies. Selected area electron diffraction patterns were collected and their appearance indicated that the nanoparticle cores are composed of MnO. Also, co-existence of the (II) and (III) oxidation states at the nanoparticle surface was verified by results achieved from infrared spectroscopy and X-ray photoelectron spectroscopy. These measurements also supported presence of a minor amount of acetate groups as well as a negligible fraction of carbonate groups at the nanoparticle surfaces. The interpretation of the IR spectra was confirmed by quantum chemical calculations using the high spin manganese nanoparticle Mn12O12(OAc)16(H2O)4, as a model system for the MnOx nanoparticle surface. Bulk MnO and Mn2O3 are known to be antiferromagnetic. The magnetic properties are however somewhat dependent of the crystallite size and changes when scaling down to the nanoregion. The MnOx (1 ≤ x ≤ 2) nanoparticles investigated in this work show a superparamagnetic behavior with a blocking temperature of approximately 12 K proven by means of SQUID measurements. The relaxivities of the nanoparticles and the Mn(OAc)2 precursors were studied with a bench top NMR analyzer verifying nanoparticle r1 and r2 of 0.5 and 6 mMs-1 respectively. The r1 relaxivity is lower than what is earlier reported for Gd based contrast agent, but improvements are expected by further surface modification, due to increased rotational time and higher water dispersability.
9.	Ahrén, Maria, 1979-, et al. (författare) Rare earth nanoparticles as contrast agent in MRI : Nanomaterial design and biofunctionalization 2007 Ingår i: IVC-17/ICSS-13 ICNT,2007. Konferensbidrag (övrigt vetenskapligt/konstnärligt)
10.	Ahrén, Maria, et al. (författare) Synthesis and Characterization of PEGylated Gd2O3 Nanoparticles for MRI Contrast Enhancement 2010 Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:8, s. 5753-5762 Tidskriftsartikel (refereegranskat)abstract Recently, much attention has been given to the development of biofunctionalized nanoparticles with magnetic properties for novel biomedical imaging. Guided, smart, targeting nanoparticulate magnetic resonance imaging (MRI) contrast agents inducing high MRI signal will be valuable tools for future tissue specific imaging and investigation of molecular and cellular events. In this study. We report a new design of functionalized ultrasmall rare earth based nanoparticles to be used as a positive contrast agent in NI RI. The relaxivity is compared to commercially available Gd based chelates. The synthesis, PEGylation, and dialysis of small (3-5 nm) gadolinium oxide (DEG-Gd2O3) nanoparticles are presented. The chemical and physical properties of the nanomaterial were investigated with Fourier transform infrared spectroscopy. X-ray photoelectron spectroscopy, transmission electron microscopy, and dynamic light scattering. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. The proton relaxation times as a function of dialysis time and functionalization were measured at 1.5 T. A capping procedure introducing stabilizing properties was designed and verified, and the dialysis effects were evaluated. A higher proton relaxivity was obtained for as-synthesized diethylene glycol (DEG)-Gd2O3 nanoparticles compared to commercial Gd-DTPA. A slight decrease of the relaxivity for as-synthesized DEG-Gd2O3 nanoparticles as a function of dialysis time was observed. The results for functionalized nanoparticles showed a considerable relaxivity increase for particles dialyzed extensively with r(1) and r(2) values approximately 4 times the corresponding values for Gd-DTPA. The microscopy study showed that PEGylated nanoparticles do not activate neutrophils in contrast to uncapped Gd2O3. Finally, the nanoparticles are equipped with Rhodamine to show that our PEGylated nanoparticles are available for further coupling chemistry, and thus prepared for targeting purposes. The long term goal is to design a powerful, directed contrast agent for MRI examinations with specific targeting possibilities and with properties inducing local contrast, that is. an extremely high MR signal at the cellular and molecular level.
11.	Amft, Martin, et al. (författare) A Molecular Mechanism for the Water-Hydroxyl Balance during Wetting of TiO2 2013 Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:33, s. 17078-17083 Tidskriftsartikel (refereegranskat)abstract We show that the formation of the wetting layer and the experimentally observed continuous shift of the H2O-OH balance toward molecular water at increasing coverage on a TiO2(110) surface can be rationalized on a molecular level. The mechanism is based on the initial formation of stable hydroxyl pairs, a repulsive interaction between these pairs, and an attractive interaction with respect to water molecules. The experimental data are obtained by synchrotron radiation photoelectron spectroscopy and interpreted with the aid of density functional theory calculations and Monte Carlo simulations.
12.	Andersson, Martin, et al. (författare) Anharmonic resonances in the C-H stretch region of ethoxy adsorbed on W(110): vibrational spectroscopy and calculations 2003 Ingår i: Surface Science. - 0039-6028. ; 532-535, s. 221-226 Tidskriftsartikel (refereegranskat)abstract We show that it is possible to understand and interpret the complex and rich C-H stretch region in the vibrational spectrum of ethoxy adsorbed on W(110) in terms of fundamental C-H stretch modes in Fermi resonance with C-H deformation overtones and combinations. The mode assignment is based on calculated C-13 isotopic shifts for an ethoxy-Cu-5 cluster. The coupling constants have been derived from calculated energy third derivatives of free ethanol and the coupling was implemented by an effective Hamiltonian matrix. The agreement with experiments is very good.
13.	Andersson, Martin, et al. (författare) Determination of the adsorption site of a polyatomic adsorbate using vibrational spectroscopy and ab initio calculations: methoxy on Cu(100) 2002 Ingår i: 7th International Conference on Nanometer-Scale Science and Technology and 21st European Conference on Surface Science. Konferensbidrag (refereegranskat)abstract Using vibrational spectroscopy and ab initio electronic structure calculations of small metal cluster models we have determined the adsorption site of methoxy on Cu(100). The experimental vibrational frequencies are very well reproduced by the model cluster representing the four-fold hollow adsorption site in contrast to calculated frequencies for model clusters representing bridge and on-top adsorption
14.	Andersson, Martin, et al. (författare) Fundamental, binary combination, and overtone modes in methoxy adsorbed on Cu(100): Infrared spectroscopy and ab initio calculations 2002 Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 106:20, s. 5200-5211 Tidskriftsartikel (refereegranskat)abstract Using surface infrared absorption spectroscopy, we have measured and assigned the vibrational spectra of six different methoxy isotopotners adsorbed on a Cu(100) surface in great detail. The assignments are based on ab initio calculations of the vibrational mode frequencies of all six isotopomers for a methoxy-Cu-5 complex. By combining different IR detectors and optical filters, we observe many, previously undetected, weak spectral features, which we can assign as various binary overtone and combination modes. On the basis of these binary modes conclusions on the intramolecular anharmonic coupling in the adsorbate can be drawn.
15.	Andersson, M P, et al. (författare) First-Principle Calculations of the Experimental Vibrational Spectrum of a Surface Adsorbate: Anharmonic Resonance Coupling between Fundamental and Binary Modes. 2003 Ingår i: Physical Review Letters. - 1079-7114. ; 90:7, s. 076103-076103 Tidskriftsartikel (refereegranskat)abstract By including relevant physical properties in our modeling of a surface adsorbate system we can, from first principles, correctly calculate all experimentally observed features in the vibrational spectrum of CH3CH2O– and CD3CH2O– adsorbed on Cu(100). That is, we reproduce the number of observed modes, the vibrational frequencies, and intensities of the modes including the presence/absence of binary overtone and combination modes. No scaling was performed. Our calculations show that the anharmonic terms of the potential energy surface of free ethanol are transferrable to the corresponding surface adsorbate, ethoxy, while the harmonic terms are not. ©2003 The American Physical Society
16.	Andersson, M P, et al. (författare) New scale factors for harmonic vibrational frequencies using the B3LYP density functional method with the triple-xi basis set 6-311+G(d,p) 2005 Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 109:12, s. 2937-2941 Tidskriftsartikel (refereegranskat)abstract We have calculated optimal frequency scaling factors for the B3LYP/ 6-311+G(d,p) method for fundamental vibrational frequencies on the basis of a set of 125 molecules. Using the new scaling factor, the vibrational frequencies calculated with the triple-zeta basis set 6-311+G(d,p) give significantly better accuracy than those calculated with the double-zeta 6-31G(d) basis set. Scale factors were also determined for low-frequency vibrations using the molecular set of 125 molecules and for zero-point energies using a smaller set of 40 molecules. We have studied the effect on the calculated vibrational frequencies for various combinations of diffuse and polarization functions added to the triple-zeta 6-311G basis set. The 6-311+G(d,p) basis set is found to give almost converged frequencies for most molecules, and we conclude that our optimum scaling factors are valid for the basis sets 6-311 G(d,p) to 6-311++G(3df,3pd). The new scale factors are 0.9679 for vibrational frequencies, 1.0100 for low-frequency vibrations, and 0.9877 for zero-point vibrational energies.
17.	Andersson, M P, et al. (författare) Surface-induced C–O bond anharmonicity of methoxy adsorbed on Cu(100): Experiments and density-functional theory calculations 2005 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 123:22, s. 1-224714 Tidskriftsartikel (refereegranskat)abstract The anharmonic properties of a surface intermediate, methoxy, adsorbed on Cu(100) are investigated by surface infrared overtone spectroscopy and density-functional-theory electronic structure calculations. The anharmonicity is measured in the zero-coverage limit, and it is observed that the anharmonicity is increased upon adsorption as compared with the free methanol. By combining experiments with calculations we demonstrate that modifications of the anharmonicity of the methoxy species is indeed induced by adsorption onto the copper surface and not by the formation of the methoxy species.
18.	Andersson, M P, et al. (författare) The adsorption site of methoxy and ethoxy on Cu(100) as determined by vibrational spectroscopy and first principle calculations 2004 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 549:1, s. 87-96 Tidskriftsartikel (refereegranskat)abstract In the present work we determine the adsorption site of two polyatomic molecules, methoxy and ethoxy, on Cu(100). This is accomplished by comparing experimental intramolecular vibrational modes to the corresponding modes calculated by first principle methods. We explore the three different high symmetry adsorption sites on top, bridge and hollow using several different metal clusters to represent the Cu(100) surface. The experimental results for both methoxy and ethoxy are best reproduced by the most realistic representation of the hollow position, a Cu-5 cluster. (C) 2003 Elsevier B.V. All rights reserved.
19.	Andersson, Martin, et al. (författare) The vibrational spectra of methyl groups in methylthiolate and methoxy adsorbed on Cu(100) 2002 Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 18:10, s. 3759-3762 Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract We show that the difference in the infrared vibrational spectrum of C-H stretch modes arising from the methyl group of two surface intermediates, methylthiolate and methoxy, originates from the difference in the methyl deformation modes frequencies of the two intermediates. Importantly, while the vibrational fingerprint of the two methyl groups are not transferable between the intermediates, the Fermi resonance coupling constants of the methyl group are.
20.	Björn, Lars Olof, et al. (författare) Ecological importance of the thermal emissivity of avian eggshells 2012 Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 1095-8541 .- 0022-5193. ; 301, s. 62-66 Tidskriftsartikel (refereegranskat)abstract Breeding birds have to divide their time between egg incubation and foraging. Particularly in cases when only one parent incubates the eggs, and especially in cold climates, the cooling of the eggs during absence from the nest may be problematic. In the present study we find that the thermal emissivity of eggshells may be ecologically important, and that an evolutionary pressure towards lower emissivity for exposed eggs in cold climates exists. We plan to experimentally compare emissivities among species in a future study. (C) 2012 Elsevier Ltd. All rights reserved.
21.	Blomquist, Jakob, et al. (författare) Inducing H/D Exchange in Ultrathin Ice Films by Proton Deficiency 2011 Ingår i: Physical Review Letters. - 1079-7114. ; 107:21 Tidskriftsartikel (refereegranskat)abstract We show that H/D exchange between H2O and D2O in ultrathin ice films adsorbed on Cu(100) does not occur through autoionization at temperatures below 140 K. The exchange is, however, facile if a proton deficiency is induced in the ice films by having small amounts of OH preadsorbed on the copper surface. The system was studied using surface infrared vibrational spectroscopy with the aid of density functional theory calculations.
22.	Blomquist, Jakob, et al. (författare) Surface adsorbate vibrations explored by infrared spectroscopy and DFT cluster calculations at the anharmonic level: CO on Cu(100). 2010 Ingår i: Physical chemistry chemical physics : PCCP. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 12, s. 14162-14168 Tidskriftsartikel (refereegranskat)abstract The vibrational properties of the CO/Cu(100) surface adsorbate system have been explored by infrared spectroscopy and DFT cluster calculations. We show that all four fundamental, FT(x,y), FR(x,y), FT(z) and ν(C-O), vibrational modes are very well reproduced with respect to experiments by the present calculations and they are at the highest level reported to date. Our work demonstrates that it is essential to include both anharmonicity and cluster relaxation when modeling the CO/Cu(100) system. The absence and presence of binary modes: 2 ×ν(C-O) and FT(z) + ν(C-O) in our experimental data are discussed as well.
23.	Blomquist, Jakob, et al. (författare) Water Dissociation on Single Crystalline Anatase TiO2(001) Studied by Photoelectron Spectroscopy 2008 Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:42, s. 16616-16621 Tidskriftsartikel (refereegranskat)abstract The adsorption of water on the anatase TiO2(001)-(4 x 1) surface is studied using synchrotron radiation-excited core level photoelectron spectroscopy. The coverage-dependent adsorption of water at low temperature is monitored and compared to the sequence obtained after heating of a water multilayer. Two adsorption phases of submonolayer coverage can be defined: Phase 1 consists only of dissociated water, observed as OH-groups. This phase is found at low coverage at low temperature (190 K) and is the only state of adsorbed water above similar to 230 K. The saturation coverage of phase 1 is consistent with dissociation on the 4-fold-coordinated Ti ridge atoms of the (4 x 1) surface reconstruction. Phase 2 is found at higher coverage, reached at lower temperature. It consists of a mixture of dissociated and molecular water with a ratio of 1:1 at 170 K. The molecular water is found to bond to the hydroxyl groups. The hydroxyl coverage of phase 2 is approximately 2 times that of phase 1. The results suggest that the OH and H2O species of phase 2 are confined to the ridges of the surface.
24.	Ceponkus, J, et al. (författare) Acceptor switching and axial rotation of the water dimer in matrices, observed by infrared spectroscopy. 2010 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 133:7 Tidskriftsartikel (refereegranskat)abstract Several isotopologues of the water dimer have been studied in different matrices (Ne, Ar, Kr, and p-H(2)) at very low temperatures. A fine structure, which is more or less matrix independent and very similar for different intramolecular fundamentals of the same isotopologic dimer, is present on the high wavenumber side of the main component. The bound OD (OH) stretches of the donor have temperature dependent components. The fine structure and temperature dependency is interpreted as evidence for acceptor switching and rotation of the water dimer around its O-O axis in the matrices studied here. The slow nuclear spin equilibration in H(2)O inhibits the thermal equilibration between the acceptor switching states in H(2)O-DOH and H(2)O-DOD. The condensed environment slows down the acceptor switching rate compared to the gas phase. The antisymmetric stretch of the proton acceptor is assigned by combining information from different matrices with the rotation-acceptor switching model.
25.	Ceponkus, J, et al. (författare) Complex Formation of Small Molecules during Isolation in Low Temperature Matrices: Water Dimers in p-H-2 and Ne Matrices 2010 Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 114:25, s. 6829-6831 Tidskriftsartikel (refereegranskat)abstract The concentrations of water dimer are compared in Ne and p-H-2 matrices at low temperatures, using infrared spectroscopy. Additional data are given for o-D-2 and Ar matrices. For a given monomer concentration, the dimer concentration is significantly higher in solid Ne (or Ar) than in solid p-H-2. In p-H-2, the dimer concentration is only slightly higher than expected for a random distribution of water in the matrix. The dimer concentration in o-D-2 matrices is intermediate between p-H-2 and noble gas matrices. This strongly suggests that most dimers form on the surface of the growing matrix, and not as the result of diffusion in the bulk of the matrix.
26.	Ceponkus, Justinas, et al. (författare) Far-Infrared Band Strengths in the Water Dimer: Experiments and Calculations. 2008 Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 112:17, s. 3921-3926 Tidskriftsartikel (refereegranskat)abstract Most fundamentals modes of the water dimer have been experimentally determined, and the frequencies have been measured in either neon or parahydrogen matrices. The band strengths of all intramolecular and most intermolecular fundamentals of the water dimer have been measured. The results are further corroborated by comparison with the corresponding data for the fully deuterated water dimer. DFT calculations of the mode frequencies and band strength are in qualitative agreement with the experimental observations.
27.	Ceponkus, J, et al. (författare) Intermolecular vibrations of different isotopologs of the water dimer: Experiments and density functional theory calculations. 2008 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 129:19 Tidskriftsartikel (refereegranskat)abstract Far infrared spectra of seven different isotopologs of the water dimer have been measured in neon matrices at 2.8 K. The experiments are interpreted with the aid of density functional theory calculations, in particular the calculated harmonic isotopic shifts were utilized. All six intermolecular vibrational modes of the water dimer and the fully deuterated water dimer are assigned based the isotopic shifts induced. 31 of a total of 42 intermolecular fundamental modes of the seven different H, D, and (18)O containing water dimers have been experimentally observed and assigned accordingly. The overall agreement between the calculations and the experiments of all isotopologs results in a complete and consistent description of these modes.
28.	Ceponkus, J, et al. (författare) Observations of Host Guest Interactions Specific to Molecular Matrices: Water Monomers and Dimers in Hydrogen Matrices. 2011 Ingår i: Journal of physical chemistry. A. - : American Chemical Society (ACS). - 1520-5215 .- 1089-5639. ; 115:27, s. 7921-7927 Tidskriftsartikel (refereegranskat)abstract Water monomers and dimers have been studied at low temperatures in matrices of solid p-H(2), o-D(2), n-H(2), and n-D(2) using infrared spectroscopy. Our data demonstrate interaction mechanisms between host matrix and guest molecules that are different from the ones observed in atomic noble gas matrices. Notably both guest/host rotational-rotational interaction and matrix induced modifications of the guest libration modes are observed. We also show that different types of interaction influence the relaxation times of some of guest modes. Water rotates freely in p-H(2) and o-D(2) but librates in n-H(2) and n-D(2). Rotational relaxation is faster in o-D(2) than in p-H(2) and faster in p-H(2) than in Ne. This is attributed to interactions between water rotation and matrix molecule rotation in p-H(2) and o-D(2). In n-H(2) and n-D(2), a strong water libration band is observed in the far-infrared, and strong water monomer vibration bands have libration satellites. Water dimer bands, close to matrix rotation bands, are perturbed by the matrix motions. The H-bonded isomer H(2)O-HOD rapidly converts to the D-bonded form H(2)O-DOH in p-H(2) and in o-D(2) but slowly in n-H(2) and n-D(2).
29.	Ceponkus, J, et al. (författare) On the structure of the matrix isolated water trimer. 2011 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 134:6 Tidskriftsartikel (refereegranskat)abstract Infrared spectra of partially deuterated water trimers have been investigated. It is found that HDO(H(2)O)(2) has a single, bound OD stretching fundamental, (HDO)(2)H(2)O two bound OD stretches. (HDO)(3) has a single, bound OD stretch and (H(2)O)(3) has a pair of bound OH stretches. Ab initio and discrete Fourier transform (DFT) calculations predict that the water trimer has C(1) symmetry with six different, isoenergetic minima. These calculations consequently give three numerically different OD stretches for HDO(H(2)O)(2), six for (HDO)(2)H(2)O, three for (HDO)(3), and three bound OH stretches for (H(2)O)(3). The connection between the observations and the pseudorotation of the trimer is discussed with the help of Wales' pseudorotation model. It is found that pseudorotation is sufficiently fast to average the effective symmetry of the A(3) trimer to C(3h) and to eliminate the difference between the different ab initio minima for A(2)B. The only exception is (H(2)O)(3) where the splitting between the different bound OH stretches is largest. Here a doublet is observed due to incomplete averaging. DFT calculations indicate that the D-bonded form of HDO(H(2)O)(2) is between 50 and 60 cm(-1) more stable than the H-bonded form. The energy difference is determined by differences in zero point vibration energy of intermolecular librations of the two forms. Attempts to measure the energy difference indicate that the energy difference is larger, of the order of 100 cm(-1).
30.	Ceponkus, J, et al. (författare) Rotation of Water in Solid Parahydrogen and Orthodeuterium. 2010 Ingår i: Journal of physical chemistry. A. - : American Chemical Society (ACS). - 1520-5215 .- 1089-5639. ; 114, s. 12979-12985 Tidskriftsartikel (refereegranskat)abstract The far-infrared spectra of solid orthodeuterium and solid normal deuterium are presented and compared to the corresponding spectra of solid parahydrogen and solid normal hydrogen. Spectra of water in orthodeuterium are compared to spectra of water in parahydrogen. The water rotation constants in orthodeuterium are approximately 80% of the rotation constants of water in parahydrogen. The S(0)(0) band of orthodeuterium gets a strong satellite in the presence of water. The position and width of the satellite depends on the isotopic composition of the water present. If there is a corresponding satellite in parahydrogen it is weak and closer to the S(0)(0) band of the matrix. The conclusion of the paper is that interaction between guest rotation and the rotation of matrix molecules must be taken into account to explain the reduction of the rotation constants in orthodeuterium.
31.	Ceponkus, J., et al. (författare) Structure and dynamics of small water clusters, trapped in inert matrices 2013 Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 581, s. 1-9 Tidskriftsartikel (refereegranskat)abstract Recent matrix isolation (p-H-2, Ne, Ar, Kr) studies of water clusters made in Lund are reviewed. Gas phase positions of water cluster bands are estimated from matrix data. Intermolecular spectra of several isotopomers of the water dimer have been obtained, and approximate band strengths have been measured. Acceptor switching of the water dimer has been observed in matrices. A few intermolecular vibrations of (H2O)(3), (D2O)(3), (H2O)(4), and (D2O)(4) have been measured. The pseudorotation of the water trimer is not quenched in matrices, and pentamer pseudorotation appears to be fast as well. Spectra of partially deuterated water tetramers support a rigid cyclic tetramer structure. The hydrogen rotation in p-H-2 may interfere with guest vibrations at frequencies near the J = 2 <- J = 0 band of solid parahydrogen. (C) 2013 Elsevier B.V. All rights reserved.
32.	Ceponkus, J., et al. (författare) The coupling between translation and rotation for monomeric water in noble gas matrices. 2013 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 138:24 Tidskriftsartikel (refereegranskat)abstract The rotation of water in noble gas matrices has been studied. It is shown that the rotation-translation coupling model of Friedmann and Kimel predicts rotation line spacings, which are close to the experimental observations for H2O, D2O, and HDO, when gas phase rotation constants are used. The model gives intensity estimates in reasonable agreement with the observations for the local oscillator bands, which accompany the rotation spectrum. It also predicts the intensity variations in the bending region of H2O between neon, argon, and krypton matrices.
33.	Ceponkus, J., et al. (författare) Water Tetramer, Pentamer, and Hexamer in Inert Matrices 2012 Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 116:20, s. 4842-4850 Tidskriftsartikel (refereegranskat)abstract The infrared spectrum of water, isolated in inert matrices, has been studied in the interval from 60 to 4000 cm(-1). Experiments with partially deuterated water combined with DFT (density functional theory) calculations have been used to investigate the structure of matrix-isolated water tetramer. A few, strong intermolecular fundamentals of the water tetramer have been observed. Mid-infrared bands due to deuterated pentamers and hexamers have been observed and are used to discuss the assignments of these water clusters.
34.	De La Garza, Randolph Glenn, et al. (författare) An ancestral hard-shelled sea turtle with a mosaic of soft skin and scutes 2022 Ingår i: Scientific Reports. - : Nature Research. - 2045-2322. ; 12:1 Tidskriftsartikel (refereegranskat)abstract The transition from terrestrial to marine environments by secondarily aquatic tetrapods necessitates a suite of adaptive changes associated with life in the sea, e.g., the scaleless skin in adult individuals of the extant leatherback turtle. A partial, yet exceptionally preserved hard-shelled (Pan-Cheloniidae) sea turtle with extensive soft-tissue remains, including epidermal scutes and a virtually complete flipper outline, was recently recovered from the Eocene Fur Formation of Denmark. Examination of the fossilized limb tissue revealed an originally soft, wrinkly skin devoid of scales, together with organic residues that contain remnant eumelanin pigment and inferred epidermal transformation products. Notably, this stem cheloniid—unlike its scaly living descendants—combined scaleless limbs with a bony carapace covered in scutes. Our findings show that the adaptive transition to neritic waters by the ancestral pan-chelonioids was more complex than hitherto appreciated, and included at least one evolutionary lineage with a mosaic of integumental features not seen in any living turtle. © 2022, The Author(s).
35.	Dorkhan, Marjan, et al. (författare) Crystalline anatase-rich titanium can reduce adherence of oral streptococci 2014 Ingår i: Biofouling (Print). - : Informa UK Limited. - 0892-7014 .- 1029-2454. ; 30:6, s. 751-759 Tidskriftsartikel (refereegranskat)abstract Dental implant abutments that emerge through the mucosa are rapidly covered with a salivary protein pellicle to which bacteria bind, initiating biofilm formation. In this study, adherence of early colonizing streptococci, Streptococcus gordonii, Streptococcus oralis, Streptococcus mitis and Streptococcus sanguinis to two saliva-coated anodically oxidized surfaces was compared with that on commercially pure titanium (CpTi). Near edge X-ray absorption (NEXAFS) showed crystalline anatase was more pronounced on the anodically oxidized surfaces than on the CpTi. As revealed by fluorescence microscopy, a four-species mixture, as well as individual bacterial species, exhibited lower adherence after 2 h to the saliva-coated, anatase-rich surfaces than to CpTi. Since wettability did not differ between the saliva-coated surfaces, differences in the concentration and/or configuration of salivary proteins on the anatase-rich surfaces may explain the reduced bacterial binding effect. Anatase-rich surfaces could thus contribute to reduced overall biofilm formation on dental implant abutments through diminished adherence of early colonizers.
36.	Engdahl, Anders, et al. (författare) Microspectroscopic infrared specular reflection studies of multi-component urinary stones at beamline D7 at the MAX IV laboratory, Lund Sweden 2015 Ingår i: IRMMW-THz 2015 - 40th International Conference on Infrared, Millimeter, and Terahertz Waves. - 9781479982721 Konferensbidrag (refereegranskat)abstract At the beamline D7 at the MAX III ring at the MAX IV laboratory we have a setup for infrared microspectroscopy which is usable from 30 to 10000 cm-1. In this project specular reflection infrared microspectroscopy was used for chemical imaging of cross-sectioned urinary stones. to determine their chemical composition and morphology simultaneously. Absorption spectral bands were recovered from reflection spectra by Kramers-Kronig transform. Use of far-infrared radiation provides high-contrast images and allows more precise constituent distribution determinations than mid-infrared because band asymmetry after the transform caused by diffuse reflection is less in the far-infrared.
37.	Engström, Maria, et al. (författare) High Proton Relaxivity for Gadolinium Oxide Nanoparticles 2006 Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer Science and Business Media LLC. - 0968-5243 .- 1352-8661. ; 19:4, s. 180-186 Tidskriftsartikel (refereegranskat)abstract 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.
38.	Eriksson, Peter, et al. (författare) Cerium Oxide Nanoparticles with Entrapped Gadolinium for High T-1 Relaxivity and ROS-Scavenging Purposes 2022 Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:24, s. 21337-21345 Tidskriftsartikel (refereegranskat)abstract Gadolinium chelates are employed worldwide today as clinical contrast agents for magnetic resonance imaging. Until now, the commonly used linear contrast agents based on the rare-earth element gadolinium have been considered safe and well-tolerated. Recently, concerns regarding this type of contrast agent have been reported, which is why there is an urgent need to develop the next generation of stable contrast agents with enhanced spin-lattice relaxation, as measured by improved T-1 relaxivity at lower doses. Here, we show that by the integration of gadolinium ions in cerium oxide nanoparticles, a stable crystalline 5 nm sized nanoparticulate system with a homogeneous gadolinium ion distribution is obtained. These cerium oxide nanoparticles with entrapped gadolinium deliver strong T-1 relaxivity per gadolinium ion (T-1 relaxivity, r(1) = 12.0 mM(-1) s(-1)) with the potential to act as scavengers of reactive oxygen species (ROS). The presence of Ce3+ sites and oxygen vacancies at the surface plays a critical role in providing the antioxidant properties. The characterization of radial distribution of Ce3+ and Ce4+ oxidation states indicated a higher concentration of Ce3+ at the nanoparticle surfaces. Additionally, we investigated the ROS-scavenging capabilities of pure gadolinium-containing cerium oxide nanoparticles by bioluminescent imaging in vivo, where inhibitory effects on ROS activity are shown.
39.	Fortin, Marc-André, et al. (författare) Polyethylene glycol-cover ultra-small Gd2O3 nanoparticles for positive contras at 1.5 T magnetic resonance clinical scanning 2007 Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:39, s. 395501- Tidskriftsartikel (refereegranskat)abstract 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.
40.	Fortin, Marc-Andre, 1976-, et al. (författare) Synthesis of gadolinium oxide nanoparticles as a contrast agent in MRI 2006 Ingår i: Trends in Nanotechnology,2006. Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
41.	Gazdzicki, Pawel, et al. (författare) Adsorption of intact methanol on Ru(0001) 2009 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 130:22 Tidskriftsartikel (refereegranskat)abstract Fourier transform infrared absorption spectroscopy has been used to study the adsorption of methanol on the clean Ru(0001) surface at T <= 80 K. Thereby, clear evidence for intact adsorption has been found. This observation contradicts previous studies which suggested an OH(OD) bond scission upon adsorption of methanol on Ru(0001), even at low temperatures, as well as partial recombinative desorption at higher T. Our conclusion is based on isotopic shifts of vibrational modes associated with the OH (OD) group of adsorbed CH3OH and CH3OD. Density functional theory (B3LYP) confirms these findings, as it reproduces the observed frequencies and isotopic shifts well. Additional support for our conclusion of nondissociative adsorption of methanol on Ru(0001) is provided by thermal desorption experiments of CH3OH coadsorbed with deuterium on Ru(0001). We find that CH3OD formation is clearly below detection threshold, while desorption of CH3OH is quite prominent; a recombinative desorption of dissociated methanol and hydrogen/deuterium as suggested in the literature is therefore discarded. At very low coverages and temperatures the presence of isolated methanol molecules or dimers is suggested. With increasing density or by annealing a low coverage methanol layer, hydrogen bonding leads to cluster formation, as evidenced by an intensity loss of those vibrational modes affected by hydrogen bonds, in conjunction with a substantial line broadening. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3151674]
42.	Gren, Johan, et al. (författare) Molecular and microstructural inventory of an isolated fossil bird feather from the Eocene Fur Formation of Denmark 2017 Ingår i: Palaeontology. - : Blackwell Publishing. - 0031-0239 .- 1475-4983. ; 60:1, s. 73-90 Tidskriftsartikel (refereegranskat)abstract An isolated, yet virtually intact contour feather (FUM-1980) from the lower Eocene Fur Formation of Denmark was analysed using multiple imaging and molecular techniques, including field emission gun scanning electron microscopy (FEG-SEM), X-ray absorption spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Additionally, synchrotron radiation X-ray tomographic microscopy (SRXTM) was employed in order to produce a digital reconstruction of the fossil. Under FEG-SEM, the proximal, plumulaceous part of the feather revealed masses of ovoid microstructures, about 1.7 μm long and 0.5 μm wide. Microbodies in the distal, pennaceous portion were substantially smaller (averaging 0.9 × 0.2 μm), highly elongate, and more densely packed. Generally, the microbodies in both the plumulaceous and pennaceous segments were aligned along the barbs and located within shallow depressions on the exposed surfaces. Biomarkers consistent with animal eumelanins were co-localized with the microstructures, to suggest that they represent remnant eumelanosomes (i.e. eumelanin-housing cellular organelles). Additionally, ToF-SIMS analysis revealed the presence of sulfur-containing organics – potentially indicative of pheomelanins – associated with eumelanin-like compounds. However, since there was no correlation between melanosome morphology and sulfur content, we conclude these molecular structures derive from diagenetically incorporated sulfur rather than pheomelanin. Melanosomes corresponding roughly in both size and morphology with those in the proximal part of FUM-1980 are known from contour feathers of extant parrots (Psittaciformes), an avian clade that has previously been reported from the Fur Formation.
43.	Henningsson, A, et al. (författare) Li insertion in thin film anatase TiO2: identification of a two-phase regime with photoelectron spectroscopy 2002 Ingår i: Chemical Physics Letters. - 0009-2614. ; 360:1-2, s. 85-90 Tidskriftsartikel (refereegranskat)abstract Li insertion into a thin anatase TiO2 film is studied for the first time in an ultra-high vacuum (UHV) environment. Using synchrotron radiation photoelectron spectroscopy, we demonstrate that the evaporated Li is inserted into the anatase and that the maximum amount that can be dissolved is 0.41 Li/Ti. Two most important properties are found in the UHV insertion process that can be directly related to electrochemical insertion: first, the Li 1s spectra suggest a two-phase regime and second, the insertion process is curtailed at the threshold for a phase transition that is not possible without the electrochemical driving force. (C) 2002 Elsevier Science B.V. All rights reserved.
44.	Jaworowski, A J, et al. (författare) Determination of NO adsorption sites on Pd(100) using core level photoemission and low energy electron diffraction 2002 Ingår i: Surface Science. - 0039-6028. ; 501:1-2, s. 74-82 Tidskriftsartikel (refereegranskat)abstract The adsorption of NO on Pd(1 0 0) is investigated with high resolution core level spectroscopy and low energy electron diffraction (LEED). Several ordered NO overlayers were observed, in agreement with earlier Studies. Our data clearly show that NO adsorbs in fourfold hollow sites at coverages tip to 0.25 -0.30 monolayer (ML) whereas at 0.5 ML only bridge sites are occupied. By a reinterpretation of previous electron energy loss spectroscopy (EELS) investigations we show that the new site assignments are in agreement the EELS data, Based on the photoemission results for the N 1s and the Pd 3d core levels we propose new structure models for the (2root2 x 2root2)R45degrees and the p(4 x 2) LEED patterns found at coverages of 0.5 and 0.25 ML, respectively. In the latter case, it is suggested that the p(4 x 2) LEED pattern is formed from domains having p(2 x 2)-NO and c(4 x 2)-2NO unit cells.
45.	Jaworowski, AJ, et al. (författare) Mn-induced NO dissociation on Pd(100) 2002 Ingår i: Surface Science. - 0039-6028. ; 501:1-2, s. 83-92 Tidskriftsartikel (refereegranskat)abstract The changes in the NO adsorption properties of Pd(1 0 0) due to the addition of Mn have been investigated using high resolution core level photoelectron spectroscopy. The Pd(1 0 0) surface was modified by forming a c(2 x 2)-PdMn surface alloy at two different Mn coverages, giving surfaces partly and fully alloyed, respectively, as shown by scanning tunneling microscopy. NO adsorption on the alloy films was found to destroy the c(2 x 2) structure. Dissociation of the NO molecules upon heating is observed, in stark contrast to NO on the clean Pd(1 0 0) surface from which all the molecules desorb intact upon heating. The dissociation process on the c(2 x 2)-PdMn-(1 x 1)-Pd mixed surface is completed at a significantly higher temperature than for the homogeneous c(2 x 2) surface. It is suggested that Mn atoms give rise to NO dissociation at lower temperatures. whereas Pd atoms situated at c(2 x 2)-(1 x 1) boundaries are responsible for the NO decomposition at higher temperatures.
46.	Kamal, Chinnathambi, et al. (författare) Core-Level Binding Energy Reveals Hydrogen Bonding Configurations of Water Adsorbed on TiO2 (110) Surface 2021 Ingår i: Physical Review Letters. - : American Physical Society (APS). - 0031-9007 .- 1079-7114. ; 126:1 Tidskriftsartikel (refereegranskat)abstract Using x-ray photoelectron spectroscopy of the oxygen 1s core level, the ratio between intact (D2O) and dissociated (OD) water in the hydrated stoichiometric TiO2 (110) surface is determined at varying coverage and temperature. In the submonolayer regime, both the D2O:OD ratio and the core-level binding energy of D2O (Delta BE) decrease with temperature. The observed variations in Delta BE are shown with density functional theory to be governed crucially and solely by the local hydrogen bonding environment, revealing a generally applicable classification and details about adsorption motifs.
47.	Karlsson, P G, et al. (författare) Interfacial properties of the nanostructured dye-sensitized solid heterojunction TiO2/RuL2(NCS)(2)/CuI 2004 Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 120:23, s. 11224-11232 Tidskriftsartikel (refereegranskat)abstract The interfaces of the nanostructured dye-sensitized solid heterojunction TiO2/Ru-dye/CuI have been studied using photoelectron spectroscopy of core and valence levels, x-ray absorption spectroscopy and atomic force microscopy. A nanostructured anatase TiO2 film sensitized with RuL2(NCS)(2) [cis-bis(4,4'-dicarboxy-2,2'-bipyridine)-bis(isothio-cyanato)-ruthenium(II)] was prepared in a controlled way using a novel combined in-situ and ex-situ (Ar atmosphere) method. Onto this film CuI was deposited in-situ. The formation of the dye-CuI interface and the changes brought upon the dye-TiO2 interface could be monitored in a stepwise fashion. A direct interaction between the dye NCS groups and the CuI is evident in the core level photoelectron spectra. Concerning the energy matching of the valence electronic levels, the photoelectron spectra indicate that the dye HOMO overlaps in energy with the Cu 3d-I 5p hydrid states. The CuI grow in the form of particles, which at the initial stages displace the dye molecules causing dye-TiO2 bond breaking. Consequently, the very efficient charge injection channel provided by the dye-TiO2 carboxylic bonding is directly affected for a substantial part of the dye molecules. This may be of importance for the functional properties of such a heterojunction. (C) 2004 American Institute of Physics.
48.	Karlsson, P. G., et al. (författare) Metal organic chemical vapor deposition of ultrathin ZrO2 films on Si(100) and Si(111) studied by electron spectroscopy 2007 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 601:4, s. 1008-1018 Tidskriftsartikel (refereegranskat)abstract The growth of ultrathin ZrO2 films on Si(100)-(2 x 1) and Si(111)-(7 x 7) has been studied with core level photoelectron spectroscopy and X-ray absorption spectroscopy. The films were deposited sequentially by chemical vapor deposition in ultra-high vacuum using zirconium tetra-tert-butoxide as precursor. Deposition of a > 50 angstrom thick film leads in both cases to tetragonal ZrO2 (t-ZrO2), whereas significant differences are found for thinner films. On Si(111)-(7 x 7) the local structure of t-ZrO2 is not observed until a film thickness of 51 angstrom is reached. On Si(100)-(2 x 1) the local geometric structure of t-ZrO2 is formed already at a film thickness of 11 angstrom. The higher tendency for the formation of t-ZrO2 on Si(100) is discussed in terms of Zr-O valence electron matching to the number of dangling bonds per surface Si atom, The Zr-O hybridization within the ZrO2 unit depends furthermore on the chemical composition of the surrounding. The precursor t-butoxy ligands undergo efficient C-O scission on Si(100), leaving carbonaceous fragments embedded in the interfacial layer. In contrast, after small deposits on Si(111) stable t-butoxy groups are found. These are consumed upon further deposition. Stable methyl and, possibly, also hydroxyl groups are found on both surfaces within a wide film thickness range. (c) 2006 Elsevier B.V. All rights reserved.
49.	Karlsson, P. G., et al. (författare) TiO2 chemical vapor deposition on Si(111) in ultrahigh vacuum: Transition from interfacial phase to crystalline phase in the reaction limited regime 2011 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 605:13-14, s. 1147-1156 Tidskriftsartikel (refereegranskat)abstract The interaction between the metal organic precursor molecule titanium(IV) isopropoxide (TTIP) and three different surfaces has been studied: Si(111)-(7 x 7), SiOx/Si(111) and TiO2. These surfaces represent the different surface compositions encountered during TTIP mediated TiO2 chemical vapor deposition on Si(111). The surface chemistry of the titanium(IV) isopropoxide precursor and the film growth have been explored by core level photoelectron spectroscopy and x-ray absorption spectroscopy using synchrotron radiation. The resulting film morphology has been imaged with scanning tunneling microscopy. The growth rate depends on both surface temperature and surface composition. The behavior can be rationalized in terms of the surface stability of isopropoxy and isopropyl groups, confirming that growth at 573 K is a reaction limited process. (C) 2011 Elsevier B.V. All rights reserved.
50.	Karlsson, P G, et al. (författare) UHV-MOCVD growth of TiO2 on SiOx/Si(111): Interfacial properties reflected in the Si 2p photoemission spectra 2005 Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 580:1-3, s. 207-217 Tidskriftsartikel (refereegranskat)abstract Metal-organic chemical vapour deposition growth of titanium oxide on moderately pre-oxidised Si(1 1 1) using the titanium(IV) isopropoxide precursor has been studied for two different growth modes, reaction-limited growth at 300 degrees C and flux-limited growth at 500 degrees C. The interfacial properties have been characterized by monitoring synchrotron radiation excited Si 2p photoemission spectra. The cross-linking from oxidised Si to bulk Si after TTIP exposure has been found to be very similar to that of SiOx/Si(1 1 1). However, the results show that the additional oxidation of Si most probably causes a corrugation of the SiOx/Si interface. Those conclusions are valid for both growth modes. A model is introduced in which the amorphous interface region is described as (TiO2)(x)(SiO2)(y) where x and y changes linearly and continuously over the interface. The model quantifies how (TiO2)(x)(SiO2)(y) mixing changes the relative intensities of the signals from silicon oxide and silicon. The method can be generalised and used for the analyses of other metal-oxides on silicon. (c) 2005 Elsevier B.V. All rights reserved.

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