| 1. |
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| 2. |
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| 3. |
- Bode, G.H., et al.
(author)
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Detection of peptide-based nanoparticles in blood plasma by ELISA
- 2015
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 10:5, s. Art. no. e0126136-
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Journal article (peer-reviewed)abstract
- Aims: The aim of the current study was to develop a method to detect peptide-linked nanoparticles in blood plasma. Materials & Methods: A convenient enzyme linked immunosorbent assay (ELISA) was developed for the detection of peptides functionalized with biotin and fluorescein groups. As a proof of principle, polymerized pentafluorophenyl methacrylate nanoparticles linked to biotin-carboxyfluorescein labeled peptides were intravenously injected in Wistar rats. Serial blood plasma samples were analyzed by ELISA and by liquid chromatography mass spectrometry (LC/MS) technology. Results: The ELISA based method for the detection of FITC labeled peptides had a detection limit of 1 ng/mL. We were able to accurately measure peptides bound to pentafluorophenyl meth-acrylate nanoparticles in blood plasma of rats, and similar results were obtained by LC/MS. Conclusions: We detected FITC-labeled peptides on pentafluorophenyl methacrylate nanoparticles after injection in vivo. This method can be extended to detect nanoparticles with different chemical compositions.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- CHAKAROV, DV, et al.
(author)
-
PHOTOSTIMULATED DESORPTION OF METAL ADATOMS - POTASSIUM ON GRAPHITE
- 1994
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In: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 311:3, s. L724-L730
-
Journal article (peer-reviewed)abstract
- Photodesorption is observed of single K atoms from a graphite surface covered with less than 1 monolayer of potassium. The desorption cross section has a threshold at homegaBAR almost-equal-to 3 eV and a maximum at homega(max)BAR almost-equal-to 4.9 eV. Polarization measurements indicate a substrate-mediated mechanism. The coverage dependence suggests that only the ionic 2D, K-phase is photoactive. The proposed mechanism includes attachment of hot electrons, photoexcited in the bulk, to the K4s adsorbate resonance of energy E(res). The band structure of graphite causes a narrow energy distribution of hot electrons, which yields homega(max)BAR almost-equal-to 2E(res).
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| 9. |
- Chakarov, D V, et al.
(author)
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Photos induced desorption and intercalation of potassium atoms deposited on graphite(0001)
- 1996
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In: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 106, s. 186-192
-
Journal article (peer-reviewed)abstract
- In addition to the photodesorption phenomenon previously observed for single K atoms from a graphite surface covered with a monolayer of potassium we present new results related to the photon stimulated interaction of potassium with graphite, which concerns alternative routes for energy relaxation of the photo excited K adatoms: photoinduced intercalation. The desorption yield has a threshold at h omega approximate to 3 eV and a maximum at h omega(max) approximate to 4.9 eV, Polarization measurements indicate a substrate-mediated mechanism. The coverage dependence suggests that only the ionic 2D, K-phase is photo active. The proposed mechanism includes attachment of photo-generated hot electrons to the K 4s adsorbate resonance of energy E(res). Assuming an analogous excitation process we discuss different mechanisms for the K photo intercalation and possible applications of the photon stimulated doping of carboneous materials at low temperature.
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| 10. |
- Gold, J, et al.
(author)
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Chemical characterization and reactivity of iron chelator-treated amphibole asbestos
- 1997
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In: ENVIRONMENTAL HEALTH PERSPECTIVES. - : US DEPT HEALTH HUMAN SERVICES PUBLIC HEALTH SERVICE. - 0091-6765. ; 105, s. 1021-1030
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Journal article (other academic/artistic)abstract
- Iron in amphibole asbestos is implicated in the pathogenicity of inhaled fibers. Evidence includes the observation that iron chelators can suppress fiber-induced tissue damage. This is believed to occur via the diminished production of fiber-associated re
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| 11. |
- Hellsing, B, et al.
(author)
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Photoinduced desorption of potassium atoms from a two dimensional overlayer on graphite
- 1997
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 106:3, s. 982-1002
-
Journal article (peer-reviewed)abstract
- We present an experimental and theoretical investigation of K atom desorption from the basal plane of graphite at 83 K induced by low energy photons (3-6 eV). The 2D potassium overlayer is characterized by low energy electron diffraction (LEED), high-resolution electron energy loss spectroscopy (HREELS), thermal desorption spectroscopy (TDS), and work function measurements. At monolayer coverage (5.2 x 10(14) atoms cm(-2)), the dependence of the cross section on photon energy has a threshold at (h) over bar omega approximate to 3.0 eV and rises up to a maximum of 1.8 +/- 0.4 x 10(-20) cm(2) at 4.8 eV. The coverage dependence of the photoyield reflects the existence of two phases of adsorbed K, dilute ionized photo-active and close-packed photo-neutral, respectively. The observed photodesorption is a single-photon, nonthermal event, consistent with a substrate-mediated mechanism. The desorption results from attachment of optically excited hot electrons to the empty 4s state of ionized potassium. The theory predicts in this case a Gaussian line shape of the photoyield vs photon energy. Fitting the model parameters to the experimental data, we determine (i) the energy and slope of the excited state potential energy curve, and (ii) the position and width of the potassium-induced 4s resonance. The present findings combined with other available data for potassium on graphite are used to construct 1D potential energy curves along the surface normal for K+ and K-0. The calculated cross sections for s- and p-polarized Light are in qualitative agreement with the measurements. (C) 1997 American Institute of Physics.
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| 12. |
- Hellsing, B, et al.
(author)
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Photoinduced desorption of potassium atoms from graphite
- 1996
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In: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 363:1-3, s. 247-251
-
Journal article (peer-reviewed)abstract
- We present an experimental and theoretical investigation of desorption of potassium atoms from the basal plane of graphite induced by photons with energies from 2 to 6 eV. The intensity of the photon flux employed in the measurements is low, and the observed photodesorption is a single-photon, non-thermal event. At monolayer coverage the photon-energy dependence of the cross section has a maximum at 4.8 eV. The experimental observations are interpreted in terms of a hot carrier mechanism, which involves attachment of optically excited substrate hot electrons to the empty 4s state of ionized potassium, and then desorption. The theory predicts a Gaussian line shape of the photoyield versus photon energy. Fitting the model parameters to the experimental data, we determine: (i) the potential energy for Gr + K+ and Gr + K-0; and (ii) the position (2.4 eV above the Fermi level) and width (0.15 eV) of the potassium 4s resonance, which is in good agreement with independent experimental observations.
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| 13. |
- Larsson Wexell, Cecilia, 1965, et al.
(author)
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Bone response to surface-modified titanium implants: studies on the early tissue response to machined and electropolished implants with different oxide thicknesses.
- 1996
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In: Biomaterials. - 0142-9612. ; 17:6, s. 605-16
-
Journal article (peer-reviewed)abstract
- The bone formation around titanium implants with varied surface properties is investigated. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits (1, 3 and 6 weeks). Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition, between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads at 6 weeks. The smooth, electropolished implants, irrespective of anodic oxidation, were surrounded by less bone than the machined implants after 1 week. After 6 weeks the bone volume as well as the bone-implant contact were lower for the merely electropolished implants than for the other three groups. Our study shows that a high degree of bone contact and bone formation are achieved with titanium implants which are modified with respect to oxide thickness and surface topography. However, the result with the smooth (electropolished) implants indicates that a reduction of surface roughness, in the initial phase, decreases the rate of bone formation in rabbit cortical bone.
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| 14. |
- Larsson Wexell, Cecilia, 1965, et al.
(author)
-
Bone response to surface modified titanium implants - studies on the tissue response after 1 year to machined and electropolished implants with different oxide thicknesses.
- 1997
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In: Journal of materials science. Materials in medicine. - 0957-4530. ; 8:12, s. 721-9
-
Journal article (peer-reviewed)abstract
- The bone formation around titanium implants with varied surface properties was investigated after 1 year in rabbits. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits. Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads. There were no significant differences between the differently prepared implant groups. Our study shows that a high degree of bone contact and bone formation is achieved after 1 year with titanium implants which are modified with respect to oxide thickness and surface topography. There is no indication that a reduction of surface roughness, which in the initial phase decreases the rate of bone formation, had any influence on the amount of bone after 1 year in rabbit cortical bone.
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| 15. |
- Olin, Håkan, et al.
(author)
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Scanning tunneling microscopy of oxidized titanium surfaces in air
- 1992
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In: Ultramicroscopy. - 0304-3991 .- 1879-2723. ; 42:Part A, s. 567-571
-
Journal article (peer-reviewed)abstract
- Using an STM in air, we have studied three different electropolished Ti surfaces. One sample was analyzed without further treatment. The second was thermally oxidized in air at 500-degrees-C. The third was exposed to an argon glow discharge and then oxidized in pure oxygen. The samples were characterized by Auger spectroscopy prior to STM measurements. Electropolished and thermally oxidized samples showed a granular structure, with a low corrugation between 2 and 10 nm. At a larger scale, the glow discharge treated sample showed a high corrugation approximately 100 nm.
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| 16. |
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| 17. |
- CHAKAROV, DV, et al.
(author)
-
INTERACTION OF WATER WITH POTASSIUM ON GRAPHITE - A HREELS STUDY
- 1993
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In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 64-5, s. 279-285
-
Journal article (peer-reviewed)abstract
- Water and coadsorbed water + potassium on the basal plane of graphite were studied with high resolution electron energy loss spectroscopy (HREELS) at 85 K and after stepwise annealing up to 500 K. Water adsorbs non-dissociatively on both clean and potassium precovered surface at 85 K. The vibration spectra, together with thermal desorption spectroscopy (TDS) reveal a series of reactions within the coadsorbed layer leading to the formation of KOH, KH, and KOx and volatile products. Eventually a precursor to CO2 formation, of yet unindentified composition and observed also in K + O-2 coadsorption studies on graphite, is observed at approximate to 27 meV.
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| 18. |
- CHAKAROV, DV, et al.
(author)
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WATER-ADSORPTION AND COADSORPTION WITH POTASSIUM ON GRAPHITE(0001)
- 1995
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 11:4, s. 1201-1214
-
Journal article (peer-reviewed)abstract
- Water and water coadsorbed with potassium on the basal plane of graphite were studied with thermal desorption spectroscopy (TDS) and high-resolution electron energy loss spectroscopy (HREELS) in the temperature range 85-900 K. Water alone adsorbs nondissociatively on the clean graphite surface at 85 K, forming hydrogen bonded aggregates. Its structure depends both on the coverage and on substrate temperature. With increasing coverage at 85 K(0.5-1.0 monolayer (ML)) the libration mode at similar to 86 meV shows a rapid upward shift, indicating a phase transition from a 2D to a 3D structure. The transition can also be induced by annealing the low coverage structure. Water coadsorption with potassium is nonreactive or reactive, depending on temperature and potassium coverage. The nonreactive coadsorption at T-s = 85 K occurs only below a critical potassium coverage of BK less than or equal to 0.3 ML. It is characterized by substantial symmetry changes of the adsorbed water molecules, compared to the pure water adsorption, and is attributed to formation of hydrated-ion species on the surface. The surface solvation number at the lowest K coverage is three to four H2O molecules per potassium atom. K and H2O react at submonolayer coverages at 120-160 K to form surface KOH, KH, KxOy, and volatile products. The surface species gradually transforms/decomposes at elevated temperatures (200-500 K) to first form potassium-oxygen complexes that then serve as precursors to graphite oxidation to CO2 at similar to 750 K.
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| 19. |
- CHAKAROV, DV, et al.
(author)
-
WATER-ADSORPTION ON GRAPHITE(0001)
- 1995
-
In: Vacuum. - 0042-207X .- 1879-2715. ; 46:8-10, s. 1109-1112
-
Journal article (peer-reviewed)abstract
- Wafer adsorption on the clean graphite (0001) surface has been studied by high-resolution electron-energy-loss spectroscopy (HREELS) and temperature-programmed desorption (TPD). At 85 K H2O adsorbs non-dissociatively forming hydrogen-bonded aggregates. The structure and the growth mode of water clusters depend on the substrate temperature and the coverage. At all coverages, above a few per cent of a monolayer (ML), the desorption is characterized by zero-order kinetics, while the HREEL spectra reveal a threshold coverage approximately 1 ML when the average co-ordination of the H2O molecules changes. Isothermal measurements of the desorption rate and HREELS measurements at elevated temperatures suggest an irreversible phase transition from amorphous to crystalline ice at approximately 135 K.
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| 20. |
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| 21. |
- Gabriel, B. L., et al.
(author)
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Site-specific adhesion of Staphylococcus epidermidis (RP12) in Ti-Al-V metal systems
- 1994
-
In: Biomaterials. - : Elsevier BV. - 0142-9612 .- 1878-5905. ; 15:8, s. 628-634
-
Journal article (peer-reviewed)abstract
- Staphylococcus epidermidis (RP12) adhesion patterns were studied on the following titanium (Ti)-aluminium (Al)-vanadium (V) metal systems: (i) microfabricated samples consisting of Ti, Al and V islands deposited onto Ti or V substrata, (ii) pure Ti, Al and V metals, and (iii) medical grade Ti6Al4-V alloy. All of these surfaces were covered with their respective oxides formed upon exposure of the metals to air. Quantitative analysis of the number of cells bound per unit area indicates that S. epidermidis (RP12) exhibits greatest adhesion to pure V surfaces. When exposed to surfaces having controlled spatial variations in chemical composition on the 10 mu m scale (microfabricated samples), the bacteria preferentially populate V islands versus Ti or Al substrata. In the case of the biphasic Ti6Al4V alloy, the bacteria tend to adhere to V-rich, mixed phase regions and phase boundaries. These findings demonstrate that enhanced and preferential adhesion of S. epidermidis (RP12) occurs on V surfaces in TI-Al-V metal systems and suggest that bacterial interactions are influenced by surface oxide composition.
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| 22. |
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| 23. |
- Hagglund, C, et al.
(author)
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In situ reactivity and FTIR study of the wet and dry photooxidation of propane on anatase TiO2
- 2005
-
In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 109:21, s. 10886-10895
-
Journal article (peer-reviewed)abstract
- The photocatalytic oxidation (PCO) of trace amounts of propane (500 ppm) on nanocrystalline anatase TiO2 has been investigated in situ as a function of temperature (T = 318-473 K), humidity (C-H2O = 0-4%), and time by means of mass spectrometry and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). Propane adsorbs associatively on TiO2 at 318 K in dry air, while at 473 K small amounts of thermal dissociation products appear on the surface. In agreement with previous studies, propane is found primarily to be converted to acetone by reactions with photogenerated oxygen radicals. Various successive reaction paths exist, where the branching depends on the temperature and hydroxylation state of the surface. Under dry conditions at 318 K, acetone oxidation is initially kinetically hindered, while, above 400 K, acetone readily decomposes. The thermally assisted reaction channel leads to detrimental bonding of surface species and inhibition of the catalytic activity. It is manifested by a coloration of the sample and suggested to be coupled to surface reduction. Under humidified conditions, there is an optimum of the PCO in C-H2O and T space, which is estimated to correspond to an equilibrium coverage of one monolayer of H2O (or bilayer). The latter reaction condition also corresponds to sustained high propane conversion and is characterized by rapid establishment of steady state rates. The optimum PCO is discussed in terms of a balance between (i) sustaining enough of a photoactive water monolayer to avoid detrimental bonding of surface species, (ii) allowing reactants to adsorb and access bulk TiO2 photoexcitations, and at the same time (iii) maximizing the thermally assisted decomposition of intermediates.
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| 24. |
- Heap, B., et al.
(author)
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Panel Discussion on Energy Efficiency
- 2010
-
In: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 39:SPEC. 1, s. 22-25
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Journal article (peer-reviewed)abstract
- The session on energy efficiency had no formal presentations and was organized as a panel discussion with four panelists. It was concluded that energy efficiency and saving measures on the short term is the most effective way to contribute to a sustainable energy system. Measures to improve and encourage energy efficiency should be implemented at all levels; municipal/local, national and super-national. Prices can be an effective instrument but need to be combined with systemic level measures. The transport sector was identified as the one with largest near future potential for increased energy efficiency. Agriculture and food is also an area with very large energy consumption and large potential for increased energy efficiency. The global population issue is yet another relevant, challenging and complex issue. It was noted that energy audits for end users in business and society increase awareness and insights into what they pay for, and they are likely to promote actions to save energy. Many measures are believed to suffer from Jevin's paradox, i.e., that more efficient use of energy just leads to more energy consumption somewhere else. Many examples were given, however, where this does not happen. Another point put forward was that measures to make the energy system more efficient do not only mean constraints and regulations but also create great opportunities for market actors and societies.
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| 25. |
- Hook, F.F, et al.
(author)
-
A comparative study of protein adsorption on titanium oxide surfaces using in situ ellipsometry, optical waveguide lightmode spectroscopy, and quartz crystal microbalance/dissipation
- 2002
-
In: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 24:2, s. 155-170
-
Journal article (peer-reviewed)abstract
- The adsorption kinetics of three model proteins - human serum albumin, fibrinogen and hemoglobin - has been measured and compared using three different experimental techniques: optical waveguide lightmode spectroscopy (OWLS), ellipsometry (ELM) and quartz crystal microbalance (QCM-D). The studies were complemented by also monitoring the corresponding antibody interactions with the pre-adsorbed protein layer. All measurements were performed with identically prepared titanium oxide coated substrates. All three techniques are suitable to follow in-situ kinetics of protein-surface and protein-antibody interactions, and provide quantitative values of the adsorbed adlayer mass. The results have, however, different physical contents. The optical techniques OWLS and ELM provide in most cases consistent and comparable results, which can be straightforwardly converted to adsorbed protein molar ('dry') mass. QCM-D, on the other hand, produces measured values that are generally higher in terms of mass. This, in turn, provides valuable, complementary information in two respects: (i) the mass calculated from the resonance frequency shift includes both protein mass and water that binds or hydrodynamically couples to the protein adlayer, and (ii) analysis of the energy dissipation in the adlayer and its magnitude in relation to the frequency shift (c.f. adsorbed mass) provides insight about the mechanical/structural properties such as viscoelasticity. © 2002 Elsevier Science B.V. All rights reserved.
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| 26. |
- Hook, F., et al.
(author)
-
Variations in coupled water, viscoelastic properties, and film thickness of a Mefp-1 protein film during adsorption and cross-linking: a quartz crystal microbalance with dissipation monitoring, ellipsometry, and surface plasmon resonance study
- 2001
-
In: Analytical Chemistry. - 0003-2700 .- 1520-6882. ; 73:24, s. 5796-804
-
Journal article (peer-reviewed)abstract
- We have measured the time-resolved adsorption kinetics of the mussel adhesive protein (Mefp-1) on a nonpolar, methyl-terminated (thiolated) gold surface, using three independent techniques: quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance, and ellipsometry. The QCM-D and ellipsometry data shows that, after adsorption to saturation of Mefp-1, cross-linking of the protein layer using NaIO4 transforms it from an extended (approximately 20 nm), water-rich, and hydrogel-like state to a much thinner (approximately 5 nm), compact, and less water-rich state. Furthermore, we show how quantitative data about the thickness, shear elastic modulus, and shear viscosity of the protein film can be obtained with the QCM-D technique, even beyond the Sauerbrey regime, if frequency (f) and energy dissipation (D) measurements measured at multiple harmonics are combined with theoretical simulations using a Voight-based viscoelastic model. The modeling result was confirmed by substituting H2O for D2O. As expected, the D2O substitution does not influence the actual adsorption behavior, but resulted in expected differences in the estimated effective density and shear viscosity. These results provide new insight and understanding about the adsorption kinetics and crosslinking behavior of Mefp-1. They also demonstrate how the above three techniques complement each other for biomolecule adsorption studies.
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| 27. |
- Johansson, S, et al.
(author)
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CO oxidation bistability diagrams for Pt/CeOx and Pt/SiO2 model catalysts prepared by electron-beam lithography
- 2001
-
In: Journal of Catalysis. - : Elsevier BV. - 0021-9517 .- 1090-2694. ; 201:2, s. 275-285
-
Journal article (peer-reviewed)abstract
- The CO oxidation bistability diagrams (i.e., the interval of gas mixing ratio beta drop P-CO/(P-CO + P-O2) vs temperature for which a bistability exists) have been determined for different electron beam lithography (EBL) fabricated supported model catalysts. Three different samples were studied, one Pt/SiO2 sample and two Pt/CeOx samples, where the support type, particle size, and interface length were varied independently. The kinetic bistability is an inherent property of the CO oxidation on Pt at certain gas mixtures and temperatures, and we find that the actual position of the bistable region is a very sensitive tool to measure differences in reaction kinetics on different samples. The bistable region is shifted considerably along the gas mixing ratio axis, beta, between the three samples (at constant temperature). Simulations show that the experimental results can be understood by introducing an oxygen reactant supply via the CeOx, support (spillover), which does not exist for SiO2. This extra supply of oxygen will maintain a high CO conversion rate up to higher relative CO partial pressures on ceria samples (by suppressing the CO poisoning effect). Energy barriers for O diffusion on CeOx, and the attachment across the Pt/CeOx interface have been estimated. The formation of a less reactive Pt state under oxidizing conditions is discussed. (C) 2001 Academic Press.
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| 28. |
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| 29. |
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| 30. |
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| 31. |
- Larsson Wexell, Cecilia, 1965, et al.
(author)
-
Bone response to surface modified titanium implants: studies on electropolished implants with different oxide thicknesses and morphology.
- 1994
-
In: Biomaterials. - 0142-9612. ; 15:13, s. 1062-74
-
Journal article (peer-reviewed)abstract
- In a series of experimental studies, bone formation was analysed around systematically modified titanium implants. In the present study, machined, electropolished and anodically oxidized implants were prepared, surface characterized and inserted in the cortical bone of rabbits (7 wks and 12 wks). SEM, scanning Auger electron spectroscopy and atomic force microscopy revealed no differences in surface composition but marked differences in oxide thickness, surface topography and roughness. Light microscopic morphology and morphometry showed that all implants were in contact with bone, and had a large proportion of bone within the threads. The smooth, electropolished implants were surrounded by less bone than the machined implants with similar oxide thickness, (4-5 nm) and the anodically oxidized implants with thicker oxides (21 nm and 180 nm, respectively) after 7 wks. These studies show that a high degree of bone contact and bone formation can be achieved with titanium implants which are modified with respect to oxide thickness and surface topography. However, it appears that a reduction of surface roughness may influence the rate of bone formation in rabbit cortical bone.
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Seidel, Y. E., et al.
(author)
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Stability of nanostructured Pt/glassy carbon electrodes prepared by colloidal lithography
- 2008
-
In: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 155:3, s. K50-K58
-
Journal article (peer-reviewed)abstract
- The stability of nanostructured Pt/glassy carbon (GC) model electrodes upon exposure to a realistic electrochemical/electrocatalytic reaction environment (continuous reaction, continuous electrolyte flow) was studied by microscopic techniques, X-ray photoelectron spectroscopy, and electrochemical measurements. The model electrodes consist of Pt nanostructures with well-defined sizes and regular spacing on planar GC substrates, and were fabricated using colloidal lithography techniques. Additional plasma treatments of the GC substrates prior to Pt deposition were tested to improve the stability of the resulting Pt/GC model electrodes. Both evaporation and sputter deposition were used for Pt-film fabrication. The model catalysts prepared by Pt evaporation were found to be rather unstable. The stability was significantly improved for sputter-deposited Pt films, and Pt sputter deposition on a GC substrate, pretreated first in oxygen plasma and then in Ar plasma, resulted in stable model electrodes with a fully intact layer of Pt nanostructures after the electrocatalytic experiments.
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| 36. |
- Thomsen, Peter, 1953, et al.
(author)
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Structure of the interface between rabbit cortical bone and implants of gold, zirconium and titanium.
- 1997
-
In: Journal of materials science. Materials in medicine. - 0957-4530. ; 8:11, s. 653-65
-
Journal article (peer-reviewed)abstract
- The role of surface properties (chemical and structural) for the interaction between biomaterials and tissue is not yet understood. In the present study, implants made of titanium, zirconium (transition metals with surface oxides) and gold (metallic surface) were inserted into the rabbit tibia. Light microscopic (LM) morphometry showed that after 1 and 6 mo the gold implants had less amount of bone within the threads and a lower degree of bone-implant contact than the titanium and zirconium implants, which did not differ from each other. These quantitative differences were supported by LM and ultrastructural observations of the interface. The ultrastructural observations in addition demonstrated that the layer of non-collagenous amorphous material located between the implant and the calcified bone was appreciably thicker around zirconium than around titanium implants. The factors potentially responsible for the observed morphological differences in the bone around the different material surfaces are discussed.
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| 37. |
- Werdinius, C, et al.
(author)
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Nanofabrication of planar model catalysts by colloidal lithography : Pt/ceria and Pt/alumina
- 2003
-
In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 19:2, s. 458-468
-
Journal article (peer-reviewed)abstract
- We present a novel method, called colloidal lithography, to prepare well-defined model catalysts on planar supports. The method facilitates fabrication of monodisperse catalyst particles with variable, well-defined size, shape, and interparticle distance. The chemical and structural composition of the constituents (i.e., catalyst particles and support materials) maybe independently varied. Large batches of model catalysts may be made in short processing times, with the dimensions of the samples only limited by the physical dimension of available support material, the processing vacuum systems, and so forth. Here we employed 2 in. Si wafers cut into 1 x 1 cm(2) pieces as the primary lithography support, onto which the support (ceria and alumina) and active catalyst materials (Pt in this case) were deposited. A detailed chemical and structural characterization is presented of the individual steps in the fabrication process. The oxygen plasma used to remove the colloidal mask residues is shown to lead to substantial but reversible Pt oxidation. As a probe reaction, to validate the nanofabrication process, CO oxidation measurements were performed on 130 nm Pt particles on an alumina or a ceria support. The reactivity measurements are in good agreement with literature data and suggest a satisfactory performance of the colloidal lithography model catalysts.
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| 38. |
- Österlund, Lars, 1967-, et al.
(author)
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Dissociative sticking of O-2 on Al(111)
- 1997
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In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 55:23, s. 15452-15455
-
Journal article (peer-reviewed)abstract
- The dissociative sticking probability, S-0, of O-2 on Al(111) has been measured as a function of incident translational and vibrational energy. S-0 rises from approximate to 10(-2) for energies approximate to 30 meV to near unity in the range 0.6-2.0 eV, demonstrating an activated dissociation event. Vibrational excitation enhances the sticking. Surface temperature has no effect on S-0. A peculiar dependence on polar angle is observed. The results are used to discuss possible mechanisms for the recent observation [H. Brune et al. Phys. Rev. Lett. 68, 624 (1992)] of widely separated O atoms after O-2 dissociation on Al(111).
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| 39. |
- Österlund, Lars, 1967-, et al.
(author)
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Lithographic Techniques in Nanocatalysis
- 2007
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In: NANOCATALYSIS. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540326458 ; , s. 269-341
-
Book chapter (peer-reviewed)
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| 40. |
- Österlund, Lars, 1967-, et al.
(author)
-
Potassium adsorption on graphite(0001)
- 1999
-
In: Surface Science. - 0039-6028 .- 1879-2758. ; 420:2-3, s. 174-189
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Journal article (peer-reviewed)abstract
- Potassium adsorption on graphite has been studied with emphasis on the two-dimensional K adlayer below one monolayer. Data are presented for the work function versus coverage, high-resolution electron energy loss spectroscopy (HREELS) vibrational spectra of K-adlayers, low energy electron diffraction and ultraviolet photoemission spectroscopy (UPS) spectra at different coverages. The data provide information regarding the vibrational properties of the K-adlayer, the metallization of the adlayer at submonolayer coverages, and the charge transfer from the It adatoms to the graphite substrate. Analysis of the work function, HREELS, and UPS data provides a qualitatively consistent picture of the charge state of the K adatoms, where at low coverages, below a critical coverage theta(c) (theta(c) = 0.2-0.3), the K adatoms are dispersed and (partially) ionized, whereas at theta > theta(c) islands of a metallic 2 x 2 K phase develop that coexist with the dispersed K adatoms up to theta = 1. We show that it is possible to understand the variation of the work function data based on a two-phase model without invoking a depolarization mechanism of adjacent dipoles, as is normally done for alkali-metal adsorption on metal surfaces. Similarly, the intensity variation as a function of coverage of the energy loss peak at 17 meV observed in HREELS, and the photoemission peak at E-b = 0.5 eV seen in UPS can be understood from a two-phase model. A tentative explanation is presented that connects apparent discrepancies in the literature concerning the electronic structure of the K adlayer. In particular, a new assignment of the K-induced states near the Fermi level is proposed. (C) 1999 Elsevier Science B.V. All rights reserved.
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- Österlund, Lars, 1967-, et al.
(author)
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Reactivity of Pt/ceria and Pt/alumina planar model catalysts prepared by colloidal lithography
- 2003
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In: Journal of Catalysis. - 0021-9517 .- 1090-2694. ; 215:1, s. 94-107
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Journal article (peer-reviewed)abstract
- We report on the structure, chemical state, and catalytic activity of nanofabricated, planar Pt/ceria and Pt/alumina model catalysts prepared by colloidal lithography. Employing extended etching times, catalyst particles are fabricated that are much smaller than the size of the polystyrene colloidal particle mask. Using CO oxidation as a probe reaction, the influence of various pretreatments has been studied. We find that the H-2/O-2 pretreatment deteriorates the reactivity on Pt/alumina, which is accompanied by blocking of the high-temperature CO adsorption sites as seen by TPD. After prolonged reactions the Pt/ceria particles show pronounced restructuring, indicating a low-temperature, reaction-induced, strong metal-support interaction, where ceria is decorating the Pt particles. In contrast, after an identical reaction history the Pt/alumina particles become facetted. The nanofabrication approach allows us to attribute the structural changes on individual particles to the integrated, macroscopic catalytic response. (C) 2003 Elsevier Science (USA). All rights reserved.
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