| 1. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 2. |
- Gustafsson, Håkan, et al.
(författare)
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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
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 115:13, s. 5469-5477
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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.
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| 3. |
- Gustafsson, Håkan, 1976-, et al.
(författare)
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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
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Ingår i: The Journal of Physical Chemistry C. - United States : American Chemical Society. - 1932-7447 .- 1932-7455. ; 115:13, s. 5469-5477
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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.
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| 4. |
- Ballem, Mohamed Ali, et al.
(författare)
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Growth of Gd2O3 nanoparticles inside mesoporous silica frameworks
- 2013
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Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 168, s. 221-224
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Tidskriftsartikel (refereegranskat)abstract
- Gadolinium oxide (Gd2O3) nanoparticles with very small size and narrow size distribution were synthesized by infiltration of Gd(NO3)(3)center dot 6H(2)O as an oxide precursor into the pores of SBA-15 mesoporous silica using a wet-impregnation technique. High resolution transmission electron microscopy and X-ray diffraction show that during the hydrothermal treatment of the precursor at 550 degrees C, gadolinium oxide nanoparticles inside the silica pores are formed. Subsequent dissolution of the silica framework in aqueous NaOH resulted in well dispersed nanoparticles with an average diameter of 3.6 +/- 0.9 nm. If GdCl3 center dot 6H(2)O is used as precursor, GdOCl is formed instead of Gd2O3. The Gd2O3 nanoparticles showed a weak antiferromagnetic behavior, as expected.
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| 5. |
- Lenz, Annika, et al.
(författare)
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ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:40, s. 17332-17341
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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.
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| 6. |
- Söderlind, Fredrik, et al.
(författare)
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Sol-gel synthesis and characterization of polycrystalline GdFeO3 and Gd3Fe5O12 thin films
- 2009
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Ingår i: Journal of Sol-Gel Science and Technology. - : Springer Science and Business Media LLC. - 0928-0707 .- 1573-4846. ; 49:2, s. 253-259
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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.
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| 7. |
- Ahrén, Maria, et al.
(författare)
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A simple polyol-free synthesis route to Gd 2O 3 nanoparticles for MRI applications : An experimental and theoretical study
- 2012
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Ingår i: Journal of nanoparticle research. - : Springer. - 1388-0764 .- 1572-896X. ; 14:8
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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.
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| 8. |
- Ahrén, Maria, et al.
(författare)
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One-step synthesis of sub 5 nm sized manganese oxide based nanoparticles
- 2013
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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.
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| 9. |
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| 10. |
- Ahrén, Maria, et al.
(författare)
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Synthesis and Characterization of PEGylated Gd2O3 Nanoparticles for MRI Contrast Enhancement
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:8, s. 5753-5762
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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.
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| 11. |
- Becker, Richard, et al.
(författare)
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Synthesis of silver nanowires in aqueous solutions
- 2010
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Ingår i: Materials letters (General ed.). - : Elsevier BV. - 0167-577X .- 1873-4979. ; 64:8, s. 956-958
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Tidskriftsartikel (refereegranskat)abstract
- Silver nanowires with a diameter of 30 nm and typical lengths of 5–10 μm have been synthesized in an aqueous medium. To initiate the reaction, citrate ions were used, and during the reaction the aromatic organicmolecules polymerize forming “straight” chain surfactants which support the formation of nanowires. Characterization by TEM and HRETM revealed the nanowires to be highly crystalline with a growth along the [110] direction.
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| 12. |
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| 13. |
- Buchholt, Kristina, 1978-, et al.
(författare)
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Electrochemically Synthesised Pd- and Au-nanoparticles as sensing layers in NOx-sensitive field effect devices
- 2008
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Ingår i: Smart Sensors and Sensing Technology. - Berlin, Heidelberg : Springer. - 9783540795896 - 9783540795902 ; , s. 63-75
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An environmental pollutant of great concern is NOx (nitrogen monoxide and nitrogen dioxide). Here we report the utilisation of electrochemically synthesised gold and palladium nanoparticles as catalytically active gate material on gas sensitive field effect sensor devices. The synthesised nanoparticles have been characterised by TEM and XPS, and the morphology of the thermally treated nanostructured sensing layers has been investigated using SEM and XPS. Measurements on the gas response of the palladium as well as the gold nanoparticle sensors towards a number of analytes found in automotive gas exhausts were performed and their response patterns were compared. The initial gas response measurements show interesting sensing properties for both the gold and the palladium nanoparticle sensors towards NOx detection.
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| 14. |
- Claisse, Antoine, 1988-
(författare)
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Multiscale modeling of nitride fuels
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nitride fuels have always been considered a good candidate for GENIV reactors, as well as space reactors, due to their high fissile density, highthermal conductivity and high melting point. In these concepts, not beingcompatible with water is not a significant problem. However, in recent years,nitride fuels started to raise an interest for application in thermal reactors,as accident tolerant or high performance fuels. However, oxide fuels havebenefited from decades of intensive research, and thousands of reactor-years.As such, a large effort has to be made on qualifying the fuel and developingtools to help assess their performances.In this thesis, the modeling side of this task is chosen. The effort istwo-fold: determining fundamental properties using atomistic models andputting together all the properties to predict the performances under irradi-ation using a fuel performance code. The first part is done combining manyframeworks. The density functional theory is the basis to compute the elec-tronic structure of the materials, to which a Hubbard correction is added tohandle the strong correlation effects. Negative side effects of the Hubbardcorrection are tackled using the so-called occupation matrix control method.This combined framework is first tested, and then used to find electronic andmechanic properties of the bulk material as well as the thermomechanicalbehavior of foreign atoms. Then, another method, the self-consistent meanfield (SCMF) one, is used to reach the dynamics properties of these foreignatoms. In the SCMF theory, the data that were obtained performing the abinitio simulations are treated to provide diffusion and kinetic flux couplingproperties.In the second step of the work, the fuel performance code TRANSURA-NUS is used to model complete fuel pins. An athermal fission gas releasemodel based on the open porosity is developed and tested on oxide fuels.A model for nitride fuels is introduced, and some correlations are bench-marked. Major issues remaining are pointed out and recommendations asto how to solve them are made.
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| 15. |
- Eriksson, Jens, et al.
(författare)
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ZnO nanoparticles or ZnO films : A comparison of the gas sensing capabilities
- 2009
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 137:1, s. 94-102
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Tidskriftsartikel (refereegranskat)abstract
- Zinc oxide is an interesting material for bio and chemical sensors. it is a semiconducting metal oxide with potential as an integrated multisensing sensor platform, which simultaneously detects Parameters like change in field effect, mass and Surface resistivity. in this investigation we have used resistive sensor measurements regarding the oxygen gas sensitivity in order to characterize sensing layers based on electrochemically produced ZnO nanoparticles and PE-MOCVD grown ZnO films. Proper annealing procedures were developed in order to get stable sensing properties and the oxygen sensitivity towards operation temperature was investigated. The ZnO nanoparticles showed a considerably increased response to oxygen as compared to the films. Preliminary investigations were also performed regarding the selectivity to other gases present in car exhausts or flue gases.
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| 16. |
- Fortin, Marc-André, et al.
(författare)
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Polyethylene glycol-cover ultra-small Gd2O3 nanoparticles for positive contras at 1.5 T magnetic resonance clinical scanning
- 2007
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 18:39, s. 395501-
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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.
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| 17. |
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| 18. |
- Göransson, Kristina, et al.
(författare)
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An experimental study on catalytic bed materials in a biomass dual fluidised bed gasifier
- 2015
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Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 81, s. 251-261
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Tidskriftsartikel (refereegranskat)abstract
- A study on in-bed material catalytic reforming of tar/CH4 has been performed in the 150 kW allothermal gasifier at Mid Sweden University (MIUN). The major challenge in biomass fluidised-bed gasification to produce high-quality syngas, is the reforming of tars and CH4. The MIUN gasifier has a unique design suitable for in-bed tar/CH4 catalytic reforming and continuously internal regeneration of the reactive bed material. This paper evaluates the catalytic effects of olivine and Fe-impregnated olivine (10%wtFe/olivine Catalyst) with reference to silica sand in the MIUN dual fluidised bed (DFB) gasifier. Furthermore, a comparative experimental test is carried out with the same operation condition and bed-materials when the gasifier is operated in the mode of single bubbling fluidised bed (BFB), in order to detect the internal regeneration of the catalytic bed materials in the DFB operation. The behaviour of catalytic and non-catalytic bed materials differs when they are used in the DFB and the BFB. Fe/olivine and olivine in the BFB mode give lower tar and CH4 content together with higher H-2 + CO concentration, and higher H-2/CO ratio, compared to DFB mode. It is hard to show a clear advantage of Fe/olivine over olivine regarding tar/CH4 catalytic reforming. (C) 2015 Elsevier Ltd. All rights reserved.
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| 19. |
- Göransson, Kristina, et al.
(författare)
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Internal tar/CH4 reforming in a biomass dual fluidised bed gasifier
- 2014
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Ingår i: Proceeding of 4th International Symposium on Gasification and its Applications.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An internal reformer is developed for in-situ catalytic reforming of tar and methane (CH4) in allothermal gasifiers. The study has been performed in the 150 kW dual fluidised bed (DFB) biomass gasifier at Mid Sweden University (MIUN). The MIUN gasifier is built for research on synthetic fuel production. Reduction of tars and CH4 (except for methanation application) in the syngas is a major challenge for commercialization of biomass fluidised-bed gasification technology towards automotive fuel production. The MIUN gasifier has a unique design with an internal reformer, where intensive contact of gas and catalytic solids improves the reforming reactions. This paper presents a study on the internal reformer operated with and without Ni-catalytic pellets, by evaluation of the syngas composition and tar/CH4 content. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases down to 5 g/m3 and the CH4 content down below 6% in the syngas. The novel design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas quality
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| 20. |
- Göransson, Kristina, et al.
(författare)
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Internal tar/CH4 reforming in a biomass dual fluidised bed gasifier.
- 2015
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Ingår i: Biomass Conversion and Biorefinery. - : Springer Science and Business Media LLC. - 2190-6815 .- 2190-6823. ; 5, s. 355-366
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Tidskriftsartikel (refereegranskat)abstract
- An internal reformer is developed for in situ catalyticreforming of tar and methane (CH4) in allothermal gasifiers.The study has been performed in the 150 kW dual fluidised bed (DFB) biomass gasifier at Mid Sweden University(MIUN). The MIUN gasifier is built for research onsynthetic fuel production. Reduction of tars and CH4 (exceptfor methanation application) in the syngas is a major challengefor commercialization of biomass fluidised-bed gasificationtechnology towards automotive fuel production. The MIUN gasifier has a unique design with an internal reformer, where intensive contact of gas and catalytic solids improves the reforming reactions. This paper presents an initial study on the internal reformer operated with and without Ni-catalytic pellets, by evaluation of the syngas composition and tar/CH4 content. A novel application of Ni-catalyst in DFB gasifiers is proposed and studied in this work. It can be concluded that the reformer with Ni-catalytic pellets clearly gives a higher H2 content together with lower CH4 and tar contents in the syngas than the reformer without Ni-catalytic pellets. The gravimetric tar content decreases down to 5 g/m3 and the CH4 content down below 6 % in the syngas. The tar content can be decreased further to lower levels, with increased gas contact to the specific surface area of the catalyst and increased catalyst surface-to-volume ratio. The new design in the MIUN gasifier increases the gasification efficiency, suppresses the tar generation and upgrades the syngas quality.
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| 21. |
- Khan, Yaqoob, et al.
(författare)
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Honeycomb β-Ni(OH)2 films grown on 3D nickel foam substrates at low temperature
- 2012
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Ingår i: Materials letters (General ed.). - : Elsevier BV. - 0167-577X .- 1873-4979. ; 69, s. 37-40
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Tidskriftsartikel (refereegranskat)abstract
- A simple method is presented to grow thick honeycomb β-Ni(OH)2 films on 3D nickel foam substrates at80 °C using nickel sulfate and ammonia as the starting materials. The porous honeycomb network structureof the films with pore openings about 0.5–1 μm wide is built from seamlessly connected polycrystallinenanowalls, approximately 10–20 nm thick. The amount of ammonia added to the growth solution and thegrowth time were found to be critical parameters in determining the morphology and pore structure ofthe films. Air annealing of the as-prepared films resulted in polycrystalline NiO films with morphologiessimilar to those of their hydroxide precursors.
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| 22. |
- Khan, Yagoob, et al.
(författare)
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On the decoration of 3D nickel foam with single crystal ZnO nanorod arrays and their cathodoluminescence study
- 2013
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Ingår i: Materials letters (General ed.). - : Elsevier. - 0167-577X .- 1873-4979. ; 90, s. 126-130
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Tidskriftsartikel (refereegranskat)abstract
- Starting with an ammonical solution of zinc acetate, dense single crystal ZnO nanorod arrays were grown directly on high surface area porous 3D nickel foam substrates using a low temperature hydrothermal route. Heterogeneous nucleation of the nanorods with diameters around 100 nm can be conveniently and reproducibly Controlled by adjusting the amount of ammonia added to the growth solution. X-ray diffraction and HRTEM analysis confirmed the single phase wurtzite structure and c-axis orientation of the as grown ZnO nanorod arrays. Cathodoluminescence measurements indicate that the as-grown nanorod arrays were rich in atomic defects and gave strong orange emissions in the visible region. The nanorod arrays on unique 3D substrate are expected to improve the sensitivity and efficiency of ZnO based electrochemical sensors and heterogeneous catalysts.
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| 23. |
- Klasson, Anna, et al.
(författare)
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Positive MRI Enhancement in THP-1 Cells with Gd2O3 Nanoparticles
- 2008
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Ingår i: Contrast Media and Molecular Imaging. - : Wiley. - 1555-4309 .- 1555-4317. ; 3:3, s. 106-111
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Tidskriftsartikel (refereegranskat)abstract
- There is a demand for more efficient and tissue-specific MRI contrast agents and recent developments involve the design of substances useful as molecular markers and magnetic tracers. In this study, nanoparticles of gadolinium oxide (Gd2O3) have been investigated for cell labeling and capacity to generate a positive contrast. THP-1, a monocytic cell line that is phagocytic, was used and results were compared with relaxivity of particles in cell culture medium (RPMI 1640). The results showed that Gd2O3-labeled cells have shorter T1 and T2 relaxation times compared with untreated cells. A prominent difference in signal intensity was observed, indicating that Gd2O3 nanoparticles can be used as a positive contrast agent for cell labeling. The r1 for cell samples was 4.1 and 3.6 s-1 mm-1 for cell culture medium. The r2 was 17.4 and 12.9 s-1 mm-1, respectively. For r1, there was no significant difference in relaxivity between particles in cells compared to particles in cell culture medium, (pr1 = 0.36), but r2 was significantly different for the two different series (pr2 = 0.02). Viability results indicate that THP-1 cells endure treatment with Gd2O3 nanoparticles for an extended period of time and it is therefore concluded that results in this study are based on viable cells.
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| 24. |
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| 25. |
- Käll, Per-Olov, et al.
(författare)
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Synthesis, structure determination and X-ray photoelectron spectroscopy characterisation of a novel polymeric silver(I) nicotinic acid complex, H[Ag(py-3-CO2)2]
- 2001
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Ingår i: Polyhedron. - 0277-5387 .- 1873-3719. ; 20:21, s. 2747-2753
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Tidskriftsartikel (refereegranskat)abstract
- Polymeric inorganic or organometallic coordination compounds represent an interesting class of materials where novel (combinations of) electrical, optical, magnetic, catalytic, or other properties are expected to occur. It has recently been shown that Ag1 complexes formed by organic N,N'-bidentate type ligands exhibit a rich structural variety encompassing ID, 2D and 3D polymers. Previous investigations of the silver(I) nicotinic acid system have revealed two different structural types, in both of which Ag1 is three-coordinated. We have investigated the system nicotinic acid (C6H5NO2/AgA in water (A = NO3-, CH3COO- and F-). In all the cases the same product precipitated, catena-{hydrogen bis[pyridine-3-carboxylato-(N,N')]silver(I)}, H[Ag(py-3-CO2)2] (M = 353.1 g mol-1). The structure can be described as a 1D polymer consisting of [Ag(C6H4NO2)2]- monomers linked via C21(12)[R21(4)] hydrogen bonds, where the connecting H+ ion is located at the same distance (1.24 Å) to the carboxyl oxygens of consecutive monomers. The measured X-ray photoelectron spectrum shows an excellent agreement with the proposed structure. FTIR measurements of the complex were also performed. © 2001 Elsevier Science Ltd. All rights reserved.
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| 26. |
- Landa, A., et al.
(författare)
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Ab initio study of advanced metallic nuclear fuels for fast breeder reactors
- 2012
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Ingår i: Actinides And Nuclear Energy Materials. - : Materials Research Society. - 9781605114217 ; , s. 67-78
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Konferensbidrag (refereegranskat)abstract
- Density-functional formalism is applied to study the ground state properties of γ-U-Zr and γ-U-Mo solid solutions. Calculated heats of formation are compared with CALPHAD assessments. We discuss how the heat of formation in both alloys correlates with the charge transfer between the alloy components. The decomposition curves for γ-based U-Zr and U-Mo solid solutions are derived from Ising-type Monte Carlo simulations. We explore the idea of stabilization of the γ-UZr2 compound against the α-Zr (hcp) structure due to increase of Zr d-band occupancy by the addition of U to Zr. We discuss how the specific behavior of the electronic density of states in the vicinity of the Fermi level promotes the stabilization of the U2Mo compound. The mechanism of possible Am redistribution in the U-Zr and U-Mo fuels is also discussed.
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| 27. |
- Landa, Alex, et al.
(författare)
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Density-functional calculations of alpha-Pu-Ga(Al) alloys
- 2007
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 444, s. 296-299
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Tidskriftsartikel (refereegranskat)abstract
- First-principles methods are employed to study the ground-state atomic volumes of alpha-Pu-Ga(Al) alloys. It is shown that a random distribution of Ga(Al) atoms in the monoclinic lattice of alpha-Pu results in a maximum expansion of this lattice and creation of the so-called alpha'-Pu phase. Any kind of ordering of Ga(Al) atoms on the monoclinic lattice results in a shrinking of the lattice constant while the ordered alpha(8)-(Pu-Ga(Al)) configuration yields the smallest lattice constant which is very close to that of pure alpha-Pu. In addition, energetics of the ordered (unrelaxed and relaxed) and disordered configurations is discussed.
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| 28. |
- Lloyd Spetz, Anita, et al.
(författare)
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New transducer material concepts for biosensors and surface functionalization
- 2009
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Ingår i: Smart Sensors, Actuators,and MEMS IV. - Bellingham, WA United States : SPIE - International Society for Optical Engineering. - 9780819476364 ; , s. 736206-
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Konferensbidrag (refereegranskat)abstract
- Wide bandgap materials like SiC, ZnO, AlN form a strong platform as transducers for biosensors realized as e.g. ISFET (ion selective field effect transistor) devices or resonators. We have taken two main steps towards a multifunctional biosensor transducer. First we have successfully functionalized ZnO and SiC surfaces with e.g. APTES. For example ZnO is interesting since it may be functionalized with biomolecules without any oxidation of the surface and several sensing principles are possible. Second, ISFET devises with a porous metal gate as a semi-reference electrode are being developed. Nitric oxide, NO, is a gas which participates in the metabolism. Resistivity changes in Ga doped ZnO was demonstrated as promising for NO sensing also in humid atmosphere, in order to simulate breath.
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| 29. |
- Nordström, Lars, et al.
(författare)
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Spin-orbit coupling in the actinide elements : A critical evaluation of theoretical equilibrium volumes
- 2001
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 63:3, s. 035103-
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Tidskriftsartikel (refereegranskat)abstract
- The difficulty of converging the contribution of the spin-orbit interaction to the total energy within an ls basis in actinide electronic structure calculations is discussed in detail. In particular, it is demonstrated that the source of the poor convergence is the treatment of the actinide 6p states. The limitation of the standard approach to relativity in full potential methods is manifested in muffin-tin based methods by a dependence of the total energy on the choice of muffin-tin radius. Despite this limitation it is found that structural phase stabilities are not affected, nor are pressure induced phase transitions. In order to treat the relativistic spin-orbit coupling in as large a part of space as possible one should, in muffin-tin based calculations, use a radius that is touching, or near touching, for all calculated volumes.
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| 30. |
- Pearce, Ruth, et al.
(författare)
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Effect of Water vapour on Gallium doped Zinc Oxide nanoparticle sensor gas response
- 2009
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Ingår i: IEEE Sensors, 2009. - Piscataway, NJ, United States : IEEE. - 9781424445486 - 9781424453351 ; , s. 2039-2043
-
Konferensbidrag (refereegranskat)abstract
- Zinc oxide is a wide band gap (similar to 3.4ev) semiconductor material, making it a promising material for high temperature applications, such as exhaust and flue environments where NO and NO2 monitoring is increasingly required due to stricter emission controls[1]. In these environments water vapour and background levels of oxygen are present and, as such, the effect of humidity on the sensing characteristics of these materials requires further study. The reaction mechanisms in the presence of water vapour are poorly understood and there is a need for deeper understanding of the principles and mechanisms of gas response of these materials. An investigation of the influence of changing water vapour (H2O) and oxygen (O-2) backgrounds on the response of nanoparticulate Ga-doped ZnO resistive sensors is presented.
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| 31. |
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| 32. |
- Pedersen, Henrik, et al.
(författare)
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Surface interactions between Y2O3 nanocrystals and organic molecules—an experimental and quantum-chemical study
- 2005
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 592:1-3, s. 124-140
-
Tidskriftsartikel (refereegranskat)abstract
- The surface interactions between Y2O3 nanocrystals and the organic molecules formic acid, diethylene glycol (DEG), and tetramethoxy silane (TMOS), have been studied experimentally and by quantum chemical calculations with the intent to elucidate the chemisorption characteristics such as adsorbate vibrational spectra and adsorption structures. Nanocrystal synthesis was performed by a colloidal method based on polyols and by a rapid combustion method. The products were experimentally characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS).In the quantum chemical calculations, the B3LYP hybrid density functional ab initio method was used to study the chemisorption of formic acid, DEG and TMOS at the surface of Y12O18 clusters. From a comparison of calculated and experimental vibrational spectra, the binding mode for formic acid on Y2O3 was inferred to be of bridge or bidentate type. The XPS and FT-IR experiments showed that DEG is chemisorbed on the particle surface. The experimental IR spectra of DEG chemisorbed on Y2O3 were consistent with an adsorption mode where the hydroxyl groups are deprotonated according to the quantum-chemical computations. The adsorption energy is of the order of 370 kJ mol−1 for formic acid, 550 kJ mol−1 for DEG, and 60 kJ mol−1 for TMOS, according to the quantum chemical calculations.
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| 33. |
- Petoral, Rodrigo M, et al.
(författare)
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Synthesis and Characterization of Tb3+-Doped Gd2O3 Nanocrystals : A Bifunctional Material with Combined Fluorescent Labeling and MRI Contrast Agent Properties
- 2009
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 113:17, s. 6913-6920
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrasmall gadolinium oxide nanoparticles doped with terbium ions were synthesized by the polyol route and characterized as a potentially bifunctional material with both fluorescent and magnetic contrast agent properties. The structural, optical, and magnetic properties of the organic-acid-capped and PEGylated Gd2O3:Tb3+ nanocrystals were studied by HR-TEM, XPS, EDX, IR, PL, and SQUID. The luminescent/fluorescent property of the particles is attributable to the Tb3+ ion located on the crystal lattice of the Gd2O3 host. The paramagnetic behavior of the particles is discussed. Pilot studies investigating the capability of the nanoparticles for fluorescent labeling of living cells and as a MRI contrast agent were also performed. Cells of two cell lines (THP-1 cells and fibroblasts) were incubated with the particles, and intracellular particle distribution was visualized by confocal microscopy. The MRI relaxivity of the PEGylated nanoparticles in water at low Gd concentration was assessed showing a higher T-1 relaxation rate compared to conventional Gd-DTPA chelates and comparable to that of undoped Gd2O3 nanoparticles.
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| 34. |
- Selegård, Linnéa, et al.
(författare)
-
Bifunctional gadolinium decorated ZnO nanocrystals integrating both enhanced MR signal and bright fluorescence
- 2013
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Gadolinium decorated ZnO nanoparticles simultaneously possess both fluorescent and MR enhancement properties. These ZnO nanoparticles are crystalline and shielded by an amorphous gadolinium acetate matrix. Interestingly, the Gd-acetate decoration enhances the fluorescence emission of the ZnO nanoparticles. The quantum yield does increase for samples with high Gd/Zn relative ratios and these samples do also show a higher colloidal stability.In addition, these nanoparticles show an enhanced relaxivity value per Gd atom (r119.9mM1s-1) compared to results earlier reported both on Gd alloyed ZnO nanoparticles and pure Gd2O3 nanoparticles. This improvement is considered to be due to the close proximity of Gd atoms and surrounding water molecules. A comprehensive study of the quantum yield and the relaxivity, as a function of composition, enable us to identify the ultimate design/composition of gadolinium decorated ZnO nanoparticles for optimum fluorescence and MR enhancement properties.
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| 35. |
- Selegård, Linnéa, et al.
(författare)
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Biotinylation of ZnO Nanoparticles and Thin Films: A Two-Step Surface Functionalization Study
- 2010
-
Ingår i: ACS APPLIED MATERIALS and INTERFACES. - : AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA. - 1944-8244 .- 1944-8252. ; 2:7, s. 2128-2135
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Tidskriftsartikel (refereegranskat)abstract
- This study reports ZnO nanoparticles and thin film surface modification using a two-step functionalization strategy. A small silane molecule was used to build up a stabilizing layer and for conjugation of biotin (vitamin B7), as a specific tag. Biotin was chosen because it is a well-studied bioactive molecule with high affinity for avidin. ZnO nanoparticles were synthesized by electrochemical deposition under oxidizing condition, and ZnO films were prepared by plasma-enhanced metal organic chemical vapor deposition. Both ZnO nanoparticles and ZnO thin films were surface modified by forming a (3-mercaptopropyl)trimethoxysilane (MPTS) layer followed by attachment of a biotin derivate. lodoacetyl-PEG2-biotin molecule was coupled to the thiol unit in MPTS through a substitution reaction. Powder X-ray diffraction, transmission electron microscopy, X-ray photoemission electron microscopy, atomic force microscopy. X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy were used to investigate the as-synthesized and functionalized ZnO materials. The measurements showed highly crystalline materials in both cases with a ZnO nanoparticle diameter of about 5 nm and a grain size of about 45 nm for the as-grown ZnO thin films. The surface modification process resulted in coupling of silanes and biotin to both the ZnO nanoparticles and ZnO thin films. The two-step functionalization strategy has a high potential for specific targeting in bioimaging probes and for recognition studies in biosensing applications.
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| 36. |
- Söderlind, Fredrik
(författare)
-
Colloidal Synthesis and Characterisation of (a) Na0.5K0.5NbO3 Thin Films; and (b) Functionalised Gd2O3 Nanocrystals
- 2004
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- (a) Thin films of the perovskite structured Na0.5K0.5NbO3 (NKN) have been synthesised with several different sol-gel methods. Only one method gave pure NKN phase while the other methods gave extra peaks in the x-ray diffraction patterns, indicating that other, unidentified, phases were present. Scanning electron microscopy revealed grain sizes ranging from about 50 to 300 nm. The films prepared by chemical methods are compared with sputtered thin films.(b) Nanocrystals of Gd2O3 have been prepared by various methods, using e.g. trioctylphosphine oxide (TOPO), diethylene glycol (DEG). The crystalline particles were of sizes 5 to 15 nm. Onto the surface of the particles, made with DEG, different carboxylic acids e.g. oleic acid or citric acid etc, were adsorbed. From IR measurements the bonding to the surface is recognised as chemisorbed via the carboxylate group in a bidentate or bridging fashion, with preference for the bridging coordination. The organic acid-particle complexes were characterised by XRPD, TEM, FTIR, Raman and XPS.
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| 37. |
- Söderlind, Fredrik, et al.
(författare)
-
Colloidal synthesis and characterization of ultrasmall perovskite GdFeO3 nanocrystals
- 2008
-
Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:8, s. 085608-
-
Tidskriftsartikel (refereegranskat)abstract
- Synthesis of very small (about 4 nm) perovskite structured gadolinium orthoferrite nanoparticles (GdFeO3) was performed by the polyol method. The material shows promising relaxivity properties and potential as a contrast agent in magnetic resonance imaging. The perovskite nanoparticles were characterized by x-ray diffraction, transmission electron microscopy, energy dispersive x-ray spectroscopy, Fourier transform infrared spectroscopy, magnetic resonance, and magnetization measurements. Upon heating in air at 800 °C for 3 h the size of the crystals increased to about 40 nm. The crystalline structure of the heat treated compound is in good agreement with perovskite GdFeO3 as the primary product. Contributions from various secondary phases were also identified, including one hitherto unknown phase with the suggested composition 'Gd3FeO6' and isostructural with Gd3GaO6. The novel 'Gd3FeO6' phase appears to be kinetically stabilized in the nano state.
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| 38. |
- Söderlind, Fredrik, 1971-
(författare)
-
Colloidal synthesis of metal oxide nanocrystals and thin films
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A main driving force behind the recent years’ immense interest in nanoscience and nanotechnology is the possibility of achieving new material properties and functionalities within, e.g., material physics, biomedicine, sensor technology, chemical catalysis, energy storing systems, and so on. New (theoretical) possibilities represent, in turn, a challenging task for chemists and physicists. An important feature of the present nanoscience surge is its strongly interdisciplinary character, which is reflected in the present work.In this thesis, nanocrystals and thin films of magnetic and ferroelectric metal oxides, e.g. RE2O3 (RE = Y, Gd, Dy), GdFeO3, Gd3Fe5O12, Na0.5K0.5NbO3, have been prepared by colloidal and sol-gel methods. The sizes of the nanocrystals were in the range 3-15 nm and different carboxylic acids, e.g. oleic or citric acid, were chemisorbed onto the surface of the nanoparticles. From FT-IR measurements it is concluded that the bonding to the surface takes place via the carboxylate group in a bidentate or bridging fashion, with some preference for the latter coordination mode. The magnetic properties of nanocrystalline Gd2O3 and GdFeO3 were measured, both with respect to magnetic resonance relaxivity and magnetic susceptibility. Both types of materials exhibit promising relaxivity properties, and may have the potential for use as positive contrast enhancing agents in magnetic resonance imaging (MRI). The nanocrystalline samples were also characterised by transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and quantum chemical calculations.Thin films of Na0.5K0.5NbO3, GdFeO3 and Gd3Fe5O12 were prepared by sol-gel methods and characterized by x-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). Under appropriate synthesis conditions, rather pure phase materials could be obtained with grain sizes ranging from 50 to 300 nm. Magnetic measurements in the temperature range 2-350 K indicated that the magnetization of the perovskite phase GdFeO3 can be described as the sum of two contributing terms. One term (mainly) due to the spontaneous magnetic ordering of the iron containing sublattice, and the other a susceptibility term, attributable to the paramagnetic gadolinium sublattice. The two terms yield the relationship M(T)=M0(T)+χ(T)*H for the magnetization. The garnet phase Gd3Fe5O12 is ferrimagnetic and showed a compensation temperature Tcomp ≈ 295 K.
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| 39. |
- Söderlind, Fredrik, et al.
(författare)
-
Sol-gel synthesis of ferroelectric (Na,K)NbO3 thin films
- 2002
-
Rapport (populärvet., debatt m.m.)abstract
- The idea of this work was to make thin films of (Na,K)NbO3 with sol-gel technique. In this work several sol-gel methods, novel and previously known, have been used, with various results. When working with sol-gel there are several parameters that can be modified, (e.g. the composition of the solution, heat treatment, etc.) which will improve or diminish the properties of the final film. The principle of sol-gel is to make a solution with the desired cations dispersed in organic solvents; furthermore the solution must have good adhesion to the substrate on which the solution is deposited.
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| 40. |
- Söderlind, Fredrik, et al.
(författare)
-
Sol–gel synthesis and characterization of Na0.5K0.5NbO3 thin films
- 2005
-
Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 281:2-4, s. 468-474
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films of the perovskite structured Na0.5K0.5NbO3 (NKN) have been synthesized with three different sol–gel methods, viz. the alkoxide method, a modified Pechini method and a somewhat novel oxalate method, based on 2-methoxy ethanol as solvent with oxalic acid and ethylene glycol as chelating ligand and stabilizer. Only one method (the modified Pechini method) gave pure NKN phase while the other two methods gave extra peaks in the X-ray diffraction patterns, indicating that other, unidentified, phases were present. SEM images revealed grain sizes ranging from 100 to 300 nm.
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| 41. |
- Söderlind, Fredrik, et al.
(författare)
-
Synthesis and characterisation of Gd2O3 nanocrystals functionalised by organic acids
- 2005
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 288:1, s. 140-148
-
Tidskriftsartikel (refereegranskat)abstract
- Nanocrystals of Gd2O3 have been prepared by various methods, using, e.g., trioctylphosphine oxide (TOPO), diethylene glycol (DEG) or glycine. The crystalline particles were of sizes 5 to 15 nm. Different carboxylic acids, e.g., oleic acid or citric acid, were adsorbed onto the surface of the particles made with DEG. IR measurements show that the molecules coordinate to the Gd2O3 surface via the carboxylate group in a bidentate or bridging manner. The organic-acid/particle complexes were characterised by XRPD, TEM, FTIR, Raman, and XPS.
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| 42. |
- Söderlind, Per, et al.
(författare)
-
Computational modeling of actinide materials and complexes
- 2010
-
Ingår i: MRS bulletin. - 0883-7694 .- 1938-1425. ; 35:11, s. 883-888
-
Tidskriftsartikel (refereegranskat)abstract
- In spite of being rare, actinide elements provide the building blocks for many fascinating condensed-matter systems, both from an experimental and theoretical perspective Experimental observations of actinide materials are difficult because of rarity, toxicity, radioactivity, and even safety and security Theory, on the other hand, has its own challenges Complex crystal and electronic structures are often encountered in actinide materials, as well as pronounced electron correlation effects Consequently, theoretical modeling of actinide materials and their 5f electronic states is very difficult Here, we review recent theoretical efforts to describe and sometimes predict the behavior of actinide materials and complexes, such as phase stability, including density functional theory (DFT), DFT in conjunction with an additional Coulomb repulsion U(DFT+U), and DFT in combination with dynamical mean-field theory (DFT+DMFT)
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| 43. |
- Söderlind, Per, et al.
(författare)
-
High-temperature phonon stabilization of γ-uranium from relativistic first-principles theory
- 2012
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 85:6, s. 060301-
-
Tidskriftsartikel (refereegranskat)abstract
- A microscopic explanation for temperature stabilization of the body-centered cubic (bcc) phase in the actinide metals is proposed. We show that for a prototype actinide, uranium, phonon-phonon interaction promotes bcc gamma-U when heated, even though at low temperatures, it is mechanically a strongly unstable phase. Utilizing the recently developed self-consistent ab initio lattice dynamics (SCAILD) scheme in conjunction with highly accurate and fully relativistic density functional theory we obtain phonon dispersion and density of states that compare well with data acquired from inelastic neutron-scattering experiments. The investigation thus establishes that high-temperature lattice dynamics can be modeled from ab initio theory even for complex materials with substantial electron correlation including the actinides.
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| 44. |
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| 45. |
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| 46. |
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| 47. |
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| 48. |
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