| 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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