| 11. |
- Hillerich, Karla, et al.
(författare)
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Epitaxial InP nanowire growth from Cu seed particles
- 2011
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 315:1, s. 134-137
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Konferensbidrag (refereegranskat)abstract
- Cu-seeded epitaxial growth of vertically aligned InP nanowires is reported for the first time. The nanowires were grown at temperatures between 290 and 420 degrees C by metal-organic vapor phase epitaxy (MOVPE) from particles formed from Cu thin films. In the temperature range of 340-370 degrees C high yields of vertically aligned nanowires could be achieved. The nanowire crystal structure and the particle composition were investigated by TEM and XEDS. The nanowires showed a zinc blende structure and a post-growth particle composition of 64 at% Cu and 36 at% In. (C) 2010 Elsevier B.V. All rights reserved.
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| 12. |
- Johansson, Jonas, et al.
(författare)
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Diameter Dependence of the Wurtzite-Zinc Blende Transition in InAs Nanowires
- 2010
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:9, s. 3837-3842
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that the crystal structure of InAs nanowires call be controlled with nanowire diameter and growth temperature. At small diameters, the nanowires exhibit a wurtzite Structure. As the diameter is increased, there is a crossover to the zinc blende structure. The crossover is less sharp at lower growth temperature and L, the crossover diameter decreases as the growth temperature is increased. We explain these results with classical nucleation theory. The strong diameter dependence is accounted for by including the Gibbs-Thomson effect in the chemical potential.
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| 13. |
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| 14. |
- Kreyling, Wolfgang G., et al.
(författare)
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Generation and characterization of stable, highly concentrated titanium dioxide nanoparticle aerosols for rodent inhalation studies
- 2011
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Ingår i: Journal of Nanoparticle Research. - : Springer Science and Business Media LLC. - 1572-896X .- 1388-0764. ; 13:2, s. 511-524
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Tidskriftsartikel (refereegranskat)abstract
- The intensive use of nano-sized titanium dioxide (TiO2) particles in many different applications necessitates studies on their risk assessment as there are still open questions on their safe handling and utilization. For reliable risk assessment, the interaction of TiO2 nanoparticles (NP) with biological systems ideally needs to be investigated using physico-chemically uniform and well-characterized NP. In this article, we describe the reproducible production of TiO2 NP aerosols using spark ignition technology. Because currently no data are available on inhaled NP in the 10-50 nm diameter range, the emphasis was to generate NP as small as 20 nm for inhalation studies in rodents. For anticipated in vivo dosimetry analyses, TiO2 NP were radiolabeled with V-48 by proton irradiation of the titanium electrodes of the spark generator. The dissolution rate of the V-48 label was about 1% within the first day. The highly concentrated, polydisperse TiO2 NP aerosol (3-6 x 10(6) cm(-3)) proved to be constant over several hours in terms of its count median mobility diameter, its geometric standard deviation, and number concentration. Extensive characterization of NP chemical composition, physical structure, morphology, and specific surface area was performed. The originally generated amorphous TiO2 NP were converted into crystalline anatase TiO2 NP by thermal annealing at 950 A degrees C. Both crystalline and amorphous 20-nm TiO2 NP were chain agglomerated/aggregated, consisting of primary particles in the range of 5 nm. Disintegration of the deposited TiO2 NP in lung tissue was not detectable within 24 h.
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| 15. |
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| 16. |
- Messing, Maria, et al.
(författare)
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A comparative study of the effect of gold seed particle preparation method on nanowire growth
- 2010
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Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 3:7, s. 506-519
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Tidskriftsartikel (refereegranskat)abstract
- Highly controlled particle-assisted growth of semiconductor nanowires has been performed for many years, and a number of novel nanowire-based devices have been demonstrated. Full control of the epitaxial growth is required to optimize the performance of devices, and gold seed particles are known to provide the most controlled growth. Successful nanowire growth from gold particles generated and deposited by various different methods has been reported, but no investigation has yet been performed to compare the effects of gold particle generation and deposition methods on nanowire growth. In this article we present a direct comparative study of the effect of the gold particle creation and deposition methods on nanowire growth characteristics and nanowire crystal structure, and investigate the limitations of the different generation and deposition methods used.
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| 17. |
- Messing, Maria
(författare)
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Engineered Nanoparticles Generation, Characterization and Applications
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- It is predicted that novel nanometer-sized structures incorporating nanoparticles will have a considerable impact on our lives during the coming decades. Engineered nanoparticles are already found in a number of commercially available products. However, many applications of these nanoparticles have only reached the stage of promising ideas or research demonstrations. The number of nanoparticle-based products on the market is therefore expected to increase considerably during the coming decades. For engineered nanoparticles to be useful in different commercial applications, it is important that their generation can be controlled. This means a stable generation process resulting in reproducible, high-quality nanoparticles with properties tailored for specific applications. In order to develop such production methods, thorough characterization of the particles generated is essential. In addition, since the impact of nanoparticles on human health and the environment has not been fully explored, the entire lifecycle of engineered nanoparticles must be thoroughly investigated. Engineered nanoparticles should not cause any harm to human health or the environment, during manufacturing or use of the product, or during disposal of the product after use. This thesis describes the manufacture of engineered nanoparticles, mainly by inert gas evaporation using a spark discharge generator and an evaporation/condensation furnace. Considerable effort has been put into investigating how different generation parameters affect particle production, so that the particle properties can be controlled and tailored to meet specific applications. To achieve this, the as-generated nanoparticles have been systematically characterized by various methods; transmission electron microscopy being the key characterization tool. The nanoparticles generated were then used in three different areas of application: as seed particles for so-called nanowires which may be useful in future devices, as model catalyst systems to provide deeper knowledge about the atomic-scale mechanisms involved in catalysis, and finally for research in the area of nano safety to learn how nanoparticles should be handled in a safe and sustainable manner.
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| 18. |
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| 19. |
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| 20. |
- Messing, Maria, et al.
(författare)
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Generation of Pd Model Catalyst Nanoparticles by Spark Discharge
- 2010
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 114:20, s. 9257-9263
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Tidskriftsartikel (refereegranskat)abstract
- We present a method to deposit Pd nanoparticles with a very small size distribution by an aerosol process onto oxide substrates for the creation of model systems in catalytic research. The Pd nanoparticles are characterized by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. We confirm the small size dispersion from the desired particle size, and we show that the particle surface coverage can he highly controlled. Further, our measurements indicate that an amorphous shell surrounding a crystalline core of the Pd particles may form during the particle synthesis and that the shell contains carbon.
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