| 1. |
- Adham, Kristi, et al.
(författare)
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Growth of branched nanowires via solution-based Au seed particle deposition
- 2023
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Ingår i: Materials Research Express. - 2053-1591. ; 10:8
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Tidskriftsartikel (refereegranskat)abstract
- Nanowires offer unprecedented flexibility as nanoscale building blocks for future optoelectronic devices, especially with respect to nanowire solar cells and light-emitting diodes. A relatively new concept is that of charge carrier diffusion-induced light-emitting diodes, for which nanowires offer an interesting architecture by use of particle-assisted core-branch growth. The branches should be homogenously distributed along the cores. However, most deposition techniques, such as aerosol particle deposition, mainly yield particles at the nanowire tips for dense nanowire arrays. In this study, we demonstrate a liquid-based approach for homogeneously distributed formation of catalytic Au particles on the core nanowire sidewalls which is cost and time-efficient. Subsequently, we demonstrate the synthesis of dispersed nanowire branches. We show that by changing the deposition parameters, we can tune the number of branches, their dimensions, and their growth direction.
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| 2. |
- Ahlqvist, Josefin, et al.
(författare)
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DNA digestion and formation of DNA-network structures with Holliday junction-resolving enzyme Hjc_15-6 in conjunction with polymerase reactions
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Ingår i: Journal of Biotechnology. - 1873-4863.
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Tidskriftsartikel (refereegranskat)abstract
- The recently identified novel Holliday junction-resolving enzyme, termed Hjc_15-6, activity investigation results imply DNA cleavage by Hjc_15-6 in a manner that potentially enhances the molecular self-assembly that may be exploited for creating DNA-networks and nanostructures. The study also demonstrates Pwo DNA polymerase acting in combination with Hjc_15-6 capability to produce large amounts of DNA that transforms into large DNA-network structures even without DNA template and primers. Furthermore, it is demonstrated that Hjc_15-6 prefers Holliday junction oligonucleotides as compared to Y-shaped oligonucleotides as well as efficiently cleaves typical branched products from isothermal DNA amplification of both linear and circular DNA templates amplified by phi29-like DNA polymerase. The assembly of large DNA network structures was observed in real time, by transmission electron microscopy, on negative stained grids that were freshly prepared, and also on the same grids after incubation for 4 days under constant cooling. Hence, Hjc_15-6 is a promising molecular tool for efficient production of various DNA origamis that may be implemented for a wide range of applications such as within medical biomaterials, catalytic materials, molecular devices and biosensors.
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| 3. |
- Arve, K, et al.
(författare)
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Analysis of the state and size of silver on alumina in effective removal of NOx from oxygen rich exhaust gas
- 2006
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Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 0000-0000. ; 6:4, s. 1076-1083
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Tidskriftsartikel (refereegranskat)abstract
- Ag/alumina catalysts with different silver contents for octane-SCR were prepared by impregnation and incipient wetness methods. Activity tests revealed that the decisive factor for high activity is not only a high dispersion of silver, but also the ability of the system to redisperse clustered silver. Determination of dispersion by TEM/HAADF and O-2-chemisorption experiments resulted in values close to each other even if the results were not directly comparable. This is suggested to be due to not complete silver reduction below 700 degrees C and the samples being very heterogeneous in terms of particle size, e.g., having a bimodal size distribution. Small charged Ag-n(delta+) clusters containing 2-8 silver atoms highly prevailed in the samples containing < 2 wt% Ag and exhibiting high octane-SCR activity In highly loaded Ag/alumina samples or those reduced and reoxidized at high temperature (> 400 degrees C), large metallic particles are stabilized, resulting in poor conversion of NOx to N-2.
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| 4. |
- Arve, K, et al.
(författare)
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Structure-activity relationship in HC-SCR of NOx, by TEM, O-2-chemisorption, and EDXS study of Ag/Al2O3
- 2006
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 110:1, s. 420-427
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Tidskriftsartikel (refereegranskat)abstract
- Ag/alumina catalysts with different silver loading (1.28 - 6 wt %) for lean NO reduction activity were prepared by impregnation and the incipient wetness method. Complementary HRTEM, HAADF, O-2-chemisorption, and EDXS studies were applied to investigate the dependence between silver particle size and catalytic activities of the prepared materials. The catalyst with the lowest silver loading (1.28 wt %) was found to be the most active catalyst in terms of reacted NO molecules per mole of silver. On the basis of the HRTEM, HAADF, and O-2-chemisorption studies it could be concluded that the mean particle size or particle size distribution of the samples alone could not explain the big difference in the activities. EDXS analyses showed on the other hand that all of the samples were very heterogeneous in terms of particle size distribution, e.g., including both small and very big particles. Furthermore, both metallic silver and mainly hexagonal silver oxide (Ag2O) were found to be present in the samples. Despite the valuable information provided by ex situ characterization of the prepared samples, it needs to be emphasized that establishing a structure-reactivity relationship for this type of catalyst requires in situ characterization.
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| 5. |
- Astromskas, Gvidas, et al.
(författare)
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Electrical characterization of thin InAs films grown on patterned W/GaAs substrates
- 2009
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Ingår i: Journal of Vacuum Science and Technology B. - : American Vacuum Society. - 1520-8567. ; 27:5, s. 2222-2226
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Tidskriftsartikel (refereegranskat)abstract
- InAs has been grown on W-GaAs patterned substrates using metal organic vapor phase epitaxy. It is shown that the W pattern guides the nucleation of the InAs on the GaAs substrate and that the islands formed may be used to embed metal features in a hybrid InAs/GaAs structure. A lower resistance (factor of 2) was measured for the hybrid structures as compared to reference structures. The reduction in the resistance is attributed to an increased carrier concentration as observed from Hall measurements on devices with different tungsten densities. Cross-sectional transmission electron microscopy investigations reveal a void-free overgrowth above the metal despite the large mismatch of the InAs/GaAs system. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3222859]
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| 6. |
- Benko, Gabor, et al.
(författare)
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Particle size and crystallinity dependent electron injection in Fluorescein 27-sensitized TiO2 films.
- 2003
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 107:6, s. 1370-1375
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Tidskriftsartikel (refereegranskat)abstract
- Influence of processing parameters, such as autoclaving and firing temperature, on the optical properties of nanocrystalline anatase TiO2 film and on the process of electron injection from the dye fluorescein 27 to the as-prepared films is studied. Transmission electron microscopy and steady-state and time-resolved femtosecond spectroscopy measurements indicate that the larger the TiO2 particle and the better its overall crystallinity, the faster the process of electron injection. Unraveling factors that control the properties of the sub-20-nm sized semiconductor particles, and by this the electron injection to them, is important for understanding the process of interfacial electron transfer from the dye to the semiconductor, as well as future optimization of the function of the photoelectrochemical cell based on dye-sensitized TiO2 films.
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| 7. |
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| 8. |
- Berg, Alexander, et al.
(författare)
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Growth and characterization of wurtzite GaP nanowires with control over axial and radial growth by use of HCl in-situ etching
- 2014
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 386, s. 47-51
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis of non-tapered wurtzite (WZ) GaP nanowires by use of in-situ etching and the structural and optical characterization thereof. HCl was evaluated as an in-situ etchant in order to impede the onset of radial growth since the WZ crystal phase in GaP nanowires preferentially grows at relatively high growth temperatures around 600 degrees C, at which strong radial growth typically occurs. Transmission electron microscopy measurements confirmed non-tapered WZ GaP nanowires after growth. Photoluminescence characterization revealed defect related red emission, possibly related to transitions within the bandgap. Raman measurements show that the phonon energies in WZ GaP are very close in energy to the phonon energies in zinc blende GaP. (C) 2013 Elsevier B.V. All rights reserved.
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| 9. |
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| 10. |
- Berg, Alexander, et al.
(författare)
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Growth parameter design for homogeneous material composition in ternary GaxIn1-xP nanowires.
- 2015
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 26:43
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Tidskriftsartikel (refereegranskat)abstract
- Ternary nanowires (NWs) often exhibit varying material composition along the NW growth axis because of different diffusion properties of the precursor molecules. This constitutes a problem for optoelectronic devices for which a homogeneous material composition is most often of importance. Especially, ternary GaInP NWs grown under a constant Ga-In precursor ratio typically show inhomogeneous material composition along the length of the NW due to the complexity of low temperature precursor pyrolysis and relative rates of growth species from gas phase diffusion and surface diffusion that contribute to synthesis of particle-assisted growth. Here, we present the results of a method to overcome this challenge by in situ tuning of the trimethylindium molar fraction during growth of ternary Zn-doped GaInP NWs. The NW material compositions were determined by use of x-ray diffraction, scanning transmission electron microscopy and energy dispersive x-ray spectroscopy and the optical properties by photoluminescence spectroscopy.
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