| 1. |
- Meyer-Holdt, J., et al.
(författare)
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Ag-catalyzed InAs nanowires grown on transferable graphite flakes
- 2016
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 27:36
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Tidskriftsartikel (refereegranskat)abstract
- Semiconducting nanowires grown by quasi-van-der-Waals epitaxy on graphite flakes are a new class of hybrid materials that hold promise for scalable nanostructured devices within opto-electronics. Here we report on high aspect ratio and stacking fault free Ag-seeded InAs nanowires grown on exfoliated graphite flakes by molecular beam epitaxy. Ag catalyzes the InAs nanowire growth selectively on the graphite flakes and not on the underlying InAs substrates. This allows for easy transfer of the flexible graphite flakes with as-grown nanowire ensembles to arbitrary substrates by a micro-needle manipulator. Besides the possibilities for fabricating novel nanostructure device designs, we show how this method is used to study the parasitic growth and bicrystal match between the graphite flake and the nanowires by transmission electron microscopy.
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| 2. |
- Abdelhamid, Hani Nasser
(författare)
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Surfactant assisted synthesis of hierarchical porous metal-organic frameworks nanosheets
- 2019
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 30:43
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional metal-organic frameworks show increasing research attention due to their unique properties including tunable thickness, simple packing into a film and membrane, and high surface-to-volume atom ratios. A bottom-up synthesis strategy using cetyltrimethylammonium bromide for the synthesis of copper-benzenedicarboxylate (Cu(BDC)) nanosheets is reported. The method offers the synthesis of hierarchical porous Cu(BDC) lamellae with micrometer lateral dimensions, and nanometer thickness (100-150 nm). Electron microscope (scanning and transmission), and N-2 adsorption isotherms confirm the formation of lamellae Cu(BDC) with mesopore size of 5-80 nm. The material has thermal stability up to 400 degrees C with good chemical stability in several organic solvents. However, the material transforms to another phase (Cu(BDC)(H2O)(2)) when soaked in water and alcohols. The transformation reduces crystal size and offers the formation of hydrogen bond resulting in an increase in the sorption of CO2 by similar to 10% compared to the pristine material Cu(BDC).
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| 3. |
- Chalangar, Ebrahim, 1984-, et al.
(författare)
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Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites
- 2018
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Ingår i: Nanotechnology. - Bristol : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 29:41
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Tidskriftsartikel (refereegranskat)abstract
- The development of future 3D-printed electronics relies on the access to highly conductive inexpensive materials that are printable at low temperatures (<100 C). The implementation of available materials for these applications are, however, still limited by issues related to cost and printing quality. Here, we report on the simple hydrothermal growth of novel nanocomposites that are well suited for conductive printing applications. The nanocomposites comprise highly Al-doped ZnO nanorods grown on graphene nanoplatelets (GNPs). The ZnO nanorods play the two major roles of (i) preventing GNPs from agglomerating and (ii) promoting electrical conduction paths between the graphene platelets. The effect of two different ZnO-nanorod morphologies with varying Al-doping concentration on the nanocomposite conductivity and the graphenedispersity are investigated. Time-dependent absorption, photoluminescence and photoconductivity measurements show that growth in high pH solutions promotes a better graphene dispersity, higher doping levels and enhanced bonding between the graphene and the ZnO nanorods. Growth in low pH solutions yields samples characterized by a higher conductivity and a reduced number of surface defects. These samples also exhibit a large persistent photoconductivity attributed to an effective charge separation and transfer from the nanorods to the graphene platelets. Our findings can be used to tailor the conductivity of novel printable composites, or for fabrication of large volumes of inexpensive porous conjugated graphene-semiconductor composites. © 2018 IOP Publishing Ltd.
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| 4. |
- Hussain, Laiq, et al.
(författare)
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Defect-induced infrared electroluminescence from radial GaInP/AlGaInP quantum well nanowire array light- emitting diodes
- 2017
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Ingår i: Nanotechnology. - Bristol : IOP Publishing. - 0957-4484 .- 1361-6528. ; 28:48
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Tidskriftsartikel (refereegranskat)abstract
- Radial GaInP/AlGaInP nanowire array light-emitting diodes (LEDs) are promising candidates for novel high-efficiency solid state lighting due to their potentially large strain-free active emission volumes compared to planar LEDs. Moreover, by proper tuning of the diameter of the nanowires, the fraction of emitted light extracted can be significantly enhanced compared to that of planar LEDs. Reports so far on radial growth of nanowire LED structures, however, still point to significant challenges related to obtaining defect-free radial heterostructures. In this work, we present evidence of optically active growth-induced defects in a fairly broad energy range in vertically processed radial GaInP/AlGaInP quantum well nanowire array LEDs using a variety of complementary experimental techniques. In particular, we demonstrate strong infrared electroluminescence in a spectral range centred around 1 eV (1.2 μm) in addition to the expected red light emission from the quantum well. Spatially resolved cathodoluminescence studies reveal a patchy red light emission with clear spectral features along the NWs, most likely induced by variations in QW thickness, composition and barriers. Dark areas are attributed to infrared emission generated by competing defect-assisted radiative transitions, or to trapping mechanisms involving non-radiative recombination processes. Possible origins of the defects are discussed.
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| 5. |
- Jafari Jam, R., et al.
(författare)
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Embedded sacrificial AlAs segments in GaAs nanowires for substrate reuse
- 2020
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Ingår i: Nanotechnology. - Bristol : Institute of Physics Publishing (IOPP). - 0957-4484 .- 1361-6528. ; 31:20
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Tidskriftsartikel (refereegranskat)abstract
- We report on the use of a sacrificial AlAs segment to enable substrate reuse for nanowire synthesis. A silicon nitride template was deposited on a p-type GaAs substrate. Then a pattern was transferred to the substrate by nanoimprint lithography and reactive ion etching. Thermal evaporation was used to define Au seed particles. Metalorganic vapour phase epitaxy was used to grow AlAs-GaAs NWs in the vapour-liquid-solid growth mode. The yield of synthesised nanowires, compared to the number expected from the patterned template, was more than 80%. After growth, the nanowires were embedded in a polymer and mechanically removed from the parent substrate. The parent substrate was then immersed in an HCl:H2O (1:1) mixture to dissolve the remaining stub of the sacrificial AlAs segment. The pattern fidelity was preserved after peeling off the nanowires and cleaning, and the semiconductor surface was flat and ready for reuse. Au seed particles were then deposited on the substrate by use of pulse electrodeposition, which was selective to the openings in the growth template, and then nanowires were regrown. The yield of regrowth was less optimal compared to the first growth but the pattern was preserved. Our results show a promising approach to reduce the final cost of III-V nanowire based solar cells. © 2020 The Author(s). Published by IOP Publishing Ltd.
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| 6. |
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| 7. |
- Gu, Xiuquan, et al.
(författare)
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ZnO based heterojunctions and their application in environmental photocatalysis
- 2016
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 27:40
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Forskningsöversikt (refereegranskat)abstract
- As an alternative to TiO2 photocatalysts, ZnO exhibits a large potential for photocatalytic (PC) applications in environmental treatments, such as degradation of wastewater, sterilization of drinking water, and air cleaning. However, the efficiency achieved with ZnO to date is far from that expected for commercialization, due to rapid charge recombination, photo-corrosion as well as poor utilization of solar energy. Fortunately, in recent years, a great number of breakthroughs have been achieved in PC performance (including activity and stability) of micro-/ nano-structured ZnO by forming heterojunctions (HJs) with metal nanoparticles (NPs), carbon nanostructures and other semiconductors. In most cases, the improvement of PC performance was ascribed to the better charge separation at the interfaces between ZnO and the other components. Sometimes, the formation of hybrids is also in favor of visible light harvesting. This review summarizes recent advances in the fields of environmental photocatalysis by ZnO based HJs, and especially emphasizes their abilities in degradation of organic pollutants or harmful substances in water. We aim to reveal the mechanism underlying the enhanced PC performance by constructing HJs, and extend the potential of ZnO HJ photocatalysts for future trends, and practical, large-scale applications in environment-related fields.
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| 8. |
- Li, Zhuang-Zhi, et al.
(författare)
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Gold/boron core-shell nanocables synthesized from gold-boron eutectic droplets
- 2008
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 19:5, s. 055606-
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Tidskriftsartikel (refereegranskat)abstract
- Metal/semiconductor coreshell coaxial nanocables are promising building blocks for nanoelectronic devices while in situ growth of these nanocables remains challenging due to the distinctly different synthesis temperature ranges required for metals and semiconductors. To overcome this difficulty, we have developed a vaporliquidsolid and oxide-assisted bimodal competition growth strategy for in situ metal/semiconductor coreshell nanocable growth. Using this process, gold/boron coreshell nanocables were obtained. A coreshell Au-B/BOx eutectic droplet formed via hydrogen gas-assisted rapid cooling was found critical for initiation of the nanocable growth. In addition, the large difference in the boron nanowire growth rates in the vapor-liquid-solid and oxide-assisted mechanisms facilitates the layered growth in the nanocables. The compatibility of this method with the vapor-liquid-solid process applied widely for semiconductor nanowire growth allows in situ connection of metal/semiconductor nanocables with semiconductor nanowires.
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| 9. |
- Margaris, G., et al.
(författare)
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Superspin glass state in a diluted nanoparticle system stabilized by interparticle interactions mediated by an antiferromagnetic matrix
- 2017
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Ingår i: Nanotechnology. - : IOP PUBLISHING LTD. - 0957-4484 .- 1361-6528. ; 28:3
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Tidskriftsartikel (refereegranskat)abstract
- In nanoparticle systems consisting of two magnetic materials (bi-magnetic nanoparticles or nanoparticles embedded in a magnetic matrix), there is a constantly growing interest in the investigation of the interplay between interparticle interactions and the nanoparticle-matrix interface exchange coupling, because of its enormous impact on a number of technological applications. The understanding of the mechanisms of such interplay is a great challenge, as it would allow controlling equilibrium and non-equilibrium magnetization dynamics of exchange coupled nanoparticles systems and finely tuning their anisotropy. Here, we provide evidence that this interplay leads to a collective superspin glass (SSG) behavior in a system of diluted ferromagnetic. (FM) nanoparticles embedded in an antiferromagnetic (AFM) matrix (5% volume fraction of Co particles in Mn film matrix). We have developed a novel mesoscopic model to study the influence of interparticle interaction on the exchange bias (EB) and the dynamical behavior of assemblies of FM nanoparticles embedded in a granular AFM matrix. Our mesoscopic model is based on reducing the amount of simulated spins to the minimum number necessary to describe the magnetic structure of the system and introducing the adequate exchange parameters between the different spins. The model replicates remarkably well the observed static and dynamical SSG properties as well as the EB behavior. In addition, the proposed model well explains the role of the significant Co/Mn alloying and of the granularity of the matrix in mediating interparticle interactions through exchange and dipole-dipole coupling between the uncompensated moments of its grains and the exchange interaction at the Co/Mn interface.
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| 10. |
- Wang, Dan, et al.
(författare)
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'Green'-synthesized near-infrared PbS quantum dots with silica-PEG dual-layer coating : ultrastable and biocompatible optical probes for in vivo animal imaging
- 2012
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 23:24, s. 245701-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, PbS semiconductor quantum dots (QDs) with near-infrared (NIR) photoluminescence were synthesized in oleic acid and paraffin liquid mixture by using an easily handled and 'green' approach. Surface functionalization of the QDs was accomplished with a silica and polyethylene glycol (PEG) phospholipid dual-layer coating and the excellent chemical stability of the nanoparticles is demonstrated. We then successfully applied the ultrastable PbS QDs to in vivo sentinel lymph node (SLN) mapping of mice. Histological analyses were also carried out to ensure that the intravenously injected nanoparticles did not produce any toxicity to the organism of mice. These experimental results suggested that our ultrastable NIR PbS QDs can serve as biocompatible and efficient probes for in vivo optical bioimaging and has great potentials for disease diagnosis and clinical therapies in the future.
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