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  • 1.
    Abrikossova, Natalia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Skoglund, Caroline
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, The Institute of Technology.
    Ahrén, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Bengtsson, Torbjorn
    University of Örebro, Sweden .
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Effects of gadolinium oxide nanoparticles on the oxidative burst from human neutrophil granulocytes2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 27, p. 275101-Article in journal (Refereed)
    Abstract [en]

    We have previously shown that gadolinium oxide (Gd2O3) nanoparticles are promising candidates to be used as contrast agents in magnetic resonance (MR) imaging applications. In this study, these nanoparticles were investigated in a cellular system, as possible probes for visualization and targeting intended for bioimaging applications. We evaluated the impact of the presence of Gd2O3 nanoparticles on the production of reactive oxygen species (ROS) from human neutrophils, by means of luminol-dependent chemiluminescence. Three sets of Gd2O3 nanoparticles were studied, i.e. as synthesized, dialyzed and both PEG-functionalized and dialyzed Gd2O3 nanoparticles. In addition, neutrophil morphology was evaluated by fluorescent staining of the actin cytoskeleton and fluorescence microscopy. We show that surface modification of these nanoparticles with polyethylene glycol (PEG) is essential in order to increase their biocompatibility. We observed that the as synthesized nanoparticles markedly decreased the ROS production from neutrophils challenged with prey (opsonized yeast particles) compared to controls without nanoparticles. After functionalization and dialysis, more moderate inhibitory effects were observed at a corresponding concentration of gadolinium. At lower gadolinium concentration the response was similar to that of the control cells. We suggest that the diethylene glycol (DEG) present in the as synthesized nanoparticle preparation is responsible for the inhibitory effects on the neutrophil oxidative burst. Indeed, in the present study we also show that even a low concentration of DEG, 0.3%, severely inhibits neutrophil function. In summary, the low cellular response upon PEG-functionalized Gd2O3 nanoparticle exposure indicates that these nanoparticles are promising candidates for MR-imaging purposes.

  • 2.
    Abrikossova, Natalia
    et al.
    Division of Molecular Surface Physics and Nanoscience, Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden .
    Skoglund, Caroline
    Division of Molecular Surface Physics and Nanoscience, Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden; Division of Clinical Medicine, Department of Biomedicine, Örebro University, Örebro, Sweden.
    Ahrén, Maria
    Division of Molecular Surface Physics and Nanoscience, Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Bengtsson, Torbjörn
    Örebro University, School of Health and Medical Sciences, Örebro University, Sweden. Division of Clinical Medicine, Department of Biomedicine, School of Health and Medical Sciences, Örebro University, Örebro, Sweden.
    Uvdal, Kajsa
    Division of Molecular Surface Physics and Nanoscience, Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Effects of gadolinium oxide nanoparticles on the oxidative burst from human neutrophil granulocytes2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 27, article id 275101Article in journal (Refereed)
    Abstract [en]

    We have previously shown that gadolinium oxide (Gd2O3) nanoparticles are promising candidates to be used as contrast agents in magnetic resonance (MR) imaging applications. In this study, these nanoparticles were investigated in a cellular system, as possible probes for visualization and targeting intended for bioimaging applications. We evaluated the impact of the presence of Gd2O3 nanoparticles on the production of reactive oxygen species (ROS) from human neutrophils, by means of luminol-dependent chemiluminescence. Three sets of Gd2O3 nanoparticles were studied, i.e. as synthesized, dialyzed and both PEG-functionalized and dialyzed Gd2O3 nanoparticles. In addition, neutrophil morphology was evaluated by fluorescent staining of the actin cytoskeleton and fluorescence microscopy. We show that surface modification of these nanoparticles with polyethylene glycol (PEG) is essential in order to increase their biocompatibility. We observed that the as synthesized nanoparticles markedly decreased the ROS production from neutrophils challenged with prey (opsonized yeast particles) compared to controls without nanoparticles. After functionalization and dialysis, more moderate inhibitory effects were observed at a corresponding concentration of gadolinium. At lower gadolinium concentration the response was similar to that of the control cells. We suggest that the diethylene glycol (DEG) present in the as synthesized nanoparticle preparation is responsible for the inhibitory effects on the neutrophil oxidative burst. Indeed, in the present study we also show that even a low concentration of DEG, 0.3%, severely inhibits neutrophil function. In summary, the low cellular response upon PEG-functionalized Gd2O3 nanoparticle exposure indicates that these nanoparticles are promising candidates for MR-imaging purposes.

  • 3. Ahmed, Towfiq
    et al.
    Haraldsen, Jason T.
    Rehr, John J.
    Di Ventra, Massimiliano
    Schuller, Ivan
    Balatsky, Alexander V.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Los Alamos National Laboratory, USA.
    Correlation dynamics and enhanced signals for the identification of serial biomolecules and DNA bases2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 12, p. 125705-Article in journal (Refereed)
    Abstract [en]

    Nanopore-based sequencing has demonstrated a significant potential for the development of fast, accurate, and cost-efficient fingerprinting techniques for next generation molecular detection and sequencing. We propose a specific multilayered graphene-based nanopore device architecture for the recognition of single biomolecules. Molecular detection and analysis can be accomplished through the detection of transverse currents as the molecule or DNA base translocates through the nanopore. To increase the overall signal-to-noise ratio and the accuracy, we implement a new 'multi-point cross-correlation' technique for identification of DNA bases or other molecules on the single molecular level. We demonstrate that the cross-correlations between each nanopore will greatly enhance the transverse current signal for each molecule. We implement first-principles transport calculations for DNA bases surveyed across a multilayered graphene nanopore system to illustrate the advantages of the proposed geometry. A time-series analysis of the cross-correlation functions illustrates the potential of this method for enhancing the signal-to-noise ratio. This work constitutes a significant step forward in facilitating fingerprinting of single biomolecules using solid state technology.

  • 4. Ahmed, Towfiq
    et al.
    Haraldsen, Jason T.
    Rehr, John J.
    Di Ventra, Massimiliano
    Schuller, Ivan
    Balatsky, Alexander V.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Correlation dynamics and enhanced signals for the identification of serial biomolecules and DNA bases2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 12, p. 125705-Article in journal (Refereed)
    Abstract [en]

    Nanopore-based sequencing has demonstrated a significant potential for the development of fast, accurate, and cost-efficient fingerprinting techniques for next generation molecular detection and sequencing. We propose a specific multilayered graphene-based nanopore device architecture for the recognition of single biomolecules. Molecular detection and analysis can be accomplished through the detection of transverse currents as the molecule or DNA base translocates through the nanopore. To increase the overall signal-to-noise ratio and the accuracy, we implement a new 'multi-point cross-correlation' technique for identification of DNA bases or other molecules on the single molecular level. We demonstrate that the cross-correlations between each nanopore will greatly enhance the transverse current signal for each molecule. We implement first-principles transport calculations for DNA bases surveyed across a multilayered graphene nanopore system to illustrate the advantages of the proposed geometry. A time-series analysis of the cross-correlation functions illustrates the potential of this method for enhancing the signal-to-noise ratio. This work constitutes a significant step forward in facilitating fingerprinting of single biomolecules using solid state technology.

  • 5.
    Amorim, Rodrigo G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Silicene as a new potential DNA sequencing device2015In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 15, article id 154002Article in journal (Refereed)
    Abstract [en]

    Silicene, a hexagonal buckled 2D allotrope of silicon, shows potential as a platform for numerous new applications, and may allow for easier integration with existing silicon-based microelectronics than graphene. Here, we show that silicene could function as an electrical DNA sequencing device. We investigated the stability of this novel nano-bio system, its electronic properties and the pronounced effects on the transverse electronic transport, i.e., changes in the transmission and the conductance caused by adsorption of each nucleobase, explored by us through the non-equilibrium Green's function method. Intriguingly, despite the relatively weak interaction between nucleobases and silicene, significant changes in the transmittance at zero bias are predicted by us, in particular for the two nucleobases cytosine and guanine. Our findings suggest that silicene could be utilized as an integrated-circuit biosensor as part of a lab-on-a-chip device for DNA sequencing.

  • 6.
    Andersson, Henrik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Manuilskiy, Anatoliy
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Haller, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Hummelgård, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sidén, Johan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Hummelgård, Christine
    Acreo Swedish ICT AB.
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Assembling surface mounted components on ink-jet printed double sided paper circuit board2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, p. Art. no. 094002-Article in journal (Refereed)
    Abstract [en]

    Printed electronics is a rapidly developing field where many components can already be manufactured on flexible substrates by printing or by other high speed manufacturing methods. However, the functionality of even the most inexpensive microcontroller or other integrated circuit is, at the present time and for the foreseeable future, out of reach by means of fully printed components. Therefore, it is of interest to investigate hybrid printed electronics, where regular electrical components are mounted on flexible substrates to achieve high functionality at a low cost. Moreover, the use of paper as a substrate for printed electronics is of growing interest because it is an environmentally friendly and renewable material and is, additionally, the main material used for many packages in which electronics functionalities could be integrated. One of the challenges for such hybrid printed electronics is the mounting of the components and the interconnection between layers on flexible substrates with printed conductive tracks that should provide as low a resistance as possible while still being able to be used in a high speed manufacturing process. In this article, several conductive adhesives are evaluated as well as soldering for mounting surface mounted components on a paper circuit board with inkjet printed tracks and, in addition, a double sided Arduino compatible circuit board is manufactured and programmed.

  • 7.
    Andersson, Henrik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Manuilskiy, Anatoliy
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Lidenmark, Cecilia
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Gao, Jinlan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Öhlund, Thomas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Forsberg, Sven
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Örtegren, Jonas
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Schmidt, Wolfgang
    Schoeller Technocell GmbH and Co. KG, Burg Gretesch, D-49086, Osnabrück, Germany.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    The influence of paper coating content on room temperature sintering of silver nanoparticle ink2013In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 24, no 45, p. Art. no. 455203-Article in journal (Refereed)
    Abstract [en]

    The resistance of inkjet printed lines using a silver nanoparticle based ink can be very dependent on the substrate. A very large difference in resistivity was observed for tracks printed on paper substrates with aluminum oxide based coatings compared to silica based coatings. Silica based coatings are often cationized with polymers using chloride as a counter ion. It is suggested that the precipitation of silver salts is the cause of the high resistivity, since papers pretreated with salt solutions containing ions that precipitate silver salts gave a high resistance. Silver nitrate has a high solubility and paper pretreated with nitrate ions gave a low resistivity without sintering. The results obtained show that, by choosing the correct type of paper substrate, it is possible to manufacture printed structures, such as interconnects on paper, without the need for, or at least to reduce the need for, post-print sintering. This phenomenon is, of course, ink specific. Inks without or with a low silver ion content are not expected to behave in this manner. In some sensor applications, a high resistivity is desired and, by using the correct combination of ink and paper, these types of sensors can be facilitated.

  • 8.
    Andersson, Mikael Svante
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Mathieu, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lee, Su Seong
    The Nanos, Inst Bioengn & Nanotechnol, Singapore 138669, Singapore..
    Normile, Peter S.
    Univ Castilla La Mancha, IRICA, E-13071 Ciudad Real, Spain.;Univ Castilla La Mancha, Dept Fis Aplicada, E-13071 Ciudad Real, Spain..
    Singh, Gurvinder
    Norwegian Univ Sci & Technol, Dept Mat Sci & Engn, N-7491 Trondheim, Norway..
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Angel De Toro, Jose
    Univ Castilla La Mancha, IRICA, E-13071 Ciudad Real, Spain.;Univ Castilla La Mancha, Dept Fis Aplicada, E-13071 Ciudad Real, Spain..
    Size-dependent surface effects in maghemite nanoparticles and its impact on interparticle interactions in dense assemblies2015In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 47, article id 475703Article in journal (Refereed)
    Abstract [en]

    The question of the dominant interparticle magnetic interaction type in random closely packed assemblies of different diameter (6.2-11.5 nm) bare maghemite nanoparticles (NPs) is addressed. Single-particle magnetic properties such as particle anisotropy and exchange bias field are first of all studied in dilute (reference) systems of these same NPs, where interparticle interactions are neglible. Substantial surface spin disorder is revealed in all particles except the smallest, viz. for diameters d = 8-11.5 nm but not for d = 6.2-6.3 nm. X-ray diffraction analysis points to a crystallographic origin of this effect. The study of closely packed assemblies of the d >= 8 nm particles observes collective (superspin) freezing that clearly appears to be governed by interparticle dipole interactions. However, the dense assemblies of the smallest particles exhibit freezing temperatures that are higher than expected from a simple (dipole) extrapolation of the corresponding temperatures found in the d >= 8 nm assemblies. It is suggested that the nature of the dominant interparticle interaction in these smaller particle assemblies is superexchange, whereby the lack of significant surface spin disorder allows this mechanism to become important at the level of interacting superspins.

  • 9. Bell, D. C.
    et al.
    Lemme, Max C.
    Harvard University, Department of Physics.
    Stern, L. A.
    RWilliams, J.
    Marcus, C. M.
    Precision cutting and patterning of graphene with helium ions2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 45, p. 455301-Article in journal (Refereed)
    Abstract [en]

    We report nanoscale patterning of graphene using a helium ion microscope configured for lithography. Helium ion lithography is a direct-write lithography process, comparable to conventional focused ion beam patterning, with no resist or other material contacting the sample surface. In the present application, graphene samples on Si/SiO(2) substrates are cut using helium ions, with computer controlled alignment, patterning, and exposure. Once suitable beam doses are determined, sharp edge profiles and clean etching are obtained, with little evident damage or doping to the sample. This technique provides fast lithography compatible with graphene, with similar to 15 nm feature sizes.

  • 10.
    Belova, Lyubov M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Dahlberg, E. D.
    Riazanova, Anastasiia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Mulders, J. J. L.
    Christophersen, C.
    Eckert, J.
    Rapid electron beam assisted patterning of pure cobalt at elevated temperatures via seeded growth2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 14, p. 145305-Article in journal (Refereed)
    Abstract [en]

    A new method of direct, rapid nano- to micro-scale patterning of high purity cobalt is presented. The method utilizes a combination of electron beam induced deposition (EBID) and seeded growth at elevated temperatures below the temperature of spontaneous thermal decomposition. Dicobalt octacarbonyl Co-2(CO)(8) is used as the precursor and carbon as a seed layer. Seeded deposition is carried out in the substrate temperature range from 55 to 75 degrees C. Deposition yield is significantly higher than conventional EBID and magnetotransport measurements indicate that resistivity, 22 mu Omega cm, and saturation magnetization, 1.55 T, are much closer to the corresponding values for bulk Co than those for standard EBID.

  • 11.
    Benedict, Samatha
    et al.
    Indian Inst Sci, Ctr Nano Sci & Engn, Bangalore, Karnataka, India..
    Lumdee, Chatdanai
    Univ Gothenburg, Dept Phys, Gothenburg, Sweden..
    Dmitriev, Alexandre
    Univ Gothenburg, Dept Phys, Gothenburg, Sweden..
    Anand, Srinivasan
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Bhat, Navakanta
    Indian Inst Sci, Ctr Nano Sci & Engn, Bangalore, Karnataka, India..
    Colloidal lithography nanostructured Pd/PdOx core-shell sensor for ppb level H2S2018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 25, article id 255502Article in journal (Refereed)
    Abstract [en]

    In this work we report on plasma oxidation of palladium (Pd) to form reliable palladium/palladium oxide (Pd/PdOx) core-shell sensor for ppb level H2S detection and its performance improvement through nanostructuring using hole-mask colloidal lithography (HCL). The plasma oxidation parameters and the sensor operating conditions are optimized to arrive at a sensor device with high sensitivity and repeatable response for H2S. The plasma oxidized palladium/palladium oxide sensor shows a response of 43.1% at 3 ppm H2S at the optimum operating temperature of 200 degrees C with response and recovery times of 24 s and 155 s, respectively. The limit of detection (LoD) of the plasma oxidised beam is 10 ppb. We further integrate HCL, a bottom-up and cost-effective process, to create nanodiscs of fixed diameter of 100 nm and varying heights (10, 15 and 20 nm) on 10 nm thin Pd beam which is subsequently plasma oxidized to improve the H2S sensing characteristics. The nanostructured Pd/PdOx sensor with nanodiscs of 100 nm diameter and 10 nm height shows an enhancement in sensing performance by 11.8% at same operating temperature and gas concentration. This nanostructured sensor also shows faster response and recovery times (15s and 100s, respectively) compared to the unstructured Pd/PdOx counterpart together with an experimental LoD of 10 ppb and the estimated limit going all the way down to 2 ppb. Material characterization of the fabricated Pd/PdOx sensors is done using UV-vis spectroscopy and x-ray photoemission spectroscopy.

  • 12.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Sadreev, A.F.
    Kirensky Institute of Physics, 660036, Krasnoyarsk, Russian Federation.
    Starikov, Anton
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Quantum chaos among nodal points and streamlines at ballistic electron transport through open quantum dots2001In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 12, no 4, p. 562-565Conference paper (Other academic)
    Abstract [en]

    We trace signatures of quantum chaos in the distribution of nodal points and streamlines for coherent electron transport through different types of quantum dots (chaotic and regular). We have calculated normalized distribution functions for the nearest distances between nodal points and found that this distribution may be used as a signature of quantum chaos for electron transport in open systems. Different chaotic billiards show the same characteristic distribution function for nodal points. This signature of quantum chaos is well reproduced using well known approaches for chaotic wavefunctions. We have also investigated the quantum flows which display some remarkable features.

  • 13.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Yakimenko, I.I.
    Bychkov, A.M.
    Centre for Quantum Computation, Clarendon Laboratory, Oxford OX1 3PU, United Kingdom, Moscow State Engineering Physics Institute, Technical University, 115409 Moscow, Russian Federation.
    On the role of electron exchange and correlation in semiconductor quantum dots2001In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 12, no 4, p. 529-532Conference paper (Other academic)
    Abstract [en]

    Spontaneous magnetization of single and coupled quantum dots formed by lateral confinement of a high-mobility two-dimensional electron gas is studied for a realistic GaAs/AlGaAs heterostructure. The modelling of the device takes into account contributions from a patterned gate, doping, surface states, and mirror charges. To explore the magnetic properties we use the Kohn-Sham local spin-density formalism including the contributions from electron correlation and exchange. We show by explicit calculations that the exchange is the dominant mechanism driving a spontaneous magnetization of a dot. The correlation potential reduces the amount of level splitting and usually affects the electron content in the dot at a given gate voltage. These effects are, however, small and may be neglected under present circumstances. Single dots with up to 50 electrons have been studied.

  • 14.
    Beyer, Jan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Suraprapapich, Suwaree
    UC San Diego, USA.
    Tu, Charles
    UC San Diego, USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Spin injection in lateral InAs quantum dot structures by optical orientation spectroscopy2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 37, p. 375401-Article in journal (Refereed)
    Abstract [en]

    Optical spin injection is studied in novel laterally-arranged self-assembled InAs/GaAs quantum dot structures, by using optical orientation measurements in combination with tunable laser spectroscopy. It is shown that spins of uncorrelated free carriers are better conserved during the spin injection than the spins of correlated electrons and holes in an exciton. This is attributed to efficient spin relaxation promoted by the electron–hole exchange interaction of the excitons. Our finding suggests that separate carrier injection, such as that employed in electrical spin injection devices, can be advantageous for spin conserving injection. It is also found that the spin injection efficiency decreases for free carriers with high momentum, due to the acceleration of spin relaxation processes.

  • 15.
    Beyer, Jan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Suraprapapich, S
    Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, USA .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Hanle effect and electron spin polarization in InAs/GaAs quantum dots up to room temperature2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 13, p. 135705-Article in journal (Refereed)
    Abstract [en]

    Hanle effect in InAs/GaAs quantum dots (QDs) is studied under optical orientation as a function of temperature over the range of 150-300 K, with the aim to understand the physical mechanism responsible for the observed sharp increase of electron spin polarization with increasing temperature. The deduced spin lifetime Ts of positive trions in the QDs is found to be independent of temperature, and is also insensitive to excitation energy and density. It is argued that the measured Ts is mainly determined by the longitudinal spin flip time (T1) and the spin dephasing time (T2 *) of the studied QD ensemble, of which both are temperatureindependent over the studied temperature range and the latter makes a larger contribution. The observed sharply rising of the QD spin polarization degree with increasing temperature, on the other hand, is shown to be induced by an increase in spin injection efficiency from the barrier/wetting layer and also by a moderate increase in spin detection efficiency of the QD.

  • 16.
    Beyer, Jan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Suraprapapich, S
    Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, USA .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Hanle effect in InAs/GaAs quantum dots up to room temperatures2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528Article in journal (Refereed)
  • 17.
    Blom, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Coronel, Ernesto
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fabrication and characterization of highly reproducible, high resistance nanogaps made by focused ion beam milling2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 28, p. 285301-Article in journal (Refereed)
    Abstract [en]

    Nanoelectrodes were fabricated combining photolithography, electron beam lithography and focused ion beam milling allowing for large scale integration and nanoengineering of the electrode properties. The structure determination by transmission and scanning electron microscopy showed a highly reproducible gap width. The atomic scale electrode structure was characterized using scanning and transmission electron microscopy. The nanogap resistances were found to be the highest hitherto reported for nanogaps, namely in the 300–1300 TΩ range. Gold nanoparticles were trapped by ac dielectrophoresis, and the electrodes were shown to be stable enough to endure empty gap voltages as high as 5 V as well as currents high enough to induce fusing of trapped nanoparticles.

  • 18.
    Bruhn, Benjamin
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Valenta, Jan
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Controlled fabrication of individual silicon quantum rods yielding high intensity, polarized light emission2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 50, p. 1-5Article in journal (Refereed)
    Abstract [en]

    Elongated silicon quantum dots (also referred to as rods) were fabricated using a lithographic process which reliably yields sufficient numbers of emitters. These quantum rods are perfectly aligned and the vast majority are spatially separated well enough to enable single-dot spectroscopy. Not only do they exhibit extraordinarily high linear polarization with respect to both absorption and emission, but the silicon rods also appear to luminesce much more brightly than their spherical counterparts. Significantly increased quantum efficiency and almost unity degree of linear polarization render these quantum rods perfect candidates for numerous applications.

  • 19. Buscaglia, M. T.
    et al.
    Buscaglia, V.
    Viviani, M.
    Petzelt, J.
    Savinov, M.
    Mitoseriu, L.
    Testino, A.
    Nanni, P.
    Harnagea, C.
    Zhao, Zhe
    Department of Physical Inorganic and Structural Chemistry, Stockholm University.
    Nygren, M.
    Ferroelectric properties of dense nanocrystalline BaTiO3 ceramics2004In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 15, no 9, p. 1113-1117Article in journal (Refereed)
    Abstract [en]

    Dense BaTiO3 ceramics with 50 nm average grain size obtained by spark plasma sintering were investigated. The dielectric data show a broad ferro-para phase transition with a maximum permittivity of approximate to1100 at 390 K and 1 kHz. The local ferroelectric switching behaviour was investigated by piezoresponse force microscopy. Typical piezoelectric hysteresis loops were recorded at different positions of the sample. The present results provide experimental evidence for polarization switching at the local scale, indicating that the critical grain size for the disappearance of ferroelectric behaviour in dense, bulk BaTiO3 nanocrystalline ceramics is below 50 nm.

  • 20. Bychkov, A.M.
    et al.
    Yakimenko, I.I.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Spin-dependent electron behaviour in quantum point contacts2000In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 11, no 4, p. 318-322Article in journal (Refereed)
    Abstract [en]

    The effect of spontaneous spin polarization in quantum point contacts (QPCs) is investigated by self-consistent modelling within the Kohn-Sham local spin-density formalism. The existence of the spin-polarized state of the QPC channel in the low-density regime is shown to change the value and the shape of the effective potential barrier for up- and down-spin electrons. We suggest that this effect can be relevant to the explanation of the anomalous 0.7-structure in the QPC conductance and may assist spin injection in potential spintronic devices.

  • 21. Chatterjee, Sanjukta
    et al.
    Nüesch, Frank
    Chu, Bryan T T
    Comparing carbon nanotubes and graphene nanoplatelets as reinforcements in polyamide 12 composites2011In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 22, no 27, p. 275714-Article in journal (Refereed)
    Abstract [en]

    We investigate the influence of nanofillers including carbon nanotubes (CNTs) and graphene nanoplatelets on a thermoplastic engineering polymer, polyamide 12 (PA12). The comparison between these two important nanofillers as to how they influence the structure and properties of the polymer is systematically studied. The polymer–nanofiller composites were prepared using a twin-screw micro-extruder and the composite was thereafter hot pressed into thin films. The structure (using wide angle x-ray diffraction and differential scanning calorimetry) and properties (through tensile testing and conductivity measurement) of the thin films have been investigated. The composites incorporating surfactant showed the best CNT distribution and dispersion, causing an improvement of up to 80% in the toughness modulus over pure PA12. Electrical percolation could also be achieved at nanofiller concentrations of 1 to 2 wt%. In this study we observed that CNT fillers bring about more pronounced improvements in PA12 compared to graphene nanoplatelets, as far as mechanical and electrical properties are concerned.

  • 22. Chen, C. L.
    et al.
    Furusho, H.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Mori, H.
    Silver nanowires with a monoclinic structure fabricated by a thermal evaporation method2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, p. 405605-Article in journal (Refereed)
    Abstract [en]

    Silver nanowires with a monoclinic structure (mono-Ag NWs) were fabricated by a thermal evaporation method for the first time. The crystal lattice parameters of the mono-Ag NWs were calculated using the UnitCell program. They are as follows: a = 0.303 nm, b = 1.140 nm, c = 0.292 nm, and β = 118.5◦. In situ annealing experiments revealed that the as-prepared mono-Ag NWs transited to fcc-Ag NWs during annealing at ∼1173 K for 60 s.

  • 23. Chen, S
    et al.
    Svedendahl, M
    Käll, M
    Gunnarsson, L
    Dmitriev, A
    Ultrahigh sensitivity made simple: nanoplasmonic label-free biosensing with an extremely low limit-of-detection for bacterial and cancer diagnostics.2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 43Article in journal (Refereed)
    Abstract [en]

    We present a simple and robust scheme for biosensing with an ultralow limit-of-detection down to several pg cm(-2) (or several tens of attomoles cm(-2)) based on optical label-free biodetection with localized surface plasmon resonances. The scheme utilizes cost-effective optical components and comprises a white light source, a properly functionalized sensor surface enclosed in a simple fluidics chip, and a spectral analyzer. The sensor surface is produced by a bottom-up nanofabrication technique with hole mask colloidal lithography. Despite its simplicity, the method is able to reliably detect protein-protein binding events at low picomolar and femtomolar concentrations, which is exemplified by the label-free detection of the extracellular adherence protein (EAP) found on the outer surface of the bacterium Staphylococcus aureus and of prostate-specific antigen (PSA), which is believed to be a prostate cancer marker. These experiments pave the way towards an ultra-sensitive yet compact biodetection platform for point-of-care diagnostics applications.

  • 24.
    Chulapakorn, Thawatchart
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sychugov, Ilya
    Royal Institute of Technology (KTH), Department of Materials and Nano Physics, SE-164 40 Kista, Sweden.
    Suvanam, Sethu Saveda
    Royal Institute of Technology (KTH), School of Information and Communication Technology, PO Box Electrum 229, SE-16440 Kista, Sweden.
    Linnros, Jan
    Royal Institute of Technology (KTH), Department of Materials and Nano Physics, SE-164 40 Kista, Sweden.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hallén, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Royal Institute of Technology, School of Information & Communication Technology, SE-16440 Kista, Sweden.
    Influence of Swift Heavy Ion Irradiation on the Photoluminescence of Si-nanoparticles and Defects in SiO22017In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 28, no 37, article id 375603Article in journal (Refereed)
    Abstract [en]

    The influence of swift heavy ion (SHI) irradiation on the photoluminescence (PL) of silicon nanoparticles (SiNPs) and defects in SiO2-film is investigated. SiNPs were formed by implantation of 70 keV Si+ and subsequent thermal annealing to produce optically active SiNPs and to remove implantation-induced defects. Seven different ion species with energy between 3-36 MeV and fluence from 10(11)-10(14) cm(-2) were employed for irradiation of the implanted samples prior to the thermal annealing. Induced changes in defect and SiNP PL were characterized and correlated with the specific energy loss of the employed SHIs. We find that SHI irradiation, performed before the thermal annealing process, affects both defect and SiNP PL. The change of defect and SiNP PL due to SHI irradiation is found to show a threshold-like behaviour with respect to the electronic stopping power, where a decrease in defect PL and an anticorrelated increase in SiNP PL after the subsequent thermal annealing are observed for electronic stopping exceeding 3-5 keV nm(-1). PL intensities are also compared as a function of total energy deposition and nuclear energy loss. The observed effects can be explained by ion track formation as well as a different type of annealing mechanisms active for SHI irradiation compared to the thermal annealing.

  • 25.
    de Souza, Fabio A. L.
    et al.
    UFES, Dept Fis, Vitoria, ES, Spain..
    Amorim, Rodrigo G.
    UFF, ICEx, Dept Fis, Volta Redonda, RJ, Brazil..
    Scopel, Wanderla L.
    UFES, Dept Fis, Vitoria, ES, Spain.;UFF, ICEx, Dept Fis, Volta Redonda, RJ, Brazil..
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Nano-structured interface of graphene and h-BN for sensing applications2016In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 27, no 36, article id 365503Article in journal (Refereed)
    Abstract [en]

    The atomically-precise controlled synthesis of graphene stripes embedded in hexagonal boron nitride opens up new possibilities for the construction of nanodevices with applications in sensing. Here, we explore properties related to the electronic structure and quantum transport of a graphene nanoroad embedded in hexagonal boron nitride, using a combination of density functional theory and the non-equilibrium Green's functions method to calculate the electric conductance. We find that the graphene nanoribbon signature is preserved in the transmission spectra and that the local current is mainly confined to the graphene domain. When a properly sized nanopore is created in the graphene part of the system, the electronic current becomes restricted to a carbon chain running along the border with hexagonal boron nitride. This circumstance could allow the hypothetical nanodevice to become highly sensitive to the electronic nature of molecules passing through the nanopore, thus opening up ways to detect gas molecules, amino acids, or even DNA sequences based on a measurement of the real-time conductance modulation in the graphene nanoroad.

  • 26. Dietzel, Dirk
    et al.
    de Wijn, Astrid S.
    Stockholm University, Faculty of Science, Department of Physics. Norwegian University of Science and Technology, Norway.
    Vorholzer, Matthias
    Schirmeisen, Andre
    Friction fluctuations of gold nanoparticles in the superlubric regime2018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 15, article id 155702Article in journal (Refereed)
    Abstract [en]

    Superlubricity, or alternatively termed structural (super)lubrictiy, is a concept where ultra-low friction is expected at the interface between sliding surfaces if these surfaces are incommensurate and thus unable to interlock. In this work, we now report on sudden, reversible, friction changes that have been observed during AFM-based nanomanipulation experiments of gold nanoparticles sliding on highly oriented pyrolythic graphite. These effects can be explained by rotations of the gold nanoparticles within the concept of structural superlubricity, where the occurrence of ultra-low friction can depend extremely sensitively on the relative orientation between the slider and the substrate. From our theoretical simulations it will become apparent how even miniscule magnitudes of rotation are compatible to the observed effects and how size and shape of the particles can influence the dependence between friction and relative orientation.

  • 27.
    Dong, Suzi
    et al.
    Department of Chemistry, National University of Singapore.
    Fan, HM
    Department of Physics, National University of Singapore.
    Zhang, Xuanjun
    Department of Chemistry, National University of Singapore.
    Loh, Kian Ping
    Department of Chemistry, National University of Singapore.
    Cheng, C-L
    Department of Physics, National Dong Hwa University.
    SOW, CH
    Department of Physics, National University of Singapore.
    Foo, YL
    Institute of Materials Research and Engineering, Singapore.
    An effective surface-enhanced Raman scattering template based on a Ag nanocluster–ZnO nanowire array2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 17, p. 175705-Article in journal (Refereed)
    Abstract [en]

    An effective surface-enhanced Raman scattering (SERS) template based on a 3D hybrid Ag nanocluster (NC)-decorated ZnO nanowire array was fabricated through a simple process of depositing Ag NCs on ZnO nanowire arrays. The effects of particle size and excitation energy on the Raman scattering in these hybrid systems have been investigated using rhodamine 6G as a standard analyte. The results indicate that the hybrid nanosystem with 150 nm Ag NCs produces a larger SERS enhancement factor of 3.2 × 108, which is much higher than that of 10 nm Ag NCs (6.0 × 106) under 532 nm excitation energy. The hybrid nanowire arrays were further applied to obtain SERS spectra of the two-photon absorption (TPA) chromophore T7. Finite-difference time-domain simulations reveal the presence of an enhanced field associated with inter-wire plasmon coupling of the 150 nm Ag NCs on adjacent ZnO nanowires; such a field was absent in the case of the 10 nm Ag NC-coated ZnO nanowire. Such hybrid nanosystems could be used as SERS substrates more effectively than assembled Ag NC film due to the enhanced light-scattering local field and the inter-wire plasmon-enhanced electromagnetic field.

  • 28.
    dos Santos, Renato B.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. University of Federal Bahia, Brazil.
    de Brito Mota, F.
    University of Federal Bahia, Brazil.
    Rivelino, R.
    University of Federal Bahia, Brazil.
    Kakanakova-Gueorguie, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Gueorguiev, Gueorgui Kustov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Van der Waals stacks of few-layer h-AlN with graphene: an ab initio study of structural, interaction and electronic properties2016In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 27, no 14, p. 145601-Article in journal (Refereed)
    Abstract [en]

    Graphite-like hexagonal AlN (h-AlN) multilayers have been experimentally manifested and theoretically modeled. The development of any functional electronics applications of h-AlN would most certainly require its integration with other layered materials, particularly graphene. Here, by employing vdW-corrected density functional theory calculations, we investigate structure, interaction energy, and electronic properties of van der Waals stacking sequences of few-layer h-AlN with graphene. We find that the presence of a template such as graphene induces enough interlayer charge separation in h-AlN, favoring a graphite-like stacking formation. We also find that the interface dipole, calculated per unit cell of the stacks, tends to increase with the number of stacked layers of h-AlN and graphene.

  • 29.
    Elfström, Niklas
    et al.
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Linnros, Jan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Biomolecule detection using a silicon nanoribbon: Accumulation mode versus inversion mode2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 23, p. 235201-Article in journal (Refereed)
    Abstract [en]

    Silicon nanoribbons were fabricated using standard optical lithography from silicon on insulator material with top silicon layer thicknesses of 100, 60 and 45 nm. Electrically these work as Schottky-barrier field-effect transistors and, depending on the substrate voltage, electron or hole injection is possible. The current through the nanoribbon is extremely sensitive to charge changes at the oxidized top surface and can be used for biomolecule detection in a liquid. We show that for detection of streptavidin molecules the response is larger in the accumulation mode than in the inversion mode, although not leading to higher detection sensitivity due to increased noise. The effect is attributed to the location in depth of the conducting channel, which for holes is closer to the screened surface charges of the biomolecules. Furthermore, the response increases for decreasing silicon thickness in both the accumulation mode and the inversion mode. The results are verified qualitatively and quantitatively through a two-dimensional simulation model on a cross section along the nanoribbon device.

  • 30. Esmaeili, M.
    et al.
    Harati Zadeh, Hamid
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Paskov, Plamen
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bergman, Peder
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Iwaya, M.
    Kamiyama, S.
    Amano, H.
    Akasaki, I
    Photoluminescence study of MOCVD-grown GaN/AlGaN MQW nanostructures: Influence of Al composition and Si doping2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 2Article in journal (Refereed)
    Abstract [en]

    A detailed study of low-temperature photoluminescence (PL) in GaN/AlGaN multiple quantum well (MQW) nanostructures has been reported. We have investigated the effect of Si doping and Al content on PL spectra and PL decay time of these structures. The temperature dependence of radiative as well as non-radiative lifetimes have been evaluated between 2K and room temperature for different Si doping. We found that radiative recombination at higher temperatures even up to RT is stronger in the doped sample, compared to the undoped one. Hole localization in GaN/AlGaN MQWs with different compositions of Al is demonstrated via PL transient decay times and LO phonon coupling. It is found that there is an increasing of the decay time at the PL peak emission with increasing Al composition. For the undoped sample, a non-exponential PL decay behaviour at 2K is attributed to localized exciton recombination. A slight upshift in QWs PL peak with increasing Al composition is observed, which is counteracted by the expected rise of the internal QW electric field with increasing Al. The localization energies have been evaluated by studying the variation of the QW emission versus temperature and we found out that the localization energy increases with increasing Al composition. © IOP Publishing Ltd.

  • 31.
    Fang, Mei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Ström, Valter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Belova, Lyubov
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Particle size and magnetic properties dependence on growth temperature for rapid mixed co-precipitated magnetite nanoparticles2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 14, p. 145601-Article in journal (Refereed)
    Abstract [en]

    Magnetite nanoparticles have been prepared by co-precipitation using a custom-designed jet mixer to achieve rapid mixing (RM) of reactants in a timescale of milliseconds. The quick and stable nucleation obtained allows control of the particle size and size distribution via a more defined growth process. Nanoparticles of different sizes were prepared by controlling the processing temperature in the first few seconds post-mixing. The average size of the nanoparticles investigated using a Tecnai transmission electron microscope is found to increase with the temperature from 3.8 nm at 1 +/- 1 degrees C to 10.9 nm for particles grown at 95 +/- 1 degrees C. The temperature dependence of the size distribution follows the same trend and is explained in terms of Ostwald ripening of the magnetite nanoparticles during the co-precipitation of Fe2+ and Fe3+. The magnetic properties were studied by monitoring the blocking temperature via both DC and AC techniques. Strikingly, the obtained RM particles maintain the high magnetization (as high as similar to 88 A m(2) kg(-1) at 500 kA m(-1)) while the coercivity is as low as similar to 12 A m(-1) with the expected temperature dependence. Besides, by adding a drop of tetramethylammonium hydroxide, aqueous ferrofluids with long term stability are obtained, suggesting their suitability for applications in ferrofluid technology and biomedicine.

  • 32.
    Forchheimer, Daniel
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Borysov, Stanislav S.
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Platz, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. Max-Planck-Institute for the Physics of Complex Systems, Germany.
    Haviland, David B.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Determining surface properties with bimodal and multimodal AFM2014In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 25, no 48, p. 485708-Article in journal (Refereed)
    Abstract [en]

    Conventional dynamic atomic force microscopy (AFM) can be extended to bimodal and multimodal AFM in which the cantilever is simultaneously excited at two or more resonance frequencies. Such excitation schemes result in one additional amplitude and phase images for each driven resonance, and potentially convey more information about the surface under investigation. Here we present a theoretical basis for using this information to approximate the parameters of a tip-surface interaction model. The theory is verified by simulations with added noise corresponding to room-temperature measurements.

  • 33.
    Forsberg, Erik
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Reversible logic based on electron waveguide Y-branch switches2004In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 15, no 4, p. S298-S302Article in journal (Refereed)
    Abstract [en]

    The lower bound of the energy required to change the state of an electron waveguide Y-branch switch is not thermally limited, and the theoretical limit is orders of magnitude lower than the energy cost of information erasure. Thus as the power dissipation due to information erasure can be avoided by the use of logically reversible gates, such gates based on electron waveguide Y-branch switches promise circuits with extremely low power dissipation. In this paper, reversible logic based on electron waveguide Y-branch switches is proposed and discussed.

  • 34.
    Forsberg, Mathias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Serban, Alexandra
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Poenaru, Iuliana
    Fraunhofer ISC, Project Group Materials Recycling and Resource Strategy IWKS, Hanau, Germany.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Junaid, Mohammad
    RWTH Aachen University, Aachen, Germany.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Stacking fault related luminescence in GaN nanorods2015In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528Article in journal (Refereed)
    Abstract [en]

    Optical and structural properties are presented for GaN nanorods grown in the [0001]direction on Si(111) substrates by direct-current reactive magnetron sputter epitaxy.Transmission electron microscopy reveals clusters of dense stacking faults (SFs) regularlydistributed along the c-axis. A strong emission at ~3.42 eV associated with basal plane SFsdemonstrates thermal stability up to room temperatures together with a relatively shortrecombination time suggesting carrier localization in the system similar to multiple quantumwells.

  • 35.
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Detection of spin reversal and nutations through current measurements2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 28, p. 285714-Article in journal (Refereed)
    Abstract [en]

    The dynamics of a single spin embedded in a tunnel junction between ferromagnetic contacts is strongly affected by the exchange coupling to the tunneling electrons. Moment reversal of the local spin induced by the bias voltage across the junction is shown to have a measurable effect on the tunneling current. Furthermore, the frequency of a harmonic bias voltage is picked up by the local spin dynamics and transferred back to the current, generating a double frequency component.

  • 36.
    Fransson, Jonas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Formation of pure two-electron triplet states in weakly coupled quantum dots attached to ferromagnetic leads2006In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 17, no 21, p. 5344-5348Article in journal (Refereed)
    Abstract [en]

    Weakly coupled quantum dots in the Pauli spin blockade regime are considered with respect to spin-dependent transport. By attaching one half-metallic and one non-magnetic lead, the Pauli spin blockade is formed by a pure triplet state with spin moment S-z = 1 or -1. Furthermore, additional spin blockade regimes emerge because of full occupation in states with opposite spin to that of the half-metallic lead.

  • 37.
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Formation of pure two-electron triplet states in weakly coupled quantum dots attached to ferromagnetic leads2006In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 17, no 21, p. 5344-5348Article in journal (Refereed)
    Abstract [en]

    Weakly coupled quantum dots in the Pauli spin blockade regime are considered with respect to spin-dependent transport. By attaching one half-metallic and one non-magnetic lead, the Pauli spin blockade is formed by a pure triplet state with spin moment S-z = 1 or -1. Furthermore, additional spin blockade regimes emerge because of full occupation in states with opposite spin to that of the half-metallic lead.

  • 38.
    Freitas, Rafael RQ
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. University of Federal Bahia, Brazil.
    de Brito Mota, F.
    University of Federal Bahia, Brazil.
    Rivelino, R.
    University of Federal Bahia, Brazil.
    de Castilho, C. M. C.
    University of Federal Bahia, Brazil.
    Kakanakova-Gueorguie, Anelia
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tuning band inversion symmetry of buckled III-Bi sheets by halogenation2016In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 27, no 5, p. 1-11, article id 055704Article in journal (Refereed)
    Abstract [en]

    First-principles calculations are employed to investigate structural, electronic and topological insulating properties of XBi (X = B, Al, Ga, and In) monolayers upon halogenation. It is known that Y-XBi (X = Ga, In, Tl; Y = F, Cl, Br, I) can originate inversion-asymmetric topological insulators with large bulk band gaps. Our results suggest that Y-XBi (X = B, Al; Y = F, Cl, Br, I) may also result in nontrivial topological insulating phases. Despite the lower atomic number of B and Al, the spin-orbit coupling opens a band gap of about 400 meV in Y-XBi (X = B, Al), exhibiting an unusual electronic behavior for practical applications in spintronics. The nature of the bulk band gap and Dirac-cone edge states in their nanoribbons depends on the group-III elements and Y chemical species. They lead to a chemical tunability, giving rise to distinct band inversion symmetries and exhibiting Rashba-type spin splitting in the valence band of these systems. These findings indicate that a large family of Y-XBi sheets can exhibit nontrivial topological characteristics, by a proper tuning, and open a new possibility for viable applications at room temperature.

  • 39.
    Galstyan, Vardan
    et al.
    CNR IDASC SENSOR Lab.
    Comini, Elisabetta
    CNR IDASC SENSOR Lab.
    Faglia, Guido
    CNR IDASC SENSOR Lab.
    Vomiero, Alberto
    CNR IDASC SENSOR Lab.
    Borgese, Laura
    INSTM and Chemistry for Technologies Laboratory.
    Bontempi, Elza
    INSTM and Chemistry for Technologies Laboratory.
    Sberveglieri, Giorgio
    CNR IDASC SENSOR Lab.
    Fabrication and investigation of gas sensing properties of Nb-doped TiO 2 nanotubular arrays2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 23, article id 235706Article in journal (Refereed)
    Abstract [en]

    Synthesis of Nb-containing titania nanotubular arrays at room temperature by electrochemical anodization is reported. Crystallization of pure and Nb-doped TiO 2 nanotubes was carried out by post-growth annealing at 400°C. The morphology of the tubes obtained was characterized by scanning electron microscopy (SEM). Crystal structure and composition of tubes were investigated by glancing incidence x-ray diffraction (GIXRD) and total reflection x-ray fluorescence (TXRF). For the first time gas sensing characteristics of Nb-doped TiO 2 nanotubes were investigated and compared to those of undoped nanotubes. The functional properties of nanotubular arrays towards CO, H 2, NO 2, ethanol and acetone were tested in a wide range of operating temperature. The introduction of Nb largely improves conductivity and enhances gas sensing performances of TiO 2 nanotubes. © 2012 IOP Publishing Ltd.

  • 40.
    Geremariam Welearegay, Tesfalem
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Rovira & Virgili Univ, Dept Elect Elect & Automat Engn, Tarragona 43007, Spain.;Mol Fingerprint Sweden AB, S-75655 Uppsala, Sweden..
    Cindemir, Umut
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Mol Fingerprint Sweden AB, S-75655 Uppsala, Sweden.
    Österlund, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Mol Fingerprint Sweden AB, S-75655 Uppsala, Sweden.
    Ionescu, Radu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Rovira & Virgili Univ, Dept Elect Elect & Automat Engn, Tarragona 43007, Spain..
    Fabrication and characterisation of ligand-functionalised ultrapure monodispersed metal nanoparticle nanoassemblies employing advanced gas deposition technique2018In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 29, no 6, article id 065603Article in journal (Refereed)
    Abstract [en]

    Here, we report for the first time the fabrication of ligand-functionalised ultrapure monodispersed metal nanoparticles (Au, Cu, and Pt) from their pure metal precursors using the advanced gas deposition technique. The experimental conditions during nanoparticle formation were adjusted in order to obtain ultrafine isolated nanoparticles on different substrates. The morphology and surface analysis of the as-deposited metal nanoparticles were investigated using scanning electron microscopy, x-ray diffraction and Fourier transform infra-red spectroscopy, which demonstrated the formation of highly ordered pure crystalline nanoparticles with a relatively uniform size distribution of similar to 10 nm (Au), similar to 4 nm (Cu) and similar to 3 nm (Pt), respectively. A broad range of organic ligands containing thiol or amine functional groups were attached to the nanoparticles to form continuous networks of nanoparticle-ligand nanoassemblies, which were characterised by scanning electron microscopy and x-ray photoelectron spectroscopy. The electrical resistance of the functional nanoassemblies deposited in the gap spacing of two microfabricated parallel Au electrodes patterned on silicon substrates ranged between tens of k Omega and tens of M Omega, which is suitable for use in many applications including (bio)chemical sensors, surface-enhanced Raman spectroscopy and molecular electronic rectifiers.

  • 41. Gholami, M.
    et al.
    Haratizadeh, H.
    Esmaeili, M.
    Amiri, R.
    Holtz, P. O.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Alternation of band gap and localization of excitons in InGaNAs nanostructures with low nitrogen content2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 31Article in journal (Refereed)
    Abstract [en]

    Continuous wave photoluminescence (cw PL) spectroscopy has been used to study the optical properties of a set of InGaNAs epilayers and single quantum wells with nitrogen concentration less than a few per cent at different temperatures and different excitation powers. We found that nitrogen has a critical role on the emission light of InGaNAs nanostructures and the recombination mechanism. The incorporation of a few per cent of nitrogen leads to shrinkage of the InGaNAs band gap. The physical origin of such band gap reduction has been investigated both experimentally and theoretically by using a band anticrossing model. We have found that localization of excitons that have been caused by incorporation of a few per cent of nitrogen in these structures is the main explanation of such anomalous behavior observed in the low-temperature photoluminescence spectra of these nanostructures. The localization energies of carriers have been evaluated by studying the variation of the quantum well (QW) emission versus temperature, and it was found that the localization energy increases with increasing nitrogen composition. Our data also show that, with increasing excitation intensity, the PL peak position moves to higher energies (blue shift) due to the filling of localized states and capture centers for excitons by photo-generated carriers.

  • 42.
    Gholami, M.
    et al.
    Physics Department, Shahrood University of Technology, PO Box 316, 3619995161, Shahrood, Iran, Department of Science, Islamic Azad University, Damghan Branch, Damghan, Iran.
    Haratizadeh, H.
    Physics Department, Shahrood University of Technology, PO Box 316, 3619995161, Shahrood, Iran, Department of Physics, Chemistry and Biology, Linkoping University, SE-581 581 83 Linkoping, Sweden.
    Esmaeili, M.
    Physics Department, Shahrood University of Technology, PO Box 316, 3619995161, Shahrood, Iran, Department of Science, Islamic Azad University, Damghan Branch, Damghan, Iran.
    Amiri, R.
    Physics Department, Shahrood University of Technology, PO Box 316, 3619995161, Shahrood, Iran.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Hammar, M.
    Department of Microelectronics and Applied Physics, School of Information and Communication Technology, Royal Institute of Technology (KTH), 16440 Kista-Stocholm, Sweden.
    Alternation of band gap and localization of excitons in InGaNAs nanostructures with low nitrogen content2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 31, p. 315705-Article in journal (Refereed)
    Abstract [en]

    Continuous wave photoluminescence (cw PL) spectroscopy has been used to study the optical properties of a set of InGaNAs epilayers and single quantum wells with nitrogen concentration less than a few per cent at different temperatures and different excitation powers. We found that nitrogen has a critical role on the emission light of InGaNAs nanostructures and the recombination mechanism. The incorporation of a few per cent of nitrogen leads to shrinkage of the InGaNAs band gap. The physical origin of such band gap reduction has been investigated both experimentally and theoretically by using a band anticrossing model. We have found that localization of excitons that have been caused by incorporation of a few per cent of nitrogen in these structures is the main explanation of such anomalous behavior observed in the low-temperature photoluminescence spectra of these nanostructures. The localization energies of carriers have been evaluated by studying the variation of the quantum well (QW) emission versus temperature, and it was found that the localization energy increases with increasing nitrogen composition. Our data also show that, with increasing excitation intensity, the PL peak position moves to higher energies (blue shift) due to the filling of localized states and capture centers for excitons by photo-generated carriers. © IOP Publishing Ltd.

  • 43.
    Gonzalez-Moya, Johan R.
    et al.
    Univ Fed Pernambuco UFPE, Recife, PE, Brazil.;Ctr Tecnol Estrateg Nordeste CETENE, Recife, PE, Brazil..
    Garcia-Basabe, Yunier
    Univ Fed Rio de Janeiro, Rio De Janeiro, RJ, Brazil.;Univ Fed Integracao Latino Amer, UNILA, Foz Do Iguacu, PR, Brazil..
    Rocco, Maria Luiza M.
    Univ Fed Rio de Janeiro, Rio De Janeiro, RJ, Brazil..
    Pereira, Marcelo B.
    Univ Fed Rio Grande do Sul, Inst Fis, Porto Alegre, RS, Brazil..
    Princival, Jefferson L.
    Univ Fed Pernambuco UFPE, Recife, PE, Brazil..
    Almeida, Luciano C.
    Univ Fed Pernambuco UFPE, Recife, PE, Brazil..
    Araujo, Carlos M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    David, Denis G. F.
    Univ Fed Bahia UFBA, Inst Fis, Salvador, BA, Brazil..
    da Silva, Antonio Ferreira
    Univ Fed Bahia UFBA, Inst Fis, Salvador, BA, Brazil..
    Machado, Giovanna
    Univ Fed Pernambuco UFPE, Recife, PE, Brazil.;Ctr Tecnol Estrateg Nordeste CETENE, Recife, PE, Brazil..
    Effects of the large distribution of CdS quantum dot sizes on the charge transfer interactions into TiO2 nanotubes for photocatalytic hydrogen generation2016In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 27, no 28, article id 285401Article in journal (Refereed)
    Abstract [en]

    Hydrogen fuels generated by water splitting using a photocatalyst and solar irradiation are currently gaining the strength to diversify the world energy matrix in a green way. CdS quantum dots have revealed a hydrogen generation improvement when added to TiO2 materials under visible-light irradiation. In the present paper, we investigated the performance of TiO2 nanotubes coupled with CdS quantum dots, by a molecular bifunctional linker, on photocatalytic hydrogen generation. TiO2 nanotubes were obtained by anodization of Ti foil, followed by annealing to crystallize the nanotubes into the anatase phase. Afterwards, the samples were sensitized with CdS quantum dots via an in situ hydrothermal route using 3-mercaptopropionic acid as the capping agent. This sensitization technique permits high loading and uniform distribution of CdS quantum dots onto TiO2 nanotubes. The XPS depth profile showed that CdS concentration remains almost unchanged (homogeneous), while the concentration relative to the sulfate anion decreases by more than 80% with respect to the initial value after similar to 100 nm in depth. The presence of sulfate anions is due to the oxidation of sulfide and occurs in greater proportion in the material surface. This protection for air oxidation inside the nanotubular matrix seemingly protected the CdS for photocorrosion in sacrificial solution leading to good stability properties proved by long duration, stable photocurrent measurements. The effect of the size and the distribution of sizes of CdS quantum dots attached to TiO2 nanotubes on the photocatalytic hydrogen generation were investigated. The experimental results showed three different behaviors when the reaction time of CdS synthesis was increased in the sensitized samples, i.e. similar, deactivation and activation effects on the hydrogen production with regard to TiO2 nanotubes. The deactivation effect was related to two populations of sizes of CdS, where the population with a shorter band gap acts as a trap for the electrons photogenerated by the population with a larger band gap. Electron transfer from CdS quantum dots to TiO2 semiconductor nanotubes was proven by the results of UPS measurements combined with optical band gap measurements. This property facilitates an improvement of the visible-light hydrogen evolution rate from zero, for TiO2 nanotubes, to approximately 0.3 mu mol cm(-2) h(-1) for TiO2 nanotubes sensitized with CdS quantum dots.

  • 44. Gowtham, S.
    et al.
    Scheicher, R. H.
    Pandey, R.
    Karna, S. P.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    First-principles study of physisorption of nucleic acid bases on small-diameter carbon nanotubes2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 12Article in journal (Refereed)
    Abstract [en]

    We report the results of our first-principles study based on density functional theory on the interaction of the nucleic acid base molecules adenine ( A), cytosine ( C), guanine ( G), thymine ( T), and uracil ( U), with a single-walled carbon nanotube (CNT). Specifically, the focus is on the physisorption of base molecules on the outer wall of a ( 5, 0) metallic CNT possessing one of the smallest diameters possible. Compared to the case for CNTs with large diameters, the physisorption energy is found to be reduced in the high-curvature case. The base molecules exhibit significantly different interaction strengths and the calculated binding energies follow the hierarchy G > A > T > C > U, which appears to be independent of the tube curvature. The stabilizing factor in the interaction between the base molecule and CNT is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study provides an improved understanding of the role of the base sequence in deoxyribonucleic acid ( DNA) or ribonucleic acid ( RNA) in their interactions with carbon nanotubes of varying diameters.

  • 45. Gowtham, S.
    et al.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    Pandey, Ravindra
    Karna, Shashi P.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Condensed Matter Theory.
    First-principles study of physisorption of nucleic acid bases on small-diameter carbon nanotubes2008In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 19, no 12, p. 125701-Article in journal (Refereed)
    Abstract [en]

    We report the results of our first-principles study based on density functional theory on the interaction of the nucleic acid base molecules adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U), with a single-walled carbon nanotube (CNT). Specifically, the focus is on the physisorption of base molecules on the outer wall of a (5, 0) metallic CNT possessing one of the smallest diameters possible. Compared to the case for CNTs with large diameters, the physisorption energy is found to be reduced in the high-curvature case. The base molecules exhibit significantly different interaction strengths and the calculated binding energies follow the hierarchy G>A>T>C>U, which appears to be independent of the tube curvature. The stabilizing factor in the interaction between the base molecule and CNT is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study provides an improved understanding of the role of the base sequence in deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) in their interactions with carbon nanotubes of varying diameters.

  • 46.
    Hajati, Y
    et al.
    Dept of Physics, Faculty of Sciences, University of Shahid Chamran, Ahwaz, Iran.
    Blom, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jafri, S H M
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Haldar, Soumyajyoti
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bhandary, Sumanta
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Shoushtari, M Z
    Dept of Physics, Faculty of Sciences, University of Shahid Chamran, Ahwaz, Iran.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Improved gas sensing activity in structurally defected bilayer graphene2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 50, p. 50550-Article in journal (Refereed)
    Abstract [en]

    Graphene is a two-dimensional material with a capability of gas sensing, which is here shown to be drastically improved by inducing gentle disorder in the lattice. We report that by using a focused ion beam technique, controlled disorder can be introduced into the graphene structure through Ga + ion irradiation. This disorder leads to an increase in the electrical response of graphene to NO 2 gas molecules by a factor of three in an ambient environment (air). Ab initio density functional calculations indicate that NO 2 molecules bind strongly to Stone–Wales defects, where they modify electronic states close to the Fermi level, which in turn influence the transport properties. The demonstrated gas sensor, utilizing structurally defected graphene, shows faster response, higher conductivity changes and thus higher sensitivity to NO 2 as compared to pristine graphene.

  • 47. He, Zeming
    et al.
    Stiewe, Christian
    Platzek, Dieter
    Karpinski, Gabriele
    Mueller, Eckhard
    Li, Shanghua
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Toprak, Muhammet
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nano ZrO2/CoSb3 composites with improved thermoelectric figure of merit2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 23, p. 235602-Article in journal (Refereed)
    Abstract [en]

    Nano ZrO2/CoSb3 composites with different ZrO 2 contents were prepared using hot pressing. The phase purity, the microstructure and the temperature-dependent transport parameters of the composites were investigated. The dimensionless figure of merit (ZT) of 0.18 of the non-dispersed CoSb3 preponderates the maximal value (0.17) of pure CoSb3 reported in the literature, which is attributed to the prepared sample having higher electrical conductivity due to the existence of a small amount of metallic Sb and lower thermal conductivity due to the fine-grained structure. Compared to non-dispersed CoSb3, a further improvement of 11% on ZT (0.20) was achieved in the composite with 0.05ZrO 2 inclusions, which resulted from the enhanced ratio of electrical conductivity to thermal conductivity and the Seebeck coefficient. The nanodispersion method provides an effective approach to improving a material's thermoelectric properties and performance.

  • 48. Heyman, A.
    et al.
    Yakimenko, I.I.
    Berggren, Karl-Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Band structure and spin polarization for a one-dimensional array of quantum point contacts2004In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 15, no 1, p. 143-148Article in journal (Refereed)
    Abstract [en]

    We have numerically studied the band structure and the spin polarization effect in a periodic one-dimensional array of quantum point contacts (QPCs) formed in a two-dimensional electron gas in a plane-layered semiconductor system. In this study we used a self-consistent model developed within the framework of the Kohn-Sham local spin-density formalism. We have found that the band structure contains a mixture of flat and dispersed bands, and the role of transverse modes in the formation of such a band structure has been clearly demonstrated. We have also shown that spin polarization occurs mainly in the regions occupied by the QPCs and that it is qualitatively similar to the spin polarization in a single QPC.

  • 49.
    Hilty, F. M.
    et al.
    Swiss Fed Inst Technol, Inst Food Sci & Nutr, Human Nutr Lab, CH-8092 Zurich, Switzerland..
    Teleki, A.
    Swiss Fed Inst Technol, Dept Mech & Proc Engn, Particle Technol Lab, CH-8092 Zurich, Switzerland..
    Krumeich, F.
    Swiss Fed Inst Technol, Electron Microscopy Ctr EMEZ, CH-8092 Zurich, Switzerland..
    Buechel, R.
    Swiss Fed Inst Technol, Dept Mech & Proc Engn, Particle Technol Lab, CH-8092 Zurich, Switzerland..
    Hurrell, R. F.
    Swiss Fed Inst Technol, Inst Food Sci & Nutr, Human Nutr Lab, CH-8092 Zurich, Switzerland..
    Pratsinis, S. E.
    Swiss Fed Inst Technol, Dept Mech & Proc Engn, Particle Technol Lab, CH-8092 Zurich, Switzerland..
    Zimmermann, M. B.
    Swiss Fed Inst Technol, Inst Food Sci & Nutr, Human Nutr Lab, CH-8092 Zurich, Switzerland..
    Development and optimization of iron- and zinc-containing nanostructured powders for nutritional applications2009In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 20, no 47, article id 475101Article in journal (Refereed)
    Abstract [en]

    Reducing the size of low-solubility iron (Fe)-containing compounds to nanoscale has the potential to improve their bioavailability. Because Fe and zinc (Zn) deficiencies often coexist in populations, combined Fe/Zn-containing nanostructured compounds may be useful for nutritional applications. Such compounds are developed here and their solubility in dilute acid, a reliable indicator of iron bioavailability in humans, and sensory qualities in sensitive food matrices are investigated. Phosphates and oxides of Fe and atomically mixed Fe/Zn-containing (primarily ZnFe(2)O(4))nanostructured powders were produced by flame spray pyrolysis (FSP). Chemical composition and surface area were systematically controlled by varying precursor concentration and feed rate during powder synthesis to increase solubility to the level of ferrous sulfate at maximum Fe and Zn content. Solubility of the nanostructured compounds was dependent on their particle size and crystallinity. The new nanostructured powders produced minimal color changes when added to dairy products containing chocolate or fruit compared to the changes produced when ferrous sulfate or ferrous fumarate were added to these foods. Flame-made Fe- and Fe/Zn-containing nanostructured powders have solubilities comparable to ferrous and Zn sulfate but may produce fewer color changes when added to difficult-to-fortify foods. Thus, these powders are promising for food fortification and other nutritional applications.

  • 50.
    Hoffmann, S
    et al.
    EMPA, Thun, Switzerland.
    Östlund, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Michler, Johann
    EMPA, Thun, Switzerland.
    Fan, H. J.
    EMPA, Thun, Switzerland.
    Zacharias, M.
    MPI, Halle, Germany.
    Christiansen, S.H.
    University Halle-Wittenberg.
    Ballif, C
    Inst. Microtechnology, Neuchatel, Switzerland.
    Fracture strength and Young’s modulus of ZnO nanowires2007In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 20, p. 205503-Article in journal (Refereed)
1234 1 - 50 of 162
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