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  • 1.
    Abdi-Jalebi, Mojtaba
    et al.
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Pazoki, Meysam
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Dar, M. Ibrahim
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Lausanne, Switzerland.
    Alsari, Mejd
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Sadhanala, Aditya
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Diyitini, Giorgio
    Univ Cambridge, Dept Mat Sci & Met, Charles Babbage Rd, Cambridge, England.
    Imani, Roghayeh
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lilliu, Samuele
    Univ Sheffield, Dept Phys & Astron, Sheffield, S Yorkshire, England; UAE Ctr Crystallog, Dubai, U Arab Emirates.
    Kullgren, Jolla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Gratzel, Michael
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Lausanne, Switzerland.
    Friend, Richard H.
    Univ Cambridge, Dept Phys, Cavendish Lab, JJ Thomson Ave, Cambridge, England.
    Dedoping of Lead Halide Perovskites Incorporating Monovalent Cations2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 7, p. 7301-7311Article in journal (Refereed)
    Abstract [en]

    We report significant improvements in the optoelectronic properties of lead halide perovskites with the addition of monovalent ions with ionic radii close to Pb2+. We investigate the chemical distribution and electronic structure of solution processed CH3NH3PbI3 perovskite structures containing Na+, Cu+, and Ag+, which are lower valence metal ions than Pb2+ but have similar ionic radii. Synchrotron X-ray diffraction reveals a pronounced shift in the main perovskite peaks for the monovalent cation-based films, suggesting incorporation of these cations into the perovskite lattice as well as a preferential crystal growth in Ag+ containing perovskite structures. Furthermore, the synchrotron X-ray photoelectron measurements show a significant change in the valence band position for Cu- and Ag-doped films, although the perovskite bandgap remains the same, indicating a shift in the Fermi level position toward the middle of the bandgap. Such a shift infers that incorporation of these monovalent cations dedope the n-type perovskite films when formed without added cations. This dedoping effect leads to cleaner bandgaps as reflected by the lower energetic disorder in the monovalent cation-doped perovskite thin films as compared to pristine films. We also find that in contrast to Ag+ and Cu+, Na+ locates mainly at the grain boundaries and surfaces. Our theoretical calculations confirm the observed shifts in X-ray diffraction peaks and Fermi level as well as absence of intrabandgap states upon energetically favorable doping of perovskite lattice by the monovalent cations. We also model a significant change in the local structure, chemical bonding of metal-halide, and the electronic structure in the doped perovskites. In summary, our work highlights the local chemistry and influence of monovalent cation dopants on crystallization and the electronic structure in the doped perovskite thin films.

  • 2.
    Dankert, Andre
    et al.
    Chalmers, Dept Microtechnol & Nanosci, SE-41296 Gothenburg, Sweden..
    Pashaei, Parham
    Chalmers, Dept Microtechnol & Nanosci, SE-41296 Gothenburg, Sweden..
    Kamalakar, M. Venkata
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Chalmers, Dept Microtechnol & Nanosci, SE-41296 Gothenburg, Sweden.
    Gaur, Anand P. S.
    Univ Puerto Rico, Dept Phys, San Juan, PR 00931 USA.;Univ Puerto Rico, Inst Funct Nanomat, San Juan, PR 00931 USA.;Iowa State Univ, Mech Engn Dept, Ames, IA 50011 USA..
    Sahoo, Satyaprakash
    Univ Puerto Rico, Dept Phys, San Juan, PR 00931 USA.;Univ Puerto Rico, Inst Funct Nanomat, San Juan, PR 00931 USA.;Inst Phys, Bhubaneswar 751005, Odisha, India..
    Rungger, Ivan
    Natl Phys Lab, Teddington TW11 0LW, Middx, England..
    Narayan, Awadhesh
    Trinity Coll Dublin, AMBER & CRANN Inst, Sch Phys, Dublin 2, Ireland.;Swiss Fed Inst Technol, Mat Theory, Wolfgang Pauli Str 27, CH-8093 Zurich, Switzerland..
    Dolui, Kapildeb
    Trinity Coll Dublin, AMBER & CRANN Inst, Sch Phys, Dublin 2, Ireland.;Univ Delaware, Dept Phys & Astron, Newark, DE 19716 USA..
    Hoque, Md. Anamul
    Chalmers, Dept Microtechnol & Nanosci, SE-41296 Gothenburg, Sweden..
    Patel, Ram Shanker
    Birla Inst Technol & Sci, Dept Phys, Pilani KK Birla Goa Campus, Zuarinagar 403726, Goa, India..
    de Jong, Michel P.
    Univ Twente, MESA Inst Nanotechnol, NL-7500 AE Enschede, Netherlands..
    Katiyar, Ram S.
    Univ Puerto Rico, Dept Phys, San Juan, PR 00931 USA.;Univ Puerto Rico, Inst Funct Nanomat, San Juan, PR 00931 USA..
    Sanvito, Stefano
    Trinity Coll Dublin, AMBER & CRANN Inst, Sch Phys, Dublin 2, Ireland..
    Dash, Saroj P.
    Chalmers, Dept Microtechnol & Nanosci, SE-41296 Gothenburg, Sweden..
    Spin-Polarized Tunneling through Chemical Vapor Deposited Multilayer Molybdenum Disulfide2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 6, p. 6389-6395Article in journal (Refereed)
    Abstract [en]

    The two-dimensional (2D) semiconductor molybdenum disulfide (MoS2) has attracted widespread attention for its extraordinary electrical-, optical-, spin-, and valley-related properties. Here, we report on spin-polarized tunneling through chemical vapor deposited multilayer MoS2 (similar to 7 nm) at room temperature in a vertically fabricated spin-valve device. A tunnel magnetoresistance (TMR) of 0.5-2% has been observed, corresponding to spin polarization of 5-10% in the measured temperature range of 300-75 K. First-principles calculations for ideal junctions result in a TMR up to 8% and a spin polarization of 26%. The detailed measurements at different temperature, bias voltages, and density functional theory calculations provide information about spin transport mechanisms in vertical multilayer MoS2 spin-valve devices. These findings form a platform for exploring spin functionalities in 2D semiconductors and understanding the basic phenomena that control their performance.

  • 3.
    Daukiya, Lakshya
    et al.
    Univ Haute Alsace, Inst Sci Mat Mulhouse, CNRS, UMR 7361, 3Bis,Rue Alfred Werner, F-68093 Mulhouse, France..
    Mattioli, Cristina
    CNRS, UPR 8011, CEMES, Nanosci Grp, 29 Rue Jeanne Marvig,BP 94347, F-31055 Toulouse, France..
    Aubel, Dominique
    Univ Haute Alsace, Inst Sci Mat Mulhouse, CNRS, UMR 7361, 3Bis,Rue Alfred Werner, F-68093 Mulhouse, France..
    Hajjar-Garreau, Samar
    Univ Haute Alsace, Inst Sci Mat Mulhouse, CNRS, UMR 7361, 3Bis,Rue Alfred Werner, F-68093 Mulhouse, France..
    Vonau, Francois
    Univ Haute Alsace, Inst Sci Mat Mulhouse, CNRS, UMR 7361, 3Bis,Rue Alfred Werner, F-68093 Mulhouse, France..
    Denys, Emmanuel
    Univ Haute Alsace, Inst Sci Mat Mulhouse, CNRS, UMR 7361, 3Bis,Rue Alfred Werner, F-68093 Mulhouse, France..
    Reiter, Guenter
    Univ Freiburg, Inst Phys, Hermann Herder Str 3, D-79104 Freiburg, Germany..
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Perrin, Elsa
    UPMC Univ Paris 06, CNRS, Dept Chim, Ecole Normale Super,PSL Res Univ, 24 Rue Lhomond, F-75005 Paris, France..
    Bocquet, Marie-Laure
    UPMC Univ Paris 06, CNRS, Dept Chim, Ecole Normale Super,PSL Res Univ, 24 Rue Lhomond, F-75005 Paris, France..
    Bena, Cristina
    CEA Saclay, Inst Phys Theor, Orme Merisiers, F-91190 Gif Sur Yvette, France.;Paris Sud, UMR 8502, CNRS, Lab Phys Solides, F-91405 Orsay, France..
    Gourdon, Andre
    CNRS, UPR 8011, CEMES, Nanosci Grp, 29 Rue Jeanne Marvig,BP 94347, F-31055 Toulouse, France..
    Simon, Laurent
    Univ Haute Alsace, Inst Sci Mat Mulhouse, CNRS, UMR 7361, 3Bis,Rue Alfred Werner, F-68093 Mulhouse, France..
    Covalent Functionalization by Cycloaddition Reactions of Pristine Defect-Free Graphene2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 1, p. 627-634Article in journal (Refereed)
    Abstract [en]

    Based on a low-temperature scanning tunneling microscopy study, we present a direct visualization of a cycloaddition reaction performed for some specific fluorinated maleimide molecules deposited on graphene. Up to now, it was widely admitted that such a cycloaddition reaction can not happen without pre-existing defects. However, our study shows that the cycloaddition reaction can be carried out on a defect-free basal graphene plane at room temperature. In the course of covalently grafting the molecules to graphene, the sp(2) conjugation of carbon atoms was broken, and local sp(3) bonds were created. The grafted molecules perturbed the graphene lattice, generating a standing-wave pattern with an anisotropy which was attributed to a (1,2) cycloaddition, as revealed by T-matrix approximation calculations. DFT calculations showed that while both (1,4) and (1,2) cycloadditions were possible on free-standing graphene, only the (1,2) cycloaddition could be obtained for graphene on SiC(0001). Globally averaging spectroscopic techniques, XPS and ARPES, were used to determine the modification in the elemental composition of the samples induced by the reaction, indicating an opening of an electronic gap in graphene.

  • 4. Dreiser, Jan
    et al.
    Waeckerlin, Christian
    Ali, Md Ehesan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Piamonteze, Cinthia
    Donati, Fabio
    Singha, Aparajita
    Pedersen, Kasper Steen
    Rusponi, Stefano
    Bendix, Jesper
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jung, Thomas A.
    Brune, Harald
    Exchange Interaction of Strongly Anisotropic Tripodal Erbium Single-Ion Magnets with Metallic Surfaces2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 5, p. 4662-4671Article in journal (Refereed)
    Abstract [en]

    We present a comprehensive study of Er(trensal) single-ion magnets deposited in ultrahigh vacuum onto metallic surfaces. X-ray photoelectron spectroscopy reveals that the molecular structure is preserved after sublimation, and that the molecules are physisorbed on Au(111) while they are chemisorbed on a Ni thin film on 0(100) single-crystalline surfaces. X-ray magnetic circular dichroism (XMCD) measurements performed on Au(111) samples covered with molecular monolayers held at temperatures down to 4 K suggest that the easy axes of the strongly anisotropic molecules are randomly oriented. Furthermore XMCD indicates a weak antiferromagnetic exchange coupling between the single-ion magnets and the ferromagnetic Ni/Cu(100) substrate. For the latter case, spin-Hamiltonian fits to the XMCD M(H) suggest a significant structural distortion of the molecules. Scanning tunneling microscopy reveals that the molecules are mobile on Au(111) at room temperature, whereas they are more strongly attached on Ni/Cu(100). X-ray photoelectron spectroscopy results provide evidence for the chemical bonding between Er(trensal) molecules and the Ni substrate. Density functional theory calculations support these findings and, in addition, reveal the most stable adsorption configuration on Ni/Cu(100) as well as the Ni-Er exchange path. Our study suggests that the magnetic moment of Er(trensal) can be stabilized via suppression of quantum tunneling of magnetization by exchange coupling to the Ni surface atoms. Moreover, it opens up pathways toward optical addressing of surface-deposited single-ion magnets.

  • 5. Freedman, Kevin J.
    et al.
    Haq, Syed Raza
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Fletcher, Michael R.
    Foley, Joe P.
    Jemth, Per
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Edel, Joshua B.
    Kim, Min Jun
    Nonequilibrium Capture Rates Induce Protein Accumulation and Enhanced Adsorption to Solid-State Nanopores2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 12, p. 12238-12249Article in journal (Refereed)
    Abstract [en]

    Single molecule capturing of analytes using an electrically biased nanopore is the fundamental mechanism in which nearly all nanopore experiments are conducted. With pore dimensions being on the order of a single molecule, the spatial zone of sensing only contains approximately a zeptoliter of volume. As a result, nanopores offer high precision sensing within the pore but provide little to no information about the analytes outside the pore. In this study, we use capture frequency and rate balance theory to predict and study the accumulation of proteins at the entrance to the pore. Protein accumulation is found to have positive attributes such as capture rate enhancement over time but can additionally lead to negative effects such as long-term blockages typically attributed to protein adsorption on the surface of the pore. Working with the folded and unfolded states of the protein domain PDZ2 from SAP97, we show that applying short (e.g., 3-25 s in duration) positive voltage pulses, rather than a constant voltage, can prevent long-term current blockades (i.e., adsorption events). By showing that the concentration of proteins around the pore can be controlled in real time using modified voltage protocols, new experiments can be explored which study the role of concentration on single molecular kinetics including protein aggregation, folding, and protein binding.

  • 6.
    Gusak, Viktoria
    et al.
    Chalmers University of Technology.
    Kasemo, Bengt
    Chalmers University of Technology.
    Hägglund, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Chalmers University of Technology.
    Thickness dependence of plasmonic charge carrier generation in ultrathin a-Si:H layers for solar cells2011In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 5, no 8, p. 6218-6225Article in journal (Refereed)
  • 7.
    Hasan, Saad A
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Rigueur, John L
    Harl, Robert R
    Krejci, Alex J
    Gonzalo-Juan, Isabel
    Rogers, Bridget R
    Dickerson, James H
    Transferable Graphene Oxide Films with Tunable Microstructures.2010In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 4, no 12, p. 7367-7372Article in journal (Refereed)
    Abstract [en]

    This report describes methods to produce large-area films of graphene oxide from aqueous suspensions using electrophoretic deposition. By selecting the appropriate suspension pH and deposition voltage, films of the negatively charged graphene oxide sheets can be produced with either a smooth "rug" microstructure on the anode or a porous "brick" microstructure on the cathode. Cathodic deposition occurs in the low pH suspension with the application of a relatively high voltage, which facilitates a gradual change in the colloids' charge from negative to positive as they adsorb protons released by the electrolysis of water. The shift in the colloids' charge also gives rise to the brick microstructure, as the concurrent decrease in electrostatic repulsion between graphene oxide sheets results in the formation of multilayered aggregates (the "bricks"). Measurements of water contact angle revealed the brick films (79°) to be more hydrophobic than the rug films (41°), a difference we attribute primarily to the distinct microstructures. Finally, we describe a sacrificial layer technique to make these graphene oxide films free-standing, which would enable them to be placed on arbitrary substrates.

  • 8. He, Yuhui
    et al.
    Tsutsui, Makusu
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Bai, Fan
    Taniguchi, Masateru
    Kawai, Tomoji
    Thermophoretic Manipulation of DNA Translocation through Nanopores2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 1, p. 538-546Article in journal (Refereed)
    Abstract [en]

    Manipulating DNA translocation through nanopore is one crucial requirement for new ultrafast sequencing methods in the sense that the polymers have to be denatured, unraveled, and then propelled through the pore with very low speed. Here we propose and theoretically explore a novel design to fulfill the demands by utilizing cross-pore thermal gradient. The high temperature in the cis reservoir is expected to transform double-stranded DNA into single strands and that temperature would also prevent those single strands from intrastrand base-pairing, thus, achieving favorable polymer conformation for the subsequent translocation and sequencing. Then, the substantial temperature drop across the pore caused by the thermal-insulating membrane separating cis and trans chambers would stimulate thermophoresis of the molecules through nanopores. Our theoretical evaluation shows that the DNA translocation speeds will be orders smaller than the electrophoretic counterpart, while high capture rate of DNA Into nanopore Is maintained, both of which would greatly benefit the sequencing.

  • 9.
    Jahn, Burkhard O.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
    Ottosson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Galperin, Michael
    Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States.
    Fransson, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Organic Single Molecular Structures for Light Induced Spin-Pump Devices2013In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 7, no 2, p. 1064-1071Article in journal (Refereed)
    Abstract [en]

    We present theoretical results on molecular structures for realistic spin-pump applications. Taking advantage of the electron spin resonance concept, we find that interesting candidates constitute triplet biradicals with two strongly spatially and energetically separated singly occupied molecular orbitals (SOMOs). Building on earlier reported stable biradicals, particularly bis(nitronyl nitroxide) based biradicals, we employ density functional theory to design a selection of potential molecular spin-pumps which should be persistent at ambient conditions. We estimate that our proposed molecular structures will operate as spin-pumps using harmonic magnetic fields in the MHz regime and optical fields in the infrared to visible light regime.

  • 10. Leijtens, Tomas
    et al.
    Stranks, Samuel D.
    Eperon, Giles E.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    McPherson, Ian J.
    Rensmo, Hakan
    Ball, James M.
    Lee, Michael M.
    Snaith, Henry J.
    Electronic Properties of Meso-Superstructured and Planar Organometal Halide Perovskite Films: Charge Trapping, Photodoping, and Carrier Mobility2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 7, p. 7147-7155Article in journal (Refereed)
    Abstract [en]

    Solution-processed organometal trihalide perovskite solar cells are attracting increasing interest, leading to high performances over 15% in thin film architectures. Here, we probe the presence of sub gap states in both solid and mesosuperstructured perovskite films and determine that they strongly influence the photoconductivity response and splitting of the quasi-Fermi levels in films and solar cells. We find that while the planar perovskite films are superior to the mesosuperstructured films in terms of charge carrier mobility (in excess of 20 cm(2) V-1 s(-1)) and emissivity, the planar heterojunction solar cells are limited in photovoltage by the presence of sub gap states and low intrinsic doping densities.

  • 11.
    Nowakowska, Sylwia
    et al.
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Mazzola, Federico
    Norwegian Univ Sci & Technol NTNU, Dept Phys, Ctr Quantum Spintron, Hogskoleringen 5,Realfagbygget D5-170, N-7491 Trondheim, Norway..
    Alberti, Mariza N.
    ETH, Lab Organ Chem, Vladimir Prelog Weg 3, CH-8093 Zurich, Switzerland..
    Song, Fei
    Univ Groningen, Zernike Inst Adv Mat, Nijenborgh 4, NL-9747 AG Groningen, Netherlands.;Chinese Acad Sci, Shanghai Inst Appl Phys, Shanghai 201204, Peoples R China..
    Voigt, Tobias
    ETH, Lab Organ Chem, Vladimir Prelog Weg 3, CH-8093 Zurich, Switzerland..
    Nowakowski, Jan
    Paul Scherrer Inst, Lab Micro & Nanotechnol, CH-5232 Villigen, Switzerland..
    Wackerlin, Aneliia
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Wackerlin, Christian
    Paul Scherrer Inst, Lab Micro & Nanotechnol, CH-5232 Villigen, Switzerland.;Empa, Swiss Fed Labs Mat Sci & Technol, Uberlandstr 129, CH-8600 Dubendorf, Switzerland..
    Wiss, Jerome
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Schweizer, W. Bernd
    ETH, Lab Organ Chem, Vladimir Prelog Weg 3, CH-8093 Zurich, Switzerland..
    Broszio, Max
    ETH, Lab Organ Chem, Vladimir Prelog Weg 3, CH-8093 Zurich, Switzerland..
    Polley, Craig
    Lund Univ, MAX IV Lab, POB 118, S-22100 Lund, Sweden..
    Leandersson, Mats
    Lund Univ, MAX IV Lab, POB 118, S-22100 Lund, Sweden..
    Fatayer, Shadi
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland.;Univ Estadual Campinas, Inst Fis Gleb Wataghin, Dept Fis Aplicada, BR-13083859 Campinas, SP, Brazil..
    Ivas, Toni
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Baljozovic, Milos
    Paul Scherrer Inst, Lab Micro & Nanotechnol, CH-5232 Villigen, Switzerland..
    Mousavi, S. Fatemeh
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Ahsan, Aisha
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Nijs, Thomas
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Popova, Olha
    Univ Basel, Dept Phys, Klingelbergstr 82, CH-4056 Basel, Switzerland..
    Zhang, Jun
    Paul Scherrer Inst, Lab Synchrotron Radiat Condensed Matter, CH-5232 Villigen, Switzerland..
    Muntwiler, Matthias
    Paul Scherrer Inst, Lab Synchrotron Radiat Condensed Matter, CH-5232 Villigen, Switzerland..
    Thilgen, Carlo
    ETH, Lab Organ Chem, Vladimir Prelog Weg 3, CH-8093 Zurich, Switzerland..
    Stohr, Meike
    Univ Groningen, Zernike Inst Adv Mat, Nijenborgh 4, NL-9747 AG Groningen, Netherlands..
    Pasti, Igor A.
    Lund Univ, MAX IV Lab, POB 118, S-22100 Lund, Sweden.;Univ Belgrade, Fac Phys Chem, Studentski Trg 12-16, Belgrade 11158, Serbia..
    Skorodumova, Natalia V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. KTH Royal Inst Technol, Dept Mat Sci & Engn, Brinellvagen 23, S-10044 Stockholm, Sweden..
    Diederich, Francois
    ETH, Lab Organ Chem, Vladimir Prelog Weg 3, CH-8093 Zurich, Switzerland..
    Wells, Justin
    Norwegian Univ Sci & Technol NTNU, Dept Phys, Ctr Quantum Spintron, Hogskoleringen 5,Realfagbygget D5-170, N-7491 Trondheim, Norway..
    Jung, Thomas A.
    Paul Scherrer Inst, Lab Micro & Nanotechnol, CH-5232 Villigen, Switzerland..
    Adsorbate-Induced Modification of the Confining Barriers in a Quantum Box Array2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 1, p. 768-778Article in journal (Refereed)
    Abstract [en]

    Quantum devices depend on addressable elements, which can be modified separately and in their mutual interaction. Self-assembly at surfaces, for example, formation of a porous (metal-) organic network, provides an ideal way to manufacture arrays of identical quantum boxes, arising in this case from the confinement of the electronic (Shockley) surface state within the pores. We show that the electronic quantum box state as well as the interbox coupling can be modified locally to a varying extent by a selective choice of adsorbates, here C60, interacting with the barrier. In view of the wealth of differently acting adsorbates, this approach allows for engineering quantum states in on-surface network architectures.

  • 12.
    Park, Byung-wook
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Jain, Sagar Motilal
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhang, Xiaoliang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Resonance Raman and Excitation Energy Dependent Charge Transfer Mechanism in Halide-Substituted Hybrid Perovskite Solar Cells2015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 2, p. 2088-2101Article in journal (Refereed)
    Abstract [en]

    Organo-metal halide perovskites (OMHPs) are materials with attractive properties for optoelectronics. They made a recent introduction in the photovoltaics world by methylammonium (MA) lead triiodide and show remarkably improved charge separation capabilities when chloride and bromide are added. Here we show how halide substitution in OMHPs with the nominal composition CH3NH3PbI2X, where X is I, Br, or Cl, influences the morphology, charge quantum yield, and local interaction with the organic MA cation. X-ray diffraction and photoluminescence data demonstrate that halide substitution affects the local structure in the OMHPs with separate MAPbI3 and MAPbCl(3) phases. Raman spectroscopies as well as theoretical vibration calculations reveal that this at the same time delocalizes the charge to the MA cation, which can liberate the vibrational movement of the MA cation, leading to a more adaptive organic phase. The resonance Raman effect together with quantum chemical calculations is utilized to analyze the change in charge transfer mechanism upon electronic excitation and gives important clues for the mechanism of the much improved photovoltage and photocurrent also seen in the solar cell performance for the materials when chloride compounds are included in the preparation.

  • 13.
    Pazoki, Meysam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Jacobsson, T. Jesper
    Swiss Fed Inst Technol, Dept Chem & Chem Engn, Lab Photomol Sci, Stn 6, CH-1015 Lausanne, Switzerland..
    Kullgren, Jolla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Swiss Fed Inst Technol, Dept Chem & Chem Engn, Lab Photomol Sci, Stn 6, CH-1015 Lausanne, Switzerland..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Photoinduced Stark Effects and Mechanism of Ion Displacement in Perovskite Solar Cell Materials2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 3, p. 2823-2834Article in journal (Refereed)
    Abstract [en]

    Organometallic halide perovskites (OMHPs) have recently emerged as a promising class of materials in photovoltaic technology. Here, we present an in-depth investigation of the physics in these systems by measuring the photoinduced absorption (PIA) in OMHPs as a function of materials composition, excitation wavelength, and modulation frequency. We report a photoinduced Stark effect that depends on the excitation wavelength and on the dipole strength of the monovalent cations in the A position of the ABX(3) perovskite. The results presented are corroborated by density functional theory calculations and provide fundamental information about the photoinduced local electric field change under blue and red excitation as well as insights into the mechanism of light induced ion displacement in OMHPs. For optimized perovskite solar cell devices beyond 19% efficiency, we show that excess thermalization energy of blue photons plays a role in overcoming the activation energy for ion diffusion.

  • 14.
    Russell, Camilla
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Molecular tools.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Jarvius, Jonas
    Cai, Yixiao
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nikolajeff, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nilsson, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Molecular tools.
    Gold Nanowire Based Electrical DNA Detection Using Rolling Circle Amplification2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 2, p. 1147-1153Article in journal (Refereed)
    Abstract [en]

    We present an electrical sensor that uses rolling circle amplification (RCA) of DNA to stretch across the gap between two electrodes, interact with metal nanoparticle seeds to generate an electrically conductive nanowire, and produce electrical signals upon detection of specific target DNA sequences. RCA is a highly specific molecular detection mechanism based on DNA probe circularization. With this technique, long single-stranded DNA with simple repetitive sequences are produced. Here we show that stretched RCA products can be metalized using silver or gold solutions to form metal wires. Upon metallization, the resistance drops from T Omega to k Omega for silver and to Omega for gold. Metallization is seeded by gold nanoparticles aligned along the single-stranded DNA product through hybridization of functionalized oligonucleotides. We show that combining RCA with electrical DNA detection produces results in readout with very high signal-to-noise ratio, an essential feature for sensitive and specific detection assays. Finally, we demonstrate detection of 10 ng of Escherichia coli genomic DNA using the sensor concept.

  • 15.
    Shi, Jingwen
    et al.
    Institute of Environmental Medicine, KI, Stockholm.
    Karlsson, Hanna L.
    Institute of Environmental Medicine, KI, Stockholm.
    Johansson, Katarina
    Institute of Environmental Medicine, KI, Stockholm.
    Gogvadze, Vladimir
    Institute of Environmental Medicine, KI, Stockholm.
    Xiao, Lisong
    Inorganic and Materials Chemistry, University of Cologne, Köln, Tyskland.
    Li, Jiangtian
    Inorganic and Materials Chemistry, University of Cologne, Köln, Tyskland.
    Burks, Terrance
    Functional Materials Microelectronics and Applied Physics, School of Information and Communication Technology, KTH, Kista.
    Garcia-Bennett, Alfonso
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Uheida, Abdusalam
    Functional Materials Microelectronics and Applied Physics, School of Information and Communication Technology, KTH, Kista.
    Muhammed, Mamoun
    Functional Materials Microelectronics and Applied Physics, School of Information and Communication Technology, KTH, Kista.
    Mathur, Sanjay
    Inorganic and Materials Chemistry, University of Cologne, Köln, Tyskland.
    Morgenstern, Ralf
    Institute of Environmental Medicine, KI, Stockholm.
    Kagan, Valerian E.
    Dept of Environmental and Occupational Health, University of Pittsburgh, PA, USA.
    Fadeel, Bengt
    Institute of Environmental Medicine, KI, Stockholm.
    Microsomal Glutathione Transferase 1 Protects Against Toxicity Induced by Silica Nanoparticles but Not by Zinc Oxide Nanoparticles2012In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 6, no 3, p. 1925-1938Article in journal (Refereed)
    Abstract [en]

    Microsomal glutathione transferase 1 (MGST1) is an antioxidant enzyme located predominantly in the mitochondrial er membrane and endoplasmk reticulum and has been shown to protect cells from lipid peroxidation induced by a variety of cytostatic drugs and pro-oxidant stimuli. We hypothesized that MGST1 may also protect against nanomaterial-induced cytotoxicity through a specific effect on lipid peroxidation. We evaluated the induction of cytotoxicity and oxidative stress by TiO2, CeO2, SiO2, and ZnO in the human MCF-7 cell line with or without overexpression of MGST1. SiO2 and ZnO nanoparticles caused dose- and time-dependent toxicity, whereas no obvious cytotoxic effects were induced by nanoparticles of TiO2 and CeO2. We also noted pronounced cytotoxicity for three out of four additional SiO2 nanoparticles tested. Overexpression of MGST1 reversed the cytotoxicity of the main SiO2 nanoparticles tested and for one of the supplementary SiO2 nanoparticles but did not protect cells against ZnO-induced cytotoxic effects. The data point toward a role of lipid peroxidation In SiO2 nanoparticle-induced cell death. For ZnO nanoparticles, rapid dissolution was observed, and the subsequent interaction of Zn2+ with cellular targets is likely to contribute to the cytotoxic effects. A direct inhibition of MGST1 by Zn2+ could provide a possible explanation for the lack of protection against ZnO nanoparticles in this model. Our data also showed that SiO2 nanoparticle-induced cytotoxicity is mitigated in the presence of serum, potentially through masking of reactive surface groups by serum proteins, whereas ZnO nanoparticles were cytotoxic both In the presence and in the absence of serum.

  • 16.
    Simonov, Konstantin A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. MAX IV, Lund University, Box 118, 22100 Lund, Sweden.
    Vinogradov, Nikolay A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. MAX IV, Lund University, Box 118, 22100 Lund, Sweden.
    Vinogradov, Alexander S.
    V.A. Fock Institute of Physics, St. Petersburg State University, 198504 St. Petersburg, Russia.
    Generalov, Alexander V.
    MAX IV, Lund University, Box 118, 22100 Lund, Sweden.
    Zagrebina, Elena M.
    V.A. Fock Institute of Physics, St. Petersburg State University, 198504 St. Petersburg, Russia.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Cafolla, Attilio A.
    School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
    Carpy, Thomas
    School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
    Cunniffe, John P.
    School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
    Preobrajenski, Alexei B.
    MAX IV, Lund University, Box 118, 22100 Lund, Sweden.
    Comment on "Bottom-Up Graphene-Nanoribbon Fabrication Reveals Chiral Edges and Enantioselectivity"2015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 4, p. 3399-3403Article in journal (Refereed)
  • 17.
    Simonov, Konstantin A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. MAX IV, Lund University, Box 118, 22100 Lund, Sweden.
    Vinogradov, Nikolay A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. MAX IV, Lund University, Box 118, 22100 Lund, Sweden.
    Vinogradov, Alexander S.
    St Petersburg State Univ, VA Fock Inst Phys, St Petersburg 198504, Russia..
    Generalov, Alexander V.
    MAX IV, Lund University, Box 118, 22100 Lund, Sweden.
    Zagrebina, Elena M.
    V.A. Fock Institute of Physics, St. Petersburg State University, 198504 St. Petersburg, Russia.
    Svirskiy, Gleb I.
    V.A. Fock Institute of Physics, St. Petersburg State University, 198504 St. Petersburg, Russia.
    Cafolla, Attilio A.
    School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
    Carpy, Thomas
    School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
    Cunniffe, John P.
    School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
    Taketsugu, Tetsuya
    Hokkaido University, Faculty of Science, Deptaprtment of Chemistry, Sapporo, Hokkaido 0600810, Japan.
    Lyalin, Andrey
    Global Research Center for Environmental & Energy Based Nanomaterials Science, Tsukuba, Ibaraki 3050044, Japan..
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Preobrajenski, Alexei B.
    MAX IV, Lund University, Box 118, 22100 Lund, Sweden.
    From Graphene Nanoribbons on Cu(111) to Nanographene on Cu(110): Critical Role of Substrate Structure in the Bottom-Up Fabrication Strategy2015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 9, p. 8997-9011Article in journal (Refereed)
    Abstract [en]

    Bottom-up strategies can be effectively implemented for the fabrication of atomically precise graphene nanoribbons. Recently, using 10,10'-dibromo-9,9'-bianthracene (DBBA) as a molecular precursor to grow armchair nanoribbons on Au(111) and Cu(111), we have shown that substrate activity considerably affects the dynamics of ribbon formation, nonetheless without significant modifications in the growth mechanism. In this paper we compare the on-surface reaction pathways for DBBA molecules on Cu(111) and Cu(110). Evolution of both systems has been studied via a combination of core-level X-ray spectroscopies, scanning tunneling microscopy, and theoretical calculations. Experimental and theoretical results reveal a significant increase in reactivity for the open and anisotropic Cu(110) surface in comparison with the close-packed Cu(111). This increased reactivity results in a predominance of the molecular substrate interaction over the intermolecular one, which has a critical impact on the transformations of DBBA on Cu(110). Unlike DBBA on Cu(111), the Ullmann coupling cannot be realized for DBBA/Cu(110) and the growth of nanoribbons via this mechanism is blocked. Instead, annealing of DBBA on Cu(110) at 250 degrees C results in the formation of a new structure: quasi-zero-dimensional flat nanographenes. Each nanographene unit has dehydrogenated zigzag edges bonded to the underlying Cu rows and oriented with the hydrogen-terminated armchair edge parallel to the [1-10] direction. Strong bonding of nanographene to the substrate manifests itself in a high adsorption energy of -12.7 eV and significant charge transfer of 3.46e from the copper surface. Nanographene units coordinated with bromine adatoms are able to arrange in highly regular arrays potentially suitable for nanotemplating.

  • 18.
    Tian, Bo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ma, Jing
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Clinical Immunology.
    Qiu, Zhen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gómez de la Torre, Teresa Zardán
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Donolato, Marco
    BluSense Diagnost, Fruebjergvej 3, DK-2100 Copenhagen, Denmark..
    Hansen, Mikkel Fougt
    Tech Univ Denmark, DTU Nanotech, Dept Micro & Nanotechnol, Bldg 345B, DK-2800 Lyngby, Denmark..
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optomagnetic Detection of MicroRNA Based on Duplex-Specific Nuclease-Assisted Target Recycling and Multilayer Core-Satellite Magnetic Superstructures2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 2, p. 1798-1806Article in journal (Refereed)
    Abstract [en]

    Superstructural assembly of magnetic nanoparticles enables approaches to biosensing by combining specially tailored properties of superstructures and the particular advantages associated with a magnetic or optomagnetic read-out such as low background signal, easy manipulation, cost-efficiency, and potential for bioresponsive multiplexing. Herein, we demonstrate a sensitive and rapid miRNA detection method based on optomagnetic read-out, duplex-specific nuclease (DSN)-assisted target recycling, and the use of multilayer core-satellite magnetic superstructures. Triggered by the presence of target miRNA and DSN-assisted target recycling, the core-satellite magnetic superstructures release their "satellites" to the suspension, which subsequently can be quantified accurately in a lowcost and user-friendly optomagnetic setup. Target miRNAs are preserved in the cleaving reaction and can thereby trigger more cleavage and release of "satellites". For singleplex detection of let-7b, a linear detection range between 10 fM and 10 nM was observed, and a detection limit of 4.8 fM was obtained within a total assay time of 70 min. Multiplexing was achieved by releasing nanoparticles of different sizes in the presence of different miRNAs. The proposed method also has the advantages of single-nucleotide mismatch discrimination and the ability of quantification in a clinical sample matrix, thus holding great promise for miRNA routine multiplex diagnostics.

  • 19.
    Wang, Zhaohui
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Carlsson, Daniel O.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Tammela, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Hua, Kai
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Zhang, Peng
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Surface Modified Nanocellulose Fibers Yield Conducting Polymer-Based Flexible Supercapacitors with Enhanced Capacitances2015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 7, p. 7563-7571Article in journal (Refereed)
    Abstract [en]

    We demonstrate that surface modified nanocellulose fibers (NCFs) can be used as substrates to synthesize supercapacitor electrodes with the highest full electrode-normalized gravimetric (127 F g(-1)) and volumetric (122 F cm(-3)) capacitances at high current densities (300 mA cm(-2) approximate to 33 A g(-1)) until date reported for conducting polymer-based electrodes with active mass loadings as high as 9 mg cm(-2). By introducing quaternary amine groups on the surface of NCFs prior to polypyrrole (PPy) polymerization, the macropore volume of the formed PPy-NCF composites can be minimized while maintaining the volume of the micro- and mesopores at the same level as when unmodified or carboxylate groups functionalized NCFs are employed as polymerization substrates. Symmetric, aqueous electrolyte-based, devices comprising these porosity-optimized electrodes exhibit device-specific volumetric energy and power densities of 3.1 mWh cm(-3) and 3 W cm(-3) respectively; which are among the highest values reported for conducting polymer electrodes in aqueous electrolytes. The functionality of the devices is verified by powering a red light-emitting diode with the device in different mechanically challenging states.

  • 20.
    Wetterskog, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Jonasson, Christian
    RISE Acreo, S-40014 Gothenburg, Sweden..
    Smilgies, Detlef-M.
    Cornell Univ, Cornell High Energy Synchrotron Source, Ithaca, NY 14853 USA..
    Schaller, Vincent
    Chalmers Ind Tekn, S-41288 Gothenburg, Sweden..
    Johansson, Christer
    RISE Acreo, S-40014 Gothenburg, Sweden..
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Colossal Anisotropy of the Dynamic Magnetic Susceptibility in Low-Dimensional Nanocube Assemblies2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 2, p. 1403-1412Article in journal (Refereed)
    Abstract [en]

    One of the ultimate goals of nanocrystal self-assembly is to transform nanoscale building blocks into a material that displays enhanced properties relative to the sum of its parts. Herein, we demonstrate that 1D needle shaped assemblies composed of Fe3-delta O4 nanocubes display a significant augmentation of the magnetic susceptibility and dissipation as compared to OD and 2D systems. The performance of the nanocube needles is highlighted by a colossal anisotropy factor defined as the ratio of the parallel to the perpendicular magnetization components. We show that the origin of this effect cannot be ascribed to shape anisotropy in its classical sense; as such, it has no analogy in bulk magnetic materials. The temperature-dependent anisotropy factors of the in- and out-of-phase components of the magnetization have an extremely strong particle size dependence and reach values of 80 and 2500, respectively, for the largest nanocubes in this study. Aided by simulations, we ascribe the anisotropy of the magnetic susceptibility, and its strong particle-size dependence to a synergistic coupling between the dipolar interaction field and a net anisotropy field resulting from a partial texture in the 1D nanocube needles.

  • 21.
    Zhang, Jinbao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Xu, Bo
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem Chem Sci & Engn, Organ Chem, SE-10044 Stockholm, Sweden.
    Johansson, Malin B
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vlachopoulos, Nick
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, EPFL FSB ISIC LSPM, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    KTH Royal Inst Technol, Ctr Mol Devices, Dept Chem Chem Sci & Engn, Organ Chem, SE-10044 Stockholm, Sweden.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, EPFL FSB ISIC LSPM, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland.
    Strategy to Boost the Efficiency of Mixed-Ion Perovskite Solar Cells: Changing Geometry of the Hole Transporting Material.2016In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 10, no 7, p. 6816-6825Article in journal (Refereed)
    Abstract [en]

    The hole transporting material (HTM) is an essential component in perovskite solar cells (PSCs) for efficient extraction and collection of the photoinduced charges. Triphenylamine- and carbazole-based derivatives have extensively been explored as alternative and economical HTMs for PSCs. However, the improvement of their power conversion efficiency (PCE), as well as further investigation of the relationship between the chemical structure of the HTMs and the photovoltaic performance, is imperatively needed. In this respect, a simple carbazole-based HTM X25 was designed on the basis of a reference HTM, triphenylamine-based X2, by simply linking two neighboring phenyl groups in a triphenylamine unit through a carbon-carbon single bond. It was found that a lowered highest occupied molecular orbital (HOMO) energy level was obtained for X25 compared to that of X2. Besides, the carbazole moiety in X25 improved the molecular planarity as well as conductivity property in comparison with the triphenylamine unit in X2. Utilizing the HTM X25 in a solar cell with mixed-ion perovskite [HC(NH2)2]0.85(CH3NH3)0.15Pb(I0.85Br0.15)3, a highest reported PCE of 17.4% at 1 sun (18.9% under 0.46 sun) for carbazole-based HTM in PSCs was achieved, in comparison of a PCE of 14.7% for triphenylamine-based HTM X2. From the steady-state photoluminescence and transient photocurrent/photovoltage measurements, we conclude that (1) the lowered HOMO level for X25 compared to X2 favored a higher open-circuit voltage (Voc) in PSCs; (2) a more uniform formation of X25 capping layer than X2 on the surface of perovskite resulted in more efficient hole transport and charge extraction in the devices. In addition, the long-term stability of PSCs with X25 is significantly enhanced compared to X2 due to its good uniformity of HTM layer and thus complete coverage on the perovskite. The results provide important information to further develop simple and efficient small molecular HTMs applied in solar cells.

  • 22.
    Zhang, Xiaoliang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Santra, Pralay Kanti
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Tian, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Malin B.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Johansson, Erik M.J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Highly Efficient Flexible Quantum Dot Solar Cells with Improved Electron Extraction Using MgZnO Nanocrystals2017In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 8, p. 8478-8487Article in journal (Refereed)
    Abstract [en]

    Colloidal quantum dot (CQD) solar cells have high potential for realizing an efficient and lightweight energy supply for flexible or wearable electronic devices. To achieve highly efficient and flexible CQD solar cells, the electron transport layer (ETL), extracting electrons from the CQD solid layer, needs to be processed at a low-temperature and should also suppress interfacial recombination. Herein, a highly stable MgZnO nanocrystal (MZO-NC) layer is reported for efficient flexible PbS CQD solar cells. Solar cells fabricated with MZONC ETL give a high power conversion efficiency (PCE) of 10.4% and 9.4%, on glass and flexible plastic substrates, respectively. The reported flexible CQD solar cell has the record efficiency to date of flexible CQD solar cells. Detailed theoretical simulations and extensive characterizations reveal that the MZO-NCs significantly enhance charge extraction from CQD solids and diminish the charge accumulation at the ETL/CQD interface, suppressing charge interfacial recombination. These important results suggest that the low-temperature processed MZO-NCs are very promising for use in efficient flexible solar cells or other flexible optoelectronic devices.

  • 23. Zhang, Youwei
    et al.
    Li, Hui
    Wang, Haomin
    Liu, Ran
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Qiu, Zhi-Jun
    On Valence-Band Splitting in Layered MoS22015In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 8, p. 8514-8519Article in journal (Refereed)
    Abstract [en]

    As a representative two-dimensional semiconducting transition-metal dichalcogenide (TMD), the electronic structure in layered MoS2 is a collective result of quantum confinement, interlayer interaction, and crystal symmetry. A prominent energy splitting in the valence band gives rise to many intriguing electronic, optical, and magnetic phenomena. Despite numerous studies, an experimental determination of valence-band splitting in few-layer MoS2 is still lacking. Here, we show how the valence-band maximum (VBM) splits for one to five layers of MoS2. Interlayer coupling is found to contribute significantly to phonon energy but weakly to VBM splitting in bilayers, due to a small interlayer hopping energy for holes. Hence, spin-orbit coupling is still predominant in the splitting. A temperature-independent VBM splitting, known for single-layer MoS2, is, thus, observed for bilayers. However, a Bose-Einstein type of temperature dependence of VBM splitting prevails in three to five layers of MoS2. In such few-layer MoS2, interlayer coupling is enhanced with a reduced interlayer distance, but thermal expansion upon temperature increase tends to decouple adjacent layers and therefore decreases the splitting energy. Our findings that shed light on the distinctive behaviors about VBM splitting in layered MoS2 may apply to other hexagonal TMDs as well. They will also be helpful in extending our understanding of the TMD electronic structure for potential applications in electronics and optoelectronics.

1 - 23 of 23
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