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  • 1. Ballav, Nirmalya
    et al.
    Waeckerlin, Christian
    Siewert, Dorota
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Jung, Thomas A.
    Emergence of On-Surface Magnetochemistry2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 14, p. 2303-2311Article in journal (Refereed)
    Abstract [en]

    The control of exchange coupling across the molecule-substrate interface is a key feature in molecular spintronics. This Perspective reviews the emerging field of on-surface magnetochemistry, where coordination chemistry is applied to surface-supported metal porphyrins and metal phthalocyanines to control their magnetic properties. The particularities of the surface as a multiatomic ligand or "surface ligand'' are introduced. The asymmetry involved in the action of a chemical ligand and a surface ligand on the same planar complexes modifies the well-established ''trans effect'' to the notion of the ''surface-trans effect". As ad-complexes on ferromagnetic substrates are usually exchange-coupled, the magnetochemical implications of the surface-trans effect are of particular interest. The combined action of the different ligands allows for the reproducible control of spin states in on-surface supramolecular architectures and opens up new ways toward building and operating spin systems at interfaces. Notably, spin-switching has been demonstrated to be controlled collectively via the interaction with a ligand (chemical selectivity) and individually via local addressing at the interface.

  • 2.
    Bi, Dongqin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Yang, Lei
    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.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Effect of Different Hole Transport Materials on Recombination in CH3NH3PbI3 Perovskite-Sensitized Mesoscopic Solar Cells2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 9, p. 1532-1536Article in journal (Refereed)
    Abstract [en]

    We report on perovskite (CH3NH3)PbI3-sensitized solid-state solar cells using spiro-OMeTAD, poly(3-hexylthiophene-2,5-diyl) (P3HT) and 4-(diethylamino)benzaldehyde diphenylhydrazone (DEH) as hole transport materials (HTMs) with a light to electricity power conversion efficiency of 8.5%, 4.5%, and 1.6%, respectively, under AM 1.5G illumination of 1000 W/m(2) intensity. Photoinduced absorption spectroscopy (PIA) shows that hole transfer occurs from the (CH3NH3)PbI3 to HTMs after excitation of (CH3NH3)PbI3. The electron lifetime (tau(e)) in these devices are in the order Spiro-OMeTAD > P3HT > DEH, while the charge transport time (t(tr)) is rather similar. The difference in tau(e) can therefore explain the lower efficiency of the devices based on P3HT and DEH. This report shows that the nature of the HTM is essential for charge recombination and elucidates that finding an optimal HTM for the perovskite solar cell includes controlling the perovskite/HTM interaction. Design routes for new HTMs are suggested.

  • 3.
    Boschloo, Gerrit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Gibson, Elizabeth A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Photomodulated Voltammetry of Iodide/Triiodide Redox Electrolytes and Its Relevance to Dye-Sensitized Solar Cells2011In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 2, no 24, p. 3016-3020Article in journal (Refereed)
    Abstract [en]

    Photomodulated voltammetry was used to determine the redox potentials of the diiodide radical (I(2)(-center dot)) in water, acetonitrile, and 3-methoxypropionitrile. Iodide/triiodide redox electrolytes were exposed to modulated blue light, resulting in I(2)(-center dot) generation. Using transparent fluorine-doped tinoxide (FTO) electrodes, two modulated photocurrent waves could be discerned in the voltammogram, from which the formal potentials for oxidation and reduction reactions of the diiodide radical were determined. E(0)'(I(2)(-center dot)/I(-)) was found to be +0.79 and +1.04 V versus NHE in acetonitrile and water, respectively. These values give guidelines for E(0)'(D(+)/D) required for efficient regeneration of dyes used in dye-sensitized solar cells.

  • 4. Canton, Sophie E.
    et al.
    Zhang, Xiaoyi
    Zhang, Jianxin
    van Driel, Tim B.
    Kjaer, Kasper S.
    Haldrup, Kristoffer
    Chabera, Pavel
    Harlang, Tobias
    Suarez-Alcantara, Karina
    Liu, Yizhu
    Perez, Jorge
    Bordage, Amelie
    Papai, Matyas
    Vanko, Gyoergy
    Jennings, Guy
    Kurtz, Charles A.
    Rovezzi, Mauro
    Glatzel, Pieter
    Smolentsev, Grigory
    Uhlig, Jens
    Dohn, Asmus O.
    Christensen, Morten
    Galler, Andreas
    Gawelda, Wojciech
    Bressler, Christian
    Lemke, Henrik T.
    Moller, Klaus B.
    Nielsen, Martin M.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Warnmark, Kenneth
    Sundstrom, Villy
    Toward Highlighting the Ultrafast Electron Transfer Dynamics at the Optically Dark Sites of Photocatalysts2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 11, p. 1972-1976Article in journal (Refereed)
    Abstract [en]

    Building a detailed understanding of the structure function relationship is a crucial step in the optimization of molecular photocatalysts employed in water splitting schemes. The optically dark nature of their active sites usually prevents a complete mapping of the photoinduced dynamics. In this work, transient X-ray absorption spectroscopy highlights the electronic and geometric changes that affect such a center in a bimetallic model complex. Upon selective excitation of the ruthenium chromophore, the cobalt moiety is reduced through intramolecular electron transfer and undergoes a spin flip accompanied by an average bond elongation of 0.20 +/- 0.03 angstrom. The analysis is supported by simulations based on density functional theory structures (B3LYP*/TZVP) and FEFF 9.0 multiple scattering calculations. More generally, these results exemplify the large potential of the technique for tracking elusive intermediates that impart unique functionalities in photochemical devices.

  • 5.
    Chabera, Pavel
    et al.
    Lund Univ, Dept Chem, Div Phys Chem, Box 124, SE-22100 Lund, Sweden..
    Kjaer, Kasper S.
    Lund Univ, Dept Chem, Div Phys Chem, Box 124, SE-22100 Lund, Sweden.;Stanford Univ, SLAC Natl Accelerator Lab, PULSE Inst, Menlo Pk, CA 94025 USA..
    Prakash, Om
    Lund Univ, Dept Chem, CAS, Box 124, SE-22100 Lund, Sweden..
    Honarfar, Alireza
    Lund Univ, Dept Chem, Div Phys Chem, Box 124, SE-22100 Lund, Sweden..
    Liu, Yizhu
    Lund Univ, Dept Chem, CAS, Box 124, SE-22100 Lund, Sweden..
    Fredin, Lisa A.
    Lund Univ, Dept Chem, Div Theoret Chem, Box 124, SE-22100 Lund, Sweden..
    Harlang, Tobias C. B.
    Lund Univ, Dept Chem, Div Phys Chem, Box 124, SE-22100 Lund, Sweden..
    Lidin, Sven
    Lund Univ, Dept Chem, CAS, Box 124, SE-22100 Lund, Sweden..
    Uhlig, Jens
    Lund Univ, Dept Chem, Div Phys Chem, Box 124, SE-22100 Lund, Sweden..
    Sundstrom, Villy
    Lund Univ, Dept Chem, Div Phys Chem, Box 124, SE-22100 Lund, Sweden..
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Persson, Petter
    Lund Univ, Dept Chem, Div Theoret Chem, Box 124, SE-22100 Lund, Sweden..
    Warnmark, Kenneth
    Lund Univ, Dept Chem, CAS, Box 124, SE-22100 Lund, Sweden..
    Fe-II Hexa N-Heterocyclic Carbene Complex with a 528 ps Metal-to-Ligand Charge-Transfer Excited-State Lifetime2018In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 9, no 3, p. 459-463Article in journal (Refereed)
    Abstract [en]

    The iron carbene complex [Fe-II(btz)(3)](PF6)(2) (where btz = 3,3'-dimethyl-1,1'-bis(p-tolyl)-4,4'-bis(1,2,3-triazol-5-ylidene)) has been synthesized, isolated, and characterized as a low-spin ferrous complex. It exhibits strong metal-to-ligand charge transfer (MLCT) absorption bands throughout the visible spectrum, and excitation of these bands gives rise to a (MLCT)-M-3 state with a 528 ps excited-state lifetime in CH3CN solution that is more than one order of magnitude longer compared with the MLCT lifetime of any previously reported Fe-II complex. The low potential of the [Fe(btz)(3)](3+)/[Fe(btz)(3)](2+) redox couple makes the (MLCT)-M-3 state of [Fe-II(btz)(3)](2+) a potent photo-reductant that can be generated by light absorption throughout the visible spectrum. Taken together with our recent results on the [Fe-III(btz)(3)](3+) form of this complex, these results show that the Fe-II and Fe-III oxidation states of the same Fe(btz)(3) complex feature long-lived MLCT and LMCT states, respectively, demonstrating the versatility of iron N-heterocyclic carbene complexes as promising light-harvesters for a broad range of oxidizing and reducing conditions.

  • 6.
    Czapla-Masztafiak, Joanna
    et al.
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland.;PSI, CH-5232 Villigen, Switzerland..
    Nogueira, Juan J.
    Univ Vienna, Inst Theoret Chem, Fac Chem, Wahringer Str 17, A-1090 Vienna, Austria..
    Lipiec, Ewelina
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland.;Swiss Fed Inst Technol, Vladimir Prelog Weg 1-5-10, CH-8093 Zurich, Switzerland..
    Kwiatek, Wojciech M.
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland..
    Wood, Bayden R.
    Monash Univ, Sch Chem, Ctr Biospectroscopy, Victoria 3800, Australia..
    Deacon, Glen B.
    Monash Univ, Sch Chem, Fac Sci, Clayton, Vic 3800, Australia..
    Kayser, Yves
    PSI, CH-5232 Villigen, Switzerland..
    Fernandes, Daniel L. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pavliuk, Mariia V.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Szlachetko, Jakub
    PSI, CH-5232 Villigen, Switzerland.;Jan Kochanowski Univ Humanities & Sci, Inst Phys, Swietokrzyska 15 St, PL-25406 Kielce, Poland..
    Gonzalez, Leticia
    Univ Vienna, Inst Theoret Chem, Fac Chem, Wahringer Str 17, A-1090 Vienna, Austria..
    Sá, Jacinto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Polish Acad Sci, Inst Phys Chem, Ul Kasprzaka 44-52, PL-01224 Warsaw, Poland..
    Direct Determination of Metal Complexes' Interaction with DNA by Atomic Telemetry and Multiscale Molecular Dynamics2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 4, p. 805-811Article in journal (Refereed)
    Abstract [en]

    The lack of molecular mechanistic understanding of the interaction between metal complexes and biomolecules hampers their potential medical use. Herein we present a robust procedure combining resonant X-ray emission spectroscopy and multiscale molecular dynamics simulations, which allows for straightforward elucidation of the precise interaction mechanism at the atomic level. The report unveils an unforeseen hydrolysis process and DNA binding of [Pt{N(p-HC6F4)CH2}(2)py(2)] (Pt103), which showed potential cytotoxic activity in the past. Pt103 preferentially coordinates to adjacent adenine sites, instead of guanine sites as in cisplatin, because of its hydrogen bond ability. Comparison with previous research on cisplatin suggests that selective binding to guanine or adenine may be achieved by controlling the acidity of the compound.

  • 7.
    D'Amario, Luca
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Antila, Liisa J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Rimgard, Belinda Pettersson
    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.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kinetic Evidence of Two Pathways for Charge Recombination in NiO-Based Dye-Sensitized Solar Cells2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 5, p. 779-783Article in journal (Refereed)
    Abstract [en]

    Mesoporous nickel oxide has been used as electrode material for p-type dye-sensitized solar cells (DSCs) for many years but no high efficiency cells have yet been obtained. One of the main issues that lowers the efficiency is the poor fill factor, for which a clear reason is still missing. In this paper we present the first evidence for a relation between applied potential and the charge recombination rate of the NiO electrode. In particular, we find biphasic recombination kinetics: a fast (15 ns) pathway attributed to the reaction with the holes in the valence band and a slow (1 ms) pathway assigned to the holes in the trap states. The fast component is the most relevant at positive potentials, while the slow component becomes more important at negative potentials. This means that at the working condition of the cell, the fast recombination is the most important. This could explain the low fill factor of NiO-based DSCs.

  • 8.
    Debbichi, L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Lebegue, S.
    Two-Dimensional Indium Selenides Compounds: An Ab Initio Study2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 15, p. 3098-3103Article in journal (Refereed)
    Abstract [en]

    We use first-principle calculations to investigate the electronic structure of InSe and In2Se3. The interlayer binding energy is found to be in the same range as for other 2D systems, and the monolayers are found to be dynamically stable, which suggest the possibility to obtain them as isolated layers. The GW approximation including spin-orbit is used to obtain the bandgaps, which are in the range relevant for application in electronics. Also, it is shown that an electric field perpendicular to the layers can induce a semiconductor to metal transition in this family of compounds.

  • 9.
    Dhara, Barun
    et al.
    IISER, Dept Chem, Pune 411008, Maharashtra, India..
    Tarafder, Kartick
    NITK, Dept Phys, Mangalore 575025, India..
    Jha, Plawan K.
    IISER, Dept Chem, Pune 411008, Maharashtra, India..
    Panja, Soumendra N.
    IISER, Dept Phys, Pune 411008, Maharashtra, India..
    Nair, Sunil
    IISER, Dept Phys, Pune 411008, Maharashtra, India..
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ballav, Nirmalya
    IISER, Dept Chem, Pune 411008, Maharashtra, India..
    Possible Room-Temperature Ferromagnetism in Self-Assembled Ensembles of Paramagnetic and Diamagnetic Molecular Semiconductors2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 24, p. 4988-4995Article in journal (Refereed)
    Abstract [en]

    Owing to long spin-relaxation time and chemically customizable physical properties, molecule-based semiconductor materials like metal-phthalocyanines offer promising alternatives to conventional dilute magnetic semiconductors/oxides (DMSs/ DMOs) to achieve room-temperature (RT) ferromagnetism. However, air-stable molecule based materials exhibiting both semiconductivity and magnetic-order at RT have so far remained elusive. We present here the concept of supramolecular arrangement to accomplish possibly RT ferromagnetism. Specifically, we observe a clear hysteresis-loop (H-c approximate to 120 Oe) at 300 K in the magnetization versus field (M H) plot of the self-assembled ensembles of diamagnetic Zn-phthalocyanine having peripheral F atoms (ZnFPc; S = 0) and paramagnetic Fe-phthalocyanine having peripehral H atoms (FePc; S = 1). Tauc plot of the self-assembled FePc center dot center dot center dot ZnFPc ensembles showed an optical band gap of similar to 1.05 eV and temperature-dependent current-voltage (I-V) studies suggest semiconducting characteristics in the material. Using DFT+U quantum-chemical calculations, we reveal the origin of such unusual ferromagnetic exchange-interaction in the supramolecular FePc center dot center dot center dot ZnFPc system.

  • 10. Engel, Nicholas
    et al.
    Atak, Kaan
    Lange, Kathrin M.
    Gotz, Malte
    Soldatov, Mikhail
    Golnak, Ronny
    Suljoti, Edlira
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Aziz, Emad F.
    DMSO-Water Clustering in Solution Observed in Soft X-ray Spectra2012In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 3, no 24, p. 3697-3701Article in journal (Refereed)
    Abstract [en]

    The significant deviation from the ideality of dimethyl sulfoxide (DMSO)/water mixtures can be addressed based on the change of the local molecular orbitals of each solvent upon mixing. Oxygen K-edge absorption and emission spectra of DMSO/water solutions were measured using the liquid microjet technique. The spectra demonstrate that the hydrogen bond network in liquid water is already influenced at small DMSO concentrations, and at the molar fraction x(DMSO) = 0.43 we find strong evidence of DMSO-water clustering reflected by the influence on the occupied molecular orbitals.

  • 11. Gennari, Marcello
    et al.
    Legalite, Florent
    Zhang, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pellegrin, Yann
    Blart, Errol
    Fortage, Jerome
    Brown, Allison M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Deronzier, Alain
    Collomb, Marie-Noelle
    Boujtita, Mohammed
    Jacquemin, Denis
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Odobel, Fabrice
    Long-Lived Charge Separated State in NiO-Based p-Type Dye-Sensitized Solar Cells with Simple Cyclometalated Iridium Complexes2014In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, no 13, p. 2254-2258Article in journal (Refereed)
    Abstract [en]

    Three new cyclometalated iridium complexes were prepared and investigated on nanocrystalline NiO cathodes. Nanosecond transient absorption spectroscopy experiments show they present a surprisingly slow geminate charge recombination upon excitation on NiO, representing thus the first examples of simple sensitizers with such feature. These complexes were used in dye-sensitized solar cells using nanocrystalline NiO film as semiconductor. The long-lived charge separated state of these Ir complexes make them compatible with other redox mediators than I-3(-)/I-, such as a cobalt electrolyte and enable to reach significantly high open circuit voltage.

  • 12.
    Hägglund, Carl
    et al.
    Stanford University, Stanford, California, USA.
    Apell, P.
    Plasmonic near-field absorbers for ultrathin solar cells2012In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 3, no 10, p. 1275-1285Article in journal (Refereed)
  • 13.
    Johansson, Malin B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhu, Huimin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Extended Photo-Conversion Spectrum in Low-Toxic Bismuth Halide Perovskite Solar Cells2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 17, p. 3467-3471Article in journal (Refereed)
    Abstract [en]

    Lead-based perovskites show very promising properties for use in solar cells; however, the toxicity of lead is a potential inhibitor for large-scale application of these solar cells. Here, a low-toxic bismuth halide, CsBi3I10, is synthesized from solution and the optical properties and crystal structure are compared with previously reported Cs3Bi2I9 perovskite, and the photovoltaic properties are also investigated. The XRD pattern suggests that the CsBi3I10 film has a layered structure with a different dominating crystal growth direction than the Cs3Bi2I9 perovskite. A band gap of 1.77 eV is obtained for the CsBi3I10 film, which is smaller than the band gap of Cs3Bi2I9 at 2.03 eV, and an extended visible light absorption spectrum is therefore obtained. The solar cell device with CsBi3I10 shows a photocurrent up to 700 nm, and this work shows therefore the possibility for increased light absorption and higher photocurrents in solar cells based on bismuth halide perovskites.

  • 14. Kan, Erjun
    et al.
    Li, Ming
    Hu, Shuanglin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Xiao, Chuanyun
    Xiang, Hongjun
    Deng, Kaiming
    Two-Dimensional Hexagonal Transition-Metal Oxide for Spintronics2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 7, p. 1120-1125Article in journal (Refereed)
    Abstract [en]

    Two-dimensional materials have been the hot subject of studies due to their great potential in applications. However, their applications in spintronics have been blocked by the difficulty in producing ordered spin structures in 2D structures. Here we demonstrated that the ultrathin films of recently experimentally realized wurtzite MnO can automatically transform into a stable graphitic structure with ordered spin arrangement via density functional calculation, and the stability of graphitic structure can be enhanced by external strain. Moreover, the antiferromagnetic ordering of graphitic MnO single layer can be switched into half-metallic ferromagnetism by small hole-doping, and the estimated Curie temperature is higher than 300 K. Thus, our results highlight a promising way toward 2D magnetic materials.

  • 15. Kislitsyn, Dmitry A
    et al.
    Kocevski, Vancho
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Mills, Jon M
    Chiu, Sheng-Kuei
    Gervasi, Christian F
    Taber, Benjamen N
    Rosenfield, Ariel E
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Rusz, Ján
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Goforth, Andrea M
    Nazin, George V
    Mapping of Defects in Individual Silicon Nanocrystals Using Real-Space Spectroscopy.2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 6, p. 1047-1054Article in journal (Refereed)
    Abstract [en]

    The photophysical properties of silicon semiconductor nanocrystals (SiNCs) are extremely sensitive to the presence of surface chemical defects, many of which are easily produced by oxidation under ambient conditions. The diversity of chemical structures of such defects and the lack of tools capable of probing individual defects continue to impede understanding of the roles of these defects in SiNC photophysics. We use scanning tunneling spectroscopy to study the impact of surface defects on the electronic structures of hydrogen-passivated SiNCs supported on the Au(111) surface. Spatial maps of the local electronic density of states (LDOS) produced by our measurements allowed us to identify locally enhanced defect-induced states as well as quantum-confined states delocalized throughout the SiNC volume. We use theoretical calculations to show that the LDOS spectra associated with the observed defects are attributable to Si-O-Si bridged oxygen or Si-OH surface defects.

  • 16. Krylov, Anna I.
    et al.
    Herbert, John M.
    Furche, Filipp
    Head-Gordon, Martin
    Knowles, Peter J.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Manby, Frederick R.
    Pulay, Peter
    Skylaris, Chris-Kriton
    Werner, Hans-Joachim
    What Is the Price of Open-Source Software?2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 14, p. 2751-2754Article in journal (Other academic)
  • 17.
    Kullgren, Jolla
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Broqvist, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Supercharged Low-Temperature Oxygen Storage Capacity of Ceria at the Nanoscale2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 4, p. 604-608Article in journal (Refereed)
    Abstract [en]

    We provide an explanation for the experimental finding of a dramatically enhancedlow-temperature oxygen storage capacity for small ceria nanoparticles. At low temperature, small octahedral ceria nanoparticles will be understoichiometric at both oxidizing and reducing conditions without showing explicit oxygen vacancies. Instead, rather than becoming stoichiometric at oxidizing conditions, such particles are stabilized through oxygen adsorption forming superoxo (O-2(-)) ions and become in this way supercharged with oxygen. Thesupercharging effect is size-dependent and largest for small nanoparticles where it gives a direct increase in the oxygen storage capacity and simultaneously provides a source of active oxygenspecies at low temperatures.

  • 18. Liao, Qinghua
    et al.
    Kamerlin, Shina Caroline Lynn
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Structure and Molecular Biology.
    Strodel, Birgit
    Development and Application of a Nonbonded Cu2+ Model That Includes the Jahn-Teller Effect2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 13, p. 2657-2662Article in journal (Refereed)
    Abstract [en]

    Metal ions are both ubiquitous to and crucial in biology. In classical simulations, they are typically described as simple van der Waals spheres, making it difficult to provide reliable force field descriptions for them. An alternative is given by nonbonded dummy models, in which the central metal atom is surrounded by dummy particles that each carry a partial charge. While such dummy models already exist for other metal ions, none is available yet for Cu2+ because of the challenge to reproduce the Jahn-Teller distortion. This challenge is addressed in the current study, where, for the first time, a dummy model including a Jahn-Teller effect is developed for Cu2+. We successfully validate its usefulness by studying metal binding in two biological systems: the amyloid-beta peptide and the mixed-metal enzyme superoxide dismutase. We believe that our parameters will be of significant value for the computational study of Cu2+'-dependent biological systems using classical models.

  • 19.
    Liao, Qinghua
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Structural Biology. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Pabis, Anna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Strodel, Birgit
    Forschungszentrum Julich, Julich, Germany; Heinrich Heine Univ Dusseldorf, Dusseldorf, Germany.
    Kamerlin, Shina Caroline Lynn
    Uppsala University, Science for Life Laboratory, SciLifeLab. Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Structural Biology.
    Extending the Nonbonded Cationic Dummy Model to Account for Ion-Induced Dipole Interactions2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 21, p. 5408-5414Article in journal (Refereed)
    Abstract [en]

    Modeling metalloproteins often requires classical molecular dynamics (MD) simulations in order to capture their relevant motions, which in turn necessitates reliable descriptions of the metal centers involved. One of the most successful approaches to date is provided by the "cationic dummy model", where the positive charge of the metal ion is transferred toward dummy particles that are bonded to the central metal ion in a predefined coordination geometry. While this approach allows for ligand exchange, and captures the correct electrostatics as demonstrated for different divalent metal ions, current dummy models neglect ion-induced dipole interactions. In the present work, we resolve this weakness by taking advantage of the recently introduced 12-6-4 type Lennard-Jones potential to include ion-induced dipole interactions. We revise our previous dummy model for Mg2+ and demonstrate that the resulting model can simultaneously reproduce the experimental solvation free energy and metal ligand distances without the need for artificial restraints or bonds. As ion-induced dipole interactions become particularly important for highly charged metal ions, we develop dummy models for the biologically relevant ions Al3+, Fe3+, and Cr3+. Finally, the effectiveness of our new models is demonstrated in MD simulations of several diverse (and highly challenging to simulate) metalloproteins.

  • 20.
    Lindblad, Rebecka
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Bi, Dongqin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Park, Byung-wook
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Oscarsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gorgoi, Mihaela
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Odelius, Michael
    Johansson, Erik M. J.
    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.
    Electronic Structure of TiO2/CH3NH3PbI3 Perovskite Solar Cell Interfaces2014In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, no 4, p. 648-653Article in journal (Refereed)
    Abstract [en]

    The electronic structure and chemical composition of efficient CH3NH3PbI3 perovskite solar cell materials deposited onto mesoporous TiO2 were studied using photoelectron spectroscopy with hard X-rays. With this technique, it is possible to directly measure the occupied energy levels of the perovskite as well as the TiO2 buried beneath and thereby determine the energy level matching of the interface. The measurements of the valence levels were in good agreement with simulated density of states, and the investigation gives information on the character of the valence levels. We also show that two different deposition techniques give results indicating similar electronic structures.

  • 21.
    Liu, Jia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Roberts, Matthew
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Younesi, Reza
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Dahbi, Mohammed
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Zhu, Jiefang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Accelerated Electrochemical Decomposition of Li2O2 under X-ray Illumination2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 23, p. 4045-4050Article in journal (Refereed)
    Abstract [en]

    This work presents the first report detailing the effect of X-rays on the electrochemical decomposition of Li2O2, which is the main reaction during the charging process in a Li-O-2 battery. An operando synchrotron radiation powder X-ray diffraction (SR-PXD) experiment was performed. The results indicate that the electrochemical decomposition of Li2O2 is dramatically accelerated under X-ray irradiation. The accelerated decomposition of Li2O2 follows a zero-order reaction, and the decomposition rate constant is proportional to the intensity of X-ray used. A mechanism for the electrochemical decomposition of Li2O2 under X-ray irradiation is proposed. These results give an insight into the charging process in Li-O-2 batteries.

  • 22.
    Maibach, Julia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Lindgren, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Eriksson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Electric potential gradient at the buried interface between Lithium-ion battery electrodes and the SEI observed using photoelectron spectroscopy2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 10, p. 1775-1780Article in journal (Refereed)
    Abstract [en]

    The buried interface between the bulk electrode material and the solid electrolyte interphase (SEI) in cycled Li-ion battery anodes is suggested to incorporate an electric potential gradient. This suggestion is based on photoelectron spectroscopy (PES) results from different anode materials that all show relative binding energy shifts between the components of the SEI and the active anode. Implications of this electric potential gradient on binding energy reference points in PES as well as on charge-transfer kinetics in Li-ion batteries are discussed. Specifically, we show that the separation of surface layer and bulk material spectral contributions (depth profiling) is crucial for consistent data interpretation. We conclude that previous interpretations of lithiation as cause for changes in PES spectra may need to be revised.

  • 23.
    Marazzi, Marco
    et al.
    Univ Lorraine Nancy, SRSMC, Theorie Modelisat Simulat, Blvd Aiguillettes, F-54000 Nancy, France.;Univ Vienna, Inst Theoret Chem, Wahringer Str 17, A-1090 Vienna, Austria..
    Mai, Sebastian
    CNRS, SRSMC, Theorie Modelisat Simulat, Blvd Aiguillettes, Nancy, France..
    Roca-Sanjuan, Daniel
    Univ Valencia, Inst Ciencia Mol, POB 22085, ES-46071 Valencia, Spain..
    Delcey, Mickael G.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Uppsala Univ, UC3, S-75105 Uppsala, Sweden..
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Uppsala Univ, UC3, S-75105 Uppsala, Sweden..
    Gonzalez, Leticia
    CNRS, SRSMC, Theorie Modelisat Simulat, Blvd Aiguillettes, Nancy, France..
    Monari, Antonio
    Univ Lorraine Nancy, SRSMC, Theorie Modelisat Simulat, Blvd Aiguillettes, F-54000 Nancy, France.;Univ Vienna, Inst Theoret Chem, Wahringer Str 17, A-1090 Vienna, Austria..
    Benzophenone Ultrafast Triplet Population: Revisiting the Kinetic Model by Surface-Hopping Dynamics2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 4, p. 622-626Article in journal (Refereed)
    Abstract [en]

    The photochemistry of benzophenone, a paradigmatic organic molecule for photosensitization, was investigated by means of surface-hopping ab initio molecular dynamics. Different mechanisms were found to be relevant within the first 600 fs after excitation; the long debated direct (S-1 -> T-1) and indirect (S-1 -> T-2 -> T-1) mechanisms for population of the low-lying triplet state are both possible, with the latter being prevalent. Moreover, we established the existence of a kinetic equilibrium between the two triplet states, never observed before. This fact implies that a significant fraction of the overall population resides in T-2, eventually allowing one to revisit the usual spectroscopic assignment proposed by transient absorption spectroscopy. This finding is of particular interest for photocatalysis as well as for DNA damages studies because both T-1 and T-2 channels are, in principle, available for benzophenone-mediated photoinduced energy transfer toward DNA.

  • 24.
    Marklund, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Biochemistry. Univ Oxford, Dept Chem, Phys & Theoret Chem Lab, South Parks Rd, Oxford GB 0X1 3QZ, England..
    Ekeberg, Tomas
    DESY, Ctr Free Electron Laser Sci, DE-22607 Hamburg, Germany..
    Moog, Mathieu
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Benesch, Justin L. P.
    Univ Oxford, Dept Chem, Phys & Theoret Chem Lab, South Parks Rd, Oxford GB 0X1 3QZ, England..
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. DESY, Ctr Free Electron Laser Sci, DE-22607 Hamburg, Germany..
    Controlling Protein Orientation in Vacuum Using Electric Fields2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 18, p. 4540-4544Article in journal (Refereed)
    Abstract [en]

    Single-particle imaging using X-ray free-electron lasers is an emerging technique that could provide high-resolution structures of macromolecules in the gas phase. One of the largest difficulties in realizing this goal is the unknown orientation of the individual sample molecules at the time of exposure. Preorientation of the molecules has been identified as a possible solution to this problem. Using molecular dynamics simulations, we identify a range of electric field strengths where proteins become oriented without losing their structure. For a number of experimentally relevant cases we show that structure determination is possible only when orientation information is included in the orientation-recovery process. We conclude that nondestructive field orientation of intact proteins is feasible and that it enables a range of new structural investigations with single particle imaging.

  • 25.
    Mirmohades, Mohammad
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Adamska-Venkatesh, Agnieszka
    Max Planck Inst Chem Energy Convers, Stiftstr 34-36, D-45470 Mulheim, Germany..
    Sommer, Constanze
    Max Planck Inst Chem Energy Convers, Stiftstr 34-36, D-45470 Mulheim, Germany..
    Reijerse, Edward
    Max Planck Inst Chem Energy Convers, Stiftstr 34-36, D-45470 Mulheim, Germany..
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lubitz, Wolfgang
    Max Planck Inst Chem Energy Convers, Stiftstr 34-36, D-45470 Mulheim, Germany..
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Following [FeFe] Hydrogenase Active Site Intermediates by Time-Resolved Mid-IR Spectroscopy2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 16, p. 3290-3293Article in journal (Refereed)
    Abstract [en]

    Time-resolved nanosecond mid-infrared spectroscopy is for the first time employed to study the [FeFe] hydrogenase from Chlamydomonas reinhardtii and to investigate relevant intermediates of the enzyme active site. An actinic 355 nm, 10 ns laser flash triggered photodissociation of a carbonyl group from the CO-inhibited state H-ox-CO to form the state H-ox, which is an intermediate of the catalytic proton reduction cycle. Time-resolved infrared spectroscopy allowed us to directly follow the subsequent rebinding of the carbonyl, re-forming H-ox-CO, and determine the reaction half-life to be t(1/2) approximate to 13 +/- 5 ms at room temperature. This gives direct information GO on the dynamics of CO inhibition of the enzyme.

  • 26. Mukhopadhyay, Saikat
    et al.
    Scheicher, Ralph H.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Pandey, Ravindra
    Karna, Shashi P.
    Sensitivity of Boron Nitride Nanotubes toward Biomolecules of Different Polarities2011In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 2, no 19, p. 2442-2447Article in journal (Refereed)
    Abstract [en]

    The effect of molecular polarity on the interaction between a boron nitride nanotube (BNNT) and amino acids is investigated with density functional theory. Three representative amino acids, namely, tryptophane (Trp), a nonpolar aromatic amino acid, and asparatic acid (Asp) and argenine (Arg), both polar amino acids are considered for their interactions with BNNT. The polar molecules, Asp and Arg, exhibit relatively stronger binding with the tubular surface of BNNT. The binding between the polar amino acid molecules and BNNT is accompanied by a charge transfer, suggesting that stabilization of the bioconjugated complex is mainly governed by electrostatic interactions. The results show modulation of the BNNT band gap by Trp. Interestingly, no change in band gap of BNNT is seen for the polar molecules Asp and Arg. The predicted higher sensitivity of BNNTs compared to carbon nanotubes (CNTs) toward amino acid polarity suggests BNNTs to be a better substrate for protein immobilization than CNTs.

  • 27.
    Murugan, N. Arul
    et al.
    AlbaNova Univ Ctr, Royal Inst Technol KTH, Sch Biotechnol, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden..
    Halldin, Christer
    Karolinska Univ Sjukhuset, Psykiatrictr, Dept Clin Neurosci CNS, S-17176 Stockholm, Sweden..
    Nordberg, Agneta
    Karolinska Univ Hosp, Dept Neurobiol Care Sci & Soc, Ctr Alzheimer Res,Translat Alzheimer Neurobiol, Karolinska Inst,Dept Geriatr Med, S-14186 Stockholm, Sweden..
    Långström, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Ågren, Hans
    AlbaNova Univ Ctr, Royal Inst Technol KTH, Sch Biotechnol, Div Theoret Chem & Biol, S-10691 Stockholm, Sweden..
    The Culprit Is in the Cave: The Core Sites Explain the Binding Profiles of Amyloid-Specific Tracers2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 17, p. 3313-3321Article in journal (Refereed)
    Abstract [en]

    The design of molecular probes and tracer molecules with specificity toward amyloid beta (A beta) fibrils is of paramount importance for the selective diagnosis of Alzheimer's disease. This requires a detailed understanding of the binding sites in amyloid targets, their number, and their binding mechanism for various tracer molecules. We adopt an integrated approach including molecular docking, molecular dynamics, and generalized Born-based free energy calculations to investigate site-specific interactions of different amyloid binding molecules. Our study reproduces the experimental results on the relative binding affinity of the tracers and amyloid binders and explains the feature of "multiple binding sites" in amyloid targets as probed by competition binding experiments. A major outcome of this study is that it is the core sites of the Afi fibrils that are responsible for the experimentally reported binding profiles of tracers in amyloid targets rather than the surface sites that received much focus in earlier investigations.

  • 28.
    Ravi, Vikash Kumar
    et al.
    IISER, Dept Chem, Pune 411008, Maharashtra, India..
    Santra, Pralay K.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. IISER, Ctr Energy Sci, Pune, India.
    Joshi, Niharika
    IISER, Dept Chem, Pune 411008, Maharashtra, India..
    Chugh, Jeetender
    IISER, Dept Chem, Pune 411008, Maharashtra, India..
    Singh, Sachin Kumar
    IISER, Dept Chem, Pune 411008, Maharashtra, India..
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ghosh, Prasenjit
    IISER, Dept Chem, Pune 411008, Maharashtra, India.;IISER, Dept Phys, Pune 411008, Maharashtra, India.;IISER, Ctr Energy Sci, Pune 411008, Maharashtra, India..
    Nag, Angshuman
    IISER, Dept Chem, Pune 411008, Maharashtra, India.;IISER, Ctr Energy Sci, Pune 411008, Maharashtra, India..
    Origin of the Substitution Mechanism for the Binding of Organic Ligands on the Surface of CsPbBr3 Perovskite Nanocubes2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 20, p. 4988-4994Article in journal (Refereed)
    Abstract [en]

    Optoelectronic properties of CsPbBr3 perovskite nanocubes (NCs) depend strongly on the interaction of the organic passivating molecules with the inorganic crystal. To understand this interaction, we employed a combination of synchrotron-based X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR) spectroscopy, and first-principles density functional theory (DFT)-based calculations. Variable energy XPS elucidated the internal structure of the inorganic part in a layer-by-layer fashion, whereas NMR characterized the organic ligands. Our experimental results confirm that oleylammonium ions act as capping ligands by substituting Cs+ ions from the surface of CsPbBr3 NCs. DFT calculations shows that the substitution mechanism does not require much energy for surface reconstruction and, in contrast, stabilizes the nanocrystal by the formation of three hydrogen bonds between the -NH3(+) moiety of oleylammonium and surrounding Br- on the surface of NCs. This substitution mechanism and its origin are in stark contrast to the usual adsorption of organic ligands on the surface of typical NCs.

  • 29.
    Sveinbjörnsson, Kári
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Aitola, Kerttu
    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.
    Pazoki, Meysam
    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. Ecole Polytech Fed Lausanne, Lab Photomol Sci, SB ISIC LSPM, CH-1015 Lausanne, Switzerland..
    Boschloo, Gerrit
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Probing Photocurrent Generation, Charge Transport, and Recombination Mechanisms in Mesostructured Hybrid Perovskite through Photoconductivity Measurements2015In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 6, no 21, p. 4259-4264Article in journal (Refereed)
    Abstract [en]

    Conductivity of methylammonium lead triiodide (MAPbI(3)) perovskite was measured on different mesoporous metal oxide scaffolds: TiO2, Al2O3, and ZrO2, as a function of incident light irradiation and temperature. It was found that MAPbI(3) exhibits intrinsic charge separation, and its conductivity stems from a majority of free charge carriers. The crystal morphology of the MAPbI(3) was found to significantly affect the photoconductivity, whereas in the dark the conductivity is governed by the perovskite in the pores of the mesoporous scaffold. The temperature-dependent conductivity measurements also indicate the presence of states within the band gap of the perovskite. Despite a relatively large amount of crystal defects in the measured material, the main recombination mechanism of the photogenerated charges is bimolecular (band-to-band), which suggests that the defect states are rather inactive in the recombination. This may explain the remarkable efficiencies obtained for perovskite solar cells prepared with wetchemical methods.

  • 30. Szlachetko, Jakub
    et al.
    Sa, Jacinto
    Nachtegaal, Maarten
    Hartfelder, Urs
    Dousse, Jean-Claude
    Hoszowska, Joanna
    Abreu Fernandes, Daniel Luis
    Shi, Hongqing
    Stampfl, Catherine
    Real Time Determination of the Electronic Structure of Unstable Reaction Intermediates during Au2O3 Reduction2014In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 5, no 1, p. 80-84Article in journal (Refereed)
  • 31. Travnikova, Oksana
    et al.
    Kimberg, Victor
    Flammini, Roberto
    Liu, Xiao-Jing
    Patanen, Minna
    Nicolas, Christophe
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Miron, Catalin
    On Routes to Ultrafast Dissociation of Polyatomic Molecules2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 14, p. 2361-2366Article in journal (Refereed)
    Abstract [en]

    Dissociation pathways for complex polyatomic molecules can sometimes be obscure due to the multitude of degrees of freedom involved. Here, we suggest the description of a dissociation mechanism implying multimode dynamics on the barrierless potential energy surface. The mechanism is elaborated from the X-ray spectroscopic analysis of the ultrafast nuclear motion in core shell excited molecules. We infer that in large molecules, dissociation pathways are observed to deviate from the two-body dissociation coordinate due to the internal motion of light linkages, which alters dissociation rates and may yield heavy products on very short time scales. The mechanism is exemplified with the case of 1-bromo-2-chloroethane, where the rotation of the C2H4-moiety leads to the dissociation of C-Cl or C-Br bonds in Cl2p or Br3d core-excited states, whose lifetimes last only similar to 7 fs.

  • 32.
    Vacher, Morgane
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Farahani, Pooria
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508000 Sao Paulo, Brazil..
    Valentini, Alessio
    Univ Liege, Dept Chim, Allee 6 Aout 11, B-4000 Liege, Belgium..
    Frutos, Luis Manuel
    Univ Alcala De Henares, Dept Quim Fis, E-28871 Madrid, Spain..
    Karlsson, Hans O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Fernández Galván, Ignacio
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    How Do Methyl Groups Enhance the Triplet Chemiexcitation Yield of Dioxetane?2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 16, p. 3790-3794Article in journal (Refereed)
    Abstract [en]

    Chemiluminescence is the emission of light as a result of a nonadiabatic chemical reaction. The present work is concerned with understanding the yield of chemiluminescence, in particular how it dramatically increases upon methylation of 1,2-dioxetane. Both ground-state and nonadiabatic dynamics (including singlet excited states) of the decomposition reaction of various methyl-substituted dioxetanes have been simulated. Methyl-substitution leads to a significant increase in the dissociation time scale. The rotation around the O-C-C-O dihedral angle is slowed; thus, the molecular system stays longer in the "entropic trap" region. A simple kinetic model is proposed to explain how this leads to a higher chemiluminescence yield. These results have important implications for the design of efficient chemiluminescent systems in medical, environmental, and industrial applications.

  • 33. Viswanatha, Ranjani
    et al.
    Naveh, Doron
    Chelikowsky, James R.
    Kronik, Leeor
    Sarma, Dipankar Das
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Magnetic Properties of Fe/Cu Codoped ZnO Nanocrystals2012In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 3, no 15, p. 2009-2014Article in journal (Refereed)
    Abstract [en]

    Free-standing ZnO nanocrystals simultaneously doped with Fe and Cu with varying Fe/Cu compositions have been synthesized using colloidal methods with a mean size of similar to 7.7 nm. Interestingly, while the Cu-doped ZnO nanocrystal remains diamagnetic and Fe-doped samples show antiferromagnetic interactions between Fe sites without any magnetic ordering down to the lowest temperature investigated, samples doped simultaneously with Fe and Cu show a qualitative departure in exhibiting ferromagnetic interactions, with suggestions of ferromagnetic order at low temperature. XAS measurements establish the presence of Fe2+ and Fe3+ ions, with the concentration of the trivalent species increasing in the presence of Cu doping, providing direct evidence of the Fe2+ + Cu2+ sic Fe3+ + Cu+ redox couple being correlated with the ferromagnetic property. Using DFT, the unexpected ferromagnetic nature of these systems is explained in terms of a double exchange between Fe atoms, mediated by the Cu atom, in agreement with experimental observations.

  • 34.
    Vovusha, Hakkim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Structure and Molecular Biology. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Sanyal, Suparna
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Structure and Molecular Biology.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Interaction of Nucleobases and Aromatic Amino Acids with Graphene Oxide and Graphene Flakes2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 21, p. 3710-3718Article in journal (Refereed)
    Abstract [en]

    In this work, we have studied interactions of nucleobases and aromatic amino acids with graphene (G) and graphene oxide (GO) flakes by ab initio density functional theory (DFT). It is evident from the results that GO complexes are stabilized by hydrogen bonding interactions whereas G complexes are stabilized by pi-pi interactions, leading to enhanced binding energies for GO complexes compared to G complexes. Moreover, time-dependent DFT (TD-DFT) calculations for the optical properties reveal that the GO nanoflakes and GO-nucleobase composite absorb visible light in the range of 400-700 nm, which may be useful for light-emitting devices. The insights obtained from our study will be useful to understand the role of GO flakes as carriers in targeted drug delivery and biosensors.

  • 35.
    Yang, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhang, Jinbao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Shen, Yang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Park, Byung-Wook
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Bi, Dongqin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Häggman, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    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.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vlachopoulos, Nick
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Snedden, Alan
    Kloo, Lars
    Jarboui, Adel
    Chams, Amani
    Perruchot, Christian
    Jouini, Mohamed
    New Approach for Preparation of Efficient Solid-State Dye-Sensitized Solar Cells by Photoelectrochemical Polymerization in Aqueous Micellar Solution2013In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 4, no 23, p. 4026-4031Article in journal (Refereed)
    Abstract [en]

    Hereby, we present a new, cost-effective, and environmentally friendly method of preparing an efficient solid-state dye-sensitized solar cell (sDSC) using a PEDOT conducting polymer as the hole conductor and a recently developed organic sensitizer. PEDOT is generated and deposited on the dye-sensitized TiO2 electrode by in situ photoelectropolymerization of bis-EDOT in aqueous micellar solution. The advantages of this approach are the use of water as the solvent and the obtainment of a sDSC simply by adding a silver layer on the as-obtained polymer film deposited on dye/TiO2 without the need for electrolytic solution. The sDSC containing the film prepared as above is compared to those where the organic dye is used to generate the same polymer film but in organic solvent. The energy conversion efficiency values of the two cells appear comparable, 4.8% for sDSC prepared in the aqueous-phase polymerized PEDOT and 6% for the sDSC prepared with in organic-phase polymerized PEDOT.

  • 36.
    Zhang, Haiyang
    et al.
    Univ Sci & Technol Beijing, Sch Chem & Biol Engn, Dept Biol Sci & Engn, Beijing 100083, Peoples R China..
    Jiang, Yang
    Beijing Univ Chem Technol, Coll Life Sci & Technol, Beijing Key Lab Bioproc, Box 53, Beijing 100029, Peoples R China..
    Yan, Hai
    Univ Sci & Technol Beijing, Sch Chem & Biol Engn, Dept Biol Sci & Engn, Beijing 100083, Peoples R China..
    Yin, Chunhua
    Univ Sci & Technol Beijing, Sch Chem & Biol Engn, Dept Biol Sci & Engn, Beijing 100083, Peoples R China..
    Tan, Tianwei
    Beijing Univ Chem Technol, Coll Life Sci & Technol, Beijing Key Lab Bioproc, Box 53, Beijing 100029, Peoples R China..
    van der Spoel, David
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Computational Biology and Bioinformatics. Uppsala University, Science for Life Laboratory, SciLifeLab.
    Free-Energy Calculations of Ionic Hydration Consistent with the Experimental Hydration Free Energy of the Proton2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 12, p. 2705-2712Article in journal (Refereed)
    Abstract [en]

    Computational free-energy correction strategies and the choice of experimental proton hydration free energy, Delta G(s)*(H+), are analyzed to investigate the apparent controversy in experimental thermodynamics of ionic hydration. Without corrections, the hydration free-energy (Delta G(hyd)) calculations match experiments with Delta G(s)*(H+) = -1064 kJ/mol as reference. Using the Galvani surface potential the resulting (real) Delta G(s)* are consistent with Delta G(s)*(H+) = -1098 kJ/mol. When applying, in an ad hoc manner, the discrete solvent correction, G(hyd) matching the "consensus" Delta G(s)*(H+) of -1112 kJ/mol are obtained. This analysis rationalizes reports on Delta G(hyd) calculations for ions using different experimental references. For neutral amino acid side chains Delta G(hyd) are independent of the water model, whereas there are large differences in Delta G(hyd) due to the water model for charged species, suggesting that long-range ordering of water around ions yields an important contribution to the Delta G(hyd). These differences are reduced significantly when applying consistent corrections, but to obtain the most accurate results it is recommended to use the water model belonging to the force field.

  • 37. Zukowski, Samual R.
    et al.
    Mitev, Pavlin D.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ben-Amotz, Dor
    CO2 Hydration Shell Structure and Transformation2017In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 8, no 13, p. 2971-2975Article in journal (Refereed)
    Abstract [en]

    The hydration-shell of CO2 is characterized using Raman multivariate curve resolution (Raman-MCR) spectroscopy combined with ab initio molecular dynamics (AIMD) vibrational density of states simulations, to validate our assignment of the experimentally observed high-frequency OH band to a weak hydrogen bond between water and CO2. Our results reveal that while the hydration-shell of CO2 is highly tetrahedral, it is also occasionally disrupted by the presence of entropically stabilized defects associated with the CO2-water hydrogen bond. Moreover, we find that the hydration-shell of CO2 undergoes a temperature-dependent structural transformation to a highly disordered (less tetrahedral) structure, reminiscent of the transformation that takes place at higher temperatures around much larger oily molecules. The biological significance of the CO2 hydration shell structural transformation is suggested by the fact that it takes place near physiological temperatures.

1 - 37 of 37
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