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  • 1. Achari, Muthuraaman Bhagavathi
    et al.
    Elumalai, Viswanathan
    Vlachopoulos, Nikolaos
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Safdari, Majid
    Gao, Jiajia
    Gardner, James M.
    Kloo, Lars
    A quasi-liquid polymer-based cobalt redox mediator electrolyte for dye-sensitized solar cells2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 40, p. 17419-17425Article in journal (Refereed)
    Abstract [en]

    Recently, cobalt redox electrolyte mediators have emerged as a promising alternative to the commonly used iodide/triiodide redox shuttle in dye-sensitized solar cells (DSCs). Here, we report the successful use of a new quasi-liquid, polymer-based electrolyte containing the Co3+/Co2+ redox mediator in 3-methoxy propionitrile solvent in order to overcome the limitations of high cell resistance, low diffusion coefficient and rapid recombination losses. The performance of the solar cells containing the polymer based electrolytes increased by a factor of 1.2 with respect to an analogous electrolyte without the polymer. The performances of the fabricated DSCs have been investigated in detail by photovoltaic, transient electron measurements, EIS, Raman and UV-vis spectroscopy. This approach offers an effective way to make high-performance and long-lasting DSCs.

  • 2.
    Alippi, Paola
    et al.
    CNR ISM, Ist Struttura Mat Consiglio Nazl Ric, Via Salaria,Km 29-300, I-00015 Rome, Italy..
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. CNR IOM, Lab Nazl TASC, C Area Sci Pk SS14 Km 163-5, I-34129 Trieste, Italy.;Univ Trieste, Dept Phys, Via Valerio 2, I-34127 Trieste, Italy..
    Paoletti, Anna Maria
    CNR ISM, Ist Struttura Mat Consiglio Nazl Ric, Via Salaria,Km 29-300, I-00015 Rome, Italy..
    Mattioli, Giuseppe
    CNR ISM, Ist Struttura Mat Consiglio Nazl Ric, Via Salaria,Km 29-300, I-00015 Rome, Italy..
    Zanotti, Gloria
    CNR ISM, Ist Struttura Mat Consiglio Nazl Ric, Via Salaria,Km 29-300, I-00015 Rome, Italy..
    Pennesi, Giovanna
    CNR ISM, Ist Struttura Mat Consiglio Nazl Ric, Via Salaria,Km 29-300, I-00015 Rome, Italy..
    Filippone, Francesco
    CNR ISM, Ist Struttura Mat Consiglio Nazl Ric, Via Salaria,Km 29-300, I-00015 Rome, Italy..
    Cossaro, Albano
    CNR IOM, Lab Nazl TASC, C Area Sci Pk SS14 Km 163-5, I-34129 Trieste, Italy..
    Verdini, Alberto
    CNR IOM, Lab Nazl TASC, C Area Sci Pk SS14 Km 163-5, I-34129 Trieste, Italy..
    Morgante, Alberto
    CNR IOM, Lab Nazl TASC, C Area Sci Pk SS14 Km 163-5, I-34129 Trieste, Italy.;Univ Trieste, Dept Phys, Via Valerio 2, I-34127 Trieste, Italy..
    Bonapasta, Aldo Amore
    CNR ISM, Ist Struttura Mat Consiglio Nazl Ric, Via Salaria,Km 29-300, I-00015 Rome, Italy..
    A Ru-Ru pair housed in ruthenium phthalocyanine: the role of a "cage" architecture in the molecule coupling with the Ag(111) surface2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 2, p. 1449-1457Article in journal (Refereed)
    Abstract [en]

    A number of studies have investigated the properties of monomeric and double-decker phthalocyanines (Pcs) adsorbed on metal surfaces, in view of applications in spintronics devices. In a combined experimental and theoretical study, we consider here a different member of the Pcs family, the (RuPc)(2) dimer, whose structure is characterized by two paired up magnetic centers embedded in a double-decker architecture. For (RuPc)(2) on Ag(111), we show that this architecture works as a preserving cage by shielding the Ru-Ru pair from a direct interaction with the surface atoms. In fact, while noticeable surface-to-molecule charge transfer occurs with the ensuing quenching of the molecular magnetic moment, such phenomena occur here in the absence of a direct Ru-Ag coupling or structural rearrangement, at variance with other Pcs and thanks to the above shielding effect. These unique properties of the (RuPc)(2) architecture are expected to permit an easy control of the surface-to-molecule charge-transfer process as well as of the molecular magnetic properties, thus making the (RuPc)(2) dimer a significant paradigm for innovative "cage" structures as well as a promising candidate for applications in spintronics nano or single-molecule devices.

  • 3.
    Amidani, Lucia
    et al.
    European Synchrotron, Rossendorf Beamline ESRF, CS40220, F-38043 Grenoble 9, France;Inst Resource Ecol, HZDR, POB 510119, D-01314 Dresden, Germany.
    Plakhova, Tatiana V.
    Lomonosov Moscow State Univ, Dept Chem, Leninskie Gory 1-3, Moscow 119991, Russia.
    Romanchuk, Anna Yu.
    Lomonosov Moscow State Univ, Dept Chem, Leninskie Gory 1-3, Moscow 119991, Russia.
    Gerber, Evgeny
    European Synchrotron, Rossendorf Beamline ESRF, CS40220, F-38043 Grenoble 9, France;Inst Resource Ecol, HZDR, POB 510119, D-01314 Dresden, Germany;Lomonosov Moscow State Univ, Dept Chem, Leninskie Gory 1-3, Moscow 119991, Russia.
    Weiss, Stephan
    Inst Resource Ecol, HZDR, POB 510119, D-01314 Dresden, Germany.
    Efimenko, Anna
    European Synchrotron, ESRF, CS40220, F-38043 Grenoble 9, France.
    Sahle, Christoph J.
    European Synchrotron, ESRF, CS40220, F-38043 Grenoble 9, France.
    Butorin, Sergei M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kalmykov, Stepan N.
    Lomonosov Moscow State Univ, Dept Chem, Leninskie Gory 1-3, Moscow 119991, Russia.
    Kvashnina, Kristina O.
    European Synchrotron, Rossendorf Beamline ESRF, CS40220, F-38043 Grenoble 9, France;Inst Resource Ecol, HZDR, POB 510119, D-01314 Dresden, Germany.
    Understanding the size effects on the electronic structure of ThO2 nanoparticles2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 20, p. 10635-10643Article in journal (Refereed)
    Abstract [en]

    Developing characterization techniques and analysis methods adapted to the investigation of nanoparticles (NPs) is of fundamental importance considering the role of these materials in many fields of research. The study of actinide based NPs, despite their environmental relevance, is still underdeveloped compared to that of NPs based on stable and lighter elements. We present here an investigation of ThO2 NPs performed with High-Energy Resolution Fluorescence Detected (HERFD) X-ray Absorption Near-Edge Structure (XANES) and with ab initio XANES simulations. The first post-edge feature of Th L-3 edge HERFD XANES disappears in small NPs and simulations considering non-relaxed structural models reproduce the trends observed in experimental data. Inspection of the simulations of Th atoms in the core and on the surface of the NP indeed demonstrates that the first post-edge feature is very sensitive to the lowering of the number of coordinating atoms and therefore to the more exposed Th atoms at the surface of the NP. The sensitivity of the L-3 edge HERFD XANES to low coordinated atoms at the surface stems from the hybridization of the d-Density of States (DOS) of Th with both O and Th neighboring atoms. This may be a common feature to other oxide systems that can be exploited to investigate surface interactions.

  • 4.
    Amira, Sami
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Spångberg, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Distorted fivefold coordination of Cu2+(aq) from a Car-Parrinello Molecular Dynamics Simulation2005In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 7, no 15, p. 2874-2880Article in journal (Refereed)
    Abstract [en]

    The solvation shell structure and dynamics of a single Cu2+ ion in a periodic box with 32 water molecules under ambient conditions has been investigated using Car–Parrinello molecular dynamics simulations in a time-window of 18 ps. Five-fold coordination with four equidistant equatorial water molecules at 2.00 and one axial water molecule at 2.45 from the Cu2+ ion is found. A hole without water molecules is found on the opposite side of the axial water. The ion–water bonding character for the equatorial water molecules is different from that of the axial water molecules, as shown by a localized orbital analysis of the electronic structure. Moreover, the calculated OD stretching vibrational band for the equatorial water molecules lies ca. 175 cm–1 below the axial-water band, in good agreement with experimental data. The equatorial-water band lies below, and the axial-water band above, the pure liquid D2O band, also in agreement with experimental data.

  • 5.
    Andersson, Rassmus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hernández, Guiomar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Mindemark, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Quantifying the ion coordination strength in polymer electrolytes2022In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 26, p. 16343-16352Article in journal (Refereed)
    Abstract [en]

    In the progress of implementing solid polymer electrolytes (SPEs) into batteries, fundamental understanding of the processes occurring within and in the vicinity of the SPE are required. An important but so far relatively unexplored parameter influencing the ion transport properties is the ion coordination strength. Our understanding of the coordination chemistry and its role for the ion transport is partly hampered by the scarcity of suitable methods to measure this phenomenon. Herein, two qualitative methods and one quantitative method to assess the ion coordination strength are presented, contrasted and discussed for TFSI-based salts of Li+, Na+ and Mg2+ in polyethylene oxide (PEO), poly(epsilon-caprolactone) (PCL) and poly(trimethylene carbonate) (PTMC). For the qualitative methods, the coordination strength is probed by studying the equilibrium between cation coordination to polymer ligands or solvent molecules, whereas the quantitative method studies the ion dissociation equilibrium of salts in solvent-free polymers. All methods are in agreement that regardless of cation, the strongest coordination strength is observed for PEO, while PTMC exhibits the weakest coordination strength. Considering the cations, the weakest coordination is observed for Mg2+ in all polymers, indicative of the strong ion-ion interactions in Mg(TFSI)(2), whilst the coordination strength for Li+ and Na+ seems to be more influenced by the interplay between the cation charge/radius and the polymer structure. The trends observed are in excellent agreement with previously observed transference numbers, confirming the importance and its connection to the ion transport in SPEs.

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  • 6.
    Andrikopoulos, Prokopis C.
    et al.
    Czech Acad Sci, BIOCEV, Inst Biotechnol, Prumyslova 595, CZ-25250 Vestec, Czech Republic..
    Liu, Yingliang
    Czech Acad Sci, BIOCEV, Inst Biotechnol, Prumyslova 595, CZ-25250 Vestec, Czech Republic..
    Picchiotti, Alessandra
    Czech Acad Sci, ELI Beamlines, Inst Phys, Za Radnici 835, CZ-25241 Dolni Brezany, Czech Republic..
    Lenngren, Nils
    Czech Acad Sci, ELI Beamlines, Inst Phys, Za Radnici 835, CZ-25241 Dolni Brezany, Czech Republic..
    Kloz, Miroslav
    Czech Acad Sci, ELI Beamlines, Inst Phys, Za Radnici 835, CZ-25241 Dolni Brezany, Czech Republic..
    Chaudhari, Aditya S.
    Czech Acad Sci, BIOCEV, Inst Biotechnol, Prumyslova 595, CZ-25250 Vestec, Czech Republic..
    Precek, Martin
    Czech Acad Sci, ELI Beamlines, Inst Phys, Za Radnici 835, CZ-25241 Dolni Brezany, Czech Republic..
    Rebarz, Mateusz
    Czech Acad Sci, ELI Beamlines, Inst Phys, Za Radnici 835, CZ-25241 Dolni Brezany, Czech Republic..
    Andreasson, Jakob
    Czech Acad Sci, ELI Beamlines, Inst Phys, Za Radnici 835, CZ-25241 Dolni Brezany, Czech Republic.;Chalmers Univ Technol, Dept Phys, Condensed Matter Phys, S-41296 Gothenburg, Sweden..
    Hajdu, J
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Molecular biophysics. Czech Acad Sci, ELI Beamlines, Inst Phys, Za Radnici 835, CZ-25241 Dolni Brezany, Czech Republic.
    Schneider, Bohdan
    Czech Acad Sci, BIOCEV, Inst Biotechnol, Prumyslova 595, CZ-25250 Vestec, Czech Republic..
    Fuertes, Gustavo
    Czech Acad Sci, BIOCEV, Inst Biotechnol, Prumyslova 595, CZ-25250 Vestec, Czech Republic..
    Femtosecond-to-nanosecond dynamics of flavin mononucleotide monitored by stimulated Raman spectroscopy and simulations2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 12, p. 6538-6552Article in journal (Refereed)
    Abstract [en]

    Flavin mononucleotide (FMN) belongs to the large family of flavins, ubiquitous yellow-coloured biological chromophores that contain an isoalloxazine ring system. As a cofactor in flavoproteins, it is found in various enzymes and photosensory receptors, like those featuring the light-oxygen-voltage (LOV) domain. The photocycle of FMN is triggered by blue light and proceeds via a cascade of intermediate states. In this work, we have studied isolated FMN in an aqueous solution in order to elucidate the intrinsic electronic and vibrational changes of the chromophore upon excitation. The ultrafast transitions of excited FMN were monitored through the joint use of femtosecond stimulated Raman spectroscopy (FSRS) and transient absorption spectroscopy encompassing a time window between 0 ps and 6 ns with 50 fs time resolution. Global analysis of the obtained transient visible absorption and transient Raman spectra in combination with extensive quantum chemistry calculations identified unambiguously the singlet and triplet FMN populations and addressed solvent dynamics effects. The good agreement between the experimental and theoretical spectra facilitated the assignment of electronic transitions and vibrations. Our results represent the first steps towards more complex experiments aimed at tracking structural changes of FMN embedded in light-inducible proteins upon photoexcitation.

  • 7. Aponte-Santamaria, Camilo
    et al.
    Hub, Jochen S.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    de Groot, Bert L.
    Dynamics and energetics of solute permeation through the Plasmodium falciparum aquaglyceroporin2010In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, no 35, p. 10246-10254Article in journal (Refereed)
    Abstract [en]

    The aquaglyceroporin from Plasmodium falciparum (PfAQP) is a potential drug target for the treatment of malaria. It efficiently conducts water and other small solutes, and is proposed to intervene in several crucial physiological processes during the parasitic life cycle. Despite the wealth of experimental data available, a dynamical and energetic description at the single-molecule level of the solute permeation through PfAQP has been lacking so far. Here we address this question by using equilibrium and umbrella sampling molecular dynamics simulations. We computed the water osmotic permeability coefficient, the pore geometry and the potential of mean force for the permeation of water, glycerol and urea. Our simulations show that the PfAQP, the human aquaporin 1 (hAQP1) and the Escherichia coli glycerol facilitator (GlpF) have nearly identical water permeabilities. The Arg196 residue at the ar/R region was found to play a crucial role regulating the permeation of water, glycerol and urea. The computed free energy barriers at the ar/R selectivity filter corroborate that PfAQP conducts glycerol at higher rates than urea, and suggest that PfAQP is a more efficient glycerol and urea channel than GlpF. Our results are consistent with a solute permeation mechanism for PfAQP which is similar to the one established for other members of the aquaglyceroporin family. In this mechanism, hydrophobic regions near the NPA motifs are the main water rate limiting barriers, and the replacement of water-arg196 interactions and solute-matching in the hydrophobic pocket at the ar/R region are the main determinants underlying selectivity for the permeation of solutes like glycerol and urea.

  • 8.
    Arafa, Wael A. A.
    et al.
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Karkas, Markus D.
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Lee, Bao-Lin
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Akermark, Torbjorn
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Liao, Rong-Zhen
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Berends, Hans-Martin
    Umea Univ, KBC, Dept Chem, SE-90187 Umea, Sweden..
    Messinger, Johannes
    Umea Univ, KBC, Dept Chem, SE-90187 Umea, Sweden..
    Siegbahn, Per E. M.
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Akermark, Bjorn
    Stockholm Univ, Dept Organ Chem, Arrhenius Lab, SE-10691 Stockholm, Sweden..
    Dinuclear manganese complexes for water oxidation: evaluation of electronic effects and catalytic activity2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 24, p. 11950-11964Article in journal (Refereed)
    Abstract [en]

    During recent years significant progress has been made towards the realization of a sustainable and carbon-neutral energy economy. One promising approach is photochemical splitting of H2O into O-2 and solar fuels, such as H-2. However, the bottleneck in such artificial photosynthetic schemes is the H2O oxidation half reaction where more efficient catalysts are required that lower the kinetic barrier for this process. In particular catalysts based on earth-abundant metals are highly attractive compared to catalysts comprised of noble metals. We have now synthesized a library of dinuclear Mn-2 (II,III) catalysts for H2O oxidation and studied how the incorporation of different substituents affected the electronics and catalytic efficiency. It was found that the incorporation of a distal carboxyl group into the ligand scaffold resulted in a catalyst with increased catalytic activity, most likely because of the fact that the distal group is able to promote proton-coupled electron transfer (PCET) from the high-valent Mn species, thus facilitating O-O bond formation.

  • 9.
    Araujo, Rafael B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Appl Mat Phys, Dept Mat & Engn, S-10044 Stockholm, Sweden..
    Evaluating bulk Nb2O2F3 for Li-battery electrode applications2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 5, p. 3530-3535Article in journal (Refereed)
    Abstract [en]

    This investigation has the primary objective of elucidating the lithium intercalation process in the crystal structure of a new niobium oxyfluoride compound Nb2O2F3. The framework of the density functional theory was applied in a generalized gradient approximation together with the hybrid functional method. It is revealed that lithium atoms intercalate in this material in a maximum concentration of one Li atom per formula unit forming LiNb2O2F3. Moreover, octahedral positions in between the layers of Nb-O-F appear as the Li preferred occupancy resulting in a structural volume expansion of only 5%. Electronic structure evolution with the insertion of lithium displays a transformation from semi-conductor to metal when half of the lithium atoms are added. This transformation occurs due to a symmetry break induced by the transition from the + 8 to + 7 oxidation state of half of the Nb2 dimers. Then, after full lithiation the symmetry is recovered and the material becomes a semiconductor again with a band gap amounting to 1 eV. The evaluated average deintercalation potential reaches 1.29 V vs. Li/Li+ with activation energy for lithium ion migration of 0.79 eV. The computed low potential of the redox reaction Nb-2(8+) to Nb-2(7+) includes niobium oxyfluoride in the map of possible materials for the anode application of Li-ion batteries.

  • 10.
    Araujo, Rafael B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Banerjee, Amitava
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Panigrahi, Puspamitra
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Hindustan Univ, Ctr Clean Energy & Nanoconvergence, Madras, Tamil Nadu, India.
    Yang, Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Araujo, C. Moyses
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Dept Mat, Appl Mat Phys, S-10044 Stockholm, Sweden.; Royal Inst Technol KTH, Dept Engn, S-10044 Stockholm, Sweden.
    Assessing Electrochemical Properties of Polypyridine and Polythiophene for Prospective Application in Sustainable Organic Batteries2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 4, p. 3307-3314Article in journal (Refereed)
    Abstract [en]

    Conducting polymers are being considered promising candidates for sustainable organic batteries mainly due to their fast electron transport properties and high recyclability. In this work, key properties of polythiophene and polypyridine have been assessed through a combined theoretical and experimental study focusing on such applications. A theoretical protocol has been developed to calculate redox potentials in solution within the framework of the density functional theory and using continuous solvation models. Here, the evolution of the electrochemical properties of solvated oligomers as a function of the length of the chain is analyzed and then the polymer properties are estimated via linear regressions using ordinary least square. The predicted values were verified against our electrochemical experiments. This protocol can now be employed to screen a large database of compounds in order to identify organic electrodes with superior properties.

  • 11.
    Araujo, Rafael B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Unveiling the charge migration mechanism in Na2O2: implications for sodium-air batteries2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 12, p. 8203-8209Article in journal (Refereed)
    Abstract [en]

    Metal-air batteries have become promising candidates for modern energy storage due to their high theoretical energy density in comparison to other storage devices. The lower overpotential of Na compared with Li makes Na-air batteries more efficient in terms of battery lifetime. Additionally, the abundance of Na over Li is another advantage for Na batteries compared to Li batteries. Na2O2 is one of the main products of sodium-air battery reactions. The efficiency of air cells is always related to the charge transport mechanisms in the formed product. To unveil these diffusion mechanisms in one of the main products of the cell reaction Na-O-2 we systematically investigate the mobility of charge carriers as well as the electronic structural properties of sodium peroxide. The framework of the density functional theory based on hybrid functional approach is used to study the mobility of charge carriers and intrinsic defects in Na2O2. Our calculations reveal that the formation of small electron and hole polarons is preferentially occurring over the delocalized state in the crystal structure of Na2O2. The migration of these small polarons displays activation energies of about 0.92 eV and 0.32 eV for the electron and hole polarons respectively, while the analysis of the charged sodium vacancy mobility reveals an activation energy of about 0.5 eV. These results suggest that the charge transport in sodium peroxide would mainly occur through the diffusion of hole polarons.

  • 12.
    Araujo, Rafael B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Barpanda, Prabeer
    Indian Inst Sci, Faraday Mat Lab, Mat Res Ctr, CV Raman Ave, Bangalore 560012, Karnataka, India..
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol KTH, Appl Mat Phys, Dept Mat & Engn, S-10044 Stockholm, Sweden..
    Na2M2(SO4)(3) (M = Fe, Mn, Co and Ni): towards high-voltage sodium battery applications2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 14, p. 9658-9665Article in journal (Refereed)
    Abstract [en]

    Sodium-ion-based batteries have evolved as excellent alternatives to their lithium-ion-based counterparts due to the abundance, uniform geographical distribution and low price of Na resources. In the pursuit of sodium chemistry, recently the alluaudite framework Na2M2(SO4)(3) has been unveiled as a high-voltage sodium insertion system. In this context, the framework of density functional theory has been applied to systematically investigate the crystal structure evolution, density of states and charge transfer with sodium ions insertion, and the corresponding average redox potential, for Na2M2(SO4)(3) (M = Fe, Mn, Co and Ni). It is shown that full removal of sodium atoms from the Fe-based device is not a favorable process due to the 8% volume shrinkage. The imaginary frequencies obtained in the phonon dispersion also reflect this instability and the possible phase transition. This high volume change has not been observed in the cases of the Co- and Ni-based compounds. This is because the redox reaction assumes a different mechanism for each of the compounds investigated. For the polyanion with Fe, the removal of sodium ions induces a charge reorganization at the Fe centers. For the Mn case, the redox process induces a charge reorganization of the Mn centers with a small participation of the oxygen atoms. The Co and Ni compounds present a distinct trend with the redox reaction occurring with a strong participation of the oxygen sublattice, resulting in a very small volume change upon desodiation. Moreover, the average deintercalation potential for each of the compounds has been computed. The implications of our findings have been discussed both from the scientific perspective and in terms of technological aspects.

  • 13.
    Araujo, Rafael Barros Neves
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Unveiling the charge migration mechanism in Na2O2 : implications for sodium air batteries2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084Article in journal (Other academic)
  • 14.
    Arruda, Lucas M.
    et al.
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany.;Minist Educ Brazil, Capes Fdn, BR-70040020 Brasilia, DF, Brazil..
    Ali, Md Ehesan
    Inst Nano Sci & Technol, Phase 10,Sect 64, Mohali 160062, Punjab, India..
    Bernien, Matthias
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Hatter, Nino
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Nickel, Fabian
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Kipgen, Lalminthang
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Hermanns, Christian F.
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Bisswanger, Timo
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Loche, Philip
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Heinrich, Benjamin W.
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Franke, Katharina J.
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Oppeneer, Peter M.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Kuch, Wolfgang
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Surface-orientation- and ligand-dependent quenching of the spin magnetic moment of Co porphyrins adsorbed on Cu substrates2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 22, p. 12688-12696Article in journal (Refereed)
    Abstract [en]

    Porphyrin molecules are particularly interesting candidates for spintronic applications due to their bonding flexibility, which allows to modify their properties substantially by the addition or transformation of ligands. Here, we investigate the electronic and magnetic properties of cobalt octaethylporphyrin (CoOEP), deposited on copper substrates with two distinct crystallographic surface orientations, Cu(100) and Cu(111), with X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD). A significant magnetic moment is present in the Co ions of the molecules deposited on Cu(100), but it is completely quenched on Cu(111). Heating the molecules on both substrates to 500 K induces a ring-closure reaction with cobalt tetrabenzoporphyrin (CoTBP) as reaction product. In these molecules, the magnetic moment is quenched on both surfaces. Our XMCD and XAS measurements suggest that the filling of the dz(2)orbital leads to a non-integer valence state and causes the quench of the spin moments on all samples except CoOEP/Cu(100), where the molecular conformation induces variations to the ligand field that lift the quench. We further employ density functional theory calculations, supplemented with on-site Coulomb correlations (DFT+U), to study the adsorption of these spin-bearing molecules on the Cu substrates. Our calculations show that charge transfer from the Cu substrates as well as charge redistribution within the Co 3d orbitals lead to the filling of the Co minority spin dz(2)orbital, causing a 'turning off' of the exchange splitting and quenching of the spin moment at the Co magnetic centers. Our investigations suggest that, by this mechanism, molecule-substrate interactions can be used to control the quenching of the magnetic moments of the adsorbed molecules.

  • 15. Arteca, G A
    et al.
    Edvinsson, T
    Elvingson, C
    Compaction of grafted wormlike chains under variable confinement2001In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 3, no 17, p. 3737-3741Article in journal (Refereed)
  • 16.
    Arul Murugan, N.
    et al.
    KTH Royal Inst Technol, Sch Engn Sci Chem Biotechnol & Hlth, Dept Theoret Chem & Biol, S-10691 Stockholm, Sweden.
    Zalesny, Robert
    Wroclaw Univ Sci & Technol, Fac Chem, Dept Phys & Quantum Chem, Wyb Wyspianskiego 27, PL-50370 Wroclaw, Poland.
    Ågren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. KTH Royal Inst Technol, Sch Engn Sci Chem Biotechnol & Hlth, Dept Theoret Chem & Biol, S-10691 Stockholm, Sweden.
    Unusual binding-site-specific photophysical properties of a benzothiazole-based optical probe in amyloid beta fibrils2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 31, p. 20334-20339Article in journal (Refereed)
    Abstract [en]

    Optical imaging of amyloid fibrils serves as a cost-effective route for the diagnosis of Alzheimer-like conformational diseases. However{,} the challenge here is to optimize the binding affinity and photophysical properties of the optical imaging agents in a way specific to certain types of amyloids. In a few occasions it is shown that novel optical imaging agents can be designed to bind to a particular type of amyloid fibril with larger binding affinity and specificity. There is also a recent report on photoluminescent polythiophenes which display photophysical properties that can be used to distinguish the variants or subtypes of amyloids (J. Rasmussen et al.{,} Proc. Natl. Acad. Sci. U. S. A.{,} 2017{,} 114(49){,} 13018–13023). Based on a multiscale modeling approach{,} here{,} we report on the complementary aspect that the photophysical properties of a benzothiazole based optical probe (referred to as BTA-3) can be specific to the binding sites in the same amyloid fibrils and we attribute this to its varying electronic structure in different sites. As reported experimentally from competitive binding assay studies for many amyloid staining molecules and tracers{,} we also show multiple binding sites in amyloid fibrils for this probe. In particular{,} BTA-3 displayed a red-shift in its low-frequency absorption band only in site-4{,} a surface site of amyloid fibrils when compared to the spectra in water solvent. In the remaining sites{,} it exhibited a less significant blue shift for the same absorption band.

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  • 17.
    Atsumi, Michiko
    et al.
    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.
    Gonzalez, Leticia
    Gourlaouen, Christophe
    Daniel, Chantal
    Ab initio and DFT analysis of the low-lying electronic states of metal dihalides: quantum chemical calculations on the neutral BrMCl (M = Cu, Ag, Au)2013In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 25, p. 10151-10157Article in journal (Refereed)
    Abstract [en]

    The electronic configuration of the electronic ground and low-lying doublet excited states of neutral metal dihalides BrMCl (M = Cu, Ag, Au) has been investigated on the basis of CASSCF/CASPT2 methods taking into account scalar relativistic effects. A preliminary study of the electronic problem in BrAgCl, based on DFT and CASSCF/CASPT2 approaches and using various basis sets, namely relativistic all-electron basis sets, effective core potentials and ab initio model potentials (AIMP), as well as non-relativistic AIMP is discussed. It is shown that single-determinant methods are not flexible enough to describe the bonding of the neutral species in the electronic ground state regardless of the basis set. The failure to allocate the single electron of BrAgCl correlates with a wrong charge distribution within the complex, which is more accentuated when using pseudopotential basis sets. The inclusion of static and dynamic correlation effects by means of CASSCF/CASPT2 methods using large relativistic all-electron basis sets provides a correct qualitative picture of the electronic structure of the BrMCl series (M = Cu, Ag, Au). The spin unrestricted KS-DFT approach leads to a reasonable description of the degenerate electronic ground state ((2)Sigma/(2)Pi) bonding in these complexes with negligible spin contamination providing comparative spin densities in the series of molecules under investigation.

  • 18.
    Augusto, Felipe A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, Av Prof Lineu Prestes 748, Sao Paulo, Brazil..
    Francés-Monerris, Antonio
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry. Univ Valencia, Inst Ciencia Mol, POB 22085, Valencia 46071, Spain..
    Fdez. Galván, Ignacio
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Roca-Sanjuán, Daniel
    Univ Valencia, Inst Ciencia Mol, POB 22085, Valencia 46071, Spain..
    Bastos, Erick L.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, Av Prof Lineu Prestes 748, Sao Paulo, Brazil..
    Baader, Wilhelm J.
    Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, Av Prof Lineu Prestes 748, Sao Paulo, Brazil..
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Theoretical Chemistry.
    Mechanism of activated chemiluminescence of cyclic peroxides: 1,2-dioxetanes and 1,2-dioxetanones2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 5, p. 3955-3962Article in journal (Refereed)
    Abstract [en]

    Almost all chemiluminescent and bioluminescent reactions involve cyclic peroxides. The structure of the peroxide and reaction conditions determine the quantum efficiency of light emission. Oxidizable fluorophores, the so-called activators, react with 1,2-dioxetanones promoting the former to their first singlet excited state. This transformation is inefficient and does not occur with 1,2-dioxetanes; however, they have been used as models for the efficient firefly bioluminescence. In this work, we use the SA-CASSCF/CASPT2 method to investigate the activated chemiexcitation of the parent 1,2-dioxetane and 1,2-dioxetanone. Our findings suggest that ground state decomposition of the peroxide competes efficiently with the chemiexcitation pathway, in agreement with the available experimental data. The formation of non-emissive triplet excited species is proposed to explain the low emission efficiency of the activated decomposition of 1,2-dioxetanone. Chemiexcitation is rationalized considering a peroxide/activator supermolecule undergoing an electron-transfer reaction followed by internal conversion.

  • 19. Ballout, Fouad
    et al.
    Krassen, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Kopf, Ilona
    Ataka, Kenichi
    Bruendermann, Erik
    Heberle, Joachim
    Havenith, Martina
    Scanning near-field IR microscopy of proteins in lipid bilayers2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 48, p. 21432-21436Article in journal (Refereed)
    Abstract [en]

    We use infrared near-field microscopy to chemically map the morphology of biological matrices. The investigated sample is built up from surface-tethered membrane proteins (cytochrome c oxidase) reconstituted in a lipid bilayer. We have carried out infrared near-field measurements in the frequency range between 1600 and 1800 cm(-1). By simultaneously recording the topography and chemical fingerprint of the protein-tethered lipid bilayer with a lateral resolution of 80 nm x 80 nm, we were able to probe locally the chemical signature of this membrane and to provide a local map of its surface morphology.

  • 20.
    Batalovic, K.
    et al.
    Univ Belgrade, Natl Inst Republ Serbia, VINCA Inst Nucl Sci, Belgrade, Serbia.;Ctr Excellence Hydrogen & Renewable Energy CONVIN, POB 522, Belgrade 11001, Serbia..
    Radakovic, J.
    Univ Belgrade, Natl Inst Republ Serbia, VINCA Inst Nucl Sci, Belgrade, Serbia.;Ctr Excellence Hydrogen & Renewable Energy CONVIN, POB 522, Belgrade 11001, Serbia..
    Bundaleski, N.
    Univ Belgrade, Natl Inst Republ Serbia, VINCA Inst Nucl Sci, Belgrade, Serbia.;Nova Univ Lisbon, Sch Sci & Technol, Ctr Phys & Technol Res, P-2829516 Caparica, Portugal..
    Rakocevic, Z.
    Univ Belgrade, Natl Inst Republ Serbia, VINCA Inst Nucl Sci, Belgrade, Serbia..
    Pasti, I
    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.
    Rangel, C. M.
    Natl Lab Energy & Geol, LNEG, Paco do Lumiar 22, P-1649038 Lisbon, Portugal..
    Origin of photocatalytic activity enhancement in Pd/Pt-deposited anatase N-TiO2 – experimental insights and DFT study of the (001) surface2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 33, p. 18536-18547Article in journal (Refereed)
    Abstract [en]

    In pursuit of the ideal photocatalyst, cheap and stable semiconductor TiO(2)is considered to be a good choice if one is able to reduce its band gap and decrease the recombination rate of charge carriers. The approach that offers such improvements for energy conversion applications is the modification of TiO(2)with nitrogen and noble metals. However, the origin of these improvements and possibilities for further design of single-atom catalysts are not always straightforward. To shed light on the atomic-scale picture, we modeled the nitrogen-doped (001) anatase TiO(2)surface as a support for palladium and platinum single-atom deposition. The thermodynamics of various synthesis routes for Pd/Pt deposition and nitrogen doping is considered based on density functional theory (DFT)-calculated energies, highlighting the effect of nitrogen doping on metal dimer formation and metal-support interaction. XPS analysis of the valence band of the modified TiO(2)nanocrystals, and the calculated charge transfer and electronic structure of single-atom catalysts supported on the (001) anatase TiO(2)surface provide an insight into modifications occurring in the valence zone of TiO(2)due to nitrogen doping and Pd/Pt deposition at the surface. DFT results also show that substitutional nitrogen doping significantly increases metal-support interaction, while interstitial nitrogen doping promotes only Pt-support interaction.

  • 21.
    Behrouznejad, F.
    et al.
    Sharif Univ Technol, Inst Nanosci & Nanotechnol, Tehran 14588, Iran..
    Taghavinia, N.
    Sharif Univ Technol, Inst Nanosci & Nanotechnol, Tehran 14588, Iran.;Sharif Univ Technol, Dept Phys, Tehran 14588, Iran..
    Pazoki, Meysam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Tajabadi, F.
    Mat & Energy Res Ctr, Nanotechnol & Adv Mat Dept, Karaj 31787316, Iran..
    Metal-based bracken-like single-sided dye-sensitized solar cells with horizontal separation2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 7, p. 5244-5252Article in journal (Refereed)
    Abstract [en]

    One of the drawbacks of typical dye-sensitized solar cells (DSCs) is their high cost and the high electrical resistance of the transparent conducting substrate. In conventional sandwich-type DSCs, only one of the FTO substrates can be replaced by a metal substrate. We investigated an all-metal-electrode single-sided DSC in which interpenetrated bracken-like Cr electrodes were created using photolithography; mesoporous TiO2 and Pt films were deposited on the laterally separated electrodes. Thermal Pt deposition and electrodeposition methods were investigated and it was found that a cyclic electrodeposition method resulted in selective Pt deposition at room temperature with a higher device performance. Cu or ZnO sacrificial layers and TiO2 or TiO2/SiO2 porous layers were used for the spacer layer that keeps the Pt electrode away from the TiO2 mesoporous layer and the optimum results were obtained when a TiO2/SiO2 layer was used. The best device had a current density of 8.47 mA cm(-2), an open circuit voltage of 0.685 V and an efficiency of 2.44%. The results of open circuit voltage decay and electrochemical impedance spectrometry showed the formation of a high-resistivity blocking layer, which was attributed to the Cr oxide formed during thermal treatment. The efficiency may be improved further by developing low-temperature fabrication processes.

  • 22.
    Benatto, L.
    et al.
    Univ Fed Parana, Dept Fis, CP 19044, BR-81531980 Curitiba, Parana, Brazil.
    Marchiori, Cleber
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Univ Fed Parana, Dept Fis, CP 19044, BR-81531980 Curitiba, Parana, Brazil.
    da Luz, M. G. E.
    Univ Fed Parana, Dept Fis, CP 19044, BR-81531980 Curitiba, Parana, Brazil.
    Koehler, M.
    Univ Fed Parana, Dept Fis, CP 19044, BR-81531980 Curitiba, Parana, Brazil.
    Electronic and structural properties of fluorene-thiophene copolymers as function of the composition ratio between the moieties: a theoretical study2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 31, p. 20447-20458Article in journal (Refereed)
    Abstract [en]

    Through theoretical analysis, we study relevant properties of some molecular structures formed by oligothiophenes (T) and dioctylfluorenes (F) units, commonly employed in the fabrication of different kinds of optical and electronic devices. For so, we first consider F-(T)(n)-F molecules with different numbers of thiophene rings (n). Among other characteristics, we calculate the dipole moment change between the ground and excited state ((ge)), a quantity that greatly influences the exciton dissociation and charge carrier mobility. We show that the planarity of the ground state geometry correlates (ge) to the exciton binding energy (E-b), with higher (ge)'s corresponding to lower E-b's when n > 3. We also unveil a relevant dependence of (ge) with the odd-even parity of n and that (ge) assumes higher values when the molecule is composed by bithiophene (instead of simple thiophenes) moieties in the syn-conformation (with the two heteroatoms pointing in the same direction). From molecules results, we then address larger systems, formed by different oligomers of F-T copolymers containing blocks of dioctylfluorenes and bithiophenes (T2). We systematic investigate their electronic and structural properties as function of the composition ratio between the T2 and F moieties. Similar to the molecules, we deduce that the magnitude of (ge) is higher for the syn conformer of the T2 unit. Moreover, the highest values of (ge) are achieved when the number of the T2 increases relative to a fixed number of the F units in the mer. Such behaviors are in agreement and actually can qualitative explain measurements in the literature on the quantum efficiency of charge carrier generation in F-T copolymers. The present findings can be helpful in designing novel materials with improved photoelectric responses.

  • 23. Blachucki, Wojciech
    et al.
    Szlachetko, Jakub
    Kayser, Yves
    Dousse, Jean-Claude
    Hoszowska, Joanna
    Fernandes, Daniel L. Abreu
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sa, Jacinto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Study of the reactivity of silica supported tantalum catalysts with oxygen followed by in situ HEROS2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 28, p. 18262-18264Article in journal (Refereed)
    Abstract [en]

    We report on the reactivity of grafted tantalum organometallic catalysts with molecular oxygen. The changes in the local Ta electronic structure were followed by in situ high-energy resolution off-resonant spectroscopy (HEROS). The results revealed agglomeration and formation of Ta dimers, which cannot be reversed. The process occurs independently of starting grafted complex.

  • 24.
    Blanco, Yina Salamanca
    et al.
    Swedish Univ Agr Sci, Dept Mol Sci, POB 7015, SE-75007 Uppsala, Sweden;Univ El Bosque, Environm Engn Program, Carrera 7b Bis 132-11, Bogota, Colombia;Univ El Bosque, Chem Dept, Carrera 7b Bis 132-11, Bogota, Colombia.
    Topel, Onder
    Swedish Univ Agr Sci, Dept Mol Sci, POB 7015, SE-75007 Uppsala, Sweden;Akdeniz Univ, Dept Chem, Fac Sci, TR-07058 Antalya, Turkey.
    Bajnoczi, Eva G.
    Swedish Univ Agr Sci, Dept Mol Sci, POB 7015, SE-75007 Uppsala, Sweden.
    Werner, Josephina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Swedish Univ Agr Sci, Dept Mol Sci, POB 7015, SE-75007 Uppsala, Sweden.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Persson, Ingmar
    Swedish Univ Agr Sci, Dept Mol Sci, POB 7015, SE-75007 Uppsala, Sweden.
    Chemical equilibria of aqueous ammonium-carboxylate systems in aqueous bulk, close to and at the water-air interface2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 23, p. 12434-12445Article in journal (Refereed)
    Abstract [en]

    Previous studies have shown that the water-air interface and a number of water molecule layers just below it, the surface region, have significantly different physico-chemical properties, such as lower relative permittivity and density, than bulk water. The properties in the surface region of water favor weakly hydrated species as neutral molecules, while ions requiring strong hydration and shielding of their charge are disfavored. In this study the equilibria NH4+(aq) + RCOO-(aq) reversible arrow NH3(aq) + RCOOH(aq) are investigated for R = CnH2n+1, n = 0-8, as open systems, where ammonia and small carboxylic acids in the gas phase above the water surface are removed from the system by a gentle controlled flow of nitrogen to mimic the transport of volatile compounds from water droplets into air. It is shown that this non-equilibrium transport of chemicals can be sufficiently large to cause a change of the chemical content of the aqueous bulk. Furthermore, X-ray photoelectron spectroscopy (XPS) has been used to determine the relative concentration of alkyl carboxylic acids and their conjugated alkyl carboxylates in aqueous surfaces using a micro-jet. These studies confirm that neutral alkyl carboxylic acids are accumulated in the surface region, while charged species, as alkyl carboxylates, are depleted. The XPS studies show also that the hydrophobic alkyl chains are oriented upwards into regions with lower relative permittivity and density, thus perpendicular to the aqueous surface. These combined results show that there are several chemical equilibria between the aqueous bulk and the surface region. The analytical studies show that the release of mainly ammonia is dependent on its concentration in the surface region, as long as the solubility of the carboxylic acid in the surface region is sufficiently high to avoid a precipitation in/on the water-air interface. However, for n-octyl- and n-nonylcarboxylic acid the solubility is sufficiently low to cause precipitation. The combined analytical and surface speciation studies in this work show that the equilibria involving the surface region are fast. The results from this study increase the knowledge about the distribution of chemical species in the surface region at and close to the water-air interface, and the transport of chemicals from water to air in open systems.

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  • 25.
    Bo, Tao
    et al.
    Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China;Dongguan Neutron Sci Ctr, Dongguan 523803, Peoples R China.
    Liu, Peng-Fei
    Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China;Dongguan Neutron Sci Ctr, Dongguan 523803, Peoples R China.
    Xu, Juping
    Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China;Dongguan Neutron Sci Ctr, Dongguan 523803, Peoples R China.
    Zhang, Junrong
    Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China;Dongguan Neutron Sci Ctr, Dongguan 523803, Peoples R China.
    Chen, Yuanbo
    Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China;Dongguan Neutron Sci Ctr, Dongguan 523803, Peoples R China.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Wang, Fangwei
    Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China;Dongguan Neutron Sci Ctr, Dongguan 523803, Peoples R China;Chinese Acad Sci, Inst Phys, Beijing Natl Lab Condensed Matter Phys, Beijing 100080, Peoples R China.
    Wang, Bao-Tian
    Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China;Dongguan Neutron Sci Ctr, Dongguan 523803, Peoples R China.
    Hexagonal Ti2B2 monolayer: a promising anode material offering high rate capability for Li-ion and Na-ion batteries2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 34, p. 22168-22178Article in journal (Refereed)
    Abstract [en]

    Combining the first-principles density functional method and crystal structure prediction techniques, we report a series of hexagonal two-dimensional transition metal borides including Sc2B2, Ti2B2, V2B2, Cr2B2, Y2B2, Zr2B2, and Mo2B2. Their dynamic and thermal stabilities are testified by phonon and molecular dynamics simulations. We investigate the potential of the two-dimensional Ti2B2 monolayer as an anode material for Li-ion and Na-ion batteries. The Ti2B2 monolayer possesses high theoretical specific capacities of 456 and 342 mA h g(-1) for Li and Na, respectively. The very high Li/Na diffusivity with an ultralow energy barrier of 0.017/0.008 eV indicates an excellent charge-discharge capability. In addition, good electronic conductivity during the whole lithiation process is found by electronic structure calculations. The very small change in volume after the adsorption of one, two, and three layers of Li and Na ions indicates that the Ti2B2 monolayer is robust. These results highlight the suitability of Ti2B2 monolayer as well as the other two-dimensional transition metal borides as excellent anode materials for both Li-ion and Na-ion batteries.

  • 26.
    Borg, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Durbeej, Bo
    Which Factors Determine the Acidity of the Phytochromobilin Chromophore of Plant Phytochrome?2008In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 10, no 18, p. 2528-2537Article in journal (Refereed)
    Abstract [en]

    Quantum chemical calculations aimed at identifying the factors controlling the acidity of phytochromobilin, the tetrapyrrole chromophore of the plant photoreceptor phytochrome, are reported. Phytochrome is converted from an inactive (Pr) to an active form (Pfr) through a series of events initiated by a Z --> E photoisomerization of phytochromobilin, forming the Lumi-R intermediate, and much controversy exists as to whether the protonation state of the chromophore (cationic in Pr with all nitrogens protonated) changes during the photoactivation. Here, relative ground (S0) and excited-state (S1) pKa s of all four pyrrole moieties of phytochromobilin in all 64 possible configurations with respect to the three methine bridges are calculated in a protein-like environment, using a recently benchmarked level of theory. Accordingly, the relationships between acidity and chromophore geometry and charge distribution, hydrogen bonding, and light absorption are investigated in some detail, and discussed in terms of possible mechanisms making a proton transfer reaction more probable along the Pr --> Pfr reaction than in the parent cationic Pr state. It is found that charge distribution in the cationic species, intra-molecular hydrogen bonding in the neutral, and hydrogen bonding with two highly conserved aspartate and histidine residues have a significant effect on the acidity, while overall chromophore geometry and electronic state are less important factors. Furthermore, based on the calculations, two processes that may facilitate a proton transfer by substantially lowering the pKa s relative to their Pr values are identified: (i) a thermal Z,anti --> Z,syn isomerization at C5, occurring after formation of Lumi-R; (ii) a perturbation of the hydrogen bonding network which in Pr comprises the nitrogens of pyrroles A, B and C and the two aspartate and histidine residues.

  • 27.
    Born, Artur
    et al.
    Uppsala Berlin Joint Lab Next Generat Photoelect, Albert Einstein Str 15, D-12489 Berlin, Germany.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.;Univ Potsdam, Inst Phys & Astronom, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany.
    Johansson, Fredrik O. L.
    KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, SE-10044 Stockholm, Sweden.;Sorbonne Univ, CNRS, Inst NanoSci Paris, INSP, F-75005 Paris, France.
    Leitner, Torsten
    Uppsala Berlin Joint Lab Next Generat Photoelect, Albert Einstein Str 15, D-12489 Berlin, Germany.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Bidermane, Ieva
    Uppsala Berlin Joint Lab Next Generat Photoelect, Albert Einstein Str 15, D-12489 Berlin, Germany.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Kuehn, Danilo
    Uppsala Berlin Joint Lab Next Generat Photoelect, Albert Einstein Str 15, D-12489 Berlin, Germany.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials. Uppsala Berlin Joint Lab Next Generat Photoelect, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Foehlisch, Alexander
    Uppsala Berlin Joint Lab Next Generat Photoelect, Albert Einstein Str 15, D-12489 Berlin, Germany.;Helmholtz Zentrum Berlin Mat & Energie, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.;Univ Potsdam, Inst Phys & Astronom, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany.
    The degree of electron itinerancy and shell closing in the core-ionized state of transition metals probed by Auger-photoelectron coincidence spectroscopy2022In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 32, p. 19218-19222Article in journal (Refereed)
    Abstract [en]

    Auger-photoelectron coincidence spectroscopy (APECS) has been used to examine the electron correlation and itinerance effects in transition metals Cu, Ni and Co. It is shown that the LVV Auger, in coincidence with 2p photoelectrons, spectra can be represented using atomic multiplet positions if the 3d-shell is localized (atomic-like) and with a self-convoluted valence band for band-like (itinerant) materials as explained using the Cini-Sawatzky model. For transition metals, the 3d band changes from band-like to localized with increasing atomic number, with the possibility of a mixed behavior. Our result shows that the LVV spectra of Cu can be represented by atomic multiplet calculations, those of Co resemble the self-convolution of the valence band and those of Ni are a mixture of both, consistent with the Cini-Sawatzky model.

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  • 28.
    Boudjemia, Nacer
    et al.
    Univ Oulu, Nano & Mol Syst Res Unit, POB 3000, Oulu 90014, Finland.
    Jankala, Kari
    Univ Oulu, Nano & Mol Syst Res Unit, POB 3000, Oulu 90014, Finland.
    Gejo, Tatsuo
    RIKEN, SPring 8 Ctr, 1-1-1 Kouto, Sayo, Hyogo 6795148, Japan;Univ Hyogo, Grad Sch Mat Sci, Kamigori, Hyogo 6781297, Japan.
    Nagaya, Kiyonobu
    RIKEN, SPring 8 Ctr, 1-1-1 Kouto, Sayo, Hyogo 6795148, Japan;Kyoto Univ, Dept Phys, Kyoto 6068502, Japan.
    Tamasaku, Kenji
    RIKEN, SPring 8 Ctr, 1-1-1 Kouto, Sayo, Hyogo 6795148, Japan.
    Huttula, Marko
    Univ Oulu, Nano & Mol Syst Res Unit, POB 3000, Oulu 90014, Finland.
    Piancastelli, Maria Novella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. RIKEN, SPring 8 Ctr, 1-1-1 Kouto, Sayo, Hyogo 6795148, Japan;Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France.
    Simon, Marc
    RIKEN, SPring 8 Ctr, 1-1-1 Kouto, Sayo, Hyogo 6795148, Japan;Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France.
    Oura, Masaki
    RIKEN, SPring 8 Ctr, 1-1-1 Kouto, Sayo, Hyogo 6795148, Japan.
    Deep core photoionization of iodine in CH3I and CF3I molecules: how deep down does the chemical shift reach?2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 10, p. 5448-5454Article in journal (Refereed)
    Abstract [en]

    Hard X-ray electron spectroscopic study of iodine 1s and 2s photoionization of iodomethane (CH3I) and trifluoroiodomethane (CF3I) molecules is presented. The experiment was carried out at the SPring-8 synchrotron radiation facility in Japan. The results are analyzed with the aid of relativistic molecular and atomic calculations. It is shown that charge redistribution within the molecule is experimentally observable even for very deep levels and is a function of the number of electron vacancies. We also show that the analysis of Auger spectra subsequent to hard X-ray photoionization can be used to provide insight into charge distribution in molecules and highlight the necessity of quantum electrodynamics corrections in the prediction of core shell binding energies in molecules that contain heavy atoms.

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  • 29.
    Boudjemia, Nacer
    et al.
    Univ Oulu, Nano & Mol Syst Res Unit, POB 300, Oulu 90014, Finland.
    Jänkälä, Kari
    Univ Oulu, Nano & Mol Syst Res Unit, POB 300, Oulu 90014, Finland.
    Püttner, Ralph
    Free Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195 Berlin, Germany.
    Marchenko, Tatiana
    Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France; Synchrotron SOLEIL, BP 48, F-91192 St Aubin, Gif Sur Yvettes, France.
    Travnikova, Oksana
    Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France; Synchrotron SOLEIL, BP 48, F-91192 St Aubin, Gif Sur Yvettes, France.
    Guillemin, Renaud
    Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France; Synchrotron SOLEIL, BP 48, F-91192 St Aubin, Gif Sur Yvettes, France.
    Journel, Loïc
    Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France; Synchrotron SOLEIL, BP 48, F-91192 St Aubin, Gif Sur Yvettes, France.
    Ismail, Iyas
    Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France; Synchrotron SOLEIL, BP 48, F-91192 St Aubin, Gif Sur Yvettes, France.
    Koulentianos, Dimitris
    Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France; Univ Gothenburg, Dept Phys, Origovägen 6B, SE-41296 Gothenburg, Sweden.
    Kosugi, Satoshi
    Sophia Univ, Dept Mat & Life Sci, Tokyo 1028554, Japan; Tokyo Gakugei Univ, Dept Phys, 4-1-1 Nukuikita Machi, Koganei, Tokyo 1848501, Japan.
    Azuma, Yoshiro
    Sophia Univ, Dept Mat & Life Sci, Tokyo 1028554, Japan; Tokyo Gakugei Univ, Dept Phys, 4-1-1 Nukuikita Machi, Koganei, Tokyo 1848501, Japan.
    Patanen, Minna
    Univ Oulu, Nano & Mol Syst Res Unit, POB 300, Oulu 90014, Finland.
    Huttula, Marko
    Univ Oulu, Nano & Mol Syst Res Unit, POB 300, Oulu 90014, Finland.
    Céolin, Denis
    Synchrotron SOLEIL, BP 48, F-91192 St Aubin, Gif Sur Yvettes, France.
    Piancastelli, Maria Novella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France.
    Simon, Marc
    Sorbonne Univ, CNRS, LCPMR, F-75005 Paris, France; Synchrotron SOLEIL, BP 48, F-91192 St Aubin, Gif Sur Yvettes, France.
    Electron spectroscopy and dynamics of HBr around the Br 1s-1 threshold2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 46, p. 26806-26818Article in journal (Refereed)
    Abstract [en]

    A comprehensive electron spectroscopic study combined with partial electron yield measurements around the Br 1s ionization threshold of HBr at ≅13.482 keV is reported. In detail, the Br 1s−1 X-ray absorption spectrum, the 1s−1 photoelectron spectrum as well as the normal and resonant KLL Auger spectra are presented. Moreover, the L-shell Auger spectra measured with photon energies below and above the Br 1s−1 ionization energy as well as on top of the Br 1s−1σ* resonance are shown. The latter two Auger spectra represent the second step of the decay cascade subsequent to producing a Br 1s−1 core hole. The measurements provide information on the electron and nuclear dynamics of deep core-excited states of HBr on the femtosecond timescale. From the different spectra the lifetime broadening of the Br 1s−1 single core-hole state as well as of the Br(2s−2,2s−12p−1,2p−2)  double core-hole states are extracted and discussed. The slope of the strongly dissociative HBr 2p−2σ* potential energy curve is found to be about −13.60 eV Å−1. The interpretation of the experimental data, and in particular the assignment of the spectral features in the KLL and L-shell Auger spectra, is supported by relativistic calculations for HBr molecule and atomic Br.

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  • 30. Brandenburg, T
    et al.
    Agåker, Marcus
    Atak, K
    Pflüger, M
    Schwanke, C
    Petit, T
    Lange, K M
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Aziz, E F
    The electronic structure of perfluorodecalin studied by soft X-ray spectroscopy and electronic structure calculations2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 42, p. 23379-23385Article in journal (Refereed)
    Abstract [en]

    Fluorine and carbon K absorption and emission spectra of liquid perfluorodecalin are presented and analyzed in terms of density functional calculations-configuration interaction. A comprehensive view of the electronic structure is given, and site-specific intramolecular interactions are investigated in detail. It is found that, while the outer fluorine atoms have excess charge in the ground state, the lowest excitations must be associated with charge transfer towards the inner carbon atoms.

  • 31.
    Brodmerkel, Maxim N.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Biochemistry.
    De Santis, Emiliano
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Biochemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Uetrecht, Charlotte
    Caleman, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics. Deutsches Elektronen-Synchrotron, DESY, Notkestrasse 85, 22607 Hamburg, Germany.
    Marklund, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Biochemistry.
    Collision induced unfolding and molecular dynamics simulations of norovirus capsid dimers reveal strain-specific stability profiles2024In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084Article in journal (Refereed)
    Abstract [en]

    Collision induced unfolding is method used with ion mobility mass spectrometry to examine protein structures and their stability. Such experiments yield information about higher order protein structures, yet are unable to provide details about the underlying processes. That information can however be provided using molecular dynamics simulations. Here, we investigate the collision induced unfolding of norovirus capsid dimers from the Norwalk and Kawasaki strains by employing molecular dynamics simulations over a range of temperatures, representing different levels of activation. The dimers have highly similar structures, but the activation reveals differences in the dynamics that arises in response to the activation.

  • 32.
    Brumboiu, Iulia Emilia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. KTH Royal Inst Technol, Dept Theoret Chem & Biol, SE-10691 Stockholm, Sweden.;Nicolaus Copernicus Univ, Fac Phys Astron & Informat, PL-87100 Torun, Poland..
    Ericsson, Leif K. E.
    Karlstad Univ, Dept Engn & Phys, SE-65188 Karlstad, Sweden..
    Blazinic, Vanja
    Karlstad Univ, Dept Engn & Phys, SE-65188 Karlstad, Sweden..
    Hansson, Rickard
    Karlstad Univ, Dept Engn & Phys, SE-65188 Karlstad, Sweden..
    Opitz, Andreas
    Humboldt Univ, Inst Phys, D-12489 Berlin, Germany..
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Moons, Ellen
    Karlstad Univ, Dept Engn & Phys, SE-65188 Karlstad, Sweden..
    Photooxidation of PC60BM: new insights from spectroscopy2022In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 42, p. 25753-25766Article in journal (Refereed)
    Abstract [en]

    This joint experimental-theoretical spectroscopy study of the fullerene derivative PC60BM ([6,6]-phenyl-C-60-butyric acid methyl ester) aims to improve the understanding of the effect of photooxidation on its electronic structure. We have studied spin-coated thin films of PC60BM by X-ray Photoelectron Spectroscopy (XPS), Near-edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, and Fourier Transform Infrared Spectroscopy (FTIR), before and after intentional exposure to simulated sunlight in air for different lengths of time. The pi* resonance in the C1s NEXAFS spectrum was found to be a very sensitive probe for the early changes to the fullerene cage, while FTIR spectra, in combination with O1s NEXAFS spectra, enabled the identification of the oxidation products. The changes observed in the spectra obtained by these complementary methods were compared with the corresponding Density Functional Theory (DFT) calculated single-molecule spectra of a large set of in silico generated oxidation products of PC60BM where oxygen atoms were attached to the C-60 cage. This comparison confirms that photooxidation of PC60BM disrupts the conjugation of the fullerene cage by a transition from sp(2) to sp(3)-hybridized carbon and causes the formation of several oxidation products, earlier proposed for C-60. The agreement between experimental and calculated IR spectra suggests moreover the presence of dicarbonyl and anhydride structures on the fullerene cage, in combination with cage opening at the adsorption site. By including PC60BM with physisorbed O-2 molecules on the cage in our theoretical description in order to model oxygen diffused through the film, the experimental O1s XPS and O1s NEXAFS spectra could be reproduced.

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  • 33.
    Caleman, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    van der Spoel, David
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    Evaporation from water clusters containing singly charged ions2007In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 9, no 37, p. 5105-5111Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics simulations were used to study the evaporation from water clusterscontaining either ClÀ, H2PO4À, Na+ or NH4+ ions. The simulations ranged between 10 and500 ns, and were performed in vacuum starting at 275 K. A number of different models were usedincluding polarizable models. The clusters contain 216 or 512 molecules, 0, 4 or 8 of which wereions. The ions with hydrogen bonding properties do not affect evaporation, even though thephosphate ions have a pronounced ion–ion structure and tend to be inside the cluster whereasammonium shows little ion–ion structure and has a distribution within the cluster similar to thatof the water molecules. Since the individual ion–water interactions are much stronger in the caseof Na+–water and ClÀ–water clusters, evaporation is somewhat slower for clusters containingthese ions. It seems therefore that the main determinant of the evaporation rate in ion–waterclusters is the strength of the interaction. Fission of droplets that contain more ions than allowedaccording to the Rayleigh limit seems to occur more rapidly in clusters containing ammoniumand sodium ions.

  • 34.
    Cappel, Ute B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Terschlüsen, Joachim A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Leitner, Torsten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Uppsala Berlin Joint Lab Next Generat Photoelectr, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Johansson, Erik M. J.
    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.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Uppsala Berlin Joint Lab Next Generat Photoelectr, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Mårtensson, Nils
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Uppsala Berlin Joint Lab Next Generat Photoelectr, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Electronic structure dynamics in a low bandgap polymer studied by time-resolved photoelectron spectroscopy2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 31, p. 21921-21929Article in journal (Refereed)
    Abstract [en]

    Means to measure the temporal evolution following a photo-excitation in conjugated polymers are a key for the understanding and optimization of their function in applications such as organic solar cells. In this paper we study the electronic structure dynamics by direct pump-probe measurements of the excited electrons in such materials. Specifically, we carried out a time-resolved photoelectron spectroscopy (TRPES) study of the polymer PCPDTBT by combining an extreme ultraviolet (XUV) high harmonic generation source with a time-of-flight spectrometer. After excitation to either the 1st excited state or to a higher excited state, we follow how the electronic structure develops and relaxes on the electron binding energy scale. Specifically, we follow a less than 50 fs relaxation of the higher exited state and a 10 times slower relaxation of the 1st excited state. We corroborate the results using DFT calculations. Our study demonstrates the power of TRPES for studying photo-excited electron energetics and dynamics of solar cell materials.

  • 35.
    Cappel, Ute
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Johansson, Erik M. J.
    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.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Energy Alignment and Surface Dipoles of Rylene Dyes adsorbed to TiO2 nanoparticles2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 32, p. 14767-14774Article in journal (Refereed)
    Abstract [en]

    The energy loss in dye-sensitized solar cells calculated from the energy difference between the lowest electronic transition of the dye and the obtained open-circuit voltage is often 1 eV or even more. To minimize this loss, it is important to accurately determine the energy alignment at the TiO2/dye/redox-mediator interface. In this study, we compared the results from electrochemistry and photoelectron spectroscopy for determining the energy alignment of three rylene dyes, two of which absorb relatively far in the red. The trends observed with the methods were different, as in the former, the energy alignment is measured relative to an external reference and includes contributions from solvent reorganization energies, while in the latter, it is measured relative to the energetics of the TiO2 and is lacking such contributions. The influence of the dyes' dipole moments on the energetics of the TiO2 was also measured and explained some of the differences in trends. Finally, we compared the injection efficiencies of the two red-absorbing dyes and found that the differences in injection efficiencies can be better explained using the energy alignment determined from photoelectron spectroscopy. This shows that the method for measuring the energetics of a DSC should be chosen according to what process one intends to study.

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    Cappel_10.1039/c1cp20911f
  • 36.
    Capron, Nathalie
    et al.
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Casier, Bastien
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Sisourat, Nicolas
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Piancastelli, Maria Novella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Simon, Marc
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Carniato, Stephane
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Correction: Probing keto–enol tautomerism using photoelectron spectroscopy2018In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 1, p. 695-695Article in journal (Refereed)
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    fulltext
  • 37.
    Capron, Nathalie
    et al.
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Casier, Bastien
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Sisourat, Nicolas
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Piancastelli, Maria Novella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Simon, Marc
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Carniato, Stephane
    Univ Paris 06, Sorbonne Univ, Lab Chim Phys Mat & Rayonnement, Paris, France; CNRS, Lab Chim Phys Mat & Rayonnement, Paris, France.
    Probing keto-enol tautomerism using photoelectron spectroscopy2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 30, p. 19991-19996Article in journal (Refereed)
    Abstract [en]

    We theoretically investigate the mechanism of tautomerism in the gas-phase acetylacetone molecule. The minimum energy path between the enolone and diketo forms has been computed using the Nudged-Elastic Band (NEB) method within the density-functional theory (DFT) using the projector augmented-wave method and generalized gradient approximation in Perdew-Wang (PW91) parametrization. The lowest transition state as well as several intermediate geometries between the two stable tautomers have been identified. The outer-valence ionization spectra for all determined geometries have been computed using the third-order non-Dyson algebraic diagrammatic construction technique. Furthermore, the oxygen core-shell ionization spectra for these geometries have been obtained using DFT and the Becke three-parameter Lee-Yang-Parr (B3LYP) functional. It is shown that all spectra depend strongly on the geometries demonstrating the possibility of following the proton-transfer dynamics using photoelectron spectroscopy in pump-probe experiments.

  • 38.
    Carlsson, Jens
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Structural Molecular Biology.
    Åqvist, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology, Structural Molecular Biology.
    Calculations of solute and solvent entropies from molecular dynamics simulations2006In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 8, no 46, p. 5385-5395Article in journal (Refereed)
    Abstract [en]

    The translational, rotational and conformational ( vibrational) entropy contributions to ligand-receptor binding free energies are analyzed within the standard formulation of statistical thermodynamics. It is shown that the partitioning of the binding entropy into different components is to some extent arbitrary, but an appropriate method to calculate both translational and rotational entropy contributions to noncovalent association is by estimating the configurational volumes of the ligand in the bound and free states. Different approaches to calculating solute entropies using free energy perturbation calculations, configurational volumes based on root-mean-square fluctuations and covariance matrix based quasiharmonic analysis are illustrated for some simple molecular systems. Numerical examples for the different contributions demonstrate that theoretically derived results are well reproduced by the approximations. Calculation of solvent entropies, either using total potential energy averages or van't Ho. plots, are carried out for the case of ion solvation in water. Although convergence problems will persist for large and complex simulation systems, good agreement with experiment is obtained here for relative and absolute ion hydration entropies. We also outline how solvent and solute entropic contributions are taken into account in empirical binding free energy calculations using the linear interaction energy method. In particular it is shown that empirical scaling of the nonpolar intermolecular ligand interaction energy effectively takes into account size dependent contributions to the binding free energy.

  • 39.
    Carlsson, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Arteca, G. A.
    Sundberg, Jill
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Elvingson, Christer
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Off-equilibrium response of grafted polymer chains subject to a variable rate of compression2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 24, p. 11757-11765Article in journal (Refereed)
    Abstract [en]

    We present Brownian dynamics simulations of single grafted semiflexible chains (i.e., "polymer mushrooms'') with varying persistence lengths, intra-chain interactions, and subject to confinement. The results from different rates of compression are presented in the cases of an approaching infinite plane and a paraboloid tip. We discuss the different behaviour observed for grafted chains with strong and weak self-attraction (i.e., "hard'' and "soft'' polymer mushrooms). In both cases the effect on the size and shape is more pronounced for a slow compression rate, especially for "hard mushrooms''. We have also studied the relaxation of the chain while the compressing plane is maintained, and when it is removed suddenly. We find that the response depends strongly on the time allowed for relaxation in the compressed state. When using instead a paraboloid tip, the overall effects are similar yet less pronounced because the chain can dodge the confining object via an "escape transition.''

  • 40.
    Carlsson, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Kamerlin, N.
    Arteca, G. A.
    Elvingson, Christer
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Brownian dynamics of a compressed polymer brush model: Off-equilibrium response as a function of surface coverage and compression rate2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 35, p. 16084-16094Article in journal (Refereed)
    Abstract [en]

    We study the compressive behaviour of a polymer-covered surface (i.e., a "polymer brush'') using Brownian dynamics simulations. The model consists of grafted chains with variable flexibility, variable intra-and inter-chain interactions, as well as different surface coverage. We discuss the polymer brush response to confinement by considering variable rates of compression under a hard plane. Our results show a small degree of inter-chain entanglement, regardless of whether the interaction is attractive or merely excluded volume. We observe that the molecular shape depends strongly on the surface coverage. Dense brushes exhibit a limited degree of lateral deformation under compression; instead, chains undergo a transition that produces a local patch with near-solid packing. This effect due to surface density can be undone partially by increasing the attractive nature of the chain interaction, by modulating the rate of compression, or by allowing "soft anchoring'', i.e., the possible Brownian drift of the grafting bead on the surface. We have also studied the polymer brush relaxation while maintaining the compressing plane, as well as after its sudden removal. We find evidence that also the relaxation depends on surface density; dense brushes appear to be configurationally frustrated at high compression and are unable to undergo swelling, regardless of the pressure applied.

  • 41.
    Carravetta, Vincenzo
    et al.
    Inst Chem & Phys Proc, CNR IPCF, Via G Moruzzi 1, I-56124 Pisa, Italy..
    de Abreu Gomes, Anderson Herbert
    Campinas Univ, Inst Phys Gleb Wataghin, Dept Appl Phys, BR-13083859 Campinas, SP, Brazil.;Brazilian Ctr Res Energy & Mat CNPEM, Brazilian Synchrotron Light Lab LNLS, POB 6192, BR-13083970 Campinas, SP, Brazil..
    Teixeira Marinho, Ricardo dos Reis
    Univ Fed Bahia, Inst Phys, BR-40170115 Salvador, BA, Brazil.;Brasilia Univ UnB, Inst Phys, BR-70919970 Brasilia, DF, Brazil..
    Ohrwall, Gunnar
    Lund Univ, MAX IV Lab, Box 118, SE-22100 Lund, Sweden..
    Ågren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Björneholm, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    de Brito, Arnaldo Naves
    Campinas Univ, Inst Phys Gleb Wataghin, Dept Appl Phys, BR-13083859 Campinas, SP, Brazil..
    An atomistic explanation of the ethanol-water azeotrope2022In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 42, p. 26037-26045Article in journal (Refereed)
    Abstract [en]

    Ethanol and water form an azeotropic mixture at an ethanol molecular percentage of similar to 91% (similar to 96% by volume), which prohibits ethanol from being further purified via distillation. Aqueous solutions at different concentrations in ethanol have been studied both experimentally and theoretically. We performed cylindrical micro-jet photoelectron spectroscopy, excited by synchrotron radiation, 70 eV above C1s ionization threshold, providing optimal atomic-scale surface-probing. Large model systems have been employed to simulate, by molecular dynamics, slabs of the aqueous solutions and obtain an atomistic description of both bulk and surface regions. We show how the azeotropic behaviour results from an unexpected concentration-dependence of the surface composition. While ethanol strongly dominates the surface and water is almost completely depleted from the surface for most mixing ratios, the different intermolecular bonding patterns of the two components cause water to penetrate to the surface region at high ethanol concentrations. The addition of surface water increases its relative vapour pressure, giving rise to the azeotropic behaviour.

  • 42.
    Caselli, Lucrezia
    et al.
    Univ Florence, Dept Chem, Florence, Italy.;CSGI, Florence, Italy..
    Ridolfi, Andrea
    Univ Florence, Dept Chem, Florence, Italy.;CSGI, Florence, Italy.;ISMN CNR, Bologna, Italy..
    Mangiapia, Gaetano
    Helmholtz Zentrum Hereon, Heinz Maier Leibnitz Zentrum MLZ, German Engn Mat Sci Ctr GEMS, Lichtenbergstr 1, D-85748 Garching, Germany..
    Maltoni, Pierfrancesco
    Univ Florence, Dept Chem, Florence, Italy.;CSGI, Florence, Italy..
    Moulin, Jean-Francois
    Helmholtz Zentrum Hereon, Heinz Maier Leibnitz Zentrum MLZ, German Engn Mat Sci Ctr GEMS, Lichtenbergstr 1, D-85748 Garching, Germany..
    Berti, Debora
    Univ Florence, Dept Chem, Florence, Italy.;CSGI, Florence, Italy..
    Steinke, Nina-Juliane
    Rutherford Appleton Lab, ISIS, Didcot, Oxon, England.;Inst Laue Langevin, Grenoble, France..
    Gustafsson, Emil
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Nylander, Tommy
    Lund Univ, Dept Chem, Phys Chem, Lund, Sweden.;Lund Univ, NanoLund, Lund, Sweden.;Lund Inst Adv Neutron & Xray Sci LINXS, Lund, Sweden..
    Montis, Costanza
    Univ Florence, Dept Chem, Florence, Italy.;CSGI, Florence, Italy..
    Interaction of nanoparticles with lipid films: the role of symmetry and shape anisotropy2022In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 5, p. 2762-2776Article in journal (Refereed)
    Abstract [en]

    The bioactivity, biological fate and cytotoxicity of nanomaterials when they come into contact with living organisms are determined by their interaction with biomacromolecules and biological barriers. In this context, the role of symmetry/shape anisotropy of both the nanomaterials and biological interfaces in their mutual interaction, is a relatively unaddressed issue. Here, we study the interaction of gold nanoparticles (NPs) of different shapes (nanospheres and nanorods) with biomimetic membranes of different morphology, i.e. flat membranes (2D symmetry, representative of the most common plasma membrane geometry), and cubic membranes (3D symmetry, representative of non-lamellar membranes, found in Nature under certain biological conditions). For this purpose we used an ensemble of complementary structural techniques, including Neutron Reflectometry, Grazing Incidence Small-Angle Neutron Scattering, on a nanometer lengthscale and Confocal Laser Scanning Microscopy on a micrometer length scale. We found that the structural stability of the membrane towards NPs is dependent on the topological characteristic of the lipid assembly and of the NPs, where a higher symmetry gave higher stability. In addition, Confocal Laser Scanning Microscopy analyses highlighted that NPs interact with cubic and lamellar phases according to two distinct mechanisms, related to the different structures of the lipid assemblies. This study for the first time systematically addresses the role of NPs shape in the interaction with lipid assemblies with different symmetry. The results will contribute to improve the fundamental knowledge on lipid interfaces and will provide new insights on the biological function of phase transitions as a response strategy to the exposure of NPs.

  • 43.
    Cheung, Ocean
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.;Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden..
    Wardecki, Dariusz
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.;Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden..
    Bacsik, Zoltan
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.;Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden..
    Vasiliev, Petr
    NeoZeo AB, Univ Vagen 10A, SE-10691 Stockholm, Sweden..
    McCusker, Lynne B.
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.;Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden.;Swiss Fed Inst Technol, Crystallog Lab, Wolfgang Pauli Str 10, CH-8093 Zurich, Switzerland..
    Hedin, Niklas
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden.;Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden..
    Highly selective uptake of carbon dioxide on the zeolite vertical bar Na10.2KCs0.8 -LTA - a possible sorbent for biogas upgrading2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 24, p. 16080-16083Article in journal (Refereed)
    Abstract [en]

    The vertical bar Na10.2KCs0.8(8)[Al12Si12O48](8)(Fm3c)-LTA zeolite adsorbs CO2-over-CH4 with a high selectivity (over 1500). The uptake of carbon dioxide is also high (3.31 mmol g(-1), 293 K, 101 kPa). This form of zeolite A is a very promising adsorbent for applications such as biogas upgrading, where keeping the adsorption of methane to a minimum is crucial.

  • 44.
    Cockcroft, Jeremy K.
    et al.
    UCL, Christopher Ingold Labs, Dept Chem, 20 Gordon St, London WC1H 0AJ, England.
    Shamsabadi, Andre
    UCL, Christopher Ingold Labs, Dept Chem, 20 Gordon St, London WC1H 0AJ, England.
    Wu, Han
    UCL, Dept Chem Engn, Torrington Pl, London WC1E 7JE, England.
    Rennie, Adrian R.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Understanding the structure and dynamics of cationic surfactants from studies of pure solid phases2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 47, p. 25945-25951Article in journal (Refereed)
    Abstract [en]

    A homologous series of n-alkyl trimethylammonium bromide surfactants, H(CH2)(n)N+(CH3)(3) Br-, from C(10)TAB to C(18)TAB have been studied systematically in the bulk over a wide range of temperatures. Common features in the structures are identified, with packing dominated by the co-ordination of the cationic head groups with bromide anions and interdigitation of the hydrocarbon chains. This arrangement provides an explanation for the thin adsorbed bilayers that have been observed at various hydrophilic surfaces from aqueous solutions in previous studies. The molecular volumes and arrangement are comparable with structures of a number of different self-assembled amphiphiles. For these surfactants with bromide counter-ions, formation of crystal hydrates was not observed. The alkyl chains are highly mobile and at high temperatures a plastic phase is found for all materials with a transition enthalpy that is similar to the melting enthalpy of many long alkyl chains. Other unexpected phase transitions depend more markedly on the hydrocarbon chain length and evidently depend on delicate balances of the various contributions to the free energy.

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  • 45.
    Couto, Rafael C.
    et al.
    Royal Inst Technol, Sch Chem Biotechnol & Hlth, Dept Theoret Chem & Biol, SE-10691 Stockholm, Sweden.;Stockholm Univ, Albanova Univ Ctr, Dept Phys, SE-10691 Stockholm, Sweden..
    Hua, Weijie
    Nanjing Univ Sci & Technol, Sch Sci, Dept Appl Phys, MIIT Key Lab Semicond Microstruct & Quantum Sensi, Nanjing 210094, Peoples R China..
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Lund Univ, Dept Phys, Box 118, S-22100 Lund, Sweden.;Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Kjellsson, Ludvig
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. European XFEL GmbH, Holzkoppel 4, D-22869 Schenefeld, Germany..
    Sorensen, Stacey L.
    Lund Univ, Dept Phys, Box 118, S-22100 Lund, Sweden..
    Kubin, Markus
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Bülow, Christine
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Timm, Martin
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Zamudio-Bayer, Vicente
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany..
    von Issendorff, Bernd
    Albert Ludwigs Univ Freiburg, Phys Inst, Hermann Herder Str 3, D-79104 Freiburg, Germany..
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Lau, J. Tobias
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindliche Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany.;Albert Ludwigs Univ Freiburg, Phys Inst, Hermann Herder Str 3, D-79104 Freiburg, Germany..
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Ågren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Tomsk State Univ, 36 Lenin Ave, Tomsk, Russia..
    Carravetta, Vincenzo
    CNR, IPCF, Via Moruzzi 1, I-56124 Pisa, Italy..
    Breaking inversion symmetry by protonation: experimental and theoretical NEXAFS study of the diazynium ion, N2H+2021In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 23, no 32, p. 17166-17176Article in journal (Refereed)
    Abstract [en]

    As an example of symmetry breaking in NEXAFS spectra of protonated species we present a high resolution NEXAFS spectrum of protonated dinitrogen, the diazynium ion N2H+. By ab initio calculations we show that the spectrum consists of a superposition of two nitrogen 1s absorption spectra, each including a pi* band, and a nitrogen 1s to H+ charge transfer band followed by a weak irregular progression of high energy excitations. Calculations also show that, as an effect of symmetry breaking by protonation, the pi* transitions are separated by 0.23 eV, only slightly exceeding the difference in the corresponding dark (symmetry forbidden) and bright (symmetry allowed) core excitations of neutral N-2. By DFT and calculations and vibrational analysis, the complex pi* excitation band of N2H+ is understood as due to the superposition of the significantly different vibrational progressions of excitations from terminal and central nitrogen atoms, both leading to bent final state geometries. We also show computationally that the electronic structure of the charge transfer excitation smoothly depends on the nitrogen-proton distance and that there is a clear extension of the spectra going from infinity to close nitrogen-proton distance where fine structures show some, although not fully detailed, similarities. An interesting feature of partial localization of the nitrogen core orbitals, with a strong, non-monotonous, variation with nitrogen-proton distance could be highlighted. Specific effects could be unraveled when comparing molecular cation NEXAFS spectra, as represented by recently recorded spectra of N-2(+) and CO+, and spectra of protonated molecules as represented here by the N2H+ ion. Both types containing rich physical effects not represented in NEXAFS of neutral molecules because of the positive charge, whereas protonation also breaks the symmetry. The effect of the protonation on dinitrogen can be separated in charge, which extends the high-energy part of the spectrum, and symmetry-breaking, which is most clearly seen in the low-energy pi* transition.

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  • 46.
    Couto, Rafael C.
    et al.
    Royal Inst Technol, Dept Theoret Chem & Biol, Sch Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden.
    Kjellsson, Ludvig
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. European XFEL GmbH, Holzkoppel 4, D-22869 Schenefeld, Germany.
    Ågren, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Royal Inst Technol, Dept Theoret Chem & Biol, Sch Chem Biotechnol & Hlth, SE-10691 Stockholm, Sweden; Tomsk State Univ, 36 Lenin Ave, Tomsk, Russia.
    Carravetta, Vincenzo
    IPCF CNR, Via Moruzzi 1, I-56124 Pisa, Italy.
    Sorensen, Stacey L.
    Lund Univ, Dept Phys, Box 118, S-22100 Lund, Sweden.
    Kubin, Markus
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Bülow, Christine
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Timm, Martin
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Zamudio-Bayer, Vicente
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany.
    von Issendorff, Bernd
    Albert Ludwigs Univ Freiburg, Phys Inst, Hermann Herder Str 3, D-79104 Freiburg, Germany.
    Lau, J. Tobias
    Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany; Albert Ludwigs Univ Freiburg, Phys Inst, Hermann Herder Str 3, D-79104 Freiburg, Germany.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Lund Univ, Dept Phys, Box 118, S-22100 Lund, Sweden; Helmholtz Zentrum Berlin Mat & Energie, Abt Hochempfindl Rontgenspektroskopie, Albert Einstein Str 15, D-12489 Berlin, Germany.
    The carbon and oxygen K-edge NEXAFS spectra of CO+2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 28, p. 16215-16223Article in journal (Refereed)
    Abstract [en]

    We present and analyze high resolution near edge X-ray absorption fine structure (NEXAFS) spectra of CO+ at the carbon and oxygen K-edges. The spectra show a wealth of features that appear very differently at the two K-edges. The analysis of these features can be divided into three parts; (i) repopulation transition to the open shell orbital – here the C(1s) or O(1s) to 5σ transition, where the normal core hole state is reached from a different initial state and different interaction than in X-ray photoelectron spectroscopy; (ii) spin coupled split valence bands corresponding to C(1s) or O(1s) to π* transitions; (iii) remainder weak and long progressions towards the double ionization potentials containing a manifold of peaks. These parts, none of which has correspondence in NEXAFS spectra of neutral molecules, are dictated by the localization of the singly occupied 5σ orbital, adding a dimension of chemistry to the ionic NEXAFS technique.

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  • 47.
    Das, Suman
    et al.
    Indian Inst Sci, Solid State & Struct Chem Unit, Bangalore 560012, Karnataka, India..
    Dutta, Dipak
    Indian Inst Sci, Solid State & Struct Chem Unit, Bangalore 560012, Karnataka, India..
    Araujo, Rafael B.
    Royal Inst Technol KTH, Dept Mat & Engn, Appl Mat Phys, S-10044 Stockholm, Sweden..
    Chakraborty, Sudip
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Bhattacharyy, Aninda J.
    Indian Inst Sci, Solid State & Struct Chem Unit, Bangalore 560012, Karnataka, India..
    Probing the pseudo-1-D ion diffusion in lithium titanium niobate anode for Li-ion battery2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 32, p. 22323-22330Article in journal (Refereed)
    Abstract [en]

    Comprehensive understanding of the charge transport mechanism in the intrinsic structure of an electrode material is essential in accounting for its electrochemical performance. We present here systematic experimental and theoretical investigations of Li+-ion diffusion in a novel layered material, viz. lithium titanium niobate. Lithium titanium niobate (exact composition Li0.55K0.45TiNbO5 center dot 1.06H(2)O) is obtained from sol-gel synthesized potassium titanium niobate (KTiNbO5) by an ion-exchange method. The Li+-ions are inserted and de-inserted preferentially into the galleries between the octahedral layers formed by edge and corner sharing TiO6 and NbO6 octahedral units and the effective chemical diffusion coefficient, is estimated to be 3.8 x 10(-11) cm(2) s(-1) using the galvanostatic intermittent titration technique (GITT). Calculations based on density functional theory (DFT) strongly confirm the anisotropic Li+-ion diffusion in the interlayer galleries and that Li+-ions predominantly diffuse along the crystallographic b-direction. The preferential Li+-ion diffusion along the b-direction is assisted by line-defects, which are observed to be higher in concentration along the b-direction compared to the a-and c-directions, as revealed by high resolution electron microscopy. The Li-Ti niobate can be cycled to low voltages (approximate to 0.2 V) and show stable and satisfactory battery performance over 100 cycles. Due to the possibility of cycling to low voltages, cyclic voltammetry and X-ray photoelectron spectroscopy convincingly reveal the reversibility of Ti3+ <-> Ti2+ along with Ti4+ <-> Ti3+ and Nb5+ <-> Nb4+.

  • 48.
    Davoudiniya, Masoumeh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Yang, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Influence of ab initio derived site-dependent hopping parameters on electronic transport in graphene nanoribbons2024In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 26, no 3, p. 1936-1949Article in journal (Refereed)
    Abstract [en]

    Graphene Nano Ribbons (GNRs) have been studied extensively due to their potential applications in electrical transport, optical devices, etc. The Tight Binding (TB) model is a common method used to theoretically study the properties of GNRs. However, the hopping parameters of two-dimensional graphene (2DG) are often used as the hopping parameters of the TB model of GNRs, which may lead to inaccuracies in the prediction of GNRs. In this work, we calculated the site-dependent hopping parameters from density functional theory and construction of Wannier orbitals for use in a realistic TB model. It has been found that due to the edge effect, the hopping parameters of edge C atoms are markedly different from the bulk part, which is prominently observed in narrow GNRs. Compared to graphene, the change of hopping parameter of edge C atoms of zigzag GNRs (ZGNRs) and armchair GNRs (AGNRs) is as high as 0.11 and 0.08 eV, respectively. Moreover, we investigated the impact of the calculated site-dependent (SD) hopping parameters on the electronic transport properties of GNRs in the absence and presence of the perpendicular electric field and dilute charged impurities using the Green function approach, Landauer–Büttiker formalism and self-consistent Born approximation. We find an electron–hole asymmetry in the electronic structure and transport properties of ZGNRs with SD hopping parameters. Furthermore, AGNRs with SD hopping energies show a band gap regardless of their width, while AGNRs with 2DG hopping parameters exhibit metallic or semiconductor phases depending on their width. In addition, electric field-induced 4-ZGNR with SD hopping parameters undergoes a metallic to n-doped semiconducting phase transition whereas for 4-ZGNR with 2DG hopping parameters and 8-AGNRs with 2DG or SD hopping parameters, the application of an electric field opens the band gap in both conduction and valence bands simultaneously. Our findings provide evidence for the electron–hole symmetry breaking in ZGNR with SD hopping parameters and make ZGNRs a suitable candidate in valleytronic devices.

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  • 49. de Jong, Wibe A
    et al.
    Bylaska, Eric
    Govind, Niranjan
    Janssen, Curtis L
    Kowalski, Karol
    Müller, Thomas
    Nielsen, Ida M B
    van Dam, Hubertus J J
    Veryazov, Valera
    Lindh, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Utilizing high performance computing for chemistry: parallel computational chemistry2010In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, no 26, p. 6896-6920Article in journal (Refereed)
    Abstract [en]

    Parallel hardware has become readily available to the computational chemistry research community. This perspective will review the current state of parallel computational chemistry software utilizing high-performance parallel computing platforms. Hardware and software trends and their effect on quantum chemistry methodologies, algorithms, and software development will also be discussed.

  • 50.
    de Lichtenberg, Casper
    et al.
    Umea Univ, Dept Chem, Linnaeus Vag 6 KBC Huset, SE-90187 Umea, Sweden..
    Messinger, Johannes
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Umea Univ, Dept Chem, Linnaeus Vag 6 KBC Huset, SE-90187 Umea.
    Substrate water exchange in the S-2 state of photosystem II is dependent on the conformation of the Mn4Ca cluster2020In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 22, no 23, p. 12894-12908Article in journal (Refereed)
    Abstract [en]

    In photosynthesis, dioxygen formation from water is catalyzed by the oxygen evolving complex (OEC) in Photosystem II (PSII) that harbours the Mn4Ca cluster. During catalysis, the OEC cycles through five redox states, S-0 to S-4. In the S-2 state, the Mn4Ca cluster can exist in two conformations, which are signified by the low-spin (LS) g = 2 EPR multiline signal and the high-spin (HS) g = 4.1 EPR signal. Here, we employed time-resolved membrane inlet mass spectrometry to measure the kinetics of (H2O)-O-18/(H2O)-O-16 exchange between bulk water and the two substrate waters bound at the Mn4Ca cluster in the S-2(LS), S-2(HS), and the S-3 states in both Ca-PSII and Sr-PSII core complexes from T. elongatus. We found that the slowly exchanging substrate water exchanges 10 times faster in the S-2(HS) than in the S-2(LS) state, and that the S-2(LS) -> S-2(HS) conversion has at physiological temperature an activation barrier of 17 +/- 1 kcal mol(-1). Of the presently suggested S-2(HS) models, our findings are best in agreement with a water exchange pathway involving a S-2(HS) state that has an open cubane structure with a hydroxide bound between Ca and Mn1. We also show that water exchange in the S-3 state is governed by a different equilibrium than in S-2, and that the exchange of the fast substrate water in the S-2 state is unaffected by Ca/Sr substitution. These findings support that (i) O5 is the slowly exchanging substrate water, with W2 being the only other option, and (ii) either W2 or W3 is the fast exchanging substrate. The three remaining possibilities for O-O bond formation in PSII are discussed.

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