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  • 1.
    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.

  • 2.
    Cappel, Ute B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Svanström, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Johansson, Fredrik O. L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Aitola, Kerttu
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Philippe, Bertrand
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Leitner, Torsten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Foehlisch, Alexander
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.;Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    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..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Rensmo, Håkan
    Partially Reversible Photoinduced Chemical Changes in a Mixed-Ion Perovskite Material for Solar Cells2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 40, p. 34970-34978Article in journal (Refereed)
    Abstract [en]

    Metal halide perovskites have emerged as materials of high interest for solar energy-to-electricity conversion, and in particular, the use of mixed-ion structures has led to high power conversion efficiencies and improved stability. For this reason, it is important to develop means to obtain atomic level understanding of the photoinduced behavior of these materials including processes such as photoinduced phase separation and ion migration. In this paper, we implement a new methodology combining visible laser illumination of a mixed-ion perovskite ((FAP-bI(3))(0.85)(MAPbBr(3))(0.15)) with the element specificity and chemical sensitivity of core-level photoelectron spectroscopy. By carrying out measurements at a synchrotron beamline optimized for low X-ray fluxes, we are able to avoid sample changes due to X-ray illumination and are therefore able to monitor what sample changes are induced by visible illumination only. We find that laser illumination causes partially reversible chemistry in the surface region, including enrichment of bromide at the surface, which could be related to a phase separation into bromide- and iodide-rich phases. We also observe a partially reversible formation of metallic lead in the perovskite structure. These processes occur on the time scale of minutes during illumination. The presented methodology has a large potential for understanding light-induced chemistry in photoactive materials and could specifically be extended to systematically study the impact of morphology and composition on the photostability of metal halide perovskites.

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  • 3.
    Lanzilotto, Valeria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Sapienza Univ Rome, Dept Chem, Ple Aldo Moro 8, I-00185 Rome, Italy.;CNR, Ist Officina Mat, IOM, Basovizza SS 14,Km 163-5, I-34149 Trieste, Italy..
    Grazioli, Cesare
    CNR, Ist Officina Mat, IOM, Basovizza SS 14,Km 163-5, I-34149 Trieste, Italy..
    Stredansky, Matus
    CNR, Ist Officina Mat, IOM, Basovizza SS 14,Km 163-5, I-34149 Trieste, Italy.;Univ Trieste, Dept Phys, Via A Valeria 2, I-34127 Trieste, Italy.;Beijing Inst Technol BIT, Sch Informat & Elect, MIIT Key Lab Low Dimens Quantum Struct & Devices, Beijing 100081, Peoples R China..
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Beijing Inst Technol BIT, Sch Informat & Elect, MIIT Key Lab Low Dimens Quantum Struct & Devices, Beijing 100081, Peoples R China..
    Schio, Luca
    CNR, Ist Officina Mat, IOM, Basovizza SS 14,Km 163-5, I-34149 Trieste, Italy..
    Goldoni, Andrea
    Elettra Sincrotrone Trieste SCpA, Basovizza SS 14,Km 163-5, I-34149 Trieste, Italy..
    Floreano, Luca
    CNR, Ist Officina Mat, IOM, Basovizza SS 14,Km 163-5, I-34149 Trieste, Italy..
    Motta, Alessandro
    Sapienza Univ Rome, Dept Chem, Ple Aldo Moro 8, I-00185 Rome, Italy.;Consortium INSTM, Via G Giusti 9, I-50121 Florence, Italy..
    Cossaro, Albano
    CNR, Ist Officina Mat, IOM, Basovizza SS 14,Km 163-5, I-34149 Trieste, Italy.;Univ Trieste, Dept Chem & Pharmaceut Sci, Via Giorgieri 1, I-34127 Trieste, Italy..
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Tailoring surface-supported water-melamine complexes by cooperative H-bonding interactions2021In: Nanoscale Advances, E-ISSN 2516-0230, Vol. 3, no 8, p. 2359-2365Article in journal (Refereed)
    Abstract [en]

    The water-splitting photo-catalysis by carbon nitride heterocycles has been the subject of recent theoretical investigations, revealing a proton-coupled electron transfer (PCET) reaction from the H-bonded water molecule to the CN-heterocycle. In this context, a detailed characterization of the water-catalyst binding configuration becomes mandatory in order to validate and possibly improve the theoretical modeling. To this aim, we built a well-defined surface-supported water/catalyst interface by adsorbing water under ultra-high vacuum (UHV) conditions on a monolayer of melamine grown on the Cu(111) surface. By combining X-ray photoemission (XPS) and absorption (NEXAFS) spectroscopy we observed that melamine adsorbed onto copper is strongly tilted off the surface, with one amino group dangling to the vacuum side. The binding energy (BE) of the corresponding N 1s component is significantly higher compared to other N 1s contributions and displays a clear shift to lower BE as water is adsorbed. This finding along with density functional theory (DFT) results reveals that two adjacent melamine molecules concurrently work for stabilizing the H-bonded water-catalyst complex: one melamine acting as a H-donor via the amino-N (NHMIDLINE HORIZONTAL ELLIPSISOHH) and another one as a H-acceptor via the triazine-N (C = NMIDLINE HORIZONTAL ELLIPSISHOH).

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  • 4.
    Lanzilotto, Valeria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Malavolti, Luigi
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy.;Max Planck Inst Struct & Dynam Matter, D-22761 Hamburg, Germany..
    Ninova, Silviya
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy.;Univ Bern, Dept Chem & Biochem, Freiestr 3, CH-3012 Bern, Switzerland..
    Cimatti, Irene
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Poggini, Lorenzo
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy.;Inst Chim Matiere Condensee Bordeaux, Grp Mol & Mat Commutables, 87 Ave Docteur Schweitzer, F-33608 Pessac, France..
    Cortigiani, Brunetto
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Mannini, Matteo
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Totti, Federico
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    Gornia, Andrea
    Univ Modena & Reggio Emilia, Dept Chem & Geol Sci, I-41125 Modena, Italy.;Univ Modena & Reggio Emilia, INSTM Res Unit, I-41125 Modena, Italy..
    Sessoli, Roberta
    Univ Florence, Dept Chem Ugo Schiff, I-50019 Sesto Fiorentino, Italy.;Univ Florence, INSTM Res Unit, I-50019 Sesto Fiorentino, Italy..
    The Challenge of Thermal Deposition of Coordination Compounds: Insight into the Case of an Fe-4 Single Molecule Magnet2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 21, p. 7693-7702Article in journal (Refereed)
    Abstract [en]

    Realization of well-controlled hybrid interfaces between solid surfaces and functional complex molecules can be hampered by the presence of contaminants originated by the fragmentation of fragile architectures based on the coordinative bond. Here, we present a morphological and spectroscopic analysis of submonolayer films obtained by sublimation of the [Fe-4(L)(2)(dpm)(6)] (Fe-4) single molecule magnet on different substrates. Though intact tetranuclear molecules can be transferred to surfaces, smaller molecular species are often codeposited. By comparison of substrates characterized by different reactivities, such as Au(111), Cu(100), and Cu2N, and employing a protocol of indirect exposure of the substrate, we infer that the observed fragments do not originate from the reaction of Fe-4 molecules with the surface but rather are produced during Fe-4 sublimation, which releases Fe(dpm)(3) as a very volatile compound. Fe(dpm)(3) undergoes substrate-dependent on-surface decomposition to final products that have been identified by combined STM, UPS, XPS, and DFT studies.

  • 5.
    Lanzilotto, Valeria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Silva, Jose Luis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Stredansky, Matus
    Univ Trieste, Dept Phys, Via A Valerio 2, I-34127 Trieste, Italy;CNR, IOM, Lab TASC, Basovizza SS-14,Km 163-5, I-34149 Trieste, Italy.
    Grazioli, Cesare
    CNR, ISM, Unit LD2, Basovizza SS-14,Km 163-5, I-34149 Trieste, Italy.
    Simonov, Konstantin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Giangrisostomi, Erika
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany.
    De Simone, Monica
    CNR, IOM, Lab TASC, Basovizza SS-14,Km 163-5, I-34149 Trieste, Italy.
    Coreno, Marcello
    CNR, ISM, Unit LD2, Basovizza SS-14,Km 163-5, I-34149 Trieste, Italy.
    Araujo, Carlos Moyses
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Spectroscopic Fingerprints of Intermolecular H-Bonding Interactions in Carbon Nitride Model Compounds2018In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 53, p. 14198-14206Article in journal (Refereed)
    Abstract [en]

    The effect of intermolecular H-bonding interactions on the local electronic structure of N-containing functional groups (amino group and pyridine-like N) that are characteristic of polymeric carbon nitride materials p-CN(H), a new class of metal-free organophotocatalysts, was investigated. Specifically, the melamine molecule, a building block of p-CN(H), was characterized by X-ray photoelectron (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The molecule was studied as a noninteracting system in the gas phase and in the solid state within a H-bonded network. With the support of DFT simulations of the spectra, it was found that the H-bonds mainly affect the N1s level of the amino group, leaving the N1s level of the pyridine-like N mostly unperturbed. This is responsible for a reduction of the chemical shift between the two XPS N1s levels relative to free melamine. Consequently, N K-edge NEXAFS resonances involving the amino N1s level also shift to lower photon energies. Moreover, the solid-state absorption spectra showed significant modification/quenching of resonances related to transitions from the amino N1s level to sigma* orbitals involving the NH2 termini.

  • 6.
    Lanzilotto, Valeria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Silva, Jose Luis
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Stredansky, Matuš
    Department of Physics University of Trieste.
    Grazioli, Cesare
    CNR-ISM, Istituto di Struttura della Materia (LD2 Unit).
    Simonov, Konstantin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Giangrisostomi, Erika
    Institute Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH.
    Ovsyannikov, Ruslan
    Institute Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH.
    de Simone, Monica
    CNR-IOM, Istituto Officina dei Materiali (Laboratorio TASC).
    Coreno, Marcello
    CNR-ISM, Istituto di Struttura della Materia (LD2 Unit).
    Araujo, Carlos Moyses
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Spectroscopic Fingerprints of Carbon Nitride Functional Groups Locked-up in Intermolecular H-bonding InteractionsIn: Chemistry: A European Journal, ISSN 0947-6539Article in journal (Refereed)
    Abstract [en]

    We have investigated the effect of intermolecular H- bonding interactions on the local electronic structure of N- functionalities, amino group and pyridine-like N, which are characteristic of a new class of metal-free polymeric photo-catalysts named graphitic carbon nitrides, g-C3N4. Specifically, we have performed a characterization of the melamine molecule, a building block of g-C3N4, combining X-ray photoemission (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The molecule has been studied in the gas phase, as non-interacting system, and in the solid state within a hydrogen bonded network. With the support of density functional theory (DFT) simulations of the spectra, we have found that the H-bonds mainly affect the N 1s level of the amino group, leaving the N 1s level of the pyridine-like N mostly unperturbed. This fact is responsible for a reduction of the chemical shift between the two XPS N 1s levels, compared to the free melamine. Consequently, N K-edge NEXAFS resonances involving the amino N 1s level also shift to lower photon energies. Moreover, the solid state absorption spectra have shown strong modification/quenching of resonances related with transitions from the amino N 1s level towards σ*orbitals involving the -NH2 terminations. 

  • 7.
    Schaefer, A.
    et al.
    Chalmers Univ Technol, Competence Ctr Catalysis, S-41296 Gothenburg, Sweden;Chalmers Univ Technol, Dept Chem & Chem Engn, S-41296 Gothenburg, Sweden.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, Stockholm, Sweden.
    Uvdal, P.
    Lund Univ, Dept Chem, Chem Phys, POB 124, SE-22100 Lund, Sweden.
    Borg, A.
    NTNU Norwegian Univ Sci & Technol, Dept Phys, NO-7491 Trondheim, Norway.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Defect-Induced Water Bilayer Growth on Anatase TiO2(101)2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 37, p. 10856-10864Article in journal (Refereed)
    Abstract [en]

    Preparing an anatase TiO2(101) surface with a high density of oxygen vacancies and associated reduced Ti species in the near-surface region results in drastic changes in the water adsorption chemistry compared to adsorption on a highly stoichiometric surface. Using synchrotron radiation excited photoelectron spectroscopy, we observe a change in the water growth mode, from layer-by-layer growth on the highly stoichiometric surface to bilayer growth on the reduced surface. Furthermore, we have been able to observe enrichment at the surface upon water adsorption. The Ti3+ enrichment occurs concomitant with effective water dissociation into hydroxyls with a very high thermal stability. The water bilayer on the reduced surface is thermally more stable than that on the stoichiometric surface, and it is more efficient in promoting further water dissociation upon heating. The results thus show how the presence of subsurface defects can alter the wetting mechanism of an oxide surface.

  • 8.
    Schaefer, A.
    et al.
    Lund Univ, Dept Synchrotron Radiat Res, POB 118, SE-22100 Lund, Sweden;Chalmers Univ Technol, Competence Ctr Catalysis, S-41296 Gothenburg, Sweden.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Cappel, Ute B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. KTH Royal Inst Technol, Div Appl Phys Chem, Dept Chem, Stockholm, Sweden.
    Uvdal, P.
    Lund Univ, Dept Chem, Chem Phys, POB 124, SE-22100 Lund, Sweden.
    Borg, A.
    NTNU Norwegian Univ Sci & Technol, Dept Phys, NO-07491 Trondheim, Norway.
    Sandell, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    First layer water phases on anatase TiO2(101)2018In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 674, p. 25-31Article in journal (Refereed)
    Abstract [en]

    The anatase TiO2(101) surface and its interaction with water is an important topic in oxide surface chemistry. Firstly, it benchmarks the properties of the majority facet of TiO2 nanoparticles and, secondly, there is a controversy as to whether the water molecule adsorbs intact or deprotonates. We have addressed the adsorption of water on anatase TiO2(101) by synchrotron radiation photoelectron spectroscopy. Three two-dimensional water structures are found during growth at different temperatures: at 100 K, a metastable structure forms with no hydrogen bonding between the water molecules. In accord with prior literature, we assign this phase to chains of disordered molecules. Growth 160 K results in a metastable structure with expressed hydrogen bonding between the water molecules. At 190 K, the water molecules become disordered as the thermal energy is too high and hence the hydrogen bonds break. The result is a structure with isolated monomers. Partial dissociation is observed for all three growths, with the molecular state only slightly favored in energy (20-40 meV) over the dissociated state. Heating of a thick film leads to more dissociation compared to a bilayer, when formed at 100 K. Thus, extending the water network facilitates proton transport and hence dissociation. The results reconcile apparent conflicting experimental results previously obtained by scanning tunneling microscopy (STM) and core level photoelectron spectroscopy.

  • 9.
    Zhang, Teng
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. BIT, Sch Informat & Elect, Beijing 100081, Peoples R China.
    Brumboiu, I. E.
    Royal Inst Technol KTH, Dept Theoret Chem & Biol, S-10691 Stockholm, Sweden;Korea Adv Inst Sci & Technol, Dept Chem, Daejeon 34141, South Korea.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Univ Roma La Sapienza, Dept Chem, Piazzale Aldo Moro 5, I-00185 Rome, Italy.
    Grazioli, C.
    Sincrotrone Trieste, Lab TASC, CNR, IOM, Trieste, Italy.
    Guarnaccio, A.
    CNR, ISM, Tito, Pz, Italy;Trieste LD2 Unit, Trieste, Italy.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Coreno, M.
    CNR, ISM, Tito, Pz, Italy;Trieste LD2 Unit, Trieste, Italy.
    de Simone, M.
    Sincrotrone Trieste, Lab TASC, CNR, IOM, Trieste, Italy.
    Santagata, A.
    CNR, ISM, Tito, Pz, Italy;Trieste LD2 Unit, Trieste, Italy.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Electronic structure modifications induced by increased molecular complexity: from triphenylamine to m-MTDATA2019In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 32, p. 17959-17970Article in journal (Refereed)
    Abstract [en]

    The starburst pi-conjugated molecule 4,4 ',4 ''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (C57H48N4, m-MTDATA), based on triphenylamine (TPA) building blocks, is widely used in optoelectronic devices due to its good electron-donor characteristics. The electronic structure of m-MTDATA was investigated for the first time in the gas phase by means of PhotoElectron Spectroscopy (PES) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. The combination of Density Functional Theory (DFT) calculations with the experimental spectra provides a comprehensive description of the molecular electronic structure. Moreover, by comparing the results with previous TPA measurements, we could shed light on how the electronic structure evolves when the molecular size is increased. We found that the C 1s photoelectron spectra of m-MTDATA and TPA are similar, due to the balance of the counter-acting effects of the electronegativity of the N atoms and the delocalization of the amine lone-pair electrons. In contrast, the increased number of N atoms (i.e. N lone pairs) in m-MTDATA determines a three-peak feature in the outermost valence binding energy region with strong contributions by the N 2p(z) orbitals. We also obtained a decrease of the HOMO-LUMO gap for m-MTDATA, which points to improved electron donating properties of m-MTDATA with respect to TPA.

  • 10.
    Zhang, Teng
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Brumboiu, I. E.
    Royal Inst Technol, Dept Theoret Chem & Biol, SE-10691 Stockholm, Sweden..
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Luder, J.
    Natl Univ Singapore, Dept Mech Engn, Singapore 117575, Singapore..
    Grazioli, C.
    ISM CNR, Trieste Unit LD2, Basovizza AREA Sci Pk, I-34149 Trieste, Italy..
    Giangrisostomi, E.
    Helmholtz Zentrum Berlin, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Ovsyannikov, R.
    Helmholtz Zentrum Berlin, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Sassa, Yasmine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Bidermane, I.
    Helmholtz Zentrum Berlin, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-12489 Berlin, Germany..
    Stupar, M.
    Univ Nova Gorica, Dept Phys, Vipavska Cesta 11C, Ajdovscina 5270, Slovenia..
    de Simone, M.
    CNR IOM, SS 14 Km 163,5, I-34149 Trieste, Italy..
    Coreno, M.
    ISM CNR, Trieste Unit LD2, Basovizza AREA Sci Pk, I-34149 Trieste, Italy..
    Ressel, B.
    Univ Nova Gorica, Dept Phys, Vipavska Cesta 11C, Ajdovscina 5270, Slovenia..
    Pedio, M.
    CNR IOM, SS 14 Km 163,5, I-34149 Trieste, Italy..
    Rudolf, P.
    Univ Groningen, Zernike Inst Adv Mat, Nijenborgh 4, NL-9747 AG Groningen, Netherlands..
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Conclusively Addressing the CoPc Electronic Structure: A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 47, p. 26372-26378Article in journal (Refereed)
    Abstract [en]

    The occupied and empty densities of states of cobalt phthalocyanine (CoPc) were investigated by photoelectron and X-ray absorption spectroscopies in the gas phase and in thin films deposited on a Au(111) surface. The comparison between the gas-phase results and density functional theory single-molecule simulations confirmed that the CoPc ground state is correctly described by the (2)A(1g) electronic configuration. Moreover, photon-energy-dependent valence photoemission spectra of both the gas phase and thin film confirmed the atomic character of the highest occupied molecular orbital as being derived from the organic ligand, with dominant contributions from the carbon atoms. Multiplet ligand-field theory was employed to simulate the Co L-edge X-ray absorption spectroscopy results.

  • 11.
    Zhang, Teng
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Brumboiu, Iulia E.
    KTH Royal Institute of Technology, Department of Theoretical Chemistry and Biology & Korea Advanced Institute of Science and Technology (KAIST), Department of Chemistry.
    Grazioli, Cesare
    ISM-CNR, Trieste LD2 Unit, Italy.
    Guarnaccio, Ambra
    ISM-CNR, Tito Scalo (Pz), Italy.
    Coreno, Marcello
    ISM-CNR, Trieste LD2 Unit, Italy.
    de Simone, Monica
    IOM-CNR, Laboratorio TASC, Sincrotrone Trieste, Basovizza, Trieste, Italy.
    Santagata, Antonio
    ISM-CNR, Tito Scalo (Pz), Italy.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lone-Pair Delocalization Effects within Electron Donor Molecules: The Case of Triphenylamine and Its Thiophene-Analog2018In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 31, p. 17706-17717Article in journal (Refereed)
    Abstract [en]

    Triphenylamine (TPA) and its thiophene-analog, N,N-diphenyl-2-thiophenamine (DPTA), are both well-known as electron-donating molecules implemented in optoelectronic devices such as organic solar cells and LEDs. Comprehensive valence and core level photoelectron spectroscopy, as well as near edge X-ray absorption spectroscopy (NEXAFS), measurements have been performed on gas phase TPA and DPTA. The experimental results have been compared to density functional theory calculations, providing a detailed description of the molecular electronic structure. Specifically, the C 1s photoelectron lines of both TPA and DPTA were resolved in the different C atom contributions and their binding energies explained as the result of two counter-acting effects: (1) the electronegativity of the nitrogen atom (and sulfur atom in DPTA) and (2) the the N (and S in DPTA) lone-pair electrons. In addition, the C K-edge NEXAFS spectrum of DPTA reveals that the lowest unoccupied molecular orbital (LUMO) energy position is affected differently if the core hole site is on the phenyl compared to the thiophene ring. The electron-donating properties of these two molecules are largely explained by the significant contribution of the N lone-pair electrons (p(z)) to the highest occupied molecular orbital. The contribution to the LUMO and to the empty density of states of the sulfur of the thiophene ring in DPTA explains the better performance of donor-pi-acceptor molecules containing this moiety and implemented in photoenergy conversion devices.

  • 12.
    Zhang, Teng
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Brumboiu, Iulia E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Grazioli, Cesare
    ISM-CNR, Trieste LD2 Unit, Italy.
    Guarnaccio, Ambra
    ISM-CNR, Tito Scalo (Pz), Italy.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ševčíková, Klára
    Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague, Czech Republic.
    Coreno, Marcello
    ISM-CNR, Trieste LD2 Unit, Italy.
    de Simone, Monica
    IOM-CNR, Laboratorio TASC, Sincrotrone Trieste, Basovizza, Trieste, Italy.
    Santagata, Antonio
    ISM-CNR, Tito Scalo (Pz), Italy.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Electronic Structure Study of Free and Adsorbed m-MTDATAManuscript (preprint) (Other academic)
    Abstract [en]

    The starburst p-conjugated molecule based on triphenylamine (TPA) building block, 4,4',4" -Tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (m-MTDATA), is widely used in optoelectronic devices due to its electron-donating properties. The electronic structure of m-MTDATA was investigated in the gas-phase and when deposited in thin films on a Au(111) surface by means of PhotoElectron Spectroscopy (PES) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. Density Functional Theory (DFT) calculations were compared to the experimental gas-phase results, providing a comprehensive description of the molecular electronic structure. Moreover, the results were compared with previous TPA measurements, shedding light on the electronic structure modification due to the increased molecular complexity.  Similar to TPA, but more complex, the binding energy of the C 1s photoelectron line of m-MTDATA results from the balance of two counter-acting effects: (1) the electronegativity of the N atoms and (2) the delocalization of lone-pair electrons of the nitrogen. Compared to TPA, the outermost valence PE spectrum of m-MTDATA shows a 3-peak feature with N 2pz character and a lowering of the binding energy of the HOMO. When adsorbed on Au(111),  the changes observed in PES and NEXAFS spectra with respect to the free molecules,  can be explained by a significant modification of m-MTDATA molecular and electronic structure, due to the molecule-substrate interaction.

  • 13.
    Zhang, Teng
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Brumboiu, Iulia E.
    Royal Institute of Technology (KTH), Department of Theoretical Chemistry and Biology.
    Lanzilotto, Valeria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Grazioli, Cesare
    ISM-CNR, Trieste LD2 Unit, Italy.
    Guarnaccio, Ambra
    ISM-CNR, Tito Scalo (Pz), Italy.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ševčíková, Klára
    Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague, Czech Republic.
    Coreno, Marcello
    ISM-CNR, Trieste LD2 Unit, Italy.
    de Simone, Monica
    IOM-CNR, Laboratorio TASC, Sincrotrone Trieste, Basovizza, Trieste, Italy.
    Santagata, Antonio
    ISM-CNR, Tito Scalo (Pz), Italy.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    X-ray Spectroscopy Investigations of TPA/Au(111): Charge Redistribution via Core Exitation?Manuscript (preprint) (Other academic)
    Abstract [en]

    Triphenylamine (TPA) is a well-known electron donor molecule largely used in photovoltaics. In this article we analyze the electronic structure modifications due to the adsorption of the molecules at a monolayer coverage on a Au(111) surface. Only a weak interaction was observed between the TPA and the gold during the adsorption process, being impossible to get more than 1ML coverage at room temperature. The characterizations have been performed by core and valence Photoelectron Spectroscopy (PES) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. The results were compared with our previous investigations on free TPA, and theoretical models were used to explain the changes of the electronic structure due to the adsorption on the metallic gold surface. The calculation confirms the weak interaction between the adsorbed TPA and the Au(111), with only a slight change of the twisting angle of the TPA phenyl rings. The resulting adsorption geometry can be used to explain the broadening of the C 1s PES line with respect to the gas-phase results and the expected absence of angle dependence in the C K-edge NEXAFS. However, a significant modification was observed in the N K-edge NEXAFS spectra of TPA/Au(111), showing a new pre-edge feature due to transitions involving out-of-plane orbitals. This pre-edge feature is ascribed to the interaction between the molecules and the surface, having a different character and energy position than the pre-edge observed for free TPA. A model, considering a TPA+ cation formed by a charge redistribution process between the adsorbate and the surface valence states seems to give a qualitative explanation of this pre-edge intensity. Since our calculations predict only a weak interaction between the TPA molecules and the gold surface, we propose that such a charge redistribution happens in the core-excited state created by photon absorption.

1 - 13 of 13
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