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  • 1.
    Giangrisostomi, Erika
    et al.
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-72489 Berlin, Germany..
    Ovsyannikov, Ruslan
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-72489 Berlin, Germany..
    Sorgenfrei, Florian
    Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Sassa, Yasmine
    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.
    Leitner, Torsten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Mitzner, Rolf
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-72489 Berlin, 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.
    Foehlisch, Alexander
    Helmholtz Zentrum Berlin GmbH, Inst Methods & Instrumentat Synchrotron Radiat Re, Albert Einstein Str 15, D-72489 Berlin, Germany.;Univ Potsdam, Inst Phys & Astron, Karl Liebknecht Str 24-25, D-14476 Potsdam, Germany..
    Low Dose Photoelectron Spectroscopy at BESSY II: Electronic structure of matter in its native state2018In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 68-78Article in journal (Refereed)
    Abstract [en]

    The implementation of a high-transmission, angular-resolved time-of-Right electron spectrometer with a 1.25 MHz pulse selector at the PM4 soft X-ray dipole beamline of the synchrotron BESSY II creates unique capabilities to inquire electronic structure via photoelectron spectroscopy with a minimum of radiation dose. Solid-state samples can be prepared and characterized with standard UHV techniques and rapidly transferred from various preparation chambers to a 4-axis temperature-controlled measurement stage. A synchronized MHz laser system enables excited-state characterization and dynamical studies starting from the picosecond timescale. This article introduces the principal characteristics of the PM4 beamline and LowDosePES end-station. Recent results from graphene, an organic hole transport material for solar cells and the transition metal dichalcogenide MoS2 are presented to demonstrate the instrument performances. (C) 2017 The Authors. Published by Elsevier B.V.

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  • 2.
    Guarnaccio, Ambra
    et al.
    Ist Struttura Mat, ISM CNR, Trieste, Italy..
    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.
    Grazioli, Cesare
    Sincrotrone Trieste, Lab TASC, IOM CNR, I-34149 Trieste, Basovizza, Italy..
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Coreno, Marcello
    Ist Struttura Mat, ISM CNR, Trieste, Italy..
    de Simone, Monica
    Sincrotrone Trieste, Lab TASC, IOM CNR, I-34149 Trieste, Basovizza, Italy..
    Fronzoni, Giovanna
    Univ Trieste, Dept Chem & Pharmaceut Sci, I-34127 Trieste, Italy..
    Toffoli, Daniele
    Univ Trieste, Dept Chem & Pharmaceut Sci, I-34127 Trieste, Italy..
    Bernes, Elisa
    Univ Trieste, Dept Chem & Pharmaceut Sci, 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.
    PPT Isolated Molecule and Its Building Block Moieties Studied by C 1s and O 1s Gas Phase X-ray Photoelectron and Photoabsorption Spectroscopies2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 18, p. 9774-9786Article in journal (Refereed)
    Abstract [en]

    The present study is focused on the comprehensive gas phase electronic structure characterization of 2,8-bis-(diphenylphosphoryl)-dibenzo[b,d]thiophene (PPT), a promising ambipolar phosphorescent host material recently introduced in organic light-emitting diodes (OLEDs). This molecular system can be considered ideally formed by two diphenylphosphine oxide (dPPO) moieties functionalizing the small dibenzothiophene (DBT) core. PPT is characterized by high triplet energy and is known as good vacuum sublimable electron transporting material for blue OLEDs. The triphenyl phosphine oxide (TPPO) molecule has been chosen as the model compound of the dPPO groups in PPT. A combined experimental and theoretical study by density functional theory of the gas phase electronic structure of TPPO and PPT has been performed through X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure spectroscopy measured at the carbon and oxygen is regions. The study represents a detailed characterization of the impact of the single building blocks on the electronic structure of the whole PPT molecule. Moreover, it confirms that the phosphine oxide groups act as breaking points of the pi-conjugation between the DBT core of PPT and the outer groups, leaving the electronic structures of the compound practically matching those of the central DBT moiety.

  • 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.
    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.

  • 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, 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. 

  • 6.
    Palmer, Michael H.
    et al.
    Univ Edinburgh, Sch Chem, Joseph Black Bldg,David Brewster Rd, Edinburgh EH9 3FJ, Midlothian, Scotland..
    Coreno, Marcello
    CNR IMIP, Lab Elettra, Trieste, Italy..
    de Simone, Monica
    CNR IOM, Lab TASC, Trieste, Italy..
    Hoffmann, Soren Vronning
    Aarhus Univ, Dept Phys & Astron, ISA, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Jones, Nykola C.
    Aarhus Univ, Dept Phys & Astron, ISA, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Grazioli, Cesare
    CNR IMIP, Lab Elettra, Trieste, Italy.;Univ Trieste, Dept Chem & Pharmaceut Sci, Trieste, Italy..
    Peterson, Kirk A.
    Washington State Univ, Dept Chem, Pullman, WA 99164 USA..
    Baiardi, Alberto
    Scuola Normale Super Pisa, Piazza Cavalieri 7, I-56126 Pisa, Italy..
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Biczysko, Malgorzata
    Shanghai Univ, Coll Sci, Int Ctr Quantum & Mol Struct, 99 Shangda Rd, Shanghai 200444, Peoples R China..
    A combined theoretical and experimental study of the ionic states of iodopentafluorobenzene2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 8, article id 084302Article in journal (Refereed)
    Abstract [en]

    A new synchrotron radiation photoelectron spectral (PES) study of iodopentafluorobenzene, together with a theoretical analysis of the spectrum, where Franck-Condon factors are discussed, gives detailed insight into the ionization processes, and this exposes the need for a reinvestigation of the vacuum ultraviolet spectral (VUV) assignments. We have calculated adiabatic ionization energies (AIEs) for several ionic states, using the equation-of-motion coupled cluster method for ionic states combined with multi-configuration self-consistent field calculation study. The AIE sequence is: (XB1)-B-2 < A(2)A(2) < (BB2)-B-2 < C2(2)B(1) < D(2)A(1) < E3(2)B(1). This symmetry sequence has a major impact on previous VUV spectral assignments, which now appear to be to optically forbidden states. Changes in the equilibrium structures for these ionic states are relatively small, but a significant decrease and increase in the C-I bond length relative to the X(1)A(1) structure occurs for the (XB1)-B-2 and (CB1)-B-2 states, respectively. The PES shows major vibrational overlaps between pairs of ionic states, X with A, and A with B. The result of these overlaps is the loss of vibrational structure and considerable broadening of the higher energy PES state. Although the baseline is nearly re-established between the A and B states, where the two bands are nearly separate, the B state is also broadened by the A state. Only the C ionic state, which shows the most highly developed vibrational structure, can be regarded as free from vibrational coupling to a neighbor state. The Franck-Condon analysis of the PES bands X, A, B, and C is described in detail; the apparent simplicity of some of these bands is illusory, since almost all the observed peaks arise from super-position of several calculated vibrational states. The experimental AIE of the A state, which is submerged under the X state envelope, has been determined by the subtraction of the calculated X state envelope from the observed PES spectrum. The overlap of these PES bands and the apparent closeness of the potential energy curves describing them have been investigated, using the state-averaged, complete active space self-consistent field method. We have identified two structures, one where the potential energy curves for the X and A states cross and another for the A and B states. At these two conical intersections (ConInts), there is zero-energy difference within each pair of states. Although similar in energy, the ConInt for the crossing of the X with A states, and that for the A with B states, shows that the open-shell occupancies correspond to the 4 lowest AIE states, and all four states that are quite different from each other. Published by AIP Publishing.

  • 7.
    Palmer, Michael H.
    et al.
    Univ Edinburgh, Sch Chem, Joseph Black Bldg,David Brewster Rd, Edinburgh EH9 3FJ, Midlothian, Scotland..
    Hoffmann, Soren Vronning
    Aarhus Univ, Dept Phys & Astron, ISA, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Jones, Nykola C.
    Aarhus Univ, Dept Phys & Astron, ISA, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Coreno, Marcello
    CNR ISM, Trieste Unit LD2, I-34149 Trieste, Italy..
    de Simone, Monica
    CNR IOM Lab TASC, I-34149 Trieste, Italy..
    Grazioli, Cesare
    CNR ISM, Trieste Unit LD2, I-34149 Trieste, Italy..
    Peterson, Kirk A.
    Washington State Univ, Dept Chem, Pullman, WA 99164 USA..
    Baiardi, Alberto
    Scuola Normale Super Pisa, Piazza Cavalieri 7, I-56126 Pisa, Italy..
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Biczysko, Malgorzata
    Shanghai Univ, Coll Sci, Int Ctr Quantum & Mol Struct, 99 Shangda Rd, Shanghai 200444, Peoples R China..
    A combined theoretical and experimental study of the valence and Rydberg states of iodopentafluorobenzene2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 17, article id 174301Article in journal (Refereed)
    Abstract [en]

    A new ultraviolet (UV) and vacuum ultraviolet (VUV) spectrum for iodopentafluorobenzene (C6F5I) using synchrotron radiation is reported. The measurements have been combined with those from a recent high-resolution photoelectron spectroscopic study. A major theoretical study, which includes both Franck-Condon (FC) and Herzberg-Teller (HT) analyses, leads to conclusions, which are compatible with both experimental studies. Our observation that the VUV multiplet at 7.926 eV in the VUV spectrum is a Rydberg state rather than a valence state leads to a fundamental reassignment of the VUV Rydberg spectrum over previous studies and removes an anomaly where some previously assigned Rydberg states were to optically forbidden states. Adiabatic excitation energies (AEEs) were determined from equations-of-motion coupled cluster with singles and doubles excitation; these were combined with time dependent density functional theoretical methods. Frequencies from these two methods are very similar, and this enabled the evaluation of both FC and HT contributions in the lower valence states. Multi-reference multi-root configuration interaction gave a satisfactory account of the principal UV+ VUV spectral profile of C6F5I, with vertical band positions and intensities. The UV spectral onset consists of two very weak transitions assigned to 1(1)B(1) (pi sigma*) and 1(1)B(2) (sigma sigma*) symmetries. The lowest unoccupied molecular orbital of a sigma*(a(1)) symmetry has a significant C-I* antibonding character. This results in considerable lengthening of the C-I bond for both these excited states. The vibrational intensity of the lowest 11B1 state is dominated by HT contributions; the 1(1)B(2) state contains both HT and FC contributions; the third band, which contains three states, two pi pi*(1(1)A(1), 2(1)B(2)) and one pi sigma*(2(1)B(1)), is dominated by FC contributions in the (1)A(1) state. In this (1)A(1) state, and the spectrally dominant bands near 6.7 ((1)A(1)) and 7.3 eV ((1)A(1) + B-1(2)), the C-I bond length is in the normal range, and FC components dominate.

  • 8.
    Palmer, Michael H.
    et al.
    Univ Edinburgh, Sch Chem, Edinburgh EH9 3FJ, Midlothian, Scotland..
    Ridley, Trevor
    Univ Edinburgh, Sch Chem, Edinburgh EH9 3FJ, Midlothian, Scotland..
    Hoffmann, Soren Vronning
    Aarhus Univ, Dept Phys & Astron, ISA, DK-8000 Aarhus C, Denmark..
    Jones, Nykola C.
    Aarhus Univ, Dept Phys & Astron, ISA, DK-8000 Aarhus C, Denmark..
    Coreno, Marcello
    CNR IMIP, Trieste, Italy..
    de Simone, Monica
    CNR IOM Lab TASC, Trieste, Italy..
    Grazioli, Cesare
    CNR IOM Lab TASC, Trieste, Italy.;Univ Trieste, Dept Chem & Pharmaceut Sci, Trieste, Italy..
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Biczysko, Malgorzata
    UOS Pisa, Natl Res Council ICCOM CNR, I-56124 Pisa, Italy.;Scuola Normale Super Pisa, I-56126 Pisa, Italy..
    Baiardi, Alberto
    Scuola Normale Super Pisa, I-56126 Pisa, Italy..
    Peterson, Kirk
    Washington State Univ, Dept Chem, Pullman, WA 99164 USA..
    Interpretation of the photoelectron, ultraviolet, and vacuum ultraviolet photoabsorption spectra of bromobenzene by ab initio configuration interaction and DFT computations2015In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 143, no 16, article id 164303Article in journal (Refereed)
    Abstract [en]

    New photoelectron, ultraviolet (UV), and vacuum UV (VUV) spectra have been obtained for bromobenzene by synchrotron study with higher sensitivity and resolution than previous work. This, together with use of ab initio calculations with both configuration interaction and time dependent density functional theoretical methods, has led to major advances in interpretation. The VUV spectrum has led to identification of a considerable number of Rydberg states for the first time. The Franck-Condon (FC) analyses including both hot and cold bands lead to identification of the vibrational structure of both ionic and electronically excited states including two Rydberg states. The UV onset has been interpreted in some detail, and an interpretation based on the super-position of FC and Herzberg-Teller contributions has been performed. In a similar way, the 6 eV absorption band which is poorly resolved is analysed in terms of the presence of two pi pi* states of (1)A(1) (higher oscillator strength) and B-1(2) (lower oscillator strength) symmetries, respectively. The detailed analysis of the vibrational structure of the 2(2)B(1) ionic state is particularly challenging, and the best interpretation is based on equation-of-motion-coupled cluster with singles and doubles computations. A number of equilibrium structures of the ionic and singlet excited states show that the molecular structure is less subject to variation than corresponding studies for iodobenzene. The equilibrium structures of the 3b(1)3s and 6b(2)3s (valence shell numbering) Rydberg states have been obtained and compared with the corresponding ionic limit structures.

  • 9.
    Palmer, Michael H.
    et al.
    Univ Edinburgh, Sch Chem, Joseph Black Bldg,David Brewster Rd, Edinburgh EH9 3FJ, Midlothian, Scotland..
    Ridley, Trevor
    Univ Edinburgh, Sch Chem, Joseph Black Bldg,David Brewster Rd, Edinburgh EH9 3FJ, Midlothian, Scotland..
    Hoffmann, Soren Vronning
    Aarhus Univ, Dept Phys & Astron, ISA, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Jones, Nykola C.
    Aarhus Univ, Dept Phys & Astron, ISA, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Coreno, Marcello
    CNR ISM, Basovizza Area Sci Pk, I-34149 Trieste, Italy..
    de Simone, Monica
    CNR IOM Lab TASC, Trieste, Italy..
    Grazioli, Cesare
    CNR IOM Lab TASC, Trieste, Italy.;Univ Trieste, Dept Chem & Pharmaceut Sci, Trieste, Italy..
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics. Uppsala Univ, Dept Phys & Astron, Uppsala, Sweden..
    Biczysko, Malgorzata
    Shanghai Univ, Coll Sci, Int Ctr Quantum & Mol Struct, 99 Shangda Rd, Shanghai 200444, Peoples R China.;Scuola Normale Super Pisa, Piazza Cavalieri 7, I-56126 Pisa, Italy..
    Baiardi, Alberto
    Scuola Normale Super Pisa, Piazza Cavalieri 7, I-56126 Pisa, Italy..
    Peterson, Kirk A.
    Washington State Univ, Dept Chem, Pullman, WA 99164 USA..
    Combined theoretical and experimental study of the valence, Rydberg, and ionic states of chlorobenzene2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144, no 12, article id 124302Article in journal (Refereed)
    Abstract [en]

    New photoelectron (PE) and ultra violet (UV) and vacuum UV (VUV) spectra have been obtained for chlorobenzene by synchrotron study with higher sensitivity and resolution than previous work and are subjected to detailed analysis. In addition, we report on the mass-resolved (2 + 1) resonance enhanced multiphoton ionization (REMPI) spectra of a jet-cooled sample. Both the VUV and REMPI spectra have enabled identification of a considerable number of Rydberg states for the first time. The use of ab initio calculations, which include both multi-reference multi-root doubles and singles configuration interaction (MRD-CI) and time dependent density functional theoretical (TDDFT) methods, has led to major advances in interpretation of the vibrational structure of the ionic and electronically excited states. Franck-Condon (FC) analyses of the PE spectra, including both hot and cold bands, indicate much more complex envelopes than previously thought. The sequence of ionic states can be best interpreted by our multi-configuration self-consistent field computations and also by comparison of the calculated vibrational structure of the B and C ionic states with experiment; these conclusions suggest that the leading sequence is the same as that of iodobenzene and bromobenzene, namely: (XB1)-B-2(3b(1)(-1)) < A(2)A(2)(1a(2)(-1)) < (BB2)-B-2(6b(2)(-1)) < (CB1)-B-2(2b(1)(-1)). The absorption onset near 4.6 eV has been investigated using MRD-CI and TDDFT calculations; the principal component of this band is B-1(2) and an interpretation based on the superposition of FC and Herzberg-Teller contributions has been performed. The other low-lying absorption band near 5.8 eV is dominated by a (1)A(1) state, but an underlying weak B-1(1) state (pi sigma*) is also found. The strongest band in the VUV spectrum near 6.7 eV is poorly resolved and is analyzed in terms of two pi pi* states of (1)A(1) (higher oscillator strength) and B-1(2) (lower oscillator strength) symmetries, respectively. The calculated vertical excitation energies of these two states are critically dependent upon the presence of Rydberg functions in the basis set, since both manifolds are strongly perturbed by the Rydberg states in this energy range. A number of equilibrium structures of the ionic and singlet excited states show that the molecular structure is less subject to variation than corresponding studies for iodobenzene and bromobenzene.

  • 10.
    Palmer, Michael H.
    et al.
    Univ Edinburgh, Sch Chem, Joseph Black Bldg,David Brewster Rd, Edinburgh EH9 3FJ, Midlothian, Scotland..
    Ridley, Trevor
    Univ Edinburgh, Sch Chem, Joseph Black Bldg,David Brewster Rd, Edinburgh EH9 3FJ, Midlothian, Scotland..
    Hoffmann, Soren Vronning
    Aarhus Univ, Dept Phys & Astron, ISA, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Jones, Nykola C.
    Aarhus Univ, Dept Phys & Astron, ISA, Ny Munkegade 120, DK-8000 Aarhus C, Denmark..
    Coreno, Marcello
    CNR, ISM, Basovizza Area Sci Pk, I-34149 Trieste, Italy..
    De Simone, Monica
    CNR, IOM Lab TASC, Trieste, Italy..
    Grazioli, Cesare
    CNR, IOM Lab TASC, Trieste, Italy.;Univ Trieste, Dept Chem & Pharmaceut Sci, Trieste, Italy..
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Biczysko, Malgorzata
    Shanghai Univ, Coll Sci, Int Ctr Quantum & Mol Struct, 99 Shangda Rd, Shanghai 200444, Peoples R China.;Scuola Normale Super Pisa, Piazza Cavalieri 7, I-56126 Pisa, Italy..
    Baiardi, Alberto
    Scuola Normale Super Pisa, Piazza Cavalieri 7, I-56126 Pisa, Italy..
    Peterson, Kirk A.
    Washington State Univ, Dept Chem, Pullman, WA 99164 USA..
    Combined theoretical and experimental study of the valence, Rydberg and ionic states of fluorobenzene2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144, no 20, article id 204305Article in journal (Refereed)
    Abstract [en]

    New photoelectron spectra (PES) and ultra violet (UV) and vacuum UV (VUV) absorption spectra of fluorobenzene recorded at higher resolution than previously, have been combined with mass-resolved (2 + 1) and (3 + 1) resonance enhanced multiphoton ionization (REMPI) spectra; this has led to the identification of numerous Rydberg states. The PES have been compared with earlier mass-analyzed threshold ionization and photoinduced Rydberg ionization (PIRI) spectra to give an overall picture of the ionic state sequence. The analysis of these spectra using both equations of motion with coupled cluster singles and doubles (EOM-CCSD) configuration interaction and time dependent density functional theory (TDDFT) calculations have been combined with vibrational analysis of both the hot and cold bands of the spectra, in considerable detail. The results extend several earlier studies on the vibronic coupling leading to conical intersections between the (XB1)-B-2 and A(2)A(2) states, and a further trio (B, C, and D) of states. The conical intersection of the X and A states has been explicitly identified, and its structure and energetics evaluated. The energy sequence of the last group is only acceptable to the present study if given as (BB2)-B-2 < (CB1)-B-2 < D(2)A(1), a conclusion which is in agreement with most previous EOM-CCSD and other calculations. However, this symmetry ordering of the B and C states forces reconsideration of the nature of the PIRI spectrum. The coupling between these two states is induced by the a(2) modes, v(12) and v(14) and we propose that the 14(1) band is observed in the (BB2)-B-2 band in the PES for the first time, because of the improved resolution. This same assignment is given to the lowest energy band in the PIRI spectrum which was previously assigned as the origin band and further conclude that the entire PIRI spectrum is induced by v(12) and v(14). The relative intensities of the various Rydberg state peaks in the VUV absorption and REMPI spectra of fluorobenzene are very similar to those observed in the equivalent spectra of benzene. Published by AIP Publishing.

  • 11.
    Roberta, Totani
    et al.
    Department of physical and chemical sciences, university of L'Aquila, Italy.
    Cesare, Grazioli
    CNR-ISM, Italy.
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Ieva, Bidermane
    Institute Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz Zentrum Berlin.
    Lüder, Johann
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Monica, de Simone
    CNR-IOM, Italy.
    Marcello, Coreno
    CNR-ISM, Italy.
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Luca, Lozzi
    Department of physical and chemical sciences, university of L'Aquila, Italy.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Electronic structure investigations of biphenylene filmsArticle in journal (Refereed)
    Abstract [en]

    Photoelectron Spectroscopy (PES) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The obtained results have been compared to previous gas phase spectra and single molecule density functional theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, NEXAFS measurements allowed characterizing the variation of the molecular arrangement with the film thickness and helped to clarify the substrate- molecule interaction. 

  • 12. Toffoli, D.
    et al.
    Guarnaccio, A.
    Grazioli, C.
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Johansson, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    de Simone, M.
    Coreno, M.
    Santagata, A.
    D’Auria, M.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Bernes, E.
    Stener, M.
    Fronzoni, G.
    Electronic Structure Characterization of a Thiophene Benzo-Annulated Series of Common Building Blocks for Donor and Acceptor Compounds Studied by Gas Phase Photoelectron and Photoabsorption Synchrotron Spectroscopies2018In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 122, no 44, p. 8745-8761Article in journal (Refereed)
    Abstract [en]

    The near-edge x-ray-absorption fine-structure (NEXAFS) and Xray photoelectron spectroscopy (XPS) spectra of benzo[b]thiophene (BBT) and dibenzothiophene (DBT) in the gas phase have been measured at the carbon Kedge and sulfur L-II,L-III-edge regions. The assignment of the spectral features has been provided by theoretical calculations based on density functional theory (DFT) and its time-dependent generalization (TDDFT) in the linear response regime. Observed trends in computed C 1s and S 2p ionization potentials (IPs) have been rationalized in terms of both the inductive effects due to the presence of S and the increased pi-electrons delocalization arising from the benzoannulation process. The analysis of the NEXAFS carbon K-edge and sulfur L-II,L-III-edge regions regions provided information on both low-lying delocalized virtual pi orbitals, and higher-lying localized sigma*(C-S) states. The evolution of the NEXAFS carbon K-edge spectral features along the series thiophene (T) and derivatives, BBT and DBT, is informative of a stabilizing effect due to increased aromaticity. This effect is however more pronounced in going from T to BBT compared to the introduction of a second annulated phenyl ring in DBT. The nature of the most intense sulfur L-II,L-III-edge NEXAFS spectral features is instead conserved along the series reflecting thus the localized nature of the virtual states involved in the S 2p core-excitation process.

  • 13.
    Totani, R.
    et al.
    Univ Aquila, Dept Phys & Chem Sci, Via Vetoio, I-67100 Coppito, Italy.;Univ Pierre & Marie Curie Paris VI, UMR CNRS 7197, Lab Reactivite Surface, Tour 43-44 3eme etage,Case 178,4 Pl Jussieu, F-75005 Paris, France..
    Grazioli, C.
    Univ Trieste, Dept Chem & Pharmaceut Sci, I-34127 Trieste, Italy.;CNR, ISM, SS 14 km 163-5, I-34149 Trieste, Basovizza, Italy..
    Zhang, T.
    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 Rad Res, Albert Einstein St 15, D-12489 Berlin, Germany..
    Lüder, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    de Simone, M.
    CNR, IOM, SS 14 Km 163-5, I-34149 Trieste, Basovizza, Italy..
    Coreno, M.
    CNR, ISM, SS 14 km 163-5, I-34149 Trieste, Basovizza, Italy..
    Brena, B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Lozzi, L.
    Univ Aquila, Dept Phys & Chem Sci, Via Vetoio, I-67100 Coppito, Italy..
    Puglia, C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Electronic structure investigation of biphenylene films2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 146, no 5, article id 054705Article in journal (Refereed)
    Abstract [en]

    Photoelectron Spectroscopy (PS) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The obtained results have been compared to previous gas phase spectra and single molecule Density Functional Theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, NEXAFS measurements allowed characterizing the variation of the molecular arrangement with the film thickness and helped to clarify the substrate-molecule interaction. Published by AIP Publishing.

  • 14.
    Ugolotti, Aldo
    et al.
    Univ Milano Bicocca, Dept Mat Sci, I-20125 Milan, Italy..
    Lanzilotto, Valeria
    Ist Off Mat, IOM CNR, I-34149 Trieste, Italy.;Sapienza Univ Roma, Dipartimento Chim, I-00185 Rome, Italy.;Univ Trieste, Dipartimento Sci Chim & Farmaceut, Via Licio Giorgieri 1, I-34127 Trieste, Italy..
    Grazioli, Cesare
    Ist Off Mat, IOM CNR, I-34149 Trieste, Italy..
    Floreano, Luca
    Ist Off Mat, IOM CNR, I-34149 Trieste, Italy.;Ist Off Mat, IOM CNR, I-34149 Trieste, Italy..
    Manuel Zamalloa-Serrano, Jorge
    Inst Ciencia Mat Madrid ICMM CSIC, ESISNA Grp, Madrid 28049, Spain..
    Stredansky, Matus
    Ist Off Mat, IOM CNR, I-34149 Trieste, Italy.;Univ Trieste, Dept Phys, I-34127 Trieste, Italy..
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. Beijing Inst Technol BIT, Sch Integrated Circuits & Elect, MIIT Key Lab Lowdimens Quantum Struct & Devices, Beijing 100081, Peoples R China..
    de Simone, Monica
    Ist Off Mat, IOM CNR, I-34149 Trieste, Italy..
    Ferraro, Lorenzo
    Univ Milano Bicocca, Dept Mat Sci, I-20125 Milan, Italy..
    Coreno, Marcello
    Ist Struttura Mat, ISM CNR, I-34149 Trieste, Italy..
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Di Valentin, Cristiana
    Univ Milano Bicocca, Dept Mat Sci, I-20125 Milan, Italy..
    In-Plane Hydrogen Bonds and Out-of-Plane Dipolar Interactions in Self-Assembled Melem Networks2023In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 23, p. 11307-11316Article in journal (Refereed)
    Abstract [en]

    Melem(2,6,10-triamino-s-heptazine) is the building block of melon,a carbon nitride (CN) polymer that is proven to produce H-2 from water under visible illumination. With the aim of bringingadditional insight into the electronic structure of CN materials,we performed a spectroscopic characterization of gas-phase melem andof a melem-based self-assembled 2D H-bonded layer on Au(111) by meansof ultraviolet and X-ray photoemission spectroscopy (UPS, XPS) andnear-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Inparallel, we performed density functional theory (DFT) simulationsof the same systems to unravel the molecular charge density redistributioncaused by the in-plane H-bonds. Comparing the experimental resultswith the spectroscopic DFT simulations, we can correlate the inducedcharge accumulation on the N-amino atoms to the red-shiftof the corresponding N 1s binding energy (BE) and of the N-amino 1s -> LUMO+n transitions. Moreover, when introducing a supportingAu(111) surface in the computational simulations, we observe a molecule-substrateinteraction that almost exclusively involves the out-of-plane molecularorbitals, leaving those engaged in the in-plane H-bonded network ratherunperturbed.

  • 15.
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Synchrotron Radiation Studies of Molecular Building Blocks for Functional Materials2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The research on new materials is a primary driving force for progress in human society. One of the most significant research topic nowadays is the development of new functional materials for technological applications, like perovskite implemented in solar cells, and graphene as a representative for the new 2D materials family. It is then crucial to fully understand the functionality of such materials from a fundamental point of view, as a complementary and useful guide to develop/design new devices of improved performance and energy efficiency.

    In the thesis, comprehensive characterizations of molecular building blocks used in i) novel energy conversion devices (CoPc, TPA, DPTA and m-MTDATA), and ii) in 2D materials (biphenylene and melamine) have been performed by PhotoElectron Spectroscopy (PES), and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy carried out at synchrotron radiation facilities, representing effective, powerful light source dedicated to the front-line materials research of great value in both science and industry. PES and NEXAFS spectroscopy, in combination with Density Functional Theory (DFT) calculations have provided a deep understanding of the electronic structure of the investigated systems in relation to their functionality. The investigations always included the combination and comparison between experimental and theoretical results. The studied molecules were characterized as free and adsorbed on surfaces, from the simple building blocks to more complex molecular systems. The characterizations allowed us to identify the electronic structure modifications due to substitutions (Paper III), increasing complexity of the molecules (Paper V), molecule-substrate interactions (Paper I, II, IV, V) and intra-molecular H-bonding interactions (Paper VI).

    List of papers
    1. Conclusively Addressing the CoPc Electronic Structure: A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study
    Open this publication in new window or tab >>Conclusively Addressing the CoPc Electronic Structure: A Joint Gas-Phase and Solid-State Photoemission and Absorption Spectroscopy Study
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    2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 47, p. 26372-26378Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    AMER CHEMICAL SOC, 2017
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-344315 (URN)10.1021/acs.jpcc.7b08524 (DOI)000417228500026 ()
    Funder
    Swedish Research CouncilCarl Tryggers foundation
    Available from: 2018-03-08 Created: 2018-03-08 Last updated: 2018-06-29Bibliographically approved
    2. Electronic structure investigations of biphenylene films
    Open this publication in new window or tab >>Electronic structure investigations of biphenylene films
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    (English)Article in journal (Refereed) Submitted
    Abstract [en]

    Photoelectron Spectroscopy (PES) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The obtained results have been compared to previous gas phase spectra and single molecule density functional theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, NEXAFS measurements allowed characterizing the variation of the molecular arrangement with the film thickness and helped to clarify the substrate- molecule interaction. 

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-307784 (URN)
    Available from: 2016-11-21 Created: 2016-11-21 Last updated: 2018-06-29
    3. Lone-Pair Delocalization Effects within Electron Donor Molecules: The Case of Triphenylamine and Its Thiophene-Analog
    Open this publication in new window or tab >>Lone-Pair Delocalization Effects within Electron Donor Molecules: The Case of Triphenylamine and Its Thiophene-Analog
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    2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 31, p. 17706-17717Article in journal (Refereed) Published
    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.

    National Category
    Physical Sciences Theoretical Chemistry Condensed Matter Physics
    Research subject
    Physics with spec. in Atomic, Molecular and Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-355118 (URN)10.1021/acs.jpcc.8b06475 (DOI)000441484600014 ()
    Funder
    Swedish Research Council, VR 2014-3776Carl Tryggers foundation
    Note

    Title in thesis list of papers: Lone Pair Delocalization Effect within Electron Donor Molecules:The Case of Triphenylamine (TPA) and Its Thiophene-Analog(DPTA)

    Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-10-15Bibliographically approved
    4. X-ray Spectroscopy Investigations of TPA/Au(111): Charge Redistribution via Core Exitation?
    Open this publication in new window or tab >>X-ray Spectroscopy Investigations of TPA/Au(111): Charge Redistribution via Core Exitation?
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    (English)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.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-355120 (URN)
    Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-06-29
    5. Electronic Structure Study of Free and Adsorbed m-MTDATA
    Open this publication in new window or tab >>Electronic Structure Study of Free and Adsorbed m-MTDATA
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    (English)Manuscript (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.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-355121 (URN)
    Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2018-06-29
    6. Spectroscopic Fingerprints of Carbon Nitride Functional Groups Locked-up in Intermolecular H-bonding Interactions
    Open this publication in new window or tab >>Spectroscopic Fingerprints of Carbon Nitride Functional Groups Locked-up in Intermolecular H-bonding Interactions
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    (English)In: Chemistry: A European Journal, ISSN 0947-6539Article in journal (Refereed) Submitted
    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. 

    National Category
    Physical Sciences
    Research subject
    Physics with spec. in Atomic, Molecular and Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-355123 (URN)
    Available from: 2018-06-29 Created: 2018-06-29 Last updated: 2020-10-22
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  • 16.
    Zhang, Teng
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Synchrotron radiation study of free and adsorbed organic molecules2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this licentiate thesis, organic molecules, namely Cobalt Phthalocyanine (CoPc) and Biphenylene, have been studied by means of synchrotron radiation-based spectroscopic methods (Photoemission Spectroscopy (PES) and X-ray Absorption Spectroscopy (XAS) in combination with Density Functional Theory (DFT) calculations.

    Paper I is a combined experimental and theoretical investigation of electronic structure of CoPc. addressing the atomic character of the Highest Occupied Molecular Orbital (HOMO) and the electronic configuration of the molecular ground state. Both these aspects are still under discussion since different experimental and theoretical studies have given controversial results. Previous works have indicated the CoPc ground state to either be described by the 2A1g or 2Eg, or by a mix of the two electronic configurations. Regrading the debated the atomic character of the HOMO of CoPc, it has been suggested to be either metal 3d-like and localized on the central Co atom or originating in the organic ligand of the molecule. In this thesis the valence photoemission results for CoPc in gas phase and as adsorbed films on Au(111) together with the DFT simulations, consistently indicate that the HOMO is derived only by the organic ligand, with mainly contribution from the carbon atoms with no metal character. Moreover, the good agreement between the experimental and theoretical results, confirms that the ground state of CoPc is correctly described by the 2A1g configuration.

    In Paper II, PES and XAS have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The results have been compared to previous gas phase spectra and single molecule Density Functional Theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, XAS measurements allowed the characterizion of the variation of the molecular arrangement with the film thickness and helped to clarify the substrate-molecule interaction.

    List of papers
    1. Exploring the electronic structure of CoPc by photoemission and absorption spectroscopy
    Open this publication in new window or tab >>Exploring the electronic structure of CoPc by photoemission and absorption spectroscopy
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    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Photoelectron spectroscopy  and X-ray absorption spectroscopy were used to investigate the occupied and empty density of states of cobalt phthalocyanine (CoPc) in the gas phase and in thin films of different thicknesses, deposited onto a Au (111) single crystal. The comparison between experimental gas phase results and density functional theory single molecule simulations confirmed that the CoPc ground state is correctly described by the 2A1g electronic configuration. Moreover, the atomic character of the highest occupied molecular orbital of CoPc was addressed by performing photon energy dependent valence photoemission spectroscopy experiments on both CoPc gas phase and film samples. Our results clearly show that the highest occupied molecular orbital is derived only from the organic ligand, with mainly contribution from the carbon atoms. Multiplet ligand field theory was employed to simulate the Co L edge X-ray absorption spectroscopy results.

    National Category
    Natural Sciences
    Research subject
    Physics with spec. in Atomic, Molecular and Condensed Matter Physics
    Identifiers
    urn:nbn:se:uu:diva-307777 (URN)
    Available from: 2016-11-21 Created: 2016-11-21 Last updated: 2016-12-07
    2. Electronic structure investigations of biphenylene films
    Open this publication in new window or tab >>Electronic structure investigations of biphenylene films
    Show others...
    (English)Article in journal (Refereed) Submitted
    Abstract [en]

    Photoelectron Spectroscopy (PES) and Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy have been used to investigate the occupied and empty density of states of biphenylene films of different thicknesses, deposited onto a Cu(111) crystal. The obtained results have been compared to previous gas phase spectra and single molecule density functional theory (DFT) calculations to get insights into the possible modification of the molecular electronic structure in the film induced by the adsorption on a surface. Furthermore, NEXAFS measurements allowed characterizing the variation of the molecular arrangement with the film thickness and helped to clarify the substrate- molecule interaction. 

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-307784 (URN)
    Available from: 2016-11-21 Created: 2016-11-21 Last updated: 2018-06-29
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  • 17.
    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.

  • 18.
    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.

  • 19.
    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.

  • 20.
    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.

  • 21.
    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.

  • 22.
    Zhang, Teng
    et al.
    Beijing Inst Technol, Sch Integrated Circuits & Elect, MIIT Key Lab Low Dimens Quantum Struct & Devices, Beijing 100081, Peoples R China..
    Svensson, Pamela
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Chemical and Bio-Molecular Physics.
    Brumboiu, Iulia Emilia
    Pohang Univ Sci & Technol POSTECH, Dept Chem, Pohang 37673, South Korea..
    Lanzilotto, Valeria
    Sapienza Univ Roma, Dept Chem, I-00185 Rome, Italy..
    Grazioli, Cesare
    IOM CNR, Lab TASC, Sincrotrone Trieste, I-34149 Trieste, Italy..
    Guarnaccio, Ambra
    ISM CNR, Ist Struttura Mat, I-85050 Tito, Pz, Italy..
    Johansson, Fredrik O.L.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials. KTH Royal Inst Technol, Dept Chem, Div Appl Phys Chem, S-10044 Stockholm, Sweden.;Sorbonne Univ, Inst Nanosci Paris, UMR CNRS 7588, F-75005 Paris, France..
    Beranova, Klara
    Elettra Sincrotrone Trieste SCpA, I-34149 Trieste, Italy.;Czech Acad Sci, FZU Inst Phys, Prague 18221, Czech Republic..
    Coreno, Marcello
    ISM CNR, Ist Struttura Mat, I-85050 Tito, Pz, Italy..
    de Simone, Monica
    IOM CNR, Lab TASC, Sincrotrone Trieste, I-34149 Trieste, Italy..
    Floreano, Luca
    IOM CNR, Lab TASC, Sincrotrone Trieste, I-34149 Trieste, Italy..
    Cossaro, Albano
    IOM CNR, Lab TASC, Sincrotrone Trieste, I-34149 Trieste, Italy.;Univ Trieste, Dept Chem & Pharmaceut Sci, I-34127 Trieste, Italy..
    Brena, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Puglia, Carla
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Clarifying the Adsorption of Triphenylamine on Au(111): Filling the HOMO-LUMO Gap2022In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 126, no 3, p. 1635-1643Article in journal (Refereed)
    Abstract [en]

    In this article, we analyze the electronic structure modifications of triphenylamine (TPA), a well-known electron donor molecule widely used in photovoltaics and optoelectronics, upon deposition on Au(111) at a monolayer coverage. A detailed study was carried out by synchrotron radiation-based photoelectron spectroscopy, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, scanning tunneling microscopy (STM), and ab initio calculations. We detect a new feature in the pre-edge energy region of the N K-edge NEXAFS spectrum that extends over 3 eV, which we assign to transitions involving new electronic states. According to our calculations, upon adsorption, a number of new unoccupied electronic states fill the energy region between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the free TPA molecule and give rise to the new feature the pre-edge region of the NEXAFS spectrum. This finding highlights the occurrence of a considerable modification of the electronic structure of TPA. The appearance of new states in the HOMO-LUMO gap of TPA when adsorbed on Au(111) has crucial implications for the design of molecular nanoelectronic devices based on similar donor systems.

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