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Publications (10 of 46) Show all publications
Ugolotti, A., Lanzilotto, V., Grazioli, C., Floreano, L., Manuel Zamalloa-Serrano, J., Stredansky, M., . . . Di Valentin, C. (2023). In-Plane Hydrogen Bonds and Out-of-Plane Dipolar Interactions in Self-Assembled Melem Networks. The Journal of Physical Chemistry C, 127(23), 11307-11316
Open this publication in new window or tab >>In-Plane Hydrogen Bonds and Out-of-Plane Dipolar Interactions in Self-Assembled Melem Networks
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2023 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 127, no 23, p. 11307-11316Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-506997 (URN)10.1021/acs.jpcc.3c01990 (DOI)001010287600001 ()
Funder
Carl Tryggers foundation
Available from: 2023-07-03 Created: 2023-07-03 Last updated: 2024-03-14Bibliographically approved
Zhang, T., Svensson, P., Brumboiu, I. E., Lanzilotto, V., Grazioli, C., Guarnaccio, A., . . . Puglia, C. (2022). Clarifying the Adsorption of Triphenylamine on Au(111): Filling the HOMO-LUMO Gap. The Journal of Physical Chemistry C, 126(3), 1635-1643
Open this publication in new window or tab >>Clarifying the Adsorption of Triphenylamine on Au(111): Filling the HOMO-LUMO Gap
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2022 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 126, no 3, p. 1635-1643Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2022
National Category
Atom and Molecular Physics and Optics Physical Chemistry Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-470563 (URN)10.1021/acs.jpcc.1c08877 (DOI)000744923800001 ()35116088 (PubMedID)
Funder
Carl Tryggers foundation
Available from: 2022-03-28 Created: 2022-03-28 Last updated: 2023-10-17Bibliographically approved
Zhang, T., Wang, T., Grazioli, C., Guarnaccio, A., Brumboiu, I. E., Johansson, F., . . . Puglia, C. (2022). Evidence of hybridization states at the donor/acceptor interface: case of m-MTDATA/PPT. Journal of Physics: Condensed Matter, 34(21), Article ID 214008.
Open this publication in new window or tab >>Evidence of hybridization states at the donor/acceptor interface: case of m-MTDATA/PPT
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2022 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 34, no 21, article id 214008Article in journal (Refereed) Published
Abstract [en]

We performed a spectroscopic study on the m-MTDATA (donor) and PPT (acceptor) molecular vertical heterostructure. The electronic properties of the donor/acceptor interface have been comprehensively characterized by synchrotron radiation-based photoelectron spectroscopy and near-edge x-ray absorption fine structure. The spectroscopic results reveal the existence of new hybridization states in the original molecular energy gap, likely attributed to the interaction between the donor and the acceptor molecules at the interface. Such hybridized states can have a significant impact on the charge transport in organic electronic devices based on donor-acceptor molecules and can explain the increased efficiency of device using such molecules.

Place, publisher, year, edition, pages
IOP Publishing, 2022
Keywords
m-MTDATA, PPT, interface, hybridized state, PES, NEXAFS, D-A heterojunction
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-472394 (URN)10.1088/1361-648X/ac5aff (DOI)000771740800001 ()35245912 (PubMedID)
Funder
Swedish Research Council, VR 2014-3776Swedish Research Council, VR 2014-6463Swedish Research Council, 2020-06409
Available from: 2022-04-20 Created: 2022-04-20 Last updated: 2022-04-20Bibliographically approved
Zhang, T., Grazioli, C., Guarnaccio, A., Brumboiu, I. E., Lanzilotto, V., Johansson, F., . . . Puglia, C. (2022). m-MTDATA on Au(111): Spectroscopic Evidence of Molecule-Substrate Interactions. The Journal of Physical Chemistry C, 126(6), 3202-3210
Open this publication in new window or tab >>m-MTDATA on Au(111): Spectroscopic Evidence of Molecule-Substrate Interactions
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2022 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 126, no 6, p. 3202-3210Article in journal (Refereed) Published
Abstract [en]

The starburst pi-conjugated molecule based on triphenylamine (TPA) building blocks, 4,4',4 ''-tris(N-3-ethylphenyl-N-phenylamino)triphenylamine (C57H48N4, m-MTDATA), is widely used in optoelectronic devices due to its electron-donating properties. The electronic structure of m-MTDATA adsorbed on an Au(111) surface was investigated by means of photoelectron spectroscopy (PES) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results were further compared to gas-hase measurements and DFT calculations. Our results clearly indicate a significant molecule-substrate interaction that induces considerable modifications on the electronic structure of the adsorbate compared to the isolated molecule. The energy level alignment analysis shows that the HOMO-LUMO gap is filled by new interface states.

Place, publisher, year, edition, pages
American Chemical Society (ACS)American Chemical Society (ACS), 2022
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-470559 (URN)10.1021/acs.jpcc.1c09574 (DOI)000766228300029 ()
Funder
Swedish Research Council, VR 2014-6463Swedish Research Council, 2014-6463Swedish Research Council, 2020-06409
Available from: 2022-03-28 Created: 2022-03-28 Last updated: 2024-01-15Bibliographically approved
Zhang, T., Grazioli, C., Yang, H., Jiang, K., Brumboiu, I. E., Jia, L., . . . Wang, Y. (2021). Spectroscopic Evidence of New Low-Dimensional Planar Carbon Allotropes Based on Biphenylene via On-Surface Ullmann Coupling. CHEMISTRY-SWITZERLAND, 3(3), 1057-1062
Open this publication in new window or tab >>Spectroscopic Evidence of New Low-Dimensional Planar Carbon Allotropes Based on Biphenylene via On-Surface Ullmann Coupling
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2021 (English)In: CHEMISTRY-SWITZERLAND, ISSN 2624-8549, Vol. 3, no 3, p. 1057-1062Article in journal (Refereed) Published
Abstract [en]

The bottom-up synthesis and preliminary characterizations of a new biphenylene-based 2D framework are presented. This new low-dimensional carbon allotrope potentially completes the many hypothesized carbon networks based on biphenylene.

Place, publisher, year, edition, pages
MDPIMDPI AG, 2021
Keywords
2D material, on-surface synthesis, biphenylene, synchrotron radiation
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-457640 (URN)10.3390/chemistry3030076 (DOI)000703017800001 ()
Available from: 2021-11-01 Created: 2021-11-01 Last updated: 2024-01-15Bibliographically approved
Lanzilotto, V., Grazioli, C., Stredansky, M., Zhang, T., Schio, L., Goldoni, A., . . . Puglia, C. (2021). Tailoring surface-supported water-melamine complexes by cooperative H-bonding interactions. Nanoscale Advances, 3(8), 2359-2365
Open this publication in new window or tab >>Tailoring surface-supported water-melamine complexes by cooperative H-bonding interactions
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2021 (English)In: Nanoscale Advances, E-ISSN 2516-0230, Vol. 3, no 8, p. 2359-2365Article in journal (Refereed) Published
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).

Place, publisher, year, edition, pages
Royal Society of ChemistryRoyal Society of Chemistry (RSC), 2021
National Category
Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-442716 (URN)10.1039/d0na01034k (DOI)000641547400019 ()
Funder
Carl Tryggers foundation
Available from: 2021-06-24 Created: 2021-06-24 Last updated: 2024-01-15Bibliographically approved
Guarnaccio, A., Zhang, T., Grazioli, C., Johansson, F., Coreno, M., de Simone, M., . . . Puglia, C. (2020). PPT Isolated Molecule and Its Building Block Moieties Studied by C 1s and O 1s Gas Phase X-ray Photoelectron and Photoabsorption Spectroscopies. The Journal of Physical Chemistry C, 124(18), 9774-9786
Open this publication in new window or tab >>PPT Isolated Molecule and Its Building Block Moieties Studied by C 1s and O 1s Gas Phase X-ray Photoelectron and Photoabsorption Spectroscopies
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2020 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 18, p. 9774-9786Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-413858 (URN)10.1021/acs.jpcc.0c01764 (DOI)000535175400016 ()
Funder
Swedish Research Council, 2014-6463Carl Tryggers foundation
Available from: 2020-06-22 Created: 2020-06-22 Last updated: 2020-06-22Bibliographically approved
Bernes, E., Fronzoni, G., Stener, M., Guarnaccio, A., Zhang, T., Grazioli, C., . . . Toffoli, D. (2020). S 2p and P 2p Core Level Spectroscopy of PPT Ambipolar Material and Its Building Block Moieties. The Journal of Physical Chemistry C, 124(127), 14510-14520
Open this publication in new window or tab >>S 2p and P 2p Core Level Spectroscopy of PPT Ambipolar Material and Its Building Block Moieties
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2020 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 127, p. 14510-14520Article in journal (Refereed) Published
Abstract [en]

The near-edge X-ray absorption fine structure (NEXAFS and X-ray photoelectron (XP) spectra of gas-phase 2,8-bis-(diphenylphosphoryl)dibenzo[b,d]thiophene (PPT) and triphenylphosphine oxide (TPPO) have been measured at the S and P L-II,L-III-edge regions. The time-dependent density functional theory (TDDFT) based on the relativistic two-component zeroth-order regular approximation approach has been used to provide an assignment of the experimental spectra, giving the contribution of the spin-orbit splitting and of the molecular-field splitting to the sulfur and phosphor binding energies. Computed XP and NEXAFS spectra agree well with the experimental measurements. In going from dibenzothiophene and TPPO to PPT, the nature of the most intense S 2p and P 2p NEXAFS features are preserved; this trend suggests that the electronic and geometric behaviors of the S and P atoms in the two building block moieties are conserved in the more complex system of PPT. This work enables us to shed some light onto the structure of the P-O bond, a still highly debated topic in the chemical literature. Since the S 2p and P 2p NEXAFS intensities provide specific information on the higher-lying localized sigma*(C-S) and sigma*(P-O) virtual MOs, we have concluded that P 3d AOs are not involved in the formation of the P-O bond. Moreover, the results support the mechanism of negative hyperconjugation, by showing that transitions toward sigma*(P-O) states occur at lower energies with respect to those toward it pi*(P-O) states.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2020
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-419645 (URN)10.1021/acs.jpcc.0c03973 (DOI)000550763500012 ()
Funder
Swedish Research Council, 20146463
Available from: 2020-09-22 Created: 2020-09-22 Last updated: 2020-09-22Bibliographically approved
Zhang, T., Brumboiu, I. E., Lanzilotto, V., Grazioli, C., Guarnaccio, A., Johansson, F., . . . Puglia, C. (2019). Electronic structure modifications induced by increased molecular complexity: from triphenylamine to m-MTDATA. Physical Chemistry, Chemical Physics - PCCP, 21(32), 17959-17970
Open this publication in new window or tab >>Electronic structure modifications induced by increased molecular complexity: from triphenylamine to m-MTDATA
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2019 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, no 32, p. 17959-17970Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-398845 (URN)10.1039/c9cp02423a (DOI)000481777100046 ()31384854 (PubMedID)
Funder
Swedish Research Council, VR 2014-6463Swedish Research Council, VR 2014-3776Carl Tryggers foundation Swedish National Infrastructure for Computing (SNIC)
Available from: 2019-12-19 Created: 2019-12-19 Last updated: 2019-12-19Bibliographically approved
Witkowski, N., Lüder, J., Bidermane, I., Farronato, M., Prevot, G., Bouvet, M., . . . Brena, B. (2019). Grafting, self-organization and reactivity of double-decker rare-earth phthalocyanine. Journal of Porphyrins and Phthalocyanines, 23(11-12), 1523-1534
Open this publication in new window or tab >>Grafting, self-organization and reactivity of double-decker rare-earth phthalocyanine
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2019 (English)In: Journal of Porphyrins and Phthalocyanines, ISSN 1088-4246, E-ISSN 1099-1409, Vol. 23, no 11-12, p. 1523-1534Article in journal (Refereed) Published
Abstract [en]

Unveiling the interplay of semiconducting organic molecules with their environment, such as inorganic materials or atmospheric gas, is the first step to designing hybrid devices with tailored optical, electronic or magnetic properties. The present article focuses on a double-decker lutetium phthalocyanine known as an intrinsic semiconducting molecule, holding a Lu ion in its center, sandwiched between two phthalocyanine rings. Carrying out experimental investigations by means of electron spectroscopies, X-ray diffraction and scanning probe microscopies together with advanced ab initio computations, allows us to unveil how this molecule interacts with weakly or highly reactive surfaces. Our studies reveal that a molecule-surface interaction is evidenced when molecules arc deposited on bare silicon or on gold surfaces together with a charge transferred from the substrate to the molecule, affecting to a higher extent the lower ring of the molecule. A new packing of the molecules on gold surfaces is proposed: an eclipse configuration in which molecules are flat and parallel to the surface, even for thick films of several hundreds of nanometers. Surprisingly, a robust tolerance of the double-decker phthalocyanine toward oxygen molecules is demonstrated, leading to weak chemisorption of oxygen below 100 K.

Place, publisher, year, edition, pages
WORLD SCI PUBL CO INC, 2019
Keywords
LuPc2, XPS, NEXAFS, GLXD, STM, DFT
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-406207 (URN)10.1142/S1088424619501736 (DOI)000508130500033 ()
Funder
Swedish Research CouncilSwedish National Infrastructure for Computing (SNIC)EU, FP7, Seventh Framework Programme, 321319EU, FP7, Seventh Framework Programme, 607232Knut and Alice Wallenberg Foundation
Available from: 2020-03-06 Created: 2020-03-06 Last updated: 2020-03-06Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6840-1570

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