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Brena, Barbara
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Publications (10 of 77) Show all publications
Brena, B. & Ouline, U. (2023). The International Science Programme 2001–2021: 20 Years of Continued Development. Publication for the ISP 60th Anniversary. Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>The International Science Programme 2001–2021: 20 Years of Continued Development. Publication for the ISP 60th Anniversary
2023 (English)Book (Other (popular science, discussion, etc.))
Abstract [en]

In 2021 the International Science Programme (ISP) at Uppsala University celebrated its 60th anniversary. In spite of the Covid-19 pandemic, ISP made its best effort to honor the occasion and organised virtual workshops, meetings, and webinars during the year. This book represents the conclusive item of the jubilee year. Here we want to present the work ISP has performed since the beginning of the new millennium, narrated directly by the voices of scientists from all over the world who are or were part of the ISP family. They can now tell the significance and the impact that ISP has had on their own careers, their institutions and their countries. The book contains also contributions by the ISP staff, describing the historical evolution of ISP during the last 20 years, including for example the investment in gender equality which has raised a large interest in the supported partners. 

ISP has a long story, starting in 1961 as the International Seminar for Research and Education in Physics, when fellows from 14 developing countries were invited to Sweden to spend one year performing research work. Today the ISP core programme, which has evolved into three different programmes in physics, chemistry and mathematics, is devoted to assisting and strengthening research capacity building in a number of low and lower-middle income countries in Africa, Asia and Latin America. ISP supports both research groups and international scientific networks, with scientists from different countries.

More recently, ISP has also been engaged as the Swedish coordinator of all Sida bilateral research programmes, as well as in other collaborations with for example Thailand International Cooperation Agency (TICA) and American Institute of Physics (AIP).

The final aim of the book is to express not only the hard work performed by ISP staff and all the partners in the supported research groups and institutions, but especially the success of the efforts and the great enthusiasm that has permeated the ISP work so far.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2023
Series
Skrifter rörande Uppsala universitet. C, Organisation och historia, ISSN 0502-7454 ; 125
Keywords
International Science Programme (ISP)
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-497080 (URN)978-91-513-1724-3 (ISBN)
Funder
Uppsala University
Available from: 2023-04-14 Created: 2023-02-23 Last updated: 2023-04-26
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
Brumboiu, I. E., Ericsson, L. K. E., Blazinic, V., Hansson, R., Opitz, A., Brena, B. & Moons, E. (2022). Photooxidation of PC60BM: new insights from spectroscopy. Physical Chemistry, Chemical Physics - PCCP, 24(42), 25753-25766
Open this publication in new window or tab >>Photooxidation of PC60BM: new insights from spectroscopy
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2022 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 24, no 42, p. 25753-25766Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2022
National Category
Physical Chemistry Theoretical Chemistry
Identifiers
urn:nbn:se:uu:diva-494527 (URN)10.1039/d2cp03514f (DOI)000855867000001 ()36128981 (PubMedID)
Funder
Swedish Research Council, 2018-07152Swedish Research Council, 2015-03778Swedish Research Council, 2014-03776Vinnova, 2018-04969Swedish Research Council Formas, 2019-02496Knut and Alice Wallenberg Foundation, KAW-2016.0059Knut and Alice Wallenberg Foundation, KAW-2013.0020Göran Gustafsson Foundation for Research in Natural Sciences and MedicineCarl Tryggers foundation German Research Foundation (DFG), 239543752
Available from: 2023-01-18 Created: 2023-01-18 Last updated: 2023-01-18Bibliographically approved
Gopakumar, G., Svensson, P., Grånäs, O., Brena, B., Schwob, L., Unger, I., . . . Lindblad, R. (2022). X-ray Induced Fragmentation of Protonated Cystine. Journal of Physical Chemistry A, 126(9), 1496-1503
Open this publication in new window or tab >>X-ray Induced Fragmentation of Protonated Cystine
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2022 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 126, no 9, p. 1496-1503Article in journal (Refereed) Published
Abstract [en]

We demonstrate site-specific X-ray induced fragmentation across the sulfur L-edge of protonated cystine, the dimer of the amino acid cysteine. Ion yield NEXAFS were performed in the gas phase using electrospray ionization (ESI) in combination with an ion trap. The interpretation of the sulfur Ledge NEXAFS spectrum is supported by Restricted Open-Shell Configuration Interaction (ROCIS) calculations. The fragmentation pathway of triply charged cystine ions was modeled by Molecular Dynamics (MD) simulations. We have deduced a possible pathway of fragmentation upon excitation and ionization of S 2p electrons. The disulfide bridge breaks for resonant excitation at lower photon energies but remains intact upon higher energy resonant excitation and upon ionization of S 2p. The larger fragments initially formed subsequently break into smaller fragments.

Place, publisher, year, edition, pages
American Chemical Society (ACS)American Chemical Society (ACS), 2022
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-470959 (URN)10.1021/acs.jpca.1c10158 (DOI)000768687200004 ()35213156 (PubMedID)
Funder
Swedish Research Council, 2018-00740Swedish Research Council, 637-2014-6929Swedish Research Council, VR 2017-04162EU, Horizon 2020, 847693
Available from: 2022-04-01 Created: 2022-04-01 Last updated: 2024-01-15Bibliographically approved
Vrube, I. I., Pervishko, A. A., Herper, H. C., Brena, B., Eriksson, O. & Yudin, D. (2020). An ab initio perspective on scanning tunneling microscopy measurements of the tunable Kondo resonance of the TbPc2 molecule on a gold substrate. Physical Review B, 101(12), Article ID 125106.
Open this publication in new window or tab >>An ab initio perspective on scanning tunneling microscopy measurements of the tunable Kondo resonance of the TbPc2 molecule on a gold substrate
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2020 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 101, no 12, article id 125106Article in journal (Refereed) Published
Abstract [en]

With recent advances in the areas of nanostructure fabrication and molecular spintronics the idea of using single molecule magnets as building blocks for the next generation electronic devices becomes viable. A particular example represents a metal-organic complex in which organic ligands surround a rare-earth element or transition metal. Recently, it was explicitly shown that the relative position of the ligands with respect to each other can be reversibly changed by the external voltage without any need of the chemical modification of the sample. This opens a way of the electrical tuning of the Kondo effect in such metal-organic complexes. In this work, we present a detailed and systematic analysis of this effect in TbPc2 from an ab initio perspective and compare the obtained results with the existing experimental data.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-408102 (URN)10.1103/PhysRevB.101.125106 (DOI)000518534400004 ()
Funder
Swedish Research Council, 2018-04383Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research StandUpeSSENCE - An eScience Collaboration
Available from: 2020-04-06 Created: 2020-04-06 Last updated: 2020-04-06Bibliographically approved
Brena, B., Sanyal, B. & Herper, H. C. (2020). Chemical Switching of the Magnetic Coupling in a MnPc Dimer by Means of Chemisorption and Axial Ligands. The Journal of Physical Chemistry C, 124(49), 27185-27193
Open this publication in new window or tab >>Chemical Switching of the Magnetic Coupling in a MnPc Dimer by Means of Chemisorption and Axial Ligands
2020 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 49, p. 27185-27193Article in journal (Refereed) Published
Abstract [en]

We present an ab initio density functional theory study of the magnetic properties of manganese phthalocyanine dimers, where we focus on the magnetic coupling between the Mn centers and on how it is affected by external factors like chemisorption or atomic axial ligands. We have studied several different configurations for the gas phase dimers, which resulted in ferromagnetic couplings of different magnitudes. For the bare dimer we find a significant ferromagnetic coupling between the Mn centers, which decreases by about 20% when a H atom is adsorbed on one of the Mn atoms and is reduced to about 7% when a Cl atom is adsorbed. The magnetic coupling is almost fully quenched when the dimer, bare or with the H ligand, is deposited on the ferromagnetic substrate Co(001). Our calculations indicate that the coupling between the two Mn atoms principally occurs via a superexchange interaction along two possible paths within a Mn-N-Mn-N four-atom loop. When these electrons get involved in chemical bonding outside the dimer itself, an appreciable alteration of the overlap between Mn and N molecular orbitals along the loop occurs, and consequently, the magnetic interaction between the Mn centers varies. We show that this is reflected by the electronic structure of the dimer in various configurations and is also visible in the structure of the atomic loop. The chemical tuning of the magnetic coupling is highly relevant for the design of nanodevices like molecular spin valves, where the molecules need to be anchored to a support.

Place, publisher, year, edition, pages
WASHINGTON DC USA: American Chemical Society (ACS), 2020
Keywords
ELECTRONIC-STRUCTURE, SPIN-INJECTION, PHTHALOCYANINE, MAGNETORESISTANCE
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-433365 (URN)10.1021/acs.jpcc.0c08448 (DOI)000599610500070 ()
Funder
Swedish Research CouncilCarl Tryggers foundation
Available from: 2021-02-03 Created: 2021-02-03 Last updated: 2021-02-24Bibliographically approved
Silva, J. L., Brena, B. & Araujo, C. M. (2020). g-C3N4/WTe2 Hybrid Electrocatalyst for Efficient Hydrogen Evolution Reaction. The Journal of Physical Chemistry C, 124(16), 8726-8735
Open this publication in new window or tab >>g-C3N4/WTe2 Hybrid Electrocatalyst for Efficient Hydrogen Evolution Reaction
2020 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 16, p. 8726-8735Article in journal (Refereed) Published
Abstract [en]

Recent experiments have highlighted the efficiency of nonprecious metal-based hybrid structures, such as g-C3N4/MoS2 and g-C3N4/graphene for hydrogen evolution reaction (HER). This work focuses on the interface effects of such hybrid heterostructures that could lead to the enhanced catalytic activity of g-C3N4. We have concentrated on the hybrid electrocatalysts with the architecture g-C3N4/X (X = WTe2, MoS2, and graphene), where the interface plays an important role in the overall HER. These promising candidates have been assessed using three main factors extracted from density functional theory calculations, namely: (i) the free energy of hydrogen adsorption on the catalytic site ΔGH, (ii) Schottky barrier potentials, and (iii) induced charge polarization across the interface. We have found that particularly g-C3N4/WTe2 displays a suitable combination of the investigated properties standing out as a potential electrocatalyst for efficient hydrogen evolution reaction. Furthermore, the electronic structure fingerprints controlling the HER thermodynamics have been investigated. In particular, the N–H bonds have been found to display strong s–p hybridization and, additionally, ΔGH decreases as the center of N p-band approaches the Fermi energy. This is also a relevant result in understanding HER mechanisms of organic compounds.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2020
Keywords
Energy, Electrocatalysts, Hydrogen Evolution Reaction, g-C3N4/WTe2
National Category
Physical Chemistry
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-408688 (URN)10.1021/acs.jpcc.9b11982 (DOI)000529225800029 ()
Funder
StandUpSwedish Research CouncilCarl Tryggers foundation eSSENCE - An eScience CollaborationSwedish National Infrastructure for Computing (SNIC)
Available from: 2020-04-11 Created: 2020-04-11 Last updated: 2020-10-22Bibliographically 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
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