Federico Loi

@cas.cz

Department of Nanocatalysis
Czech Academy of Sciences, J. Heyrovský Institute of Physical Chemistry

Federico Loi


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https://researchid.co/fed.loi95

RESEARCH, TEACHING, or OTHER INTERESTS

Physical and Theoretical Chemistry, Condensed Matter Physics, Spectroscopy, Surfaces and Interfaces
13

Scopus Publications

100

Scholar Citations

6

Scholar h-index

5

Scholar i10-index

Scopus Publications

  • Unraveling Nanoarchitectonics-Driven Metal–Support Interactions and Size Effects Governing CO Oxidation Activity of Size-Selected Pt Clusters on TiO2 and SnO2 Supports
    Stanislav Valtera, Mykhailo Vaidulych, Federico Loi, Kevin Oldenburg, Ingo Barke, Magda Zlámalová, Hana Tarábková, Ladislav Kavan, Paulo Perez, Scott L. Anderson, Stephan Bartling, Štefan Vajda
    Small Structures, 2026
    Supported size‐selected clusters represent a unique class of materials offering high tunability of the chemical properties with high efficiency of material utilization. Herein, Pt n ( n = 13, 40) clusters supported on two technologically relevant supports, TiO 2 and SnO 2 , were studied for CO oxidation under atmospheric pressure conditions. The catalytic activity was found to be directly influenced by both cluster size and support material, with Pt 40 /TiO 2 showing the highest activity. In situ near‐ambient‐pressure X‐ray photoelectron spectroscopy (NAP‐XPS) revealed that, in general, a higher metallicity of the clusters promotes catalytic activity. However, the final oxidation state of Pt does not solely determine the activity, which rather evolves from a combination of factors, including strong metal–support interactions (SMSI) and size‐dependent effects. Ex situ XPS and ion scattering spectroscopy (ISS) measurements on used catalysts highlighted the role of SMSI, particularly in the case of SnO 2 , where SnO 2 overgrowth was suggested to enhance chemical stability and sintering resistance, as witnessed by stability tests conducted using NAP‐XPS. However, this overgrowth also limited access to active Pt sites, reducing CO adsorption and O 2 activation, ultimately leading to lower catalytic activity of Pt n /SnO 2 compared to TiO 2 ‐supported catalysts.
  • Limitations in Determining Oxidation States in Condensed Matter at the Subnanometric Scale
    Deborah Perco, Monica Pozzo, Andrea Berti, Federico Loi, Paolo Lacovig, Silvano Lizzit, Aras Kartouzian, Ueli Heiz, Dario Alfè, Alessandro Baraldi
    Journal of the American Chemical Society, 2025
    The oxidation state is a fundamental chemical concept commonly employed to rationalize, classify, and predict the chemical reactivity of a variety of compounds. Understanding and defining the elemental oxidation state of solid materials at the atomic level becomes increasingly complex as their physical dimensions are reduced from tens of nanometers─where properties are still dominated by bulk or outer atomic crystal plane characteristics, to the subnanometric limit. In this work, we highlight the significant limitations in determining even a basic quantity, such as the oxidation state, when oxidized low-nuclearity mass-selected clusters are investigated by means of X-ray photoelectron spectroscopy (XPS), widely recognized as the elective approach to resolve different oxidations states. The lack of crystalline order in these nanoclusters, unlike that in periodic bulk systems and in solid surfaces, leads to a broad distribution of measured core levels, as shown in the case study of W nanoclusters. These cannot be unambiguously assigned to a valence state based solely on the knowledge of bulk matter behavior but need close comparison with specific theoretical modeling. Our results emphasize the substantial challenges inherent in understanding the unique properties of nanoscale materials, particularly in making a rigorous and quantitative determination of a fundamental property that takes a relevant role in many chemical processes, and represent crucial knowledge for advancing technologies that rely on the miniaturization of matter in various processes.
  • The Interaction of Sub-Monolayer Ta Adatoms and Clusters with Oxygen at the Pt(111) Interface
    Kevin Bertrang, Tobias Hinke, Sebastian Kaiser, Matthias Knechtges, Federico Loi, Paolo Lacovig, Mirali Jahangirzadeh Varjovi, Friedrich Esch, Alessandro Baraldi, Sergio Tosoni, Aras Kartouzian, Ueli Heiz
    Journal of Physical Chemistry C, 2025
    High Resolution Image Download MS PowerPoint Slide The interaction of submonolayer quantities of size-selected and soft-landed Ta n ( n = 4, 5, 6, 8, 13) clusters with Pt(111) is investigated employing high-resolution X-ray photoelectron spectroscopy (HR-XPS), scanning tunneling microscopy (STM), and density functional theory (DFT) simulations. The deposited clusters are monodispersed and stable under ultrahigh vacuum (UHV) conditions at 40 K. They display a size-specific trend in photoemission spectra, which is reasoned in terms of the distinct in plane coordination of Ta atoms in the clusters. Both the Ta coordination number and distance from the Pt surface influence its Bader charge and, accordingly, the oxidation state of the atoms in the Ta cluster. They already fragment in the presence of low amounts of oxygen and form a common oxidation product observed for all cluster sizes. Based on our observations, we propose an oxidation mechanism in the example of Ta 8 clusters, which is closely comparable to the one discussed in gas-phase studies on the oxidation of cationic Ta clusters of similar size. Concomitant to oxidation-induced fragmentation, the agglomeration into Ta-oxide islands with Ta in an oxidation state of +5 is observed. However, the strong interaction with the Pt surface leads to Ta 4f orbital photoemission features that differ from those commonly observed for Ta 2 O 5 . Computational insights concerning the structure of the Ta-oxide islands indicate flat agglomerates that agree with STM observations. They suggest distinct Ta 4f photoemission contributions from interfacial and surface-related Ta configurations. The respective HR-XPS spectra display specific core-level shifts as a function of bonding configuration and vicinity to the Pt surface. By annealing at 900 K in UHV, we observe oxygen loss and concomitant intermixing of Ta atoms with the Pt subsurface lattice to which results in the formation of a Ta–Pt alloy. These species, Ta-oxide islands, and Ta–Pt alloy, can reversibly interconvert by oxidative surface segregation and reductive intermixing.
  • Unraveling the interaction of Ta atoms with Pt(111)
    Kevin Bertrang, Tobias Hinke, Sebastian Kaiser, Matthias Knechtges, Federico Loi, Luca Sbuelz, Paolo Lacovig, Luca Bignardi, Friedrich Esch, Alessandro Baraldi, Sergio Tosoni, Aras Kartouzian, Ulrich Heiz
    Surfaces and Interfaces, 2025
    This study investigates the interaction between Ta and Pt by following the evolution of Ta atoms upon their evaporation in sub-monolayer quantities (∼2 % ML) on a Pt(111) single crystal in vacuo at 40 K. Adsorption and bonding configurations are studied employing high-resolution X-ray photoelectron spectroscopy (HR-XPS). This is combined with density functional theory (DFT) calculations and reference measurements on atomically precise supported clusters that allow disentangling the contributions of distinct surface species to the complex Ta 4f spectra. The transient Ta atom mobility upon evaporation allows - besides atomic adsorption on the terraces - for atom migration to the Pt(111) step edges and the formation of small monolayer ad-islands even at 40 K. Interestingly, the Ta species bonded with Pt can be easily oxidized using a photon-induced O 2 dissociation process, showing the extremely high oxygen affinity of Ta even under the applied ultra-high vacuum (UHV) conditions. Annealing to 900 K leads to the sub-surface migration of Ta and the formation of a sub-surface alloy with Pt. Here, the extremely sharp Ta core-level components are observed at binding energies corresponding to a nominal oxidation state of +2, as confirmed by calculations of the projected density of states (pDOS). This sub-surface alloy is resistant to facile oxidation by atomic oxygen, unlike the Ta surface species that remain susceptible to oxidation. The oxide species and the sub-surface alloy are, however, perfectly interconvertible upon annealing to 900 K in vacuum, respectively in an oxygen environment, and thereby reveal an intriguing interplay between reductive intermixing of Ta and Pt and oxidative Ta segregation.
  • Unveiling Inequality of Atoms in Ultrasmall Pt Clusters: Oxygen Adsorption Limited to the Uppermost Atomic Layer
    Federico Loi, Luca Bignardi, Deborah Perco, Andrea Berti, Paolo Lacovig, Silvano Lizzit, Aras Kartouzian, Ulrich Heiz, Dario Alfè, Alessandro Baraldi
    Small Structures, 2024
    The concept of preferential atomic and molecular adsorption site is of primary relevance in heterogeneous catalysis. In the case of ultrasmall size‐selected clusters, distinguishing the role played by each atom in a reaction is extremely challenging due to their reduced size and peculiar structures. Herein, it is revealed how the inequivalent atoms composing graphene‐supported Pt12 and Pt13 clusters behave differently in the photoinduced dissociation of O2, with only those in the uppermost layer of the clusters being involved in the reaction. In this process, the epitaxial graphene support plays a fundamental active role: its corrugation and pinning induced by the presence of the clusters are crucial for defining the preferential adsorption site on the Pt atomic agglomerates, facilitating the lateral diffusion of physisorbed oxygen at a distance that induces its selective adsorption in the topmost layer of the clusters, and inducing an inhomogeneous charge distribution within the clusters which directly affects the O2 adsorption. The inhomogeneous oxidation of the clusters is resolved by means of synchrotron‐based X‐ray photoelectron spectroscopy and supported by ab initio density functional theory calculations. The possibility to identify the active sites on Pt clusters induced by cluster–support interactions has the potential to enhance the experimentally supported design of nanocatalysts.
  • Information hidden behind a single peak in the C 1s spectrum of graphene on Ir(111)
    Cecilia Botta, Federico Loi, Dario Alfè, Alessandro Baraldi
    Applied Surface Science, 2024
  • The highest oxidation state observed in graphene-supported sub-nanometer iron oxide clusters
    Deborah Perco, Federico Loi, Luca Bignardi, Luca Sbuelz, Paolo Lacovig, Ezequiel Tosi, Silvano Lizzit, Aras Kartouzian, Ueli Heiz, Alessandro Baraldi
    Communications Chemistry, 2023
    Size-selected iron oxide nanoclusters are outstanding candidates for technological-oriented applications due to their high efficiency-to-cost ratio. However, despite many theoretical studies, experimental works on their oxidation mechanism are still limited to gas-phase clusters. Herein we investigate the oxidation of graphene-supported size-selected Fen clusters by means of high-resolution X-ray Photoelectron Spectroscopy. We show a dependency of the core electron Fe 2p3/2 binding energy of metallic and oxidized clusters on the cluster size. Binding energies are also linked to chemical reactivity through the asymmetry parameter which is related to electron density of states at the Fermi energy. Upon oxidation, iron atoms in clusters reach the oxidation state Fe(II) and the absence of other oxidation states indicates a Fe-to-O ratio close to 1:1, in agreement with previous theoretical calculations and gas-phase experiments. Such knowledge can provide a basis for a better understanding of the behavior of iron oxide nanoclusters as supported catalysts.
  • Breakdown of the correlation between oxidation states and core electron binding energies at the sub-nanoscale
    Federico Loi, Monica Pozzo, Luca Sbuelz, Luca Bignardi, Paolo Lacovig, Ezequiel Tosi, Silvano Lizzit, Aras Kartouzian, Ulrich Heiz, Rosanna Larciprete, Dario Alf è, Alessandro Baraldi
    Applied Surface Science, 2023
    X-ray photoelectron spectroscopy is a powerful analytical tool to fingerprint the atomic oxidation state. However, the well-established trend that is found for bulk, ultra-thin films and surface oxides, which is usually characterized by an incremental binding energy shift upon increasing oxidation state, may not apply at the sub-nanoscale where reduced dimensionality and quantum size effects play a relevant role. Here we investigate through a combined experimental and theoretical approach the oxidation of size-selected Ag7 and Ag11 clusters supported on graphene, revealing an anomalous Ag 3d5/2 core level shift trend upon increasing O coverage. We show that the negative core level shift trend typical of Ag reverts back in the case of the highest Ag(III) oxidation state, an effect that is due to the peculiar electronic structure of Ag nano-oxides. Our results highlight the great care needed to extend at the zero-dimensional scale the knowledge acquired for the spectral interpretation of 3D and 2D materials.
  • Oxidation at the sub-nanoscale: oxygen adsorption on graphene-supported size-selected Ag clusters
    Federico Loi, Monica Pozzo, Luca Sbuelz, Luca Bignardi, Paolo Lacovig, Ezequiel Tosi, Silvano Lizzit, Aras Kartouzian, Ueli Heiz, Dario Alfè, Alessandro Baraldi
    Journal of Materials Chemistry A, 2022
    Oxidizing size-selected Ag11 clusters on graphene reveals the formation of a bulk-like structure already for few-atom aggregates. The appearance of a bulk AgO crystal structure differs from that observed for metallic clusters of similar size.
  • Atomic Undercoordination in Ag Islands on Ru(0001) Grown via Size-Selected Cluster Deposition: An Experimental and Theoretical High-Resolution Core-Level Photoemission Study
    Luca Sbuelz, Federico Loi, Monica Pozzo, Luca Bignardi, Eugenio Nicolini, Paolo Lacovig, Ezequiel Tosi, Silvano Lizzit, Aras Kartouzian, Ueli Heiz, Dario Alfé, Alessandro Baraldi
    Journal of Physical Chemistry C, 2021
    The possibility of depositing precisely mass-selected Ag clusters (Ag1, Ag3, and Ag7) on Ru(0001) was instrumental in determining the importance of the in-plane coordination number (CN) and allowed us to establish a linear dependence of the Ag 3d5/2 core-level shift on CN. The fast cluster surface diffusion at room temperature, caused by the low interaction between silver and ruthenium, leads to the formation of islands with a low degree of ordering, as evidenced by the high density of low-coordinated atomic configurations, in particular CN = 4 and 5. On the contrary, islands formed upon Ag7 deposition show a higher density of atoms with CN = 6, thus indicating the formation of islands with a close-packed atomic arrangement. This combined experimental and theoretical approach, when applied to clusters of different elements, offers the perspective to reveal nonequivalent local configurations in two-dimensional (2D) materials grown using different building blocks, with potential implications in understanding electronic and reactivity properties at the atomic level.
  • Growth Mechanism and Thermal Stability of a MoS2-Graphene Interface: A High-Resolution Core-Level Photoelectron Spectroscopy Study
    Federico Loi, Luca Sbuelz, Paolo Lacovig, Daniel Lizzit, Luca Bignardi, Silvano Lizzit, Alessandro Baraldi
    Journal of Physical Chemistry C, 2020
  • MOKE setup exploiting a nematic liquid crystal modulator
    R. Ciprian, F. Loi, E. Busetto, V. Bonanni, B. Casarin, A. Caretta, M. Solzi, M. Malvestuto
    Review of Scientific Instruments, 2018
  • Giant magneto-electric coupling in 100 nm thick Co capped by ZnO nanorods
    Giovanni Vinai, Barbara Ressel, Piero Torelli, Federico Loi, Benoit Gobaut, Regina Ciancio, Barbara Casarin, Antonio Caretta, Luca Capasso, Fulvio Parmigiani, Francesco Cugini, Massimo Solzi, Marco Malvestuto, Roberta Ciprian
    Nanoscale, 2018

RECENT SCHOLAR PUBLICATIONS

  • Revisiting the Hydrogen Oxidation Reaction on Gold: The Role of Trace Impurities
    JM Hermann, MM Elnagar, F Loi, LA Kibler, Š Vajda, T Jacob
    2026.0
  • Unraveling Nanoarchitectonics‐Driven Metal–Support Interactions and Size Effects Governing CO Oxidation Activity of Size‐Selected Pt Clusters on TiO2 and SnO2 Supports
    S Valtera, M Vaidulych, F Loi, K Oldenburg, I Barke, M Zlámalová, ...
    Small Structures 7 (1), e202500702 , 2026
    2026.0
  • Limitations in determining oxidation states in condensed matter at the subnanometric scale
    D Perco, M Pozzo, A Berti, F Loi, P Lacovig, S Lizzit, A Kartouzian, U Heiz, ...
    Journal of the American Chemical Society 147 (25), 21501-21511 , 2025
    2025.0
    Citations: 7
  • The Interaction of Sub-Monolayer Ta Adatoms and Clusters with Oxygen at the Pt (111) Interface
    K Bertrang, T Hinke, S Kaiser, M Knechtges, F Loi, P Lacovig, ...
    The Journal of Physical Chemistry C 129 (13), 6511-6523 , 2025
    2025.0
    Citations: 1
  • Unraveling the interaction of Ta atoms with Pt (111)
    K Bertrang, T Hinke, S Kaiser, M Knechtges, F Loi, L Sbuelz, P Lacovig, ...
    Surfaces and Interfaces 56, 105640 , 2025
    2025.0
    Citations: 2
  • Unveiling Inequality of Atoms in Ultrasmall Pt Clusters: Oxygen Adsorption Limited to the Uppermost Atomic Layer
    F Loi, L Bignardi, D Perco, A Berti, P Lacovig, S Lizzit, A Kartouzian, ...
    Small Structures 5 (11), 2400250 , 2024
    2024.0
    Citations: 5
  • Information hidden behind a single peak in the C 1s spectrum of graphene on Ir (111)
    C Botta, F Loi, D Alfe, A Baraldi
    Applied Surface Science 646, 158913 , 2024
    2024.0
    Citations: 3
  • Oxidation of Transition and Noble Metal Size-Selected Clusters Supported on Epitaxial Graphene
    F Loi
    Università degli Studi di Trieste , 2023
    2023.0
  • Breakdown of the correlation between oxidation states and core electron binding energies at the sub-nanoscale
    F Loi, M Pozzo, L Sbuelz, L Bignardi, P Lacovig, E Tosi, S Lizzit, ...
    Applied Surface Science 619, 156755 , 2023
    2023.0
    Citations: 17
  • The highest oxidation state observed in graphene-supported sub-nanometer iron oxide clusters
    D Perco, F Loi, L Bignardi, L Sbuelz, P Lacovig, E Tosi, S Lizzit, ...
    Communications Chemistry 6 (1), 61 , 2023
    2023.0
    Citations: 18
  • Oxidation at the sub-nanoscale: oxygen adsorption on graphene-supported size-selected Ag clusters
    F Loi, M Pozzo, L Sbuelz, L Bignardi, P Lacovig, E Tosi, S Lizzit, ...
    Journal of Materials Chemistry A 10 (27), 14594-14603 , 2022
    2022.0
    Citations: 12
  • Atomic undercoordination in Ag islands on Ru (0001) grown via size-selected cluster deposition: an experimental and theoretical high-resolution core-level photoemission study
    L Sbuelz, F Loi, M Pozzo, L Bignardi, E Nicolini, P Lacovig, E Tosi, S Lizzit, ...
    The Journal of Physical Chemistry C 125 (17), 9556-9563 , 2021
    2021.0
    Citations: 6
  • Growth Mechanism and Thermal Stability of a MoS 2 –Graphene Interface: A High-Resolution Core-Level Photoelectron Spectroscopy Study
    F Loi, L Sbuelz, P Lacovig, D Lizzit, L Bignardi, S Lizzit, A Baraldi
    The Journal of Physical Chemistry C 124 (38), 20889-20897 , 2020
    2020.0
    Citations: 12
  • MOKE setup exploiting a nematic liquid crystal modulator
    R Ciprian, F Loi, E Busetto, V Bonanni, B Casarin, A Caretta, M Solzi, ...
    Review of Scientific Instruments 89 (10) , 2018
    2018.0
    Citations: 4
  • Giant magneto–electric coupling in 100 nm thick Co capped by ZnO nanorods
    G Vinai, B Ressel, P Torelli, F Loi, B Gobaut, R Ciancio, B Casarin, ...
    Nanoscale 10 (3), 1326-1336 , 2018
    2018.0
    Citations: 13
  • Information Hidden Behind a Single Peak in the C1s Spectrum of Graphene on Ir (111)
    A BARALDI, C Botta, F Loi, D Alfè
    Available at SSRN 4576263 , 0

MOST CITED SCHOLAR PUBLICATIONS

  • The highest oxidation state observed in graphene-supported sub-nanometer iron oxide clusters
    D Perco, F Loi, L Bignardi, L Sbuelz, P Lacovig, E Tosi, S Lizzit, ...
    Communications Chemistry 6 (1), 61 , 2023
    2023.0
    Citations: 18
  • Breakdown of the correlation between oxidation states and core electron binding energies at the sub-nanoscale
    F Loi, M Pozzo, L Sbuelz, L Bignardi, P Lacovig, E Tosi, S Lizzit, ...
    Applied Surface Science 619, 156755 , 2023
    2023.0
    Citations: 17
  • Giant magneto–electric coupling in 100 nm thick Co capped by ZnO nanorods
    G Vinai, B Ressel, P Torelli, F Loi, B Gobaut, R Ciancio, B Casarin, ...
    Nanoscale 10 (3), 1326-1336 , 2018
    2018.0
    Citations: 13
  • Oxidation at the sub-nanoscale: oxygen adsorption on graphene-supported size-selected Ag clusters
    F Loi, M Pozzo, L Sbuelz, L Bignardi, P Lacovig, E Tosi, S Lizzit, ...
    Journal of Materials Chemistry A 10 (27), 14594-14603 , 2022
    2022.0
    Citations: 12
  • Growth Mechanism and Thermal Stability of a MoS 2 –Graphene Interface: A High-Resolution Core-Level Photoelectron Spectroscopy Study
    F Loi, L Sbuelz, P Lacovig, D Lizzit, L Bignardi, S Lizzit, A Baraldi
    The Journal of Physical Chemistry C 124 (38), 20889-20897 , 2020
    2020.0
    Citations: 12
  • Limitations in determining oxidation states in condensed matter at the subnanometric scale
    D Perco, M Pozzo, A Berti, F Loi, P Lacovig, S Lizzit, A Kartouzian, U Heiz, ...
    Journal of the American Chemical Society 147 (25), 21501-21511 , 2025
    2025.0
    Citations: 7
  • Atomic undercoordination in Ag islands on Ru (0001) grown via size-selected cluster deposition: an experimental and theoretical high-resolution core-level photoemission study
    L Sbuelz, F Loi, M Pozzo, L Bignardi, E Nicolini, P Lacovig, E Tosi, S Lizzit, ...
    The Journal of Physical Chemistry C 125 (17), 9556-9563 , 2021
    2021.0
    Citations: 6
  • Unveiling Inequality of Atoms in Ultrasmall Pt Clusters: Oxygen Adsorption Limited to the Uppermost Atomic Layer
    F Loi, L Bignardi, D Perco, A Berti, P Lacovig, S Lizzit, A Kartouzian, ...
    Small Structures 5 (11), 2400250 , 2024
    2024.0
    Citations: 5
  • MOKE setup exploiting a nematic liquid crystal modulator
    R Ciprian, F Loi, E Busetto, V Bonanni, B Casarin, A Caretta, M Solzi, ...
    Review of Scientific Instruments 89 (10) , 2018
    2018.0
    Citations: 4
  • Information hidden behind a single peak in the C 1s spectrum of graphene on Ir (111)
    C Botta, F Loi, D Alfe, A Baraldi
    Applied Surface Science 646, 158913 , 2024
    2024.0
    Citations: 3
  • Unraveling the interaction of Ta atoms with Pt (111)
    K Bertrang, T Hinke, S Kaiser, M Knechtges, F Loi, L Sbuelz, P Lacovig, ...
    Surfaces and Interfaces 56, 105640 , 2025
    2025.0
    Citations: 2
  • The Interaction of Sub-Monolayer Ta Adatoms and Clusters with Oxygen at the Pt (111) Interface
    K Bertrang, T Hinke, S Kaiser, M Knechtges, F Loi, P Lacovig, ...
    The Journal of Physical Chemistry C 129 (13), 6511-6523 , 2025
    2025.0
    Citations: 1
  • Revisiting the Hydrogen Oxidation Reaction on Gold: The Role of Trace Impurities
    JM Hermann, MM Elnagar, F Loi, LA Kibler, Š Vajda, T Jacob
    2026.0
  • Unraveling Nanoarchitectonics‐Driven Metal–Support Interactions and Size Effects Governing CO Oxidation Activity of Size‐Selected Pt Clusters on TiO2 and SnO2 Supports
    S Valtera, M Vaidulych, F Loi, K Oldenburg, I Barke, M Zlámalová, ...
    Small Structures 7 (1), e202500702 , 2026
    2026.0
  • Oxidation of Transition and Noble Metal Size-Selected Clusters Supported on Epitaxial Graphene
    F Loi
    Università degli Studi di Trieste , 2023
    2023.0
  • Information Hidden Behind a Single Peak in the C1s Spectrum of Graphene on Ir (111)
    A BARALDI, C Botta, F Loi, D Alfè
    Available at SSRN 4576263 , 0