Browsing by Author "Saavedra-Torres, Mario"

Now showing 1 - 7 of 7
  • No Thumbnail Available
    Item
    A new zero-dimensional (0D) hybrid bismuth (III) halide: Synthesis, crystal structure, thermal analysis, photophysical properties and DFT calculations
    (2024) Msaoura, Selma; Benito, Monica; Molins, Elies; Khirouni, Kamel; Zarate, Ximena; Saavedra-Torres, Mario; Schott, Eduardo; Houas, Ammar; Rayes, Ali
    Low-dimensional organic-inorganic hybrid Bi(III) halides, with organic N, O-heterocycles, are promising solid -state photoluminescent materials, but are underexplored. In this work, we present the synthesis and charac-terization of a novel bismuth (III) hybrid salt, namely (C8H12NO)(4)[Bi2Cl10] (referred as (1)). (1) was synthesized using a solvent-evaporation method and extensively characterized using various techniques. The crystal structure of (1) was determined to be zero-dimensional (0D). In this structure, the individual bioctahedral [Bi2Cl10](4-) dimers, which share edges, are completely isolated from each other. These dimers are separated by large 4-methoxybenzylammonium cations (C8H12NO)(+). The latter are crucial for the crystal structural stability by balancing [Bi2Cl10](4-) dimer charges and maintaining overall integrity. Solid-state diffuse reflectance UV-Vis spectrum demonstrates that (1) is a semiconductor with a band gap of 3.32 eV. Its photoluminescence spectrum exhibits intense blue emission when exposed to UV light, with CIE chromaticity coordinates of (0.22, 0.21). Theoretical calculations suggest that the emission with multiple centers originates both from a charge transition between (C8H12NO)(+) and Bi2Cl104- ions and from excited-state proton transfer (ESPT) processes related to fluo-rescence properties. These ESPT processes occur through C-H center dot center dot center dot pi and C-H center dot center dot center dot O intermolecular hydrogen bonding between the organic cations.
  • No Thumbnail Available
    Item
    Computational design and properties elucidation of new (FAPbI3)1,x- y(MAPbBr3)y(CsPbBr3)x photoactive systems for their application in perovskite solar cells
    (2023) Borges-Martinez, Merlys; Saavedra-Torres, Mario; Schott, Eduardo; Zarate, Ximena
    The stability and performance of perovskites (PKs) in PK solar cells are a research target, which has been addressed in this work. The theoretical design of new PKs was carried out, based on the different composition of Cs. Specifically, PKs of the type (FAPbI3)1_x-y(MAPbBr3)y(CsPbBr3)x (where MA= methylammonium and FA= formamidinium) with 0
  • No Thumbnail Available
    Item
    Furfural adsorption on V2O5 surface: A combined experimental-theoretical study
    (2024) Lizana, Ignacio; Schott, Eduardo; Saavedra-Torres, Mario; Hidalgo-Rosa, Yoan; Pecchi, Gina; Karelovic, Alejandro; Zarate, Ximena
    The adsorption of furfural on the V 2 O 5 surface was investigated using experimental and theoretical methods. In situ Diffuse Reflectance Infrared Fourier-Transform Spectroscopy results show the presence of physi- and chemisorption phenomena, where trans -furfural is mostly chemisorbed at the beginning of the adsorption process. These results are in agreement with theoretical DFT results, as the most thermodynamically favored configurations corresponds to the chemisorbed trans -furfural (T1) and cis -furfural (C1) with binding energies of -1.83 and -2.05 eV.
  • No Thumbnail Available
    Item
    Modification of a commercial activated carbon with nitrogen and boron: Hydrogen storage application
    (2023) Morande, Arturo; Lillo, Patricio; Blanco, Elodie; Pazo, Cesar; Belen Dongil, Ana; Zarate, Ximena; Saavedra-Torres, Mario; Schott, Eduardo; Canales, Roberto; Videla, Alvaro; Escalona, Nestor
    The present study evaluates the effect of heteroatom doping (N and B) and thermal treatment modification of activated carbon, in different sequences over hydrogen storage capacity. All the materials were characterized by N2-physisorption, XRD, TPD, and XPS. H2 adsorption was measured at-196 degrees C and correlated with physico-chemical properties, while a density-functional theory model was employed to analyze the hydrogen adsorp-tion. Results have shown that there is an effect of the modification order on the storage capacity, which was related to increments of the specific surface area or the nature of the functional groups. An optimum nitrogen doping temperature was detected at 500 degrees C and was associated with the presence of pyridone groups. This sample had the highest hydrogen capacity ca. 2.34 % at 0.93 bar. Such value was extrapolated to 7.86 wt% at 30 bar using the Dubinin-Astakhov adsorption model, making it a promising material for hydrogen storage.
  • No Thumbnail Available
    Item
    Quantum chemical elucidation of the luminescence mechanism in a europium(iii) co-doped UiO-66 chemosensor selective to mercury(ii)
    (2025) Hidalgo-Rosa, Yoan; Echevarría-Valdés, Yoslainy; Saavedra-Torres, Mario; Paez-Hernández, Dayán; Schott Verdugo, Eduardo Enrique; Zárate, Ximena
    Lanthanide(iii) ions can be incorporated into metal-organic frameworks (MOFs) to form Ln@MOFs through post-synthetic procedures. This makes the MOFs efficient luminescent chemical sensors for detecting trace amounts of heavy metals. In this report, a quantum chemical theoretical protocol has been carried out to elucidate the detection principle of the turn-off luminescence mechanism in a Eu@UiO-66(DPA)-type MOF selective to Hg2+ ions. UiO-66(DPA) is an iso-reticular MOF of UiO-66 constructed from the Zr6-cluster [Zr6(μ3-O)4(μ3-OH)4]12+ and the ligands 1,4-benzenedicarboxylate (BDC) and 2,6-pyridinedicarboxylate (DPA) as linkers. The sensitization and energy transfer (ET) in UiO-66(DPA) doped with Eu3+ were analyzed using multireference ab initio CASSCF/NEVPT2 methods and time-dependent density functional theory (TD-DFT). The cluster model used in the calculations comprises the Z6-cluster/BDC/DPA fragments with the DPA ligand coordinating to Eu3+ or Hg2+ ions. The proposed sensitization pathway involves intersystem crossing from S1(DPA) to T1(DPA), a plausible subsequent energy transfer from T1(DPA) to the 5D1 state of Eu3+, and then vibrational relaxation to the emissive 5D0 state. These results also suggest that the electronic states of the BDC ligand can be strengthened by the population of the T1 electronic states of the DPA antenna via ET. Periodic DFT calculations confirm the electronic state mixture of BDC and DPA linkers in the conduction bands, just above the electronic state of Eu3+ ions, which is in concordance with the proposed Eu3+ sensitization pathways. The assessed optical properties (absorption and emission) of Hg2+@UIO-66(DPA) explain the experimental behavior of this chemosensor when the Hg2+ ion replaces the Eu3+ ion and the luminescence diminishes.
  • No Thumbnail Available
    Item
    Quantum chemical elucidation of the luminescence mechanism in a europium(iii) co-doped UiO-66 chemosensor selective to mercury(ii)
    (2025) Hidalgo-Rosa, Yoan; Echevarría-Valdés, Yoslainy; Saavedra-Torres, Mario; Paez-Hernández, Dayán; Schott Verdugo, Eduardo Enrique; Zárate, Ximena
    Lanthanide(iii) ions can be incorporated into metal-organic frameworks (MOFs) to form Ln@MOFs through post-synthetic procedures. This makes the MOFs efficient luminescent chemical sensors for detecting trace amounts of heavy metals. In this report, a quantum chemical theoretical protocol has been carried out to elucidate the detection principle of the turn-off luminescence mechanism in a Eu@UiO-66(DPA)-type MOF selective to Hg2+ ions. UiO-66(DPA) is an iso-reticular MOF of UiO-66 constructed from the Zr6-cluster [Zr6(μ3-O)4(μ3-OH)4]12+ and the ligands 1,4-benzenedicarboxylate (BDC) and 2,6-pyridinedicarboxylate (DPA) as linkers. The sensitization and energy transfer (ET) in UiO-66(DPA) doped with Eu3+ were analyzed using multireference ab initio CASSCF/NEVPT2 methods and time-dependent density functional theory (TD-DFT). The cluster model used in the calculations comprises the Z6-cluster/BDC/DPA fragments with the DPA ligand coordinating to Eu3+ or Hg2+ ions. The proposed sensitization pathway involves intersystem crossing from S1(DPA) to T1(DPA), a plausible subsequent energy transfer from T1(DPA) to the 5D1 state of Eu3+, and then vibrational relaxation to the emissive 5D0 state. These results also suggest that the electronic states of the BDC ligand can be strengthened by the population of the T1 electronic states of the DPA antenna via ET. Periodic DFT calculations confirm the electronic state mixture of BDC and DPA linkers in the conduction bands, just above the electronic state of Eu3+ ions, which is in concordance with the proposed Eu3+ sensitization pathways. The assessed optical properties (absorption and emission) of Hg2+@UIO-66(DPA) explain the experimental behavior of this chemosensor when the Hg2+ ion replaces the Eu3+ ion and the luminescence diminishes.
  • No Thumbnail Available
    Item
    Rare-earth-based metal-organic frameworks with improved visible-light-harvesting properties: a quantum chemistry study
    (2023) Hidalgo-Rosa, Yoan; Saavedra-Torres, Mario; Koivisto, Bryan D.; Treto-Suarez, Manuel A.; Paez-Hernandez, Dayan; Zarate, Ximena; Schott, Eduardo
    This report proves that improving the visible-light-harvesting properties in rare-earth-based metal-organic frameworks (RE-MOFs) (labelled as RE-UiO-66, UiO = University of Oslo MOFs), with the aim of performing as potential visible-light-driven photocatalysts, is achievable. Thus, the design of MOFs with specific applications, especially those involving sunlight and material interactions, represents a growing field, which has been addressed in the herein work using quantum mechanical tools. We achieved to relate the light absorption properties with the structure in systems Y-UiO-66, Sc-UiO-66 and La-UiO-66, by evaluating the inclusion of well-known electron donor substituents in the structure of the 1,4-benzenedicarboxylate (BDC) linker (i.e. BDC-R, R: -CH3, -OH, -SH and -NH2). The electronic structure and optical properties of Y-UiO-66 were rigorously investigated using computational techniques combining molecular and periodic density functional theory (DFT) calculations. As a remarkable result, it was shown that including the groups -SH or -NH2 in the BDC linker, induced a shift in the absorption bands to the visible region (>= 400 nm). Hence, a group of new RE-MOFs materials with optimal structural and photocatalytic properties is proposed. This could encourage researchers to prepare these new materials to be tested in photocatalysis, such as cleaving the C-H bond, water splitting or photocatalytic degradation of organic contaminants.