Persona:
Gavira Vallejo, José María

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0000-0002-6037-5731
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Gavira Vallejo
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José María
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2020 - 20212
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Fecha de finalización: 2021 × Fecha de inicio: 2020 ×

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Mostrando 1 - 2 de 2
  • Miniatura
    Publicación
    Impact of Small Adsorbates in the Vibrational Spectra of Mg- and Zn-MOF-74 Revealed by First-Principles Calculations
    (American Chemical Society, 2020) Romero Muñiz, Carlos; Merkling, Patrick; Calero, Sofía; Gavira Vallejo, José María
    In this work, we analyze the influence of small adsorbates on the vibrational spectra of Mg- and Zn-metal–organic framework MOF-74 by means of first-principles calculations. In particular, we consider the adsorption of four representative species of different interaction strengths: Ar, CO2, H2O, and NH3. Apart from a comprehensive characterization of the structural and energetic aspects of empty and loaded MOFs, we use a fully quantum ab initio approach to evaluate the Raman and IR activities of the normal modes, leading to the construction of the whole vibrational spectra. Under this approach, not only are we able to proceed with the complete assignment of the spectra in terms of the usual internal coordinates but also we can discern the most relevant vibrational fingerprints of the adsorbates and their impact on the whole MOF spectra. On the one hand, some of the typical vibrational modes of the small molecules are slightly shifted but still visible when adsorbed on the MOFs, especially those appearing at high wavenumbers where the empty MOFs lack IR/Raman signals. On the other hand, some bands arising from the organic ligands are affected by the presence of the absorbates, displaying non-negligible frequency shifts, in agreement with recent experiments. We find a strong correlation between all of these frequency shifts and the interaction strength of the adsorbate with the hosting framework. The findings presented in this work expand the capabilities of vibrational spectroscopy techniques to analyze porous materials and can be useful for the design of sensors and new devices based on MOF technology.
  • No hay miniatura disponible
    Publicación
    Rock Art
    (The Royal Society of Chemistry, 2021-06-04) Hernanz, Antonio; Gavira Vallejo, José María
    An overview of representative studies on rock art paintings applying physicochemical techniques to investigate their composition is presented. Advantages and limitations of the different techniques, protocols and recommendations for sampling and proposals to deal with difficulties are discussed. Portable instrumentation and non-destructive multi-technique methodology are highly advisable. Contamination and the presence of non-pictorial materials must always be taken into account because rock art is an open-air scenario. Accretions, alterations, deterioration and possible remedies are considered. The results obtained are very useful for archaeologists and conservators. The use of new techniques and instrumentation augurs a promising future in this field.