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Oxy-fluorides

Oxy-fluorides

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Bactericidal materials for healthcare

Biocidal activity of inorganic compounds can be enhanced or generated through selected partial cationic substitution or/and nanostructuring of particles. Several synthetic routes are used to prepare nanometer and micrometer sized particles of the targeted compositions. The stability of those particles in liquid and air is also thoroughly studied since it determines both their activity and use over time.

  Researchers

  • Gwenaël Corbel
  • Abdelhadi Kassiba
  • Amandine Guiet
  • Monique Body
  • Christophe Legein

Structural characterization by solid state NMR

In this research focus, high-resolution solid state nuclear magnetic resonance (NMR) spectroscopy is used to investigate structure, disorder and dynamics in materials. Current areas of interest mainly include fluoride solid electrolytes, hybrid materials and anode materials for batteries. As an example regarding the latter, the various environments of fluorine atoms have been identified in pristine as well as in lithiated, magnesiated and aluminisiated cation defective hydroxyfluorinated anatase. Such solid state NMR studies then contribute to a better understanding of the intercalation chemistry of lithium, magnesium and aluminum into the host frameworks. Research also involves the development of new experiments for paramagnetic materials and studies of hybrid perovskites for optoelectronic applications.

 

Researchers

  • Monique Body
  • Christophe Legein
  • Jens Dittmer

Related papers

  • Chem. Mater. 2017, 29, 3813
  • Angew. Chem. Int. Ed. 2017, 56, 16067
  • Nat. Mater. 2017, 16, 1142
  • Dalton Trans. 2015, 44, 19625

Projects

  • ANR FLUOBAT
  • ANR MORELESS

DFT modelling of NMR parameters and NMR crystallography

The second solid state NMR axis concerns density functional theory (DFT) modeling of NMR parameters and NMR crystallography, both applied to inorganic fluorides.

Recent advances that enable to accurately determine NMR parameters in periodic systems have revolutionized the application of density functional theory (DFT) calculations in solid-state NMR spectroscopy. The use of first-principles calculations aids in both the interpretation and assignment of complex spectra. For example, the 39K NMR spectrum of KYF4 does not allow the determination of the parameters of the six K sites. Nonetheless, its shape is well reproduced by the calculated spectrum evidencing the accuracy of the DFT calculated NMR parameters.

Assigning NMR lines to the crystallographic sites can help to enlighten the structural factors influencing the NMR parameters for a given nucleus. For instance, in the crystalline materials from the KF-YF3 binary system, the 89Y isotropic chemical shift values correlate with the number K atoms present in the Y second coordination sphere, i.e., the next nearest neighbors (NNN). The comparison of the 1H (proton) NMR shifts calculated from the full crystal structure, from the (organic) cations alone and from an isolated cation provides a quantitative way of assessing H bonding in hybrid (oxy)fluorides.

Furthermore, calculations provide a method for evaluating potential structural models against experimental data for disordered materials. The deviations from periodicity, such as compositional and/or positional disorder, often produce the physical properties. NMR provides a useful tool for studying disordered materials such as NbO2F in which both the anions occupy the same sites.

The combination of experiment with first-principles calculations offers an approach for drawing accurately such disordered structures.

 

Researchers

  • Monique Body
  • Christophe Legein
  • Jens Dittmer

Related papers

  • Inorg. Chem. 2017, 56, 5219
  • Cryst. Growth Design 2018, 18, 6873
  • Dalton Trans. 2019, 48, 587
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