(71)Ga-(77)Se connectivities and proximities in gallium selenide crystal and glass probed by solid-state NMR.

Author(s) Nagashima, H.; Trébosc, J.; Calvez, L.; Pourpoint, F.; Mear, F.; Lafon, O.; Amoureux, J.P.
Journal J Magn Reson
Date Published 2017 Jul 22

We introduce two-dimensional (2D) (71)Ga-(77)Se through-bond and through-space correlation experiments. Such correlations are achieved using (i) the J-mediated Refocused Insensitive Nuclei Enhanced by Polarization Transfer (J-RINEPT) method with (71)Ga excitation and (77)Se Carr-Purcell-Meiboon-Gill (CPMG) detection, as well as (ii) the J- or dipolar-mediated Hetero-nuclear Multiple-Quantum Correlation (J- or D-HMQC) schemes with (71)Ga excitation and quadrupolar CPMG (QCPMG) detection. These methods are applied to the crystalline β-Ga2Se3 and the 0.2Ga2Se3-0.8GeSe2 glass. Such glass leads to a homogeneous and reproducible glass-ceramic, which is a good alternative to single-crystalline Ge and polycrystalline ZnSe materials for making lenses transparent in the IR range for thermal imaging applications. We show that 2D (71)Ga-(77)Se correlation experiments allow resolving the (77)Se signals of molecular units, which are not resolved in the 1D (77)Se CPMG spectrum. Additionally, the build-up curves of the J-RINEPT and the J-HMQC experiments allow the estimate of the (71)Ga-(77)Se J-couplings via one and three-bonds in the three-dimensional network of β-Ga2Se3. Furthermore, these build-up curves show that the one-bond (1)J71Ga-77Se couplings in the 0.2Ga2Se3-0.8GeSe2 glass are similar to those measured for β-Ga2Se3. We also report 2D (71)Ga Satellite Transition Magic-Angle Spinning (STMAS) spectrum of β-Ga2Se3 using QCPMG detection at high magnetic field and high Magic-Angle Spinning frequency using large radio frequency field. Such spectrum allows separating the signal of β-Ga2Se3 and that of an impurity.

DOI 10.1016/j.jmr.2017.07.009
ISSN 1096-0856
Citation J Magn Reson. 2017;282:7182.

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