Preface to the virtual special issue on advanced NMR on glasses
Résumé
Since the end of the 50’s, Nuclear Magnetic Resonance (NMR) has proven to be a valuable technique for the characterisation of glasses. With the introduction of the high resolution technique of magic angle spinning (MAS) and together with the availability of high magnetic fields, 1D MAS-NMR has now become the standard technique to determine and quantify the boron or aluminium coordination states as well as the silicate or phosphate Qn speciation. But the last 20 years have seen a tremendous amount of more sophisticated NMR techniques becoming - almost routinely- available, which can also be used to provide additional structural information at a larger length scale and/or with a better resolution. This family of NMR techniques, referred to as advanced NMR, has also greatly benefitted from technical and methodological improvements and can now be used to edit 2D map showing spatial proximity or chemical connectivity, to produce better resolution spectra for quadrupolar nuclei, to provide new insights into impact on structural disorder on NMR lineshape, or to determine interatomic distances...
In this Virtual Special Issue of the Journal of Non-Crystalline Solids, worldwide-recognized teams were asked for reviews or scientific articles showing how advanced solid state NMR can be applied to vitreous materials. Special attention was paid to publish pedagogic papers that can be easily handled by the whole glass community researchers. Phosphate based glasses have been extensively studied by advanced NMR within the last twenty years. This VSI contains two papers using combination of advanced 1D/2D NMR techniques to investigate the structure of fluoro-phosphate (Jinjun Ren et al., Shanghai Institute of Optics and Fine Mechanics) [1] and boro-phosphate (Grégory Tricot et al., University of Lille) [2] based glasses. Very detailed analysis of 1D NMR spectra lineshape of quadrupolar nuclei (I> ½) in amorphous materials was investigated by Josef Zwanziger et al. (Dalhousie university) in a paper focusing on the Czjzek model [3]. Hellmut Eckert et al. (University of Muenster, University of Sao Paulo) provided a complete reviewing of NMR and EPR applications on rare-earth containing glasses and glass ceramics [4]. Analysis of chalcogenide glasses by 29Si, 31P, 77Se and 125Te 1D and 2D homonuclear correlation NMR was reviewed by Sabyasachi Sen et al. (University of California at Davis) [5]. Sung Keun Lee et al. (Seoul National University) used 1D and MQ-MAS 11B, 27Al and 17O NMR experiments and 11B DQ-SQ experiments to investigate the structure of Na2O-B2O3 and Na2O-B2O3-Al2O3-SiO2 systems [6]. Mattias Eden et al. (Stockholm university) used 17O MAS-NMR and 27Al 1D and 2D DQ-SQ to highlight the presence of unexpected [4]Al-O-[4]Al and [4]Al-NBO bonds in rare earth aluminosilicate glasses [7]
To conclude, we would like to thank all the contributors and we do hope that this VSI will be helpful for the entire glass community. We believe that many users of standard 1D NMR will see how advanced NMR can be used to complete structural models and we are looking forward to seeing more and more groups using these advanced NMR techniques within the next years.