Modifier cation effects on (29)Si nuclear shielding anisotropies in silicate glasses

• Published in: Journal of magnetic resonance (1997) Vol. 268; pp. 95 - 106
• Main Authors: Baltisberger, Jay H, Florian, Pierre, Keeler, Eric G, Phyo, Pyae A, Sanders, Kevin J, Grandinetti, Philip J
• Format: Journal Article
• Language: English
• Published: United States 01.07.2016
• Subjects: Si NMR; Magic-angle flipping; Silicate disproportionation; Akali silicate glass; Echo train acquisition; Alkaline earth silicate glass; Paramagnetic relaxation enhancement; Nuclear shielding tensor
• ISSN: 1096-0856
• DOI: 10.1016/j.jmr.2016.05.003

We have examined variations in the (29)Si nuclear shielding tensor parameters of SiO4 tetrahedra in a series of seven alkali and alkaline earth silicate glass compositions, Cs2O·4.81 SiO2, Rb2O·3.96 SiO2, Rb2O·2.25 SiO2, K2O·4.48 SiO2, Na2O·4.74 SiO2, BaO·2.64 SiO2, and SrO·2.36 SiO2, using natural abundance (29)Si two-dimensional magic-angle flipping (MAF) experiments. Our analyses of these 2D spectra reveal a linear dependence of the (29)Si nuclear shielding anisotropy of Q((3)) sites on the Si-non-bridging oxygen bond length, which in turn depends on the cation potential and coordination of modifier cations to the non-bridging oxygen. We also demonstrate how a combination of Cu(2+) as a paramagnetic dopant combined with echo train acquisition can reduce the total experiment time of (29)Si 2D NMR measurements by two orders of magnitude, enabling higher throughput 2D NMR studies of glass structure.