A high-resolution natural abundance ³³S MAS NMR study of the cementitious mineral ettringite

Abstract

Despite the widespread occurrence of sulfur in both natural and man-made materials, the S nucleus has only rarely been utilised in solid-state NMR spectroscopy on account of its very low natural abundance (0.76%), low NMR frequency (ν = 30.7 MHz at B = 9.4 T), and significant nuclear quadrupole moment (spin I = 3/2, Q = -69.4 mb). Satellite-transition magic angle spinning (STMAS) is an NMR method for obtaining high-resolution spectra of half-integer quadrupolar nuclei (spin I > 1/2) in solids and is notable for its intrinsic sensitivity advantage over the similar multiple-quantum (MQMAS) method, especially for nuclei with low NMR frequencies. In this work we demonstrate the feasibility of natural abundance S STMAS NMR experiments at B = 9.4 T and 20.0 T using a model sulfate sample (NaSO + KSO in a 1 : 1 molar ratio). Furthermore, we undertake a natural abundance S STMAS NMR study of the cement-forming mineral ettringite (CaAl(SO)(OH)·26HO) at B = 9.4 T and 20.0 T, resolving a discrepancy in the literature between two previous conventional S MAS NMR studies and obtaining an alternative set ofS NMR parameters that is simultaneously consistent with the MAS and STMAS data at both field strengths.

Recent progress in solid‐state nuclear magnetic resonance of half‐integer spin low‐γ quadrupolar nuclei applied to inorganic materials

“…The isotropic shifts of the three SO 4 2-were only separated by $1 ppm and needed the differences in the larger second-order quadrupolar shifts at the lower field to really separate them (Figure 9). [171] Sulphur plays an important role in the internal processes of the Earth and is transported in hydrous silicate melts where its oxidation state can range widely from −2 to +6, which has a profound effect on its chemistry. A range of silicate glasses were investigated, requiring isotopic enrichment as typically only 0.5% sulphur was present.…”

“…These are titanium-based, with current technology using an MgCl 2 support and TiCl 4 catalyst. An initial report using 35 Cl to examine the MgCl 2 support, as for 25 Mg (vide supra) showed both the effect of ball milling used in activation and that the particle morphology induced a [171] Reproduced from the reference with permission of the copyright holder preferred orientation in the rotor and hence a curious lineshape. [145] Nevertheless, it showed signal enhancement techniques and DFT calculations could be applied to these systems.…”

Natural abundance solid-state 33S NMR study of NbS3: applications for battery conversion electrodes

“…Indeed, in many such systems the precise redox mechanisms remain poorly understood, with direct evidence of S 2 2− coming primarily from Raman spectroscopy. 8 Whereas many prior studies on Li-ion battery materials have employed 6/7 Li solid-state NMR experiments, 9,10 very few solid-state 33 S NMR studies of any kind have been reported, due to the low gyromagnetic ratio (1 13 ⁄ that of 1 H), very low natural abundance (0.76%), and large quadrupolar moment (I = 3/2) of 33 S. [11][12][13][14][15] Recent 33 S NMR studies of Li-S and Mg-S battery systems have identified the discharge products (Li2S and MgS), 16,17 which contain S 2− in tetrahedral environments, but the technique has not been applied to study sulfide-based conversion electrodes. Previous 33 S NMR studies on functional inorganic sulfides include TM disulfides (e.g., MoS2 and TiS2), where trigonal pyramidal S 2− environments give rise to large quadrupolar coupling constants (CQ) of 2-10 MHz and correspondingly broad NMR powder patterns via second-order quadrupolar (SOQ) broadening of the I = 3/2 central transition.…”

Developing Novel Lipidated Glycotherapeutics

“…This is a challenge, especially in sulfated compounds, as 33 S NMR requires the detection of a low-sensitivity nucleus with a low natural abundance of only 0.33%. 180 Due to these limitations, implementing 33 S HMBC experiments to link the signals to the corresponding carbons is practically unfeasible.…”