Field sweep broadline NMR spectroscopy

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

An overview is presented of recent progress in the solid-state nuclear magnetic resonance (NMR) observation of low-γ nuclei, with a focus on applications to inorganic materials. The technological and methodological advances in the last 20 years, which have underpinned the increased accessibility of low-γ nuclei for study by solid-state NMR techniques, are summarised, including improvements in hardware, pulse sequences and associated computational methods (e.g., first principles calculations and spectral simulation). Some of the key initial observations from inorganic materials of these nuclei are highlighted along with some recent (most within the last 10 years) illustrations of their application to such materials. A summary of other recent reviews of the study of low-γ nuclei by solid-state NMR is provided so that a comprehensive understanding of what has been achieved to date is available.

Field-stepwise-swept QCPMG solid-state 115In NMR of indium oxide

Experimental and theoretical investigations of indium-115 electric-field-gradient (EFG) tensors of indium(III) oxide, In₂O₃, have been presented. Field-stepwise-swept QCPMG solid-state ¹¹⁵In NMR experiments are carried out at T ​= ​120 ​K, observed at 52.695 ​MHz, and in the range of external magnetic fields between 4.0 and 6.5 ​T. The spectral simulations yield the quadrupolar coupling constant, C_Q value, of 183(2) MHz and the asymmetry parameter, η_Q, of 0.05(5), for In(1), and that of 126(2) MHz and η_Q of 0.86(5) for In(2). Quantum chemical calculations are carried out to provide ¹¹⁵In EFG tensor orientations with respect to the molecular structure. A relationship between operative frequencies and variable ranges of external magnetic fields is briefly discussed for field-swept solid-state ¹¹⁵In NMR.

Enhanced efficiency of solid-state NMR investigations of energy materials using an external automatic tuning/matching (eATM) robot

We have developed and explored an external automatic tuning/matching (eATM) robot that can be attached to commercial and/or home-built magic angle spinning (MAS) or static nuclear magnetic resonance (NMR) probeheads. Complete synchronization and automation with Bruker and Tecmag spectrometers is ensured via transistor-transistor-logic (TTL) signals. The eATM robot enables an automated "on-the-fly" re-calibration of the radio frequency (rf) carrier frequency, which is beneficial whenever tuning/matching of the resonance circuit is required, e.g. variable temperature (VT) NMR, spin-echo mapping (variable offset cumulative spectroscopy, VOCS) and/or in situ NMR experiments of batteries. This allows a significant increase in efficiency for NMR experiments outside regular working hours (e.g. overnight) and, furthermore, enables measurements of quadrupolar nuclei which would not be possible in reasonable timeframes due to excessively large spectral widths. Additionally, different tuning/matching capacitor (and/or coil) settings for desired frequencies (e.g.⁷Li and ³¹P at 117 and 122MHz, respectively, at 7.05 T) can be saved and made directly accessible before automatic tuning/matching, thus enabling automated measurements of multiple nuclei for one sample with no manual adjustment required by the user. We have applied this new eATM approach in static and MAS spin-echo mapping NMR experiments in different magnetic fields on four energy storage materials, namely: (1) paramagnetic ⁷Li and ³¹P MAS NMR (without manual recalibration) of the Li-ion battery cathode material LiFePO₄; (2) paramagnetic ¹⁷O VT-NMR of the solid oxide fuel cell cathode material La₂NiO_4+δ; (3) broadband ⁹³Nb static NMR of the Li-ion battery material BNb₂O₅; and (4) broadband static ¹²⁷I NMR of a potential Li-air battery product LiIO₃. In each case, insight into local atomic structure and dynamics arises primarily from the highly broadened (1-25MHz) NMR lineshapes that the eATM robot is uniquely suited to collect. These new developments in automation of NMR experiments are likely to advance the application of in and ex situ NMR investigations to an ever-increasing range of energy storage materials and systems.

QuadFit--a new cross-platform computer program for simulation of NMR line shapes from solids with distributions of interaction parameters

A new Java computer program called QuadFit has been written to simulate NMR line shapes from solid materials. The program takes into account the major interactions, with a key feature that distributions of isotropic chemical shift and quadrupolar interaction parameters can be calculated, which are often encountered in amorphous and disordered materials. The quadrupolar interaction can be simulated for all the transitions for both half-integer and integer spins. The utility of the program is demonstrated with examples of (27)Al (nuclear spin I=5/2) in an atomically disordered aluminoborate mullite, (65)Cu (I=3/2) in CuInSe(2) and (10)B (I=3) in amorphous B(2)O(3). The program has good cross-platform compatibility and is written for high stability. The program has been designed with an easy to use graphical interface. It can be run efficiently on any reasonably powerful PC and is freely available from the Warwick website (http://go.warwick.ac.uk/quadfit).