X-ray and neutron scattering

Abstract:

In this work, we present a variable-temperature ²³Na NMR and variable-temperature and variable-frequency electron paramagnetic resonance (EPR) analysis of the local structure of a layered P2 Na-ion battery cathode material, Na_0.67[Mg_0.28Mn_0.72]O₂ (NMMO). For the first time, we elucidate the superstructure in this material by using synchrotron X-ray diffraction and total neutron scattering and show that this superstructure is consistent with NMR and EPR spectra. To complement our experimental data, we carry out ab initio calculations of the quadrupolar and hyperfine ²³Na NMR shifts, the Na⁺ ion hopping energy barriers, and the EPR g-tensors. We also describe an in-house simulation script for modeling the effects of ionic mobility on variable-temperature NMR spectra and use our simulations to interpret the experimental spectra, available upon request. We find long-zigzag-type Na ordering with two different types of Na sites, one with high mobility and the other with low mobility, and reconcile the tendency toward Na⁺/vacancy ordering to the preservation of local electroneutrality. The combined magnetic resonance methodology for studying local paramagnetic environments from the perspective of electron and nuclear spins will be useful for examining the local structures of materials for devices.

Abstract:

Objective

The coronavirus disease 2019 (COVID-19) pandemic highlighted the importance of robust infection prevention and control (IPAC) practices to maintain patient and staff safety. However, healthcare workers (HCWs) face many barriers that affect their ability to follow these practices. We identified barriers affecting HCW adherence to IPAC practices during the pandemic in British Columbia, Canada.

Design

Cross-sectional web-based survey.

Setting

Acute care, long-term care or assisted living, outpatient, mental health, prehospital care, and home care.

Participants

Eligible respondents included direct-care providers and IPAC professionals working in these settings in all health authorities across British Columbia.

Methods

We conducted a web-based survey from August to September 2021 to assess respondent knowledge and attitudes toward IPAC within the context of the COVID-19 pandemic. Respondents were asked to rate the extent to which various barriers affected their ability to follow IPAC practices throughout the pandemic and to make suggestions for improvement.

Results

The final analysis included 2,488 responses; 36% of respondents worked in acute care. Overall, perceptions of IPAC practice among non-IPAC professionals were positive. The main self-perceived barriers to adherence included inadequate staffing to cover absences (58%), limited space in staff rooms (57%), multibed rooms (51%), and confusing messages about IPAC practices (51%). Common suggestions for improvement included receiving more support from IPAC leadership and clearer communication about required IPAC practices.

Conclusions

Our findings highlight frontline HCW perspectives regarding priority areas of improvement for IPAC practices. They will inform policy and guideline development to prevent transmission of COVID-19 and future emerging infections.

Abstract:

Recently, increased attention has been focused on amorphous metal-organic frameworks (MOFs) and, more specifically, MOF glasses, the first new glass category discovered since the 1970s. In this work, we explore the fabrication of a compositional series of hybrid blends, the first example of blending a MOF and inorganic glass. We combine ZIF-62(Zn) glass and an inorganic glass, 30Na₂O-70P₂O₅, to combine the chemical versatility of the MOF glass with the mechanical properties of the inorganic glass. We investigate the interfacial interactions between the two components using pair distribution function analysis and solid state NMR spectroscopy, and suggest potential interactions between the two phases. Thermal analysis of the blend samples indicated that they were less thermally stable than the starting materials and had a T_g shifted relative to the pristine materials. Annular dark field scanning transmission electron microscopy tomography, X-ray energy dispersive spectroscopy (EDS), nanoindentation and ³¹P NMR all indicated close mixing of the two phases, suggesting the formation of immiscible blends.

Abstract:

The interface within a composite is critically important for the chemical and physical properties of these materials. However, experimental structural studies of the interfacial regions within metal-organic framework (MOF) composites are extremely challenging. Here, we provide the first example of a new MOF composite family, i.e., using an inorganic glass matrix host in place of the commonly used organic polymers. Crucially, we also decipher atom-atom interactions at the interface. In particular, we dispersed a zeolitic imidazolate framework (ZIF-8) within a phosphate glass matrix and identified interactions at the interface using several different analysis methods of pair distribution function and multinuclear multidimensional magic angle spinning nuclear magnetic resonance spectroscopy. These demonstrated glass-ZIF atom-atom correlations. Additionally, carbon dioxide uptake and stability tests were also performed to check the increment of the surface area and the stability and durability of the material in different media. This opens up possibilities for creating new composites that include the intrinsic chemical properties of the constituent MOFs and inorganic glasses.