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The severity of the cancer statistics around the globe and the complexity involving the behavior of cancer cells inevitably calls for contributions from multidisciplinary areas of research. As such, materials science became a powerful asset to support biological research in comprehending the macro and microscopic behavior of cancer cells and untangling factors that may contribute to their progression or remission. The contributions of cellular water dynamics in this process have always been debated and, in recent years, experimental works performed with Quasielastic neutron scattering (QENS) brought new perspectives to these discussions. In this review, we address these works and highlight the value of QENS in comprehending the role played by water molecules in tumor cells and their response to external agents, particularly chemotherapy drugs. In addition, this paper provides an overview of QENS intended for scientists with different backgrounds and comments on the possibilities to be explored with the next-generation spectrometers under construction. [ABSTRACT FROM AUTHOR]

Neutron diffraction and spectroscopy offer unique insight into structures and properties of solids and molecular materials. All neutron instruments located at the various neutron sources are distinct, even if their designs are based on similar principles, and thus, they are usually less familiar to the community than commercial X‐ray diffractometers and optical spectrometers. Major neutron instruments in the USA, which are open to scientists around the world, and examples of their use in coordination chemistry research are presented here, along with a list of similar instruments at main neutron facilities in other countries. The reader may easily and quickly find from this minireview an appropriate neutron instrument for research. The instruments include single‐crystal and powder diffractometers to determine structures, inelastic neutron scattering (INS) spectrometers to probe magnetic and vibrational excitations, and quasielastic neutron scattering (QENS) spectrometers to study molecular dynamics such as methyl rotation on ligands. Key and unique features of the diffraction and neutron spectroscopy that are relevant to inorganic chemistry are reviewed. Major instruments in the USA for (1) single‐crystal and powder neutron diffraction and (2) inelastic neutron scattering (INS) and quasielastic neutron scattering (QENS) spectroscopy are presented with examples of their use in coordination chemistry. Similar instruments at main neutron facilities in other countries are listed for the reader to find a suitable neutron instrument for research. [ABSTRACT FROM AUTHOR]

We present the first, to our knowledge, study of solid state oxygen translational diffusion by quasielastic neutron scattering. Such studies in the past might have been precluded by relatively low diffusivities of oxygen anions in the temperature range amenable to neutron scattering experiments. To explore the potential of the quasielastic scattering technique, which can deduce atomic diffusion jump length of oxygen anions through the momentum transfer dependence of the scattering signal, we have selected the fastest known oxygen conductor, bismuth oxide. We have found the oxygen anion jump length in excellent agreement with the nearest oxygen-vacancy distance in the anion sublattice of the fluorite-related structure of bismuth oxide. [ABSTRACT FROM AUTHOR]

Uranyl fluoride is a three-layer, hexagonal structure with significant stacking disorder in thec-direction. It supports a range of unsolved ‘thermodynamic’ hydrates with 0–2.5 water molecules per uranium atom, and perhaps more. However, the relationship between water, hydrate crystal structures, and thermodynamic results, collectively representing the chemical pathway through these hydrate structures, has not been sufficiently elucidated. We used high-resolution quasielastic neutron scattering to study the dynamics of water in partially hydrated uranyl fluoride powder over the course of 4 weeks under closed conditions. The spectra are composed of two quasielastic components: one is associated with translational diffusive motion of water that is approximately five to six times slower than bulk water, and the other is a slow (on the order of 2–300 ps), spatially bounded water motion. The translational component represents water diffusing between the weakly bonded layers in the crystal, while the bounded component may represent water trapped in subnanometre ‘pockets’ formed by the space between uranium-centred polymerisation units. Complementary neutron and X-ray diffraction measurements do not show any significant structural changes, suggesting that a chemical conversion of the material does not occur in the thermodynamically isolated system on this timescale. [ABSTRACT FROM AUTHOR]

We propose a modification of the neutron wide-angle velocity selector (WAVES) device that enables inelastic (in particular, quasielastic) scattering measurements not relying on the neutron time-of-flight. The proposed device is highly suitable for a steady-state neutron source, somewhat similar to a triple-axis spectrometer, but with simultaneous selection of the incident and final neutron energy over a broad range of scattering momentum transfer. Both the incident and final neutron velocities are defined by the WAVES geometry and rotation frequency. The variable energy transfer is achieved through the natural variation of the velocity of the transmitted neutrons as a function of the scattering angle component out of the equatorial plane. [ABSTRACT FROM AUTHOR]

Using quasielastic neutron scatteringspectroscopy, we measuredthe averaged translational diffusion of water in solutions of biologicallyrelevant salts, NaCl, a kosmotrope, and KCl, a chaotrope. The analysisrevealed the striking difference in the influence of these ions onwater dynamics. While the averaged water diffusion slows down in thepresence of the structure making (kosmotrope) Na+ion,the diffusion becomes faster in the presence of the structure breaking(chaotrope) K+ion. The latter means that, despite strongCoulombic interactions introduced by the K+ions, theirdisruption of the hydrogen-bonding network is so significant thatit leads to faster diffusion of the water molecules. [ABSTRACT FROM AUTHOR]

Abstract: Using quasielastic neutron scattering, we compare dynamics in single-element liquids, glass-forming selenium and non glass-forming gallium. There is a single jump-diffusion process in gallium, whereas in selenium there is also a faster, spatially localized process. The fast and slow processes describe β- and α-relaxation, respectively. We then analyze an archetypical glass-former, glycerol, to show that the two-component fit, with β- and α-relaxations explicitly separated, yields the correct value for the translational diffusion coefficient and provides information on the spatial localization of the β-relaxation that is not experimentally accessible otherwise. [Copyright &y& Elsevier]

Abstract: The diffusion of methane confined in nano-porous carbon aerogel with the average pore size 48Å and porosity ∼60% was investigated as a function of pressure at T =298K using quasi-elastic neutron scattering (QENS). The diffusivity of methane shows a clear effect of confinement: it is about two orders of magnitude lower than in bulk at the same thermodynamic conditions and is close to the diffusivity of liquid methane at 100K (i.e. ∼90K below the liquid–gas critical temperature T C ≈191K). The diffusion coefficient (D) of methane initially increases with pressure by a factor of ∼2.5 from 3.47±0.41×10−10 m2 s−1 at 0.482MPa to D =8.55±0.33×10−10 m2 s−1 at 2.75MPa and starts to decrease at higher pressures. An explanation of the observed non-monotonic behavior of the diffusivity in the confined fluid is based on the results of small-angle neutron scattering experiments of the phase behavior of methane in a similar carbon aerogel sample. The initial increase of the diffusion coefficient with pressure is explained as due to progressive filling of bigger pores in which molecular mobility in the internal pore volume is less affected by the sluggish liquid-like molecular mobility in the adsorbed phase. Subsequent decrease of D, is associated with the effect of intermolecular collisions, which result in a lower total molecular mobility with pressure, as in the bulk state. The results are compared with the available QENS data on the methane diffusivity in zeolites, metal organic frameworks, and porous silica as well as with the molecular dynamics simulations of methane in nano-porous carbons and silica zeolites. [Copyright &y& Elsevier]

Abstract: Monophase thorium–zirconium hydrides (ThZr2H x ) have been fabricated starting from a metallic alloy and the hydrogen stoichiometry determined by X-ray diffraction. Incoherent Quasielastic Neutron Scattering (IQNS) on the hydrides was conducted over the temperature range 650–750K at the Backscattering Silicon Spectrometer (BASIS) at the Spallation Neutron Source (SNS) at ORNL. The isotropic Chudley–Elliott model was utilized to analyze the quasielastic linewidth broadening data as function of momentum transfer. The diffusion coefficient and average jump distance of hydrogen atoms in ThZr2H5.6 and ThZr2H6.2 were extracted from the measurements. [Copyright &y& Elsevier]

Background and Objectives: As an mRNA-based vaccine, the Pfizer-BioNTech COVID-19 vaccine has stringent cold storage requirements to preserve functionality of the mRNA active ingredient. To this end, lipid components of the vaccine formulation play an important role in stabilizing and protecting the mRNA molecule for long-term storage. The purpose of the current study was to measure molecular-level dynamics as a function of temperature in the Pfizer-BioNTech COVID-19 vaccine to gain microscopic insight into its thermal stability. Materials and Methods: We used quasielastic and inelastic neutron scattering to probe (1) the vaccine extracted from the manufacturer-supplied vials and (2) unperturbed vaccine in the original manufacturer-supplied vials. The latter measurement was possible due to the high penetrative power of neutrons. Results: Upon warming from the low-temperature frozen state, the vaccine in its original form exhibits two-step melting, indicative of a two-phase morphology. Once the melting is completed (above 0 °C), vaccine re-freezing cannot restore its original two-phase state. This observation is corroborated by the changes in the molecular vibrational spectra. The molecular-level mobility measured in the resulting single-phase state of the re-frozen vaccine greatly exceeds the mobility measured in the original vaccine. Conclusions: Even a brief melting (above 0 °C) leads to an irreversible alteration of the two-phase morphology of the original vaccine formulation. Re-freezing of the vaccine results in a one-phase morphology with much increased molecular-level mobility compared to that in the original vaccine, suggesting irreversible deterioration of the vaccine's in-storage stability. Neutron scattering can be used to distinguish between the vibrational spectra characteristic of the original and deteriorated vaccines contained in the unperturbed original manufacturer-supplied vials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Apilimod and tetrandrine reportedly work better than remdesivir against SARS-CoV-2. • We find that apilimod and tetrandrine show much reduced methyl rotational barriers. • Low potential barriers lead to pronounced quantum effects at low temperatures. • Low potential barriers lead to fast methyl rotation at physiological temperatures. • Screening studies of the energy landscape can help identify promising drug candidates. A recent screening study highlighted a molecular compound, apilimod, for its efficacy against the SARS-CoV-2 virus, while another compound, tetrandrine, demonstrated a remarkable synergy with the benchmark antiviral drug, remdesivir. Here, we find that because of significantly reduced potential energy barriers, which also give rise to pronounced quantum effects, the rotational dynamics of the most dynamically active methyl groups in apilimod and tetrandrine are much faster than those in remdesivir. Because dynamics of methyl groups are essential for biochemical activity, screening studies based on the computed potential energy profiles may help identify promising candidates within a given class of drugs. [ABSTRACT FROM AUTHOR]

We used quasielastic neutron scattering (QENS) to studythe dynamicsof phenanthrenequinone (PQ) on the surface of onion-like carbon (OLC),or so-called carbon onions, as a function of surface coverage andtemperature. For both the high- and low-coverage samples, we observedtwo diffusion processes; a faster process and nearly an order of magnitudeslower process. On the high-coverage surface, the slow diffusion processis of long-range translational character, whereas the fast diffusionprocess is spatially localized on the length scale of ∼4.7Å. On the low-coverage surface, both diffusion processes arespatially localized; on the same length scale of ∼4.7 Åfor the fast diffusion and a somewhat larger length scale for theslow diffusion. Arrhenius temperature dependence is observed exceptfor the long-range diffusion on the high-coverage surface. We attributethe fast diffusion process to the generic localized in-cage dynamicsof PQ molecules, and the slow diffusion process to the long-rangetranslational dynamics of PQ molecules, which, depending on the coverage,may be either spatially restricted or long-range. On the low-coveragesurface, uniform surface coverage is not attained, and the PQ moleculesexperience the effect of spatial constraints on their long-range translationaldynamics. Unexpectedly, the dynamics of PQ molecules on OLC as a functionof temperature and surface coverage bears qualitative resemblanceto the dynamics of water molecules on oxide surfaces, including practicallytemperature-independent residence times for the low-coverage surface.The dynamics features that we observed may be universal across differentclasses of surface adsorbates. [ABSTRACT FROM AUTHOR]

Quasielastic neutron scattering (QENS) was used to investigate the diffusion dynamics of hydration water on the surface of futile (TiO2) nanopowder. The dynamics measurements utilizing two inelastic instruments, a backscattering spectrometer and a disk chopper spectrometer, probed the fast, intermediate, and slow motions of the water molecules on the time scale of picoseconds to more than a nanosecond. We employed a model-independent analysis of the data collected at each value of the scattering momentum transfer to investigate the temperature dependence of several diffusion components. All of the probed components were present in the studied temperature range of 230-320 K, providing, at a first sight, no evidence of discontinuity in the hydration water dynamics. However, a qualitative change in the elastic scattering between 240 and 250 K suggested a surface freezing-melting transition, when the motions that were localized at lower temperatures became delocalized at higher temperatures. On the basis of our previous molecular dynamics simulations of this system, we argue that interpretation of QENS data from such a complex interfacial system requires at least qualitative input from simulations, particularly when comparing results from spectrometers with very different energy resolutions and dynamic ranges. [ABSTRACT FROM AUTHOR]

Abstract The diffusion dynamics of a series of lithium sulfate substituted phosphate glass materials xLi 2 SO 4 ⋅(1 − x)LiPO 3 has been probed by quasielastic neutron scattering. Amorphous Li ion conductors are attractive as electrolyte materials for all-solid state batteries because they are highly isotropic and chemically stable. Local disorder is expected to reduce barriers to ion migration – leading to improved ionic conductivity relative to their crystalline counterpart – while minimizing unwanted electron transport. We report Li self-diffusion in these materials on a length scale comparable to the interatomic spacings, obtaining values D ≃ 55 ± 4 × 10−8 cm2/s at 450 K. Elastic neutron scattering measurements show an alteration of the phosphate chain backbone of the glass material. Highlights • Amorphous Li electrolyte materials xLi 2 SO 4 (1-x)LiPO 3 are probed via quasielastic neutron scattering • Li ion diffusion is found to isotropic on length (few Å) and time scales (ns) probed by neutron backscattering spectroscopy • The diffusion constant for compositions x=0.3 & 0.4 is found to be 55x10−8 cm/s, diffusion for x=0 was below detection limit. [ABSTRACT FROM AUTHOR]

Abstract: A diffusive behavior of Li+ ion in a garnet-type oxide, Li5+ x La3Zr x Nb2−x012 with x =0–2, has been investigated by both a positive muon-spin relaxation (μ +SR) and quasi-elastic neutron scattering (QENS) technique using powder samples. The μ +SR results revealed that Li+ ions start to diffuse above ~150K for the whole samples measured. The activation energy of Li diffusion (Ea ) estimated from the μ +SR data was in good agreement with Ea obtained by the QENS measurements. However, both Ea s were about a half of Ea of ionic conductivity of Li+ (σ Li), which was evaluated by AC-impedance measurements on sintered pellets. This indicated the serious effect of grain boundary and/or surface on Ea . Furthermore, since the diffusion coefficient of Li+ estimated by μ +SR is roughly independent of x, the number of mobile Li+ in the garnet lattice was found to be the predominant parameter to determine σ Li. [Copyright &y& Elsevier]

The temperature-dependent diffusivity D(T) of hydrogen solute atoms trapped at dislocations- dislocation pipe diffusion of hydrogen-in deformed polycrystalline PdH, (ϰ ~ 10-3 [H]/ [Pd]) has been quantified with quasielastic neutron scattering between 150 and 400 K. We observe diffusion coefficients for trapped hydrogen elevated by one to two orders of magnitude above bulk diffusion. Arrhenius diffusion behavior has been observed for dislocation pipe diffusion and regular bulk diffusion, the latter in well-annealed poly crystalline Pd. For regular bulk diffusion of hydrogen in Pd we find D(T) = D0exp(-Eα/kT) = 0.005exp(-0.23 eV/kT) cm2/s , in agreement with the known diffusivity of hydrogen in Pd. For hydrogen dislocation pipe diffusion we find D(T) ≃ 10-5exp (-E α/kT ) cm2/s , where Eα = 0.042 and 0.083 eV for concentrations of 0.52 × 10-3 and 1.13 × 10-3 [H]/ [Pd], respectively. Ab initio computations provide a physical basis for the pipe diffusion pathway and confirm the reduced barrier height. [ABSTRACT FROM AUTHOR]

Atomistic molecular dynamics (MD) simulations were carried out to investigate the local dynamics of polyelectrolyte dendrimers dissolved in deuterium oxide (D2O) and its dependence on molecular charge. Enhanced segmental dynamics upon increase in molecular charge is observed, consistent with quasielastic neutron scattering (QENS) measurements. A strong coupling between the intradendrimer local hydration level and segmental dynamics is also revealed. Compelling evidence shows these findings originate from the electrostatic interaction between the hydrocarbon components of a dendrimer and the invasive water. This combined study provides fundamental insight into the dynamics of charged polyelectrolytes and the solvating water molecules. [ABSTRACT FROM AUTHOR]

The translational dynamics of hydration water confined in calcium-silicate-hydrate (C-S-H) gel was studied by quasielastic neutron scattering spectroscopy in the temperature range from 280 to 230 K. The stretch exponent β, the self-diffusion constant D, the average translational relaxation time <τ>, and the temperature dependence of confinement radius α extracted from the elastic fraction of immobile water molecules p(Q) were obtained from the analyses of the low- Q spectra according to the relaxing cage model. Measurements were made using C-S-H of three different water contents, 10%, 17%, and 30%. Among the three samples of C-S-H gel with different water contents, the values of β decrease with increasing water contents, while α increases. The values of D and <τ> are insensitive to temperature for the two lower water contents, as opposed to the 30% case where a slight variation is observed. The trend for violation of the Stokes-Einstein relation is only visible in the case of 30% water content. [ABSTRACT FROM AUTHOR]