Small-angle Neutron Scattering Research Articles

(Digital Presentation) Small-Angle Neutron Scattering Analysis of Fuel Cell Materials

In order to improve the reaction efficiency of fuel cells, the structure of carbon and ionomer affecting electronic and proton conduction and the distribution of voids affecting oxygen diffusion and drainage have been studied to find the guideline for the optimum structure of the catalyst layer. In this study we are developing a method to evaluate the dispersed structure of carbon and ionomer and the thickness of the ionomer layer by using the small and wide angle neutron scattering instrument, TAIKAN at the Materials and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). The dependence of ionomer-to-carbon weight ratio of small-angle neutron scattering (SANS) cross section of the solid carbon catalyst layer and the hollow carbon catalyst layer was evaluated comparatively. Furthermore, the relative humidity dependence of SANS cross section of the solid carbon catalyst layer and the hollow carbon catalyst layer was also evaluated by using the contrast variation method.This presentation is based on results obtained from a project, JPNP20003, subsidized by a New Energy and Industrial Technology Development Organization (NEDO).

The Multitype Pore Structure Evolution Characteristics of Ziliujing Formation Shale from the Northeastern Sichuan Basin in China: Experimental Study Using Small Angle Neutron Scattering Technology

The high complexity and heterogeneity of shale pore compositions and abundant nanopores complicate the multiscale characterization of a shale reservoir pore structure. As the degree of geological evolution changes, the pore structure and connectivity also undergo complex changes and the thermal simulation experiment is a practical method to reveal the evolution characteristics of shale within a relatively short time period using the time–temperature compensation principle. In this study, thermal simulation experiments were used to obtain shale samples of the Ziliujing Formation in Northeastern Sichuan Basin with different evolution degrees. The pore structure of the samples was quantitatively characterized by SANS combined with N2 adsorption and mercury injection capillary pressure (MICP) methods. The pore morphology was qualitatively characterized by the field emission scanning electron microscopy (FE-SEM) experiment. Finally, the influence of thermal evolution on the pore structure of shale samples was investigated. The results show that the pore size distribution of SANS is similar to that of MICP and N2 adsorption methods, and the pore volume is mainly concentrated in 5–100 nm. The porosity and pore specific surface area obtained by the three characterization methods showed the trend of SANS > MICP > N2 adsorption, and the difference in pore structure was mainly affected by fluid accessibility. With the increase in thermally simulated temperature, the total pore volume and pore specific surface area of shale samples show a trend of an increase first and then a decrease. The proportion of >10 nm pores increases gradually, and the fraction of closed pores shows a downward trend as a whole. Basically, with the increase in thermally simulated temperature, the pore connectivity is enhanced, and the sample heterogeneity is weakened, all of which are conducive to the migration of shale reservoir fluid. Overall, clarifying the evolution of closed pores in shale reservoirs is of great significance for estimating original oil and gas reserves more accurately and improving oil and gas recovery.

Is Ficoll a Colloid or Polymer? A Multitechnique Study of a Prototypical Excluded-Volume Macromolecular Crowder

The in-cell environment is crowded with macromolecules, and the consequent reduction in free volume, based on the hard-sphere paradigm, is central to understanding macromolecular motions. A much-used model crowder, Ficoll, often assumed to be a compact, if not rigid, colloidal particle, is studied by rheology, small-angle neutron scattering, nuclear magnetic resonance diffusometry, and relaxometry. We find that the Ficoll suspension viscosity scales linearly with concentration cF in the dilute limit and as ∼cF3.8 at high cF, i.e, consistent with the 15/4 (de Gennes) scaling for a reptating polymer. The form factor of Ficoll, obtained via small-angle neutron scattering (SANS), resembles either a Gaussian polymer or a soft polymer blob. From NMR diffusion measurements, we obtain an effective volume fraction for Ficoll that accounts for Ficoll-bound water in two ways and show that each results in a volume occupancy of 60% to 70% in the crowding limit, much larger than the traditionally reported values of around 30%. If we persist with the colloid paradigm and examine the dependence of the zero-q structure factor obtained via SANS in terms of this effective volume fraction, we find that only a combination of particle softness and interparticle attractions, quantified using a computational model, can replicate the experimental S(0). The stark difference between effective and traditional volume occupancies affects the interpretation of previous experiments on macromolecular crowding and might explain the intriguing non-monotonicity observed in the dependence of protein relaxation rates on crowder concentration.

Domain Structure, Thermal and Mechanical Properties of Polycaprolactone-Based Multiblock Polyurethane-Ureas under Control of Hard and Soft Segment Lengths.

A series of multiblock polyurethane-ureas (PUU) based on polycaprolactone diol (PCL) with a molecular mass of 530 or 2000 g/mol, as well as hard segments of different lengths and structures, were synthesized by the step-growth polymerization method. The chemical structure of the synthesized multiblock copolymers was confirmed by IR- and NMR-spectroscopy. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were used to determine the relaxation and phase transition temperatures for the entire series of the obtained PUU. The X-ray diffraction (XRD) method made it possible to identify PUU compositions in which the crystallizability of soft segments (SS) is manifested due to their sufficient length for self-organization and structuring. Visualization of the crystal structure and disordering of the stacking of SS with an increase in their molecular mobility during heating are shown using optical microscopy. The change in the size of the hard phase domains and the value of the interdomain distance depending on the PCL molecular mass, as well as the length and structure of the hard block in the synthesized PUU, were analyzed using small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS). The evolution of the domain structure upon passing through the melting and crystallization temperatures of PUU soft blocks was studied using SANS. The studies carried out made it possible to reveal the main correlations between the chemical structure of the synthesized PUU and their supramolecular organization as well as thermal and mechanical properties.

Analysis of time-of-flight small-angle neutron scattering data on mesoscopic crystals such as magnetic vortex lattices.

Bragg diffracted intensities and q values for crystalline structures with long repeat distances may be obtained by small-angle neutron scattering (SANS) investigations. An account is given of the methods, advantages and disadvantages of obtaining such data by the multichromatic time-of-flight method, compared with the more traditional quasi-monochromatic SANS method. This is illustrated with data obtained from high-magnetic-field measurements on magnetic vortex line lattices in superconductors on the former HFM/EXED instrument at Helmholtz-Zentrum Berlin. The methods have application to other mesoscopic crystalline structures investigated by SANS instruments at pulsed sources.

Characterization of Precipitated Phase in Cu–Ni–Si Alloy by Small-Angle X-ray Scattering, Small Angle Neutron Scattering and Atom Probe Tomography

Characterization of Precipitated Phase in Cu–Ni–Si Alloy by Small-Angle X-ray Scattering, Small Angle Neutron Scattering and Atom Probe Tomography

Self-Assembly and Micellar Transition in CTAB Solutions Triggered by 1-Octanol.

This study exploits higher-order micellar transition ranging from ellipsoidal to rodlike to wormlike induced by 1-octanol (C8OH) in an aqueous solution of cetyltrimethylammonium bromide (CTAB), characterizing phase behavior, rheology, and small-angle neutron scattering (SANS). The phase diagram for the ternary system CTAB-C8OH-water was constructed, which depicted the varied solution behavior. Such performance was further inferred from the rheology study (oscillatory-shear frequency sweep (ω) and viscosity (η)) that displayed an interesting solution behavior of CTAB solutions as a function of C8OH. It was observed that at low C8OH concentrations, the solutions appeared viscous/viscoelastic fluids that changed to an elastic gel with an infinite relaxation time at higher concentrations of C8OH, thereby confirming the existence of distinct micelle morphologies. Small-angle neutron scattering (SANS) provided various micellar parameters such as aggregation numbers (Nagg) and micellar size/shape. The experimental results were further validated with a computational simulation approach. The molecular dynamic (MD) study offered an insight into the molecular interactions and aggregation behavior through different analyses, including radial distribution function (RDF), radius of gyration (Rg), and solvent-accessible surface area (SASA).

Skyrmion alignment and pinning effects in the disordered multiphase skyrmion material Co8Zn8Mn4

Underlying disorder in skyrmion materials may both inhibit and facilitate skyrmion reorientations and changes in topology. The identification of these disorder-induced topologically active regimes is critical to realizing robust skyrmion spintronic implementations, yet few studies exist for disordered bulk samples. Here, we employ small-angle neutron scattering (SANS) and micromagnetic simulations to examine the influence of skyrmion order on skyrmion lattice formation, transition, and reorientation dynamics across the phase space of a disordered polycrystalline Co$_{8}$Zn$_{8}$Mn$_{4}$ bulk sample. Our measurements reveal a new disordered-to-ordered skyrmion square lattice transition pathway characterized by the novel promotion of four-fold order in SANS and accompanied by a change in topology of the system, reinforced through micromagnetic simulations. Pinning responses are observed to dominate skyrmion dynamics in the metastable triangular lattice phase, enhancing skyrmion stabilization through a remarkable and previously undetected skyrmion memory effect which reproduces previous ordering processes and persists in zero field. These results uncover the cooperative interplay of anisotropy and disorder in skyrmion formation and restructuring dynamics, establishing new tunable pathways for skyrmion manipulation.

Mechanism of endosomal escape by pH-responsive nucleic-acid vectors.

Successful intracellular delivery of nucleic acids (NAs) hinges on many factors, one of them being NAs' efficacious escape from endosomes. As competent NA vectors, pH-responsive gemini surfactants (GSs) might achieve high efficacy by facilitating endosomal escape. However, how the GSs assist the escape remains debated as many proposed mechanisms still lack experimental support, which hinders replication and further improvement of the efficient delivery. Here, via UV, fluorescence spectroscopy, and small-angle neutron scattering (SANS), we examined a pH-responsive GS's and a pH-unresponsive GS's capabilities to compact DNA and withstand binding competition, and their interactions with model endosomal and lysosomal membranes, at varied pHs. Acidification-driven enhancement of DNA-compaction capability and of stability against binding competition were found specific to the pH-responsive GS. Alongside the pH-responsive GS's structural perturbation to the membranes as observed with SANS, the features suggest that pH-responsive GSs facilitate endosomal escape by releasing excess GS molecules from DNA-GS complexes upon acidification in endosome maturation, with the released GS molecules disrupting endosomal and lysosomal membranes and thereby assisting the escape. A general design principle for NA vectors is proposed on the basis of this experimental finding.

Electrosorption-induced deformation of a porous electrode with non-convex pore geometry in electrolyte solutions: A theoretical study

Porous carbon is well known as a good candidate for the development of electrochemical double-layer capacitors. Predominantly, many conventional carbons are microporous and often well described by the assumption of slit pore geometry. However, there is a class of carbons that is significantly different from the others, namely templated mesoporous carbons. In this work, we study electrosorption-induced deformation in CMK-3–like mesopores having non-convex geometry. Our mean-field approach is based on the modified Poisson-Boltzmann equation taking into account the excluded volume of the ions within the hard-sphere model. We assume that the deformation is caused by two effects: ion osmotic pressure and electrostatic interactions of the electric double layers on charged rods. We estimated the pore-load modulus of the CMK-3–like material and found an agreement with the previously obtained values by small-angle neutron scattering (SANS) data analysis. Additionally, we studied the differential capacitance in the non-convex pore geometry and found that the behavior of the differential capacitance profiles was similar to that of the profiles obtained for flat electric double layers: the crowding regime at rather high electric potentials and more pronounced profile asymmetry with increasing differences in the ionic sizes.

Quantifying the Solution Structure of Metal Nanoclusters Using Small‐Angle Neutron Scattering

AbstractMetal nanoclusters are a unique class of synthetic material, as their crystal structures can be resolved using X‐ray diffraction, and their chemical formula can be precisely determinated from mass spectroscopy. However, a complete structure characterization by these two techniques is often a challenging task. Here, we utilize small‐angle neutron scattering (SANS) to directly quantify the key structure parameters of a series of silver and gold nanoclusters in solution. The results not only correlate well to their crystallographic structures, but also allow the quantification of the counterions layer surrounding charged nanoclusters in solution. Furthermore, when combining with X‐ray scattering, it is possible to estimate the molecular weight of both the metal core and the ligand shell of nanoclusters. This work offers an alternative characterization tool for nanoclusters without the requirement of crystallization or gas phase ionization.

Quantifying the Solution Structure of Metal Nanoclusters Using Small-Angle Neutron Scattering.

Metal nanoclusters are a unique class of synthetic material, as their crystal structures can be resolved using X-ray diffraction, and their chemical formula can be precisely determinated from mass spectroscopy. However, a complete structure characterization by these two techniques is often a challenging task. Here, we utilize small-angle neutron scattering (SANS) to directly quantify the key structure parameters of a series of silver and gold nanoclusters in solution. The results not only correlate well to their crystallographic structures, but also allow the quantification of the counterions layer surrounding charged nanoclusters in solution. Furthermore, when combining with X-ray scattering, it is possible to estimate the molecular weight of both the metal core and the ligand shell of nanoclusters. This work offers an alternative characterization tool for nanoclusters without the requirement of crystallization or gas phase ionization.

Nanostructuring with Surfactants: The Self-Assembly of a New Poly(thiophene-phenylene) Conjugated Polymer Bearing Azacrown Ether Pendant Groups.

We report the synthesis of a new conjugated polymer bearing crown ether moieties, poly[(N(1-aza-[18]crown-6)carbamido)thiophene-2,5-diyl-alt-1,4-phenylene] (BG2). In water, BG2 forms a dispersion with a slightly cloudy appearance. We have studied the effect of adding surfactants, with different polar head groups, on these polymer-polymer aggregates. Special attention is given to the system with the anionic surfactant, sodium dodecyl sulfate (SDS). The combination of photophysical techniques with electrical conductivity, NMR (1H, 13C, and 27Na), DFT calculations, molecular dynamics simulations, and small-angle neutron scattering (SANS) provides a detailed picture on the behavior of the SDS/BG2 system in aqueous solution and in thin films. NMR, electric conductivity, and DFT results suggest that hydrophilic interactions occur between the polar headgroup of the surfactant (OSO3- Na+) and the aza-[18]-crown-6 moiety. DFT calculations confirmed the capability of BG2 to form stable complexes with the Na+ cations, where the cation can be either inside the azacrown cavity or sandwiched between the cavity and the polymer chain, which seem to determine the position of the surfactant hydrocarbon chain and, therefore, be responsible for the disruption of the BG2 aggregates and subsequent increase in the photoluminescence quantum yields. SANS measurements, made with hydrogenated and deuterated SDS in D2O, clearly show how micron-sized aggregates of BG2 are broken down by SDS and then how BG2 becomes preferentially incorporated within joint colloidal particles of BG2 and SDS with increasing [SDS]/[BG2] molar ratio.

Hierarchical self-assembly in ionic liquid crosslinked polyelectrolyte gels as a citric acid sensor

The design of an enzyme-free biocompatible electrochemical platform for the detection of citric acid is discussed. We have studied sol-gel transition in DNA ionic liquid solution triggered by the ionic liquid (IL), (1-Octyl-3-methylimidazolium Chloride [C8mim][Cl]; concentration= 0.1 to 1.0% (w/v)). Rheology and Small-angle neutron scattering (SANS) studies characterized their viscoelastic and microstructural properties. The gel modulus was found to vary from 10 to 60 Pa concomitant with a tunable temperature of gelation. SANS data yielded the persistence length of DNA (50 ± 12 nm) and the mesh size of these gels (ξ = 2.5±0.5 nm). Remarkably, this ionogel served as an excellent electrochemical sensor for citric acid detection in the application window of 0.02-0.08 mM analyte concentration with a detection limit of 1.510-8 molL-1. Yet another non-trivial application of the versatile DNA gel is demonstrated here.

Hydrogen bonding of nanoconfined water in ionic liquids

1-Alkyl-3-methylimidazolium nitrate ([Cnmim][NO3], n = 4, 6, and 8)-D2O provided a small-angle neutron scattering (SANS) peak, representing D2O aggregations (Abe et al., J. Phys. Chem. Lett. 5 (2014) 1175 and J. Mol. Liq. 346 (2022) 117035). Nanoconfined water (water pocket) appeared in the water-rich region, with a size distribution that was almost monodispersed. The water pocket in [C4mim][NO3] was characterized by the hydrogen bonding (Abe et al., J. Mol. Liq. 210 (2015) 200). In this work, the hydrogen bonding state of [Cnmim][NO3]-D2O (n = 2, 6, and 8) was examined by Raman spectroscopy. The water concentration dependencies of the OD stretching band of D2O indicated that the hydrogen bonding state of the water pocket was invariant. The hydrogen/deuteron (H/D) exchange reaction was observed only in [C6mim][NO3]-D2O, with the H/D exchange completed within 1 h. Moreover, large pD values were observed only in [C6mim][NO3]-D2O, and the kinetic pD behavior supported the H/D exchange.

Small-angle neutron scattering study of mesoscale magnetic disordering and skyrmion phase suppression in the frustrated chiral magnet Co6.75Zn6.75Mn6.5.

Co-Zn-Mn chiral cubic magnets display versatile magnetic skyrmion phases, including equilibrium phases stable far above and far below room temperature, and the facile creation of robust far-from-equilibrium skyrmion states. In this system, compositional disorder and magnetic frustration are key ingredients that have profound effects on the chiral magnetism. Reported here are studies of the magnetism in Co6.75Zn6.75Mn6.5 by magnetometry, small-angle neutron scattering (SANS), magnetic diffuse neutron scattering and Lorentz transmission electron microscopy (LTEM). While features in magnetometry and LTEM often give standard indications for skyrmion formation, they are not readily observed from the measurements on this system. Instead, skyrmion lattice correlations are only revealed by SANS, and they are found to form an orientationally disordered structure in a minority fraction of the sample. The majority fraction of the sample always displays orientationally disordered helical spin correlations, which undergo further disordering along the radial direction on cooling below the critical temperature (T c ≃ 102 K). The near-complete suppression of the skyrmion phase, and the process of disordering on cooling, are attributed to competing magnetic interactions that dominate over the ferromagnetic interaction expected to favour chiral magnetism in this system. These competing interactions start to develop above T c and become further enhanced towards low temperatures. The present observations of co-existing and disordered magnetic correlations over multiple length scales are not unique to Co6.75Zn6.75Mn6.5 but are seemingly common to the family of Co-Zn-Mn compounds with finite Mn, and their accurate description presents a challenge for theoretical modelling. In addition, this study highlights a need for neutron instrumentation capable of the comprehensive measurement of magnetic correlations over expanded ranges of momentum transfer in such multiple-length-scale magnets.

Monitoring the precipitation of the hardening phase in the new VDM® Alloy 780 by in-situ high-temperature small-angle neutron scattering, neutron diffraction and complementary microscopy techniques

The hardening phase precipitation process plays an important role in the development of new Ni-base superalloys. In the present work, we apply a powerful combination of complementary characterization techniques to characterize in-situ the γ’ precipitation in the new VDM® Alloy 780. During the whole heat treatment process, in-situ time-of-flight (TOF) neutron diffraction (ND) unambiguously identified the γ’ phase as well as its weight fraction and the misfit with the matrix while in-situ small-angle neutron scattering (SANS) provided precise precipitates’ size analysis. Atom probe tomography (APT) and scanning electron microscopy (SEM) provided detailed microstructural characterization and chemical composition of the phases necessary for a proper neutron scattering data evaluation. This contribution reveals more detailed information on the nucleation, growth, and Ostwald ripening processes starting from the early precipitation stage in bulk samples using the complementary microstructure investigation methods. The nucleation and growth kinetics of precipitates at 720 °C depend on heating rates and the size distribution obtained in the pre-heating history of the sample. A subsequent heat treatment step at 620 °C, typically used in Ni-base superalloys, does not lead to similar progressive precipitation or growth. The expected matrix-diffusion-controlled Ostwald ripening process of the γ’ precipitates was in-situ monitored by SANS on a full precipitation hardened sample at expected operating temperatures (750 °C) showing slower coarsening kinetics than other reported Ni-based superalloys.

Protein Condensation at Nanopore Entrances as Studied by Differential Scanning Calorimetry and Small-Angle Neutron Scattering.

The condensation of globular myoglobin (Mb) at the pore entrances of mesoporous silica (MPS) with a series of pore diameters (4.2, 6.4, 7.7, and 9.0 nm) was examined by differential scanning calorimetry (DSC) and contrast-matching small-angle neutron scattering (CM-SANS) experiments. The DSC measurements were performed to estimate the amount of Mb adsorbed at two different adsorption sites, namely, the pore interior and the pore entrance regions. The CM-SANS measurements were conducted to observe condensation of Mb molecules at the pore entrance regions. Notably, the nanopore entrance with a diameter close to twice that of the Mb diameter was found to be the specific cavity to facilitate the condensation of globular Mb. The Mb condensation occurred at the entrances of the 6.4 nm pore during the adsorption uptake from concentrated Mb solutions, whereas the adsorption uptake from diluted Mb solutions induced the condensation of Mb at the entrances of the 7.7 nm pore.

Revisiting neutron studies of reentrant spin glasses: the role of small-angle scattering

The application is discussed of neutron methods to the study of reentrant spin glasses (RSGs), close to the transition towards a `canonical' spin glass (SG). The focus is on two emblematic systems, namely Au1−x Fe x and amorphous a-Fe1−x Mn x . A set of experimental results is presented to highlight their peculiar static and dynamic properties. The role of small-angle neutron scattering (SANS) is stressed as an important tool to unravel the structure of these complex systems over mesoscopic length scales. Finally, recent SANS results performed under an applied magnetic field in the region of the RSG → SG transition are presented. They show that vortex-like defects are present in the RSG region up to the critical line and vanish in the SG region. These defects, which develop only in a ferromagnetic medium, could be a key feature to probe the emergence of long-range magnetic order.

Cholesterol Mediated Stable Vesicles: A Nano Drug Delivery Vehicle for Anti‐cancer Drugs Curcumin and 5‐Fluorourecil

AbstractHierarchical self‐assembly of new age surfactants, surface‐active ionic liquids (SAILs) has attracted increasing interests because of its close resemblance to membrane mimetic structure and its application in drug delivery. Among these self‐assembled structures, thermodynamically stable vesicular nanoaggregates are of great importance due to its structure that can carry both, hydrophilic and hydrophobic molecules within its core and bilayers, respectively. Here, we report the ester functionalized SAILs to synergistically interact with cholesterol, the natural sterol to transform the micellar nano‐aggregates to the vesicular nano‐aggregates with outstanding stability with dilution, pH, and temperature. The molecular self‐assembly formed was studied through state of the art analytical techniques including small‐angle neutron scattering (SANS) and fluorescence resonance energy transfer (FRET) upon varying the cholesterol/SAIL ratio. The thermodynamically stable vesicular nano‐aggregates were further used as the nano‐vehicles for the encapsulation and sustained release of the anticancer drugs, curcumin and 5‐flurouracil. Results of the present study could pave way for the realistic drug delivery applications of these thermodynamically stable nano‐aggregates and replace the traditional lipid based vesicle systems.