Ultra-small-angle Neutron Scattering Research Articles

Neutron Scattering Analysis of Cryptococcus neoformans Polysaccharide Reveals Solution Rigidity and Repeating Fractal-like Structural Patterns.

Cryptococcus neoformans is a fungal pathogen that can cause life-threatening brain infections in immunocompromised individuals. Unlike other fungal pathogens, it possesses a protective polysaccharide capsule that is crucial for its virulence. During infections, Cryptococcus cells release copious amounts of extracellular polysaccharides (exo-PS) that interfere with host immune responses. Both exo-PS and capsular-PS play pivotal roles in Cryptococcus infections and serve as essential targets for disease diagnosis and vaccine development strategies. However, understanding their structure is complicated by their polydispersity, complexity, sensitivity to sample isolation and processing, and scarcity of methods capable of isolating and analyzing them while preserving their native structure. In this study, we employ small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) for the first time to investigate both fungal cell suspensions and extracellular polysaccharides in solution. Our data suggests that exo-PS in solution exhibits collapsed chain-like behavior and demonstrates mass fractal properties that indicate a relatively condensed pore structure in aqueous environments. This observation is also supported by scanning electron microscopy (SEM). The local structure of the polysaccharide is characterized as a rigid rod, with a length scale corresponding to 3-4 repeating units. This research not only unveils insights into exo-PS and capsular-PS structures but also demonstrates the potential of USANS for studying changes in cell dimensions and the promise of contrast variation in future neutron scattering studies.

Direct In Situ Determination of the Surface Area and Structure of Deposited Metallic Lithium within Lithium Metal Batteries Using Ultra Small and Small Angle Neutron Scattering

AbstractDespite being the major cause of safety and performance issues in lithium metal batteries, experimental difficulties in quantifying directly the morphology of lithium deposited at electrode surfaces have meant that the mechanism of metallic lithium growth within batteries remains elusive. This study demonstrates that quantitative detail about the morphology of metallic lithium within batteries can be derived non‐destructively and directly using in situ ultra‐small and small‐angle neutron scattering. This information is obtained over a large electrode area in cells where lithium deposition processes are typical of real‐world applications. Complex variations of surface area and interfacial distances 1–10 µm and 100–300 nm are revealed in size that are influenced by current density and cell cycling history, providing valuable insight into the growth of metallic lithium features detrimental to battery performance. Such quantitative insight into the process of lithium growth is required for the development of safer high‐performance lithium metal batteries.

Shear influence on colloidal cluster growth: a SANS and USANS study.

This study examines the time evolution of silica/water clusters where the formation of a gel network from unitary silica particles is interrupted by a simple Couette shear field. The aim is to enable the general understanding of this simple system by examining the microscopic basis for the changes in viscosity by providing structural inputs from small-angle scattering for a simple theoretical model. The experimental system is an 8.3 nm particle silica solution (Ludox) where the gelation has been initiated by lowering the pH in a Couette cell providing a constant shear rate of 250 s-1. A unified small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) procedure is described to measure the scattered intensity in a wavevector range of 3 × 10-4 ≤ q (nm-1) ≤ 3.1 × 10-1, probing structural changes over a broad range of length scales from the nanometre to the micrometre. Scattering data provide a new means of better understanding the behaviour of colloidal clusters when subjected to an external applied shear over a continuous time sequence after gel initiation; a fit of the time-dependent scattered intensity leads to an estimation of the cluster's effective volume fraction and size as a function of time. A reductionist theoretical basis is described to predict the time-dependent viscosity behaviour of the sheared colloidal suspension gel-initiated cluster growth from the volume fraction of the clusters.

Small-Angle Neutron Scattering Investigation of Oil Recovery in Mineralogically Distinct Wolfcamp Shale Strata

Understanding and improving hydrocarbon yields during enhanced oil recovery (EOR) in unconventional reservoirs is complicated by the intrinsic mineralogical and geochemical heterogeneity of shale formations. In this study, we utilized small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) to investigate the degree of oil retention and its location in the nanoporous shale matrix for two mineralogically distinct shale samples. The two samples, dubbed “dark” and “light” based on their color, were taken from adjacent strata in a Wolfcamp shale core. While both samples contained kerogen, the dark sample contained more kerogen and clay (43.7 wt %) while the light sample contained more calcite (54.9 wt %). Samples were presaturated with decane, a model hydrocarbon, prior to pressure cycling with methane. Results showed significantly more retention of decane in 1.5–10 nm radius pores of both, likely indicating that oil is retained within kerogen nanopores. Although the dark sample had a higher porosity of 8.7%, versus 3.3% for the light sample, more pores were accessible to decane and a higher percentage of the imbibed decane was removable from the light sample compared to the dark sample. The majority of decane was not recoverable for the dark sample, indicating that EOR with methane can be challenging. These new findings can help to model expected recoveries of in-place oil from heterogeneous shale formations, as well as inform improved EOR strategies.

Microstructural evolution during acid induced gelation of cow, goat, and sheep milk probed by time-resolved (ultra)-small angle neutron scattering

Milks from small ruminant animals, such as goat and sheep, have gained increasing interest from the industry for the manufacture of various dairy products such as yoghurts. Heat treatment of milk is typically applied to improve the yoghurt texture. Here, time-resolved ultra-small angle neutron scattering (USANS) and small-angle neutron scattering (SANS) were employed to probe in situ the microstructural evolution of cow, goat, and sheep milks in D2O during acidification as affected by the heat treatment. Milk gelation can be envisaged as the progressive aggregation of the building blocks (casein micelles) in a fractal manner, which leads to the formation of micron scaled (∼3–10 μm) protein agglomerates. The heat treatment considerably enhanced the gelation of all milks, which is reflected by a faster increase in the fractal dimensions and aggregate sizes. For all three types of milks, similar final plateau fractal dimensions were observed for unheated (∼2.2–2.4) and heated milks (∼2.4–2.5), suggesting similar mass fractal microstructures in the size range probed by USANS. The final storage modulus after 10 h (G′final) follow the order of heated sheep milk ≈ sheep milk ≈ heated cow milk > cow milk > heated goat milk > goat milk. The colloidal calcium phosphate (CCP) dissolution kinetics tracked by SANS followed a similar trend as the evolution of the sample acidity (pD-value) and are not significantly affected by the types of milk or the heat treatment. This study shows a great potential of using time resolved USANS and SANS to investigate the microstructural evolution of protein aggregation and gelation.

OPUS: an easy way to push the limits of SANS instruments towards USANS

Chemistry and physics have made major advances in recent years, yielding much more complex systems with high hierarchical order across multiple length scales. Accordingly, characterization tools are required that can elucidate the structure of such new materials over all length scales. Simultaneous small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) measurements are a unique tool to study such complexity and can be applied to very different fields of science. The OPUS (Option USANS) project is the study of a USANS option for SANS instruments, designed to be very versatile and easy to implement. The main idea is to provide the opportunity to study at the same time, and under the same experimental conditions, complex systems such as polymers, bio-systems, complex fibres and self-assembling systems. More specifically, this work presents the design of an option that could be applied to the suite of SANS instruments at the European Spallation Source (ESS) which will allow exploration of a Q range with a minimum Q down to one order of magnitude lower than the value attainable with the standard SANS instrument at the ESS. The proposed setup, based on the SAMBA (small-angle multi-beam analysis) approach, is very easy and fast to implement on a conventional SANS instrument and constitutes a multi-beam approach involving two multi-slits and a set of lenses near the sample position. This contribution describes all the focusing elements necessary to attain the proposed configuration and a detailed study using McStas simulations to optimize all the parameters involved for two SANS instruments: the future LoKI at the ESS and the present D11 at the Institut Laue–Langevin, the latter used as a benchmark for the model. Simulations performed without taking into account gravity effects show that the multi-beam approach allows extending the Q ranges to 9 × 10−5–7 × 10−4 Å−1 and 5 × 10−5–3 × 10−4 Å−1 for LoKI and D11, respectively.

Effect of high temperature on nanopores in cokes

Small Angle Neutron Scattering and Ultra Small Angle Neutron Scattering were used to study the effect of annealing at temperatures of 1400 and 1600 °C, in an inert atmosphere, on the pore size distribution of three cokes prepared from Australian coals. The pore size range investigated was 1 nm to 2 µm. It was found that annealing substantially changed the size distribution of these pores in similar ways for all three cokes examined, despite the difference in rank and maceral composition of the starting coals. The pore sizes at which the greatest percentage changes in numbers occurred on heating was around 10 nm, with an increase in the number of both open and closed pores, by up to a factor of four after annealing at 1600 °C. For pores in the size range 100 nm to 2 µm, the number of closed pores decreased slightly and the number of open pores increased substantially; new open pores were created. The percentage increase in pore numbers introduced by annealing decreased with increasing pore size above 100 nm, but even at 2 µm pore radius, some samples showed a 50 % increase in total pore numbers. Annealing at greater temperature or longer time had a greater effect on pore numbers.

Neutron physics investigations of fundamental processes of statistical mechanics

Studies in spin dynamics of disordered media and multiple ultra-small angle neutron scattering are considered. The experiments were carried out on unique installations designed in ITEP laboratory of neutron physics: beta-NMR spectrometer and universal neutron diffractometer. The main attention is paid to random walks in disordered systems and ultra-small angle neutron scattering (USANS) on objects with space correlations in positions of scatterers. Synthesis of concentration expansion, semi-phenomenological theory and numerical simulations produced satisfactory description of the nuclear polarization transfer within disordered 8Li–6Li spin subsystem in LiF single crystal. The theory of USANS starts from eikonal approximation for the scattering amplitude, which (a) reproduces the phenomenological Moliere–Bethe theory for the observable neutron angular distributions for uncorrelated random positions of scatterers, and (b) gives a possibility to take into account their spatial correlations.

Ordered Mesoporous Silica Prepared in Different Solvent Conditions: Application for Cu(II) and Pb(II) Adsorption.

In this work, the synthesis of ordered mesoporous silica of MCM-41 type was investigated aimed at improving its morphology by varying the synthesis conditions in a one-pot process, employing different temperatures and solvent conditions. 2-methoxyethanol was used as co-solvent to ethanol. The co-solvent ratio and the synthesis temperature were varied. The pore morphology of the materials was characterized by nitrogen porosimetry and small angle neutron scattering (SANS), and the particle morphology by transmission electron microscopy (TEM) and ultra-small angle neutron scattering (USANS). The thermal behavior was investigated by simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC) measurements. The SANS and N2 sorption results demonstrated that a well-ordered mesoporous structure was obtained at all conditions in the synthesis at room temperature. Addition of methoxyethanol led to an increase of the pore wall thickness. Simultaneously, an increase of methoxyethanol content led to lowering of the mean particle size from 300 to 230 nm, according to the ultra-small angle scattering data. The ordered porosity and high specific surfaces make these materials suitable for applications such as adsorbents in environmental remediation. Batch adsorption measurements of metal ion removal from aqueous solutions of Cu(II) and Pb(II) showed that the materials exhibit dominantly monolayer surface adsorption characteristics. The adsorption capacities were 9.7 mg/g for Cu(II) and 18.8 mg/g for Pb(II) at pH 5, making these materials competitive in performance to various composite materials.

How to avoid multiple scattering in strongly scattering SANS and USANS samples

Small Angle Neutron Scattering (SANS) and Ultra Small Angle Neutron Scattering (USANS) are the only available experimental techniques to provide seamless non-destructive measurements of the geometry of the accessible and inaccessible pore structure of rocks from sub-nanopore size to the scale of macropores. They have therefore become the measurement of choice for tight reservoir rocks such as organic rich shales. A simplifying assumption in the analysis is, however, that during the path of neutrons through the sample each neutron is only scattered once. Shales are samples with a high scattering power and Multiple Scattering (MS) may occur which requires special modelling for deconvolution of the results. The approach to avoid MS is to simply reduce the sample thickness to <0.15–0.5 mm. Here, wepresent a systematic method on wavelength selection and preparation of samples to optimise extraction of microstructural data and minimise parasitic errors. Experimentally measured SAS transmission (TSAS) values are used as a practical criterion for estimation of the extent of MS.Generous beamtime allocations allowed robust testing revealing that sample thicknesses can be twice as thick as predicted using the standard protocol. Analysing thicker samples is particularly beneficial for statistically relevant characterisation of heterogeneous samples making the new protocol the method of choice for such samples.

Structure evolution of nanodiamond aggregates: a SANS and USANS study.

Ultra-small-angle neutron scattering (USANS) and small-angle neutron scattering (SANS) measurements, covering length scales from micrometres to nanometres, were made to investigate the structure of nanodiamonds (NDs) and their suspensions. These nanodiamonds were produced by two different techniques, namely by the detonation method and by the laser ablation of a carbon-hydro-carbon mixture. The (U)SANS results indicated the presence of structures four orders of magnitude larger than the dimensions of a single ND particle, consisting of aggregations of ND particles. This aggregation of the ND particles was studied by employing the contrast variation technique. Two different solvents, namely H2O and dimethyl sulfoxide (and their deuterated counterparts), were used to understand the role of hydrogen in the shape and size of the aggregates. The analysis of experimental data from SANS measurements also reveals the ND particles to have an ellipsoidal structure. Using a defined shape model and the SANS contrast variation technique, it was possible to characterize the non-diamond outer shell of the particles and determine the outer layer thickness. This clarification of the structure of the NDs will allow better preparation of suspensions/samples for various applications. Understanding the structure of NDs at multiple length scales also provides crucial knowledge of particle-particle interaction and its effect on the aggregation structures.

Probing oil recovery in shale nanopores with small-angle and ultra-small-angle neutron scattering

Increasing oil production from unconventional shale reservoirs is crucial to meet growing energy demands while achieving lower carbon emission than conventional crude oil. Enhanced oil recovery (EOR) has been proposed to improve hydrocarbon recovery rates through the injection of a fluid into the reservoir to facilitate residual oil release from the shale formation. However, economical and sustainable implementation of EOR requires advanced knowledge of fluid behavior in nano-sized pore spaces in shale. In this study, we utilize small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) as experimental probes to examine decane removal from a shale nano- to micro-porous matrix, utilizing methane as the injectant. The extent of decane saturation and recovery post-methane pressurization is quantified for clay-rich and carbonate-rich shale samples. A key finding is that extraction of decane by methane on depressurization is related to the methane-decane critical point. Furthermore, we found that although clay-rich shale had a much higher porosity of 5.6%, compared with 1.2% for carbonate-rich shale, decane was more easily removed from the carbonate-rich matrix, leading to similar hydrocarbon yields. These promising results demonstrate the ability of SANS and USANS to provide key insights into oil recovery from nano- to micron-sized pores in shale matrices. Combined with effects of various fractures on fluid behavior in shale, this experimental technique can be used to assess the viability of EOR injectants.

Physical disruption of gel particles on the macroscale does not affect the study of protein gel structure on the micro or nanoscale

Small and Ultra Small Angle Neutron Scattering (SANS and USANS) are commonly used techniques for the nano- and microstructural characterisation of systems such as polymers, gels, and aggregates. In many cases, for practical purposes, disruption of the larger structures into smaller particles may be necessary to meet the requirements of the specific sample environment used. However, a lack of knowledge about its effect on the nano- and microstructure prevents the adoption of this simple approach. In our study, we used a newly developed recirculated flow set-up designed for the in-situ measurement of blended transglutaminase-induced acid gels (TG). The average gel size reduction of distributions examined herein (d50; 1020, 462, and 294 μm) did not noticeably alter the integrity of gel structure at the interior of the particle. This study validates the proposed approach as an effective way to examine structural elements at a micro- or nanoscale using in-situ neutron scattering techniques.

Accessibility of Pores to Methane in New Albany Shale Samples of Varying Maturity Determined Using SANS and USANS

The accessibility of pores to methane has been investigated in Devonian New Albany Shale Formation early-mature (Ro = 0.50%) to post-mature (Ro = 1.40%) samples. A Marcellus Shale Formation sample was included to expand the maturation range to Ro 2.50%. These are organic matter-rich rocks with total organic carbon (TOC) values of 3.4 to 14.4% and porosity values of 2.19 to 6.88%. Contrast matching small-angle neutron scattering (SANS) and ultra-small angle neutron scattering (USANS) techniques were used to generate porosity-related data before and after pressure cycling under hydrostatic (in a vacuum and at 500 bar of deuterated methane) and uniaxial stress (0 to ca. 350 bar) conditions. Our results showed that the accessible porosity was small for the samples studied, ranging from zero to 2.9%. No correlation between the accessible porosity and TOC or mineralogical composition was revealed, and the most likely explanation for porosity variation was related to the thermal transformation of organic matter and hydrocarbon generation. Pressure caused improvements in accessible porosity for most samples, except the oil window sample (Ro = 0.84%). Our data show that densification of methane occurs in nanopores, generally starting at diameters smaller than 20 nm, and that the distribution of methane density is affected by pressure cycling.

Dual Transient Networks of Polymer and Micellar Chains: Structure and Viscoelastic Synergy.

Dual transient networks were prepared by mixing highly charged long wormlike micelles of surfactants with polysaccharide chains of hydroxypropyl guar above the entanglement concentration for each of the components. The wormlike micelles were composed of two oppositely charged surfactants potassium oleate and n-octyltrimethylammonium bromide with a large excess of anionic surfactant. The system is macroscopically homogeneous over a wide range of polymer and surfactant concentrations, which is attributed to a stabilizing effect of surfactants counterions that try to occupy as much volume as possible in order to gain in translational entropy. At the same time, by small-angle neutron scattering (SANS) combined with ultrasmall-angle neutron scattering (USANS), a microphase separation with the formation of polymer-rich and surfactant-rich domains was detected. Rheological studies in the linear viscoelastic regime revealed a synergistic 180-fold enhancement of viscosity and 65-fold increase of the longest relaxation time in comparison with the individual components. This effect was attributed to the local increase in concentration of both components trying to avoid contact with each other, which makes the micelles longer and increases the number of intermicellar and interpolymer entanglements. The enhanced rheological properties of this novel system based on industrially important polymer hold great potential for applications in personal care products, oil recovery and many other fields.

Effect of NaCl and CaCl2 concentration on the rheological and structural characteristics of thermally-induced quinoa protein gels

The effect of ionic strength on the heat-induced gelation of quinoa protein isolates (QPI) at pH 7 was investigated. The gelation behaviour and gel strength were characterised by oscillatory rheology. The microstructural characteristics of QPI solutions and gels were probed by ultra-small angle neutron scattering (USANS), small-angle X-ray and neutron scattering (SAXS, SANS), and confocal laser scanning microscopy (CLSM). This suite of techniques provided structural details covering a wide range of length scales from tens of micron to nanometre. It was found that the gelation temperature decreased from 73 °C to 40 °C and the G* (1 Hz) increased from ∼67 Pa to ∼1285 Pa with increasing concentration of NaCl from 0 to 200 mM. A particle size of ∼32 Å and ∼57 Å was identified within the QPI gel containing 0–200 mM NaCl from SAXS and SANS, respectively and whose size decreased upon addition of CaCl2. For all QPI samples, heat treatment promoted protein aggregation on the micron scale, while a larger structural unit (Rg∼ 170 nm) was kept intact as revealed by USANS. A similar mass fractal structure (df = 2) was observed in the QPI gels containing 0–200 mM NaCl, while CaCl2 addition caused the formation of large protein agglomerates (Rg∼2.5–4.0 μm) with a more compact and denser structural organisation (df = 2.5) inside the protein blobs. CLSM showed that the QPI gels containing CaCl2 are prone to phase separation. Overall, this finding shows the thermal gelation behaviour of QPI can be modulated by the ion type and concentration, which is similarly observed in other globular protein systems. These results provide useful information for the design and preparation of quinoa gels for food applications.

Ultra-small-angle neutron scattering study on temperature-dependent precipitate evolution in CoCrFeNiMo0.3 high entropy alloy

Phase evolution of CoCrFeNiMo0.3 high entropy alloy (HEA) under different annealing temperatures was investigated by means of ultra-small-angle neutron scattering (USANS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). For the as-cast CoCrFeNiMo0.3 alloy, a dendritic structure consisting of mainly face-centered cubic (FCC) solid solution matrix and small amount of micro-sized σ precipitates was observed. Upon isothermal annealing, secondary phase precipitation occurred and precipitates with two size ranges (i.e., microscale and nanoscale) generated in the alloy. These precipitates were identified as newly formed μ and σ phases. Specifically, the size distribution of the nanoscale μ precipitates was determined by USANS measurements. It was found that the size of the nanoscale precipitates increased with the annealing temperature, jumping from 72 nm at 750 °C to 258 nm at 800 °C, which contributed to the sharp drop in hardness of the alloy. The present alloy maintained high hardness within a wide temperature range of 550–750 °C, which makes it a promising material for structural applications at intermediate temperatures.

Analyses of hierarchical structures in vulcanized SBR rubber by using contrast-variation USANS and SANS

The hierarchical structures of poly(styrene-ran-butadiene) (SBR) rubber vulcanized with sulfur in a swollen state were investigated by using the contrast-variation ultra-small-angle neutron scattering (USANS) and small-angle neutron scattering (SANS) techniques. The following three levels of hierarchical structure were found: (i) ZnO clusters surrounded by dense SBR networks of the order of 1000 Å in size, (ii) dense networks of SBR in the size range of 70–100 Å and (iii) a mesh size of the network of the order of 10 Å. In addition to the three kinds of structure, dense networks without ZnO of the order of 1000 Å were also observed. These last networks were formed by ZnO's reaction with sulfur. However, the ZnO clusters disappeared, which is associated with the diffusion of Zn.

Feasibility of Probing the Filler Restructuring in Magnetoactive Elastomers by Ultra-Small-Angle Neutron Scattering

Ultra-small-angle neutron scattering (USANS) experiments are reported on isotropic magnetoactive elastomer (MAE) samples with different concentrations of micrometer-sized iron particles in the presence of an in-plane magnetic field up to 350 mT. The effect of the magnetic field on the scattering curves is observed in the scattering vector range between 2.5 × 10−5 and 1.85 × 10−4 Å−1. It is found that the neutron scattering depends on the magnetization history (hysteresis). The relation of the observed changes to the magnetic-field-induced restructuring of the filler particles is discussed. The perspectives of employing USANS for investigations of the internal microstructure and its changes in magnetic field are considered.

Controlled drug release: On the evolution of physically entrapped drug inside the electrospun poly(lactic-co-glycolic acid) matrix

The drug loading and releasing properties of poly(lactic-co-glycolic acid) (PLGA) were approached with the application of neutron techniques. The neutron reflection (NR) study on the response of PLGA material to vapor and to bulk water revealed that the hydration of PLGA origins from the molecular compatibility between water and PLGA. Hydration is reversible with regard to the change in humidity and temperature. Capecitabine as drug was embedded in the electrospun PLGA fibers. Small angle neutron scattering (SANS) was able to disclose the domain of entrapped drug inside the fibers and trace its evolution over time when the electrospun membrane was incubated in D2O buffer solution. The evolution of drug domains is discussed in terms of the concentration dependence, the temperature dependence, and the relevance between the drug diffusion inside the polymer matrix and the drug release out to the medium. It was observed that, at 20 °C the drug-related domains are relatively small (~ 100 Å) and relax extremely slow while at 37 °C the drug-related domains are relatively larger (~ 200 Å) and relax faster. These behaviors can be related to the glassy property of structural material. The transportation of drug through the polymer matrix relies on the global relaxation of PLGA chains. The variation of fiber diameter vs. incubation time was followed by ultra-small angle neutron scattering (USANS). The bi-phasic or tri-phasic release kinetics from a series of fibers with different drug loading (2%, 5%, 10%, 20%, 30%, 40%, 50%) were discussed based on the SANS and USANS discovery.