Structural Characterization of Biomaterials by Means of Small Angle X-rays and Neutron Scattering (SAXS and SANS), and Light Scattering Experiments

Scattering techniques represent non-invasive experimental approaches and powerful tools for the investigation of structure and conformation of biomaterial systems in a wide range of distances, ranging from the nanometric to micrometric scale. More specifically, small-angle X-rays and neutron scattering and light scattering techniques represent well-established experimental techniques for the investigation of the structural properties of biomaterials and, through the use of suitable models, they allow to study and mimic various biological systems under physiologically relevant conditions. They provide the ensemble averaged (and then statistically relevant) information under in situ and operando conditions, and represent useful tools complementary to the various traditional imaging techniques that, on the contrary, reveal more local structural information. Together with the classical structure characterization approaches, we introduce the basic concepts that make it possible to examine inter-particles interactions, and to study the growth processes and conformational changes in nanostructures, which have become increasingly relevant for an accurate understanding and prediction of various mechanisms in the fields of biotechnology and nanotechnology. The upgrade of the various scattering techniques, such as the contrast variation or time resolved experiments, offers unique opportunities to study the nano- and mesoscopic structure and their evolution with time in a way not accessible by other techniques. For this reason, highly performant instruments are installed at most of the facility research centers worldwide. These new insights allow to largely ameliorate the control of (chemico-physical and biologic) processes of complex (bio-)materials at the molecular length scales, and open a full potential for the development and engineering of a variety of nano-scale biomaterials for advanced applications.     

Small angle neutron scattering and its application in battery systems

Small angle neutron scattering is a powerful, non-destructive technique that can provide both structural and compositional information. Recently, it has been applied to the field of battery research and has helped elucidate some of the phenomena that are traditionally difficult to probe, including lithiation mechanisms, solid electrolyte interface formation/composition, and electrode microstructure. Specific components of interest can be selectively probed through the application of targeted experiments, contrast variation, and specific composition/structural models gained from complementary data from other analytical techniques.     

Recent progress on polymer dynamics by neutron scattering: From simple polymers to complex materials

The recent (from 2010 onward) contributions of quasielastic neutron scattering techniques (time of flight, backscattering, and neutron spin echo) to the characterization and understanding of dynamical processes in soft materials based on polymers are analyzed. The selectivity provided by the combination of neutron scattering and isotopic—in particular, proton/deuterium—labeling allows the isolated study of chosen molecular groups and/or components in a system. This opportunity, together with the capability of neutrons to provide space/time resolution at the relevant length scales in soft matter, allows unraveling the nature of the large variety of molecular motions taking place in materials of increasing complexity. As a result, recent relevant works can be found dealing with dynamical process which associated characteristic lengths and nature are as diverse as, for example, phenyl motions in a glassy linear homopolymer like polystyrene and the chain dynamics of a polymer adsorbed on dispersed clay platelets. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

High-Performance Alkaline Seawater Electrolysis with Anomalous Chloride Promoted Oxygen Evolution Reaction

A highly selective and durable oxygen evolution reaction (OER) electrocatalyst is the bottleneck for direct seawater splitting because of side reactions primarily caused by chloride ions (Cl⁻). Most studies about OER catalysts in seawater focus on the repulsion of the Cl⁻ to reduce its negative effects. Herein, we demonstrate that the absorption of Cl⁻ on the specific site of a popular OER electrocatalyst, nickel-iron layered double hydroxide (NiFe LDH), does not have a significant negative impact; rather, it is beneficial for its activity and stability enhancement in natural seawater. A set of in situ characterization techniques reveals that the adsorption of Cl⁻ on the desired Fe site suppresses Fe leaching, and creates more OER-active Ni sites, improving the catalyst's long-term stability and activity simultaneously. Therefore, we achieve direct alkaline seawater electrolysis for the very first time on a commercial-scale alkaline electrolyser (AE, 120 cm² electrode area) using the NiFe LDH anode. The new alkaline seawater electrolyser exhibits a reduction in electricity consumption by 20.7 % compared to the alkaline purified water-based AE using commercial Ni catalyst, achieving excellent durability for 100 h at 200 mA cm⁻².     

Characterization of polymer materials by scattering techniques,with applications to block copolymers

The application of six techniques—static and dynamic light scattering, small-angle neutron and X-ray scattering, neutron and X-ray reflectivity—to the characterization of polymer materials is summarized. Emphasis is placed on the similarities and differences among the various techniques, and on recent advances in experimental practice. Twelve examples from the recent literature are described, most of which concern block copolymers. A brief introduction to block copolymer properties is also provided.     

Synthesis and Characterization of Poly(ethylene glycol) Dimethacrylate Hydrogels

Facile synthesis and detailed characterization of photo-polymerizable and biocompatible poly(ethylene glycol) dimethacrylates (PEGDM) and their hydrogels are described. Combined analyses of ¹H NMR and MALDI-TOF MS confirmed the formation of prepolymers of high purity and narrow mass distribution (PD < 1.02). A systematic investigation into the structure and mechanical properties of PEGDM hydrogels was performed to characterize the relationships between the network structure and gel properties. Small-angle neutron scattering was used to characterize the structural features of hydrogels with respect to their semidilute solution precursors. A well-defined structural length scale (correlation length) manifested as a maximum in the scattering intensity was observed for hydrogels derived from high molecular mass PEGDMs and/or high oligomer mass fractions. Hydrogels derived from lower molecular mass PEGDMs and/or low oligomer mass fractions exhibited multiple correlation lengths suggesting the formation of inhomogeneous gel structures. The shear moduli, determined from uniaxial compression measurement, showed that the gel structures correlate well with the gel mechanical properties.     

Small-angle X-Ray and neutron scattering in food colloids

Small-angle and ultra-small-angle X-ray and neutron scattering techniques provide structural information on the nanometre-to-micron length scale. This review describes recent examples and advances of these techniques in the field of food colloids. The article highlights the structural information that can be extracted when applied to all macronutrient classes, namely fats, carbohydrates and proteins, and mixtures thereof, as well as covering emerging applications and future opportunities.     

中子深度剖析技术研究可充锂金属负极

可充锂金属负极严重的界面不稳定性和安全问题极大限制了其商业化应用,对于锂的沉积/溶出行为以及锂枝晶的成核生长机理的清楚认识将有利于更高效的可充锂金属负极改性研究。然而,由于锂金属的高反应活性所带来的产物复杂性及其形貌多样性给原位谱学表征带来了诸多的困难。中子深度剖析(Neutron Depth Profiling,NDP)技术由于其高穿透特性、定量非破坏性、且对锂的高灵敏性,在实时研究锂金属电池中锂的电化学行为上显示出广阔的应用前景。本文首先简要介绍了NDP技术的测试原理及提高其空间/时间分辨率的方法,同时总结分析了近年来NDP技术在液态/固态电池体系中锂金属负极研究的应用,并展望了NDP技术今后的发展前景。     

Dual length morphological model for bulk‐heterojunction,polymer‐based solar cells

We present a dual length morphological model for the active layer of bulk‐heterojunction, polymer‐based solar cells using results from neutron and X‐ray scattering techniques. Two critical characteristic lengths are found in the mixtures composed of poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM). A characteristic length at 15 nm is the local characteristic of the P3HT crystals and PCBM agglomerations, which is independent of the bulk composition upon relaxation by thermal annealing. Conversely, a larger bicontinuous structure described by Teubner–Strey model with phase distances between 23 and 35 nm forms only after thermal annealing, which is highly correlated to the bulk compositions. These results suggest phase separation between the polymer and fullerene can only be partially manipulated by simple processing techniques such as coating conditions and annealing, and a more rigorous design of the morphology should be implemented in the future. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym. Phys. 2014 , 52, 387–396     

燃料电池电极表界面催化氧还原反应的STM研究进展

催化氧还原反应的电催化剂是燃料电池的一个重要组成部分. 从分子尺度研究催化氧还原反应中所涉及的表界面反应机理,不仅有利于深入理解催化机理,更有利于指导人们合理地设计新型的电催化剂. 本文结合近年来国内外的研究工作,概述了通过扫描隧道显微镜研究燃料电池内部催化氧还原反应过程中所涉及的表面形貌变化、单分子结构变化、中间体的观测以及反应产物调控等方面最新进展,并展望了该研究领域的发展趋势.     

In-Situ/Operando X-ray Characterization of Metal Hydrides

In this article, the capabilities of soft and hard X-ray techniques, including X-ray absorption (XAS), soft X-ray emission spectroscopy (XES), resonant inelastic soft X-ray scattering (RIXS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), and their application to solid-state hydrogen storage materials are presented. These characterization tools are indispensable for interrogating hydrogen storage materials at the relevant length scales of fundamental interest, which range from the micron scale to nanometer dimensions. Since nanostructuring is now well established as an avenue to improve the thermodynamics and kinetics of hydrogen release and uptake, due to properties such as reduced mean free paths of transport and increased surface-to-volume ratio, it becomes of critical importance to explicitly identify structure-property relationships on the nanometer scale. X-ray diffraction and spectroscopy are effective tools for probing size-, shape-, and structure-dependent material properties at the nanoscale. This article also discusses the recent development of in-situ soft X-ray spectroscopy cells, which enable investigation of critical solid/liquid or solid/gas interfaces under more practical conditions. These unique tools are providing a window into the thermodynamics and kinetics of hydrogenation and dehydrogenation reactions and informing a quantitative understanding of the fundamental energetics of hydrogen storage processes at the microscopic level. In particular, in-situ soft X-ray spectroscopies can be utilized to probe the formation of intermediate species, byproducts, as well as the changes in morphology and effect of additives, which all can greatly affect the hydrogen storage capacity, kinetics, thermodynamics, and reversibility. A few examples using soft X-ray spectroscopies to study these materials are discussed to demonstrate how these powerful characterization tools could be helpful to further understand the hydrogen storage systems.     

Ultra-small-angle X-ray and neutron scattering study of colloidal dispersions

The ultra-small-angle X-ray and neutron scattering techniques are useful techniques for the investigation of colloidal systems. The very high small-angle resolution of these scattering techniques has provided important and novel information to elucidate the formation mechanism of colloidal crystals. The Bonse–Hart optical system is expected to become a standard tool for investigating mesoscopic structures.     

铂基氧还原电催化剂的结构演变

质子交换膜燃料电池的商业化有望在不久的将来实现更清洁的能源社会.然而,氧还原反应缓慢的反应动力学和苛刻的条件对质子交换膜燃料电池的寿命和成本产生了巨大的挑战.之前大多数铂基催化剂的设计都将重点更多地放在提高活性上.随着质子交换膜燃料电池的商业化,寿命问题也受到了更多的关注.对整个生命周期中结构演变进行深入地了解,有助于...     

Several Key Factors for Efficient Electrocatalytic Water Splitting: Active Site Coordination Environment,Morphology Changes and Intermediates Identification

Water-splitting has emerged as a promising alternative strategy to produce clean hydrogen fuel. However, current electrocatalytic water splitting suffers from sluggish kinetics, thus developing efficient electrocatalysts is crucial. Identifying reaction centers discloses the reaction mechanism and will undoubtedly facilitate the design and optimization of efficient water splitting electrocatalysts. This review summarizes several advances involving the identification of the actual active sites and intermediates capture on the catalytic surface. The morphology and valence states change on 2D materials are chose to illustrate how structural evolution affect catalytic activity. Specifically, in situ/ex situ electron microscopy techniques that used for the characterization of catalytic sites, and spectroscopy techniques that used to detect active intermediates at the molecular level are highlighted. In addition, several perspectives, such as the development of new in situ techniques and electrokinetic analysis methods, are emphasized to shed light on future research.     

Time-resolved small-angle neutron scattering study of polyethylene crystallization from solution

With time-resolved small-angle neutron scattering (TR-SANS), the crystallization kinetics of polyethylene from deuterated o-xylene solutions upon a temperature jump have been investigated. On the basis of a morphological model of coexisting lamellar stacks and coil chains in solution, experimental data have been quantitatively analyzed to provide structural information, such as the lamellar long period, the lamellar crystal thickness, the thickness of the amorphous layers between lamellae, the degree of crystallinity, and the crystal growth rate at various degrees of undercooling. The viability of TR-SANS for studying polymer crystallization is demonstrated through the consistency of these measurements and well-established knowledge of polyethylene crystallization from xylene solutions. One unique feature of this experimentation is that both the growth of lamellar crystals and the condensation of coil chains from solution are monitored simultaneously. The ratio of the crystal growth to the chain consumption rate decreases rapidly with a decreasing degree of undercooling. The Avrami analysis suggests that the growth mechanism approaches two-dimensional behavior at higher temperatures, and this is consistent with the observation of an increasing ratio of the sharp-surface area to the bulk crystal growth rate with temperature. The limitations, possible remedies, and potentials of TR-SANS for studying polymer crystallization are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3133–3147, 2004     

Viscosity reduction in polymer nanocomposites: Insights from dynamic neutron and X-ray scattering

The addition of nanoparticles to a polymer matrix can in certain cases induce a reduction in viscosity, with respect to the pure matrix, in the resulting composites. This counterintuitive phenomenon cannot be explained using the most common rheological models. For this reason, it has been chosen as a good example in this paper to demonstrate the value and methods of dynamic X-ray and neutron scattering techniques for the investigation of polymer nanocomposites. An overview of the main results on this topic is presented together with an introduction to the basic concepts relating to X-ray photon correlation spectroscopy, neutron backscattering, and neutron spin echo measurements.     

Structural characterization of protein–polymer conjugates for biomedical applications with small-angle scattering

Protein–polymer conjugates, typically consisting of one or more polymers covalently attached to a protein, are an increasingly common component in biotechnology. Polymers can increase circulation time, alter immune responses, and influence the self-assembly of proteins to which they are attached. To understand and take full advantage of the benefits that protein–polymer conjugates provide, there is a strong need for structural characterization of both the conjugates and their self-assembled structures. Although X-ray crystallography is suitable for determining protein structure, protein–polymer conjugates do not generally crystallize, requiring the use of alternative techniques. Small-angle scattering, with neutrons in particular, is one such technique. In this article, we review recent work in the area of protein–polymer conjugates and highlight the important role that structure plays. We then highlight shape-dependent and shape-independent approaches for structural characterization of protein–polymer conjugates and future directions in small-angle scattering interpretation. We conclude by introducing a new model that we suggest may be useful in the future to acquire more detailed structural properties.     

Spinodal decomposition of a polystyrene/poly(cyclohexyl acrylate-stat-butyl methacrylate) blend

Summary The dynamics of spinodal decomposition (SD) after a temperature jump from a kinetically formed single phase state into the unstable part of the two-phase region has been studied with a blend of polystyrene and poly(cyclohexyl acrylate-statbutyl methacrylate). The time evolution of the structure factor has been examined by small-angle neutron and light-scattering techniques. The combination of the different techniques gave access to a wide wave vector and time range covering a large range of length scales. The activation energy of the diffusion process during spinodal decomposition was determined by a scaling analysis of the later stages of SD, because early stages of SD could not be resolved.