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Macromolecules 55(19), 8757 - 8765 (2022). doi:10.1021/acs.macromol.2c01326, Dynamics of nanoparticles (NPs) in microscopic networks, in particular, localization and transport, play a key role in designing new functional nanocomposites and drug delivery systems. To this aim, it is crucial to understand the interplay between the network structure and dynamics on the microscopic scale which determines NP diffusion. Here, we study the localization and transport of spherical NPs in photorheological wormlike micellar nanocomposites where the mobility of the NPs is controlled by the network mesh size and the micelle length, which can be tuned by UV-illumination. The macroscopic viscoelastic properties are measured by classical rheology, while X-ray photon correlation spectroscopy and nanorheology provide information on the microscopic NP dynamics on length scales on the order of the network mesh size. On long time scales, the data reveal that transport through the network is determined by the ratio between the NP size and the network mesh size, while upon UV illumination, the NP mobility is drastically enhanced. On shorter time scales, the influence of the dynamical and structural micelle properties on the NP dynamics under confinement is explored and indicates an anomalous speed-up of the dynamics, which is discussed in the context of changes in the local structure and non-linear phenomena such as strain stiffening and hopping motion., Published by Soc., Washington, DC

International audience; The Complex System and Biomedical Sciences (CBS) group at the European Synchrotron Radiation Facility (ESRF) in Grenoble is dedicated to the study of a broad family of materials and systems, including soft and hard condensed matter, nanomaterials, and biological materials. The main experimental methods used for this purpose are X-ray diffraction, reflectivity, scattering, photon correlation spectroscopy, and time-resolved X-ray scattering/diffraction. After a recent and successful Extremely Brilliant Source (EBS) upgrade, the Grenoble synchrotron has become the first of the 4th generation high energy facilities, which offers unprecedented beam parameters for its user community, bringing new experimental opportunities for the exploration of the nanoscale structure, kinetics, and dynamics of a myriad of systems. In this contribution, we present the impact of the recent upgrade on the selected beamlines in the CBS group and a summary of recent scientific activities after the facility reopening.

Combined coherent X-ray diffraction imaging and wide-angle X-ray diffraction is demonstrated to study the morphology, internal structure and mineralogy of shale fragments. Estimates of the unconnected nanoscale pore structure of shale microparticles are obtained., Despite the abundance of shales in the Earth’s crust and their industrial and environmental importance, their microscale physical properties are poorly understood, owing to the presence of many structurally related mineral phases and a porous network structure spanning several length scales. Here, the use of coherent X-ray diffraction imaging (CXDI) to study the internal structure of microscopic shale fragments is demonstrated. Simultaneous wide-angle X-ray diffraction (WAXD) measurement facilitated the study of the mineralogy of the shale microparticles. It was possible to identify pyrite nanocrystals as inclusions in the quartz–clay matrix and the volume of closed unconnected pores was estimated. The combined CXDI–WAXD analysis enabled the establishment of a correlation between sample morphology and crystallite shape and size. The results highlight the potential of the combined CXDI–WAXD approach as an upcoming imaging modality for 3D nanoscale studies of shales and other geological formations via serial measurements of microscopic fragments.

The self-transformation of solid microspheres into complex core-shell and hollow architectures cannot be explained by classical Ostwald ripening alone. Here, coherent X-ray diffraction imaging and 3D X-ray fluorescence were used to visualize in 3D the formation of hollow microparticles of calcium carbonate in the presence of polystyrene sulfonate (PSS). During the dissolution of the core made from 10-25 nm crystals, the shell developed a global spheroidal shape composed of an innermost layer of 30 nm particles containing high PSS content on which oriented vaterite crystals grew with their

This article presents a combined approach where quantitative forward-scattering coherent diffraction imaging (CDI) is supported by crystal diffraction using 8.1 keV synchrotron X-ray radiation. The method allows the determination of the morphology, mass density and crystallinity of an isolated microscopic specimen. This approach is tested on three homogeneous samples made of different materials with different degrees of crystallinity. The mass density and morphology are revealed using three-dimensional coherent diffraction imaging with a resolution better than 36 nm. The crystallinity is extracted from the diffraction profiles measured simultaneously with coherent diffraction patterns. The presented approach extends CDI to structural characterization of samples when crystallinity aspects are of interest.

International audience; Peculiar temporal intermittent microscopic dynamics has been recently reported during structural relaxation in metallic glasses, though its origin is poorly understood. By using x-ray photon correlation spectroscopy, we have investigated the atomic motions in a model system of metallic glass with distinct stability and in situ stress states. We find that the microscopic dynamics can be tuned from dramatically nonmonotonous to monotonous. The intermittent dynamics is always accompanied by the activation of a secondary relaxation process, as indicated by the drop of the initial nonergodic plateau of the intensity-intensity correlation function. Both phenomena depend on the material state and can be suppressed by simultaneously lowering the fictive temperature and external loading, leading the glass in a stationary metastable state which appears independent on the thermal history of the system.

X-ray photon correlation spectroscopy is used to study the dynamics of the glass former B 2 O 3 across the glass transition temperature, T g . The obtained data confirm that while the structural re...

Predictive and quantitative understanding of ion and mass transport in liquid and polymeric electrolytes is at the heart of electrochemistry. Here, the goal is to accurately simulate the performance of an electrochemical cell, for which the temperature- and concentration-dependent transport coefficients of a given electrolyte, as well as the thermodynamic mean salt molal activity coefficient, must be known. These are the conductivity, σ, the salt diffusion coefficient, D, and the cation transference number, t+. The transport coefficients must hence be extracted with high accuracy from experimental measurements. The transference number is defined as the ratio of current carried by the cation to the total electric current. Its importance with regards to energy density and power density was recognized in the early 1990s by Doyle, Fuller and Newman (1). Nevertheless, researchers still argue about transference number values, even in baseline systems such as lithium bistrifluoromethanesulfonimidate (LiTFSI) in Poly(ethylene oxide) (PEO) (2). The transference number can be measured via the steady-state Bruce-Vincent polarization method (3, 4), the Balsara-Newman method (5), as well as pulsed field gradients NMR (pfg-NMR) (6) and pulsed field gradients electrophoretic NMR (e-NMR) (2). Despite extensive efforts towards unified results of these approaches, in particular as a function of ion concentration, a clear picture has not yet emerged. Towards this end, we developed an alternative approach towards determining the ion transport properties. Specifically, we directly and operando measured precise microscopic and macroscopic physical properties of the electrolyte upon cell polarization in a Li/electrolyte/Li cell, combined this with calculations via concentrated solution theory continuum modelling (CM), and rationalized our findings with microscopic insight from molecular dynamics (MD) simulations. We utilized a well-studied benchmark model system electrolyte consisting of PEO and LiTFSI at Li+ to EO molar ratio of r = 0.1. Under constant voltage polarization, we directly measured the velocity associated with electrolyte and ions via heterodyne synchrotron X-ray photon correlation spectroscopy (XPCS), and the TFSI- concentration gradient from electrode to electrode via X-ray absorption microscopy (XAM). The significance of our results lies in the unification of microscopic and macroscopic predictions from simulation with experimental measurements as well as the self-consistent determination of a concentration-independent transference numbers of approximately 0.2. Our study paves the way for further length- and time-scale bridging understanding of ion transport. 1. M. Doyle, T. F. Fuller, J. Newman, The Importance of the Lithium Ion Transference Number in Lithium Polymer Cells. Electrochimica Acta 39, 2073-2081 (1994). 2. M. P. Rosenwinkel, M. Schönhoff, Lithium Transference Numbers in PEO/LiTFSA Electrolytes Determined by Electrophoretic NMR. Journal of The Electrochemical Society 166, A1977-A1983 (2019). 3. J. Evans, C. A. Vincent, P. G. Bruce, Electrochemical Measurement of Transference Numbers in Polymer Electrolytes. Polymer 28, 2324-2328 (1987). 4. P. G. BRUCE, C. A. VINCENT, STEADY STATE CURRENT FLOW IN SOLID BINARY ELECTROLYTE CELLS. J. Electroanal. Chem. 225, 1-17 (1987). 5. D. M. Pesko, S. Sawhney, J. Newman, N. P. Balsara, Comparing Two Electrochemical Approaches for Measuring Transference Numbers in Concentrated Electrolytes. Journal of The Electrochemical Society 165, A3014-A3021 (2018). 6. D. M. Pesko et al., Negative transference numbers in poly(ethylene oxide)-based electrolytes. Journal of the Electrochemical Society 164, E3569-E3575 (2017).

The simplest route to synthesize porous calcium carbonate in large quantity is to mix concentrated aqueous solutions containing Ca2+ and CO32– ions. The formed vaterite microspheres have a porous structure, but are not thermodynamically stable. Heating above 350 °C induces a solid-state transformation of vaterite into the most stable phase, calcite, while maintaining an unusual spheroidal morphology. Here, by using three-dimensional coherent X-ray diffraction imaging, the morphological evolution associated with the thermally induced phase transition is studied. We observe that despite an overall similar pore volume, the pore geometry differs markedly before and after annealing. Before annealing, the microspheres display elongated and nanometer sized pores, while after annealing they exhibit large and open pores. During transition, the specific surface area decreases from 7 m2/g for vaterite to 3 m2/g for calcite. The general trend resulting from 3D observations is that the solid state phase transition is ...

This work presents measurements of laser-induced solid-solid phase transitions in Co nanoparticles, using time-resolved wide-angle x-ray scattering with ε phase into a mixed phase of 2/3 hcp and 1/3 fcc character during the first 100 ps. The measured scattering signal observed at the shortest investigated time delay of 20 ps has less scattering intensity at the dominant fcc/hcp Bragg peak positions compared to the difference signal acquired at 100 ps. This suggests the formation of a partially disordered solid intermediate phase on the sub-100-ps timescale.

International audience; Characterization of the wavefront of an X-ray beam is of primary importance for all applications where coherence plays a major role. Imaging techniques based on numerically retrieving the phase from interference patterns are often relying on an a-priori assumption of the wavefront shape. In Coherent X-ray Diffraction Imaging (CXDI) a planar incoming wave field is often assumed for the inversion of the measured diffraction pattern, which allows retrieving the real space image via simple Fourier transformation. It is therefore important to know how reliable the plane wave approximation is to describe the real wavefront. Here, we demonstrate that the quantitative wavefront shape and flux distribution of an X-ray beam used for CXDI can be measured by using a micrometer size metal-coated polymer sphere serving in a similar way as the hole array in a Hartmann wavefront sensor. The method relies on monitoring the shape and center of the scattered intensity distribution in the far field using a 2D area detector while raster-scanning the microsphere with respect to the incoming beam. The reconstructed X-ray wavefront was found to have a well-defined central region of approximately 16 mu m diameter and a weaker, asymmetric, intensity distribution extending 30 mu m from the beam center. The phase front distortion was primarily spherical with an effective radius of 0.55 m which matches the distance to the last upstream beam-defining slit, and could be accurately represented by Zernike polynomials. (C) 2016 Optical Society of America

Fullerene intercalation between the side chains of conjugated polymers has a detrimental impact on both charge separation and charge transport processes in bulk heterojunction (BHJ) organic photovoltaic cells (OPVs). In situ grazing incidence X‐ray scattering experiments allow to characterize the structure formation, drying kinetics, and intercalation in blends of phenyl‐c61‐butyric acid methyl ester (PC60BM) and poly(2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) named (pBTTT‐C14) from their 1,2‐orthodichlorobenzene (oDCB) solutions with different volume fractions of dodecanoic acid methyl ester (Me12) as a solvent additive. The structure formation process during evaporation of the solvent:additive mixture can be described by five periods, which are correlated to a multistep contraction of the lamellar stacking of the bimolecular crystals. The onset of crystallization is delayed by increasing the additive volume fraction in the coating solution leading to a promoted crystallinity. A conclusive picture of fullerene intercalation and additive‐tuned structural evolution during the drying of thin films of the polymer:fullerene BHJ blends will be presented.

This paper reports on coherent scattering experiments in the low-count regime with less than one photon per pixel per acquisition on average, conducted with two detectors based on the Eiger single-photon-counting chip. The obtained photon-count distributions show systematic deviations from the expected Poisson–gamma distribution, which result in a strong overestimation of the measured speckle contrast. It is shown that these deviations originate from an artificial increase of double-photon events, which is proportional to the detected intensity and inversely proportional to the exposure time. The observed miscounting effect may have important implications for new coherent scattering experiments emerging with the advent of high-brilliance X-ray sources. Different correction schemes are discussed in order to obtain the correct photon distributions from the data. A successful correction is demonstrated with the measurement of Brownian motion from colloidal particles using X-ray speckle visibility spectroscopy.

International audience; The dynamics of the order fluctuations in the AuAgZn2 close to the critical point (Tc≃609 K) was observed by coherent x-ray scattering. With the high beam intensity of the ID10 ESRF beamline and with the new pixel detector, the dynamics was measured with a few tens of millisecond resolution. The intensity connected to the diffuse scattering corresponding to fluctuations was unambiguously distinguished from the surface pretransitional ordering occurring in this system close to Tc. The variations of the fluctuation time with temperature and wave vectors were measured in this system belonging to the universality class of Ising second order transition with a nonconserved order parameter. The direct observation of the critical slowing down in the vicinity of the second-order transition led to an estimate of the dynamic exponent z≃1.96(11), in rough agreement with theory (model “A” of Hohenberg and Halperin [Rev. Mod. Phys. 49, 435 (1977)]).

Amorphous calcium carbonate is found in the early stages of biomineral formation. Its moldability and its kinetic persistence against crystallization make it of potential interest to the development of biomimetic materials. The presence of water and of inorganic impurities such as Mg2+ has been reported to increase its kinetic stability. Yet, the precise mechanisms of stabilization as well as the link between structural dynamics and crystallization kinetics are still missing. Here, we report the vibrational and diffusive dynamics of water and other atomic constituents in a series of Mg2+-doped solid amorphous calcium carbonates revealed using coherent X-ray and incoherent neutron scattering. This unique combination of techniques presents a novel view on the nanoscopic dynamic behavior of these amorphous materials: the presence of Mg2+ results in a higher frequency of structural rearrangements within the material. However, this increased dynamic behavior does not translate into a higher crystallization kin...

Bone fracture risk is influenced by bone quality, which encompasses bone's composition as well as its multiscale organization and architecture. Aging and disease deteriorate bone quality, leading to reduced mechanical properties and higher fracture incidence. Largely unexplored is how bone quality and mechanical competence progress during longitudinal bone growth. Human femoral cortical bone was acquired from fetal (n = 1), infantile (n = 3), and 2- to 14-year-old cases (n = 4) at the mid-diaphysis. Bone quality was assessed in terms of bone structure, osteocyte characteristics, mineralization, and collagen orientation. The mechanical properties were investigated by measuring tensile deformation at multiple length scales via synchrotron X-ray diffraction. We find dramatic differences in mechanical resistance with age. Specifically, cortical bone in 2- to 14-year-old cases exhibits a 160% greater stiffness and 83% higher strength than fetal/infantile cases. The higher mechanical resistance of the 2- to 14-year-old cases is associated with advantageous bone quality, specifically higher bone volume fraction, better micronscale organization (woven versus lamellar), and higher mean mineralization compared with fetal/infantile cases. Our study reveals that bone quality is superior after remodeling/modeling processes convert the primary woven bone structure to lamellar bone. In this cohort of female children, the microstructural differences at the femoral diaphysis were apparent between the 1- to 2-year-old cases. Indeed, the lamellar bone in 2- to 14-year-old cases had a superior structural organization (collagen and osteocyte characteristics) and composition for resisting deformation and fracture than fetal/infantile bone. Mechanistically, the changes in bone quality during longitudinal bone growth lead to higher fracture resistance because collagen fibrils are better aligned to resist tensile forces, while elevated mean mineralization reinforces the collagen scaffold. Thus, our results reveal inherent weaknesses of the fetal/infantile skeleton signifying its inferior bone quality. These results have implications for pediatric fracture risk, as bone produced at ossification centers during children's longitudinal bone growth could display similarly weak points. © 2019 American Society for Bone and Mineral Research.

Coherent x-ray diffraction imaging (CXDI) is becoming an important 3D quantitative microscopy technique, allowing structural investigation of a wide range of delicate mesoscale samples that cannot be imaged by other techniques like electron microscopy. Here we report high-resolution 3D CXDI performed on spherical microcomposites consisting of a polymer core coated with a triple layer of nickel–gold–silica. These composites are of high interest to the microelectronics industry, where they are applied in conducting adhesives as fine-pitch electrical contacts—which requires an exceptional degree of uniformity and reproducibility. Experimental techniques that can assess the state of the composites non-destructively, preferably also while embedded in electronic chips, are thus in high demand. We demonstrate that using CXDI, all four different material components of the composite could be identified, with radii matching well to the nominal specifications of the manufacturer. Moreover, CXDI provided detailed maps of layer thicknesses, roughnesses, and defects such as holes, thus also facilitating cross-layer correlations. The side length of the voxels in the reconstruction, given by the experimental geometry, was 16 nm. The effective resolution enabled resolving even the thinnest coating layer of ∼20 nm nominal width. We discuss critically the influence of the weak phase approximation and the projection approximation on the reconstructed electron density estimates, demonstrating that the latter has to be employed. We conclude that CXDI has excellent potential as a metrology tool for microscale composites.

This is the author final draft version of article https://doi.org/10.1103/PhysRevLett.120.135504 As ultrastable metallic glasses (UMGs) are promising candidates to solve the stability issues of conventional metallic glasses, their study is of exceptional interest. By means of x -ray photon correlation spectroscopy, we have investigated the stability of UMGs at the atomic level. We find a clear signature of ultrastability at the atomic level that results in slower relaxation dynamics of UMGs with respect to conventional (rapidly quenched) metallic glasses, and in a peculiar acceleration of the dynamics by near T g annealing. This surprising phenomenon, called here anti-aging, can be understood in the framework of the potential energy landscape. For all samples, the structural relaxation process can be described with a highly compressed shape of the density fluctuations, unaffected by thermal treatments and regardless of the ultrastability of the glass.

A major limitation to the use of coherent X-ray diffraction imaging (CXDI) for imaging soft materials like polymers and biological tissue is that the radiation can cause extensive damage to the sample under investigation. In this study, CXDI has been used to monitor radiation-induced structural changes in metal-coated poly(methyl methacrylate) microspheres. Using a coherent undulator X-ray beam with 8.10 keV photon energy, 14 tomograms at a resolution of ∼30 nm were measured consecutively, which resulted in an accumulated dose of 30 GGy. The three-dimensional images confirmed that the polymer core was strongly affected by the absorbed dose, giving pronounced mass loss. Specifically, as the metal–polymer composite was exposed to the X-ray beam, a bubble-like region of reduced density grew within the composite, almost filling the entire volume within the thin metallic shell in the last tomogram. The bubble seemed to have its initiation point at a hole in the metal coating, emphasizing that the free polymer surface plays an important role in the degradation process. The irradiation of an uncoated polystyrene microsphere gave further evidence for mass loss at the free surface as the radius decreased with increased dose. The CXDI study was complemented by X-ray photon correlation spectroscopy, which proved efficient in establishing exposure dose limits. Our results demonstrate that radiation-induced structural changes at the tens of nanometer scale in soft materials can be followed as a function of dose, which is important for the further development of soft-matter technology.

Lensless, coherent X-ray diffraction microscopy has been drawing considerable attentions for tomographic imaging of whole human cells. In this study, we performed cryogenic coherent X-ray diffraction imaging of human erythrocytes with and without malaria infection. To shed light on structural features near the surface, “ghost cells” were prepared by the removal of cytoplasm. From two-dimensional images, we found that the surface of erythrocytes after 32 h of infection became much rougher compared to that of healthy, uninfected erythrocytes. The Gaussian roughness of an infected erythrocyte surface (69 nm) is about two times larger than that of an uninfected one (31 nm), reflecting the formation of protein knobs on infected erythrocyte surfaces. Three-dimensional tomography further enables to obtain images of the whole cells with no remarkable radiation damage, whose accuracy was estimated using phase retrieval transfer functions to be as good as 64 nm for uninfected and 80 nm for infected erythrocytes, respectively. Future improvements in phase retrieval algorithm, increase in degree of coherence, and higher flux in combination with complementary X-ray fluorescence are necessary to gain both structural and chemical details of mesoscopic architectures, such as cytoskeletons, membraneous structures, and protein complexes, in frozen hydrated human cells, especially under diseased states.

Coherent X-ray diffraction imaging is a lensless imaging technique where an iterative phase-retrieval algorithm is applied to the speckle pattern, the far-field diffraction pattern produced by an isolated object. To ensure convergence to a unique solution, the diffraction pattern must be oversampled by a factor of two or more. Since the resolution in real space depends on the maximum wave vector where the intensity is detected,i.e.on the detector field of view, there is a practical limitation on oversampling in reciprocal space and resolution in real space that is ultimately determined by the number of pixels. This work shows that it is possible to reduce the effective pixel size and maintain the detector field of view by applying a linear combination method to shifted diffraction patterns. The feasibility of the method is demonstrated by reconstructing the images of test objects from diffraction patterns oversampled in each dimension by factors of 1.3 and 1.8 only. The described approach can be applied to any diffraction or imaging technique where the resolution is compromised by a large pixel size.

Dense colloidal dispersions exhibit complex wave-vector-dependent diffusion, which is controlled by both direct particle interactions and indirect nonadditive hydrodynamic interactions mediated by the solvent. In bulk the hydrodynamic interactions are probed routinely, but in confined geometries their studies have been hitherto hindered by additional complications due to confining walls. Here we solve this issue by combining high-energy x-ray photon correlation spectroscopy and small-angle x-ray-scattering experiments on colloid-filled microfluidic channels to yield the confined fluid's hydrodynamic function in the short-time limit. Most importantly, we find the confined fluid to exhibit a strongly anisotropic hydrodynamic function, similar to its anisotropic structure factor. This observation is important in order to guide future theoretical research.

Almost all physical processes in solids are influenced by phonons, but their effect is frequently overlooked. In this paper, we investigate the photoluminescence of large silicon nanoparticles (approximately 100 nm size, synthesized by chemical vapor deposition) in the visible to the infrared detection range. We find that upon increasing laser irradiance, an enormous photoluminescence emission band appears in the infrared. Its intensity exhibits a superlinear power dependence, increasing over four orders of magnitude in the investigated pump power range. Particles of different sizes as well as different shapes in porous layers are investigated. The results are discussed taking into account the efficient generation of phonons under high-power pumping and the reduced capability, porosity dependent, of the silicon nanoparticles to exchange energy with each other and with the substrate. Our findings are relevant for heat management strategies in silicon.

The collective diffusion of dense fluids in spatial confinement is studied by combining high-energy (21 keV) x-ray photon correlation spectroscopy and small-angle x-ray scattering from colloid-filled microfluidic channels. We find the structural relaxation in confinement to be slower compared to the bulk. The collective dynamics is wave vector dependent, akin to the de Gennes narrowing typically observed in bulk fluids. However, in stark contrast to the bulk, the structure factor and de Gennes narrowing in confinement are anisotropic. These experimental observations are essential in order to develop a microscopic theoretical description of collective diffusion of dense fluids in confined geometries., Physical Review Letters, 116 (16), ISSN:0031-9007, ISSN:1079-7114

International audience; We report X-ray Photon Correlation Spectroscopy (XPCS) measurements of microscale dynamics in Langmuir-Schaeffer deposited multilayers of a photosensitive azopolymer with a low concentration of gold nanoparticles embedded. Correlation functions were measured as a function of exchanged momentum and illumination conditions (dark and UV light) and fitted with the Kohlrausch-Williams-Watts (KWW) exponential form. The microscopic dynamic of the nanoparticles was quantified, evidencing a non-Brownian superdiffusive behavior with relaxation times tau ≈ q^-1, a result analogous to what previously had been observed in the pure azopolymer [D. Orsi et al., submitted to Phys. Rev. E (2010)]. Such behavior has been related to intermittent rearrangements [L. Cipelletti et al., Phys. Rev. Lett. 84, 2275-2278 (2000)] or random dipolar interactions within an elastic medium [J.-P. Bouchaud and E. Pitard, Eur. Phys. J. E 6, 231-236 (2001)]. Photoperturbation with UV light makes the dynamics faster, in accordance with the reduction of the viscosity of the polymer found by shear rheology, but the KWW form of the correlation functions persists. At constant temperature, the dynamics of the nanoparticles embedded in the polymeric matrix is sensibly faster than the slow microscopic dynamic of the polymer. At the same time, the Vogel-Fulcher-Tammann (VFT) law for the relaxation times indicates a less pronounced temperature dependence than for the pure polymer, resulting in a slightly lower activation temperature T_A.

Investigations of the dynamic process of the appearance of the Verwey transition in magnetite are performed by simultaneous measurements of magnetic susceptibility χ AC and the intensity of the ( 1 1 1 2 2 ) superstructure peak, using the coherent X-ray diffraction (CXD) technique. The results suggest that while the volume of a new low-temperature monoclinic phase increases gradually across the transition, it is initially in the form of grains too small to form the well-developed superlattice reflection. Finally, at the end of the transition, those small grains coalesce into micrometer size structural domains, reflected in ( 1 1 1 2 2 ) superlattice peak.

Grazing-Incidence Small Angle X-ray Scattering (GISAXS) and X-Ray Photon Correlation Spectroscopy (XPCS) studies of island growth in two different systems are presented: 5 ML of iron on MgO(001) and 10 ML of iron on Au(001). Due to a missing conducting surface Fe/MgO thinner than approximately 20 ML could not be studied previously by common methods like STM. Fe/Au(001) is interesting as atoms of gold diffuse easily through iron layers and form precipitates. The coarsening dynamics of these precipitates is investigated by XPCS in GISAXS geometry. Their growth depends on the crystallographic directions of the substrate and correlates with the morphology measured by STM microscopy. Measurements were performed at the ESRF in Grenoble.

Since its first experimental demonstration in 1999, coherent diffractive imaging (CDI) has been applied to image a broad range of samples using advanced synchrotron radiation, X-ray free-electron lasers, high harmonic generation and electrons. Here, the first experimental demonstration of cryogenic CDI for quantitative three-dimensional imaging of whole frozen-hydrated cells is reported. As a proof of principle, the three-dimensional mass density of the sub-cellular organization of a Neospora caninum cell is determined based on its natural contrast., A structural understanding of whole cells in three dimensions at high spatial resolution remains a significant challenge and, in the case of X-rays, has been limited by radiation damage. By alleviating this limitation, cryogenic coherent diffractive imaging (cryo-CDI) can in principle be used to bridge the important resolution gap between optical and electron microscopy in bio-imaging. Here, the first experimental demonstration of cryo-CDI for quantitative three-dimensional imaging of whole frozen-hydrated cells using 8 keV X-rays is reported. As a proof of principle, a tilt series of 72 diffraction patterns was collected from a frozen-hydrated Neospora caninum cell and the three-dimensional mass density of the cell was reconstructed and quantified based on its natural contrast. This three-dimensional reconstruction reveals the surface and internal morphology of the cell, including its complex polarized sub-cellular structure. It is believed that this work represents an experimental milestone towards routine quantitative three-dimensional imaging of whole cells in their natural state with spatial resolutions in the tens of nanometres.

Coherent diffraction imaging is a high-resolution imaging technique whose potential can be greatly enhanced by applying the extrapolation method presented here. We demonstrate enhancement in resolution of a non-periodical object reconstructed from an experimental X-ray diffraction record which contains about 10% missing information, including the pixels in the center of the diffraction pattern. A diffraction pattern is extrapolated beyond the detector area and as a result, the object is reconstructed at an enhanced resolution and better agreement with experimental amplitudes is achieved. The optimal parameters for the iterative routine and the limits of the extrapolation procedure are discussed., 12 pages, 4 figures

Parabolic refractive x-ray lenses are novel optical components for the hard x-ray range from about 5 keV to about 120 keV. They are compact, robust, and easy to align and to operate. They can be used like glass lenses are used for visible light, the main difference being that the numerical aperture is much smaller than 1 (of the order of 10−4–10−3). They have been developed at Aachen University and are made of beryllium, boron, aluminium and silicon. Their main applications are in micro- and nanofocusing, in imaging by absorption and phase contrast. In combination with tomography they allow for three-dimensional imaging of opaque media with sub-micrometre resolution. Finally, they can be used in speckle spectroscopy by means of coherent x-ray scattering. References to a number of applications are given.

X-ray photon correlation spectroscopy (XPCS) is a novel technique for the study of slow dynamics in disordered materials. It overcomes limitations of visible light scattering techniques such as multiple scattering or limitations in Q-range by using coherent X-rays from third generation synchrotron radiation sources. Applications to the static and dynamic behavior of complex fluids and to slow dynamics in hard condensed matter systems are reviewed.

Medipix-1 is a photon-counting pixel detector array with 64×64 pixels of 170×170 μm pitch. We present some recent evaluation results of Medipix-1 in various X-ray analysis techniques using synchrotron beams or conventional X-ray generators. We have characterised the detector energy response from 6 to 23 keV. On an ESRF undulator beamline we have obtained SAXS data of comparable quality as with a conventional photon counter or with a CCD-based system. In materials diffraction we have used the energy discrimination capability of the detector to improve the quality of diffraction data.

The lattice dynamics of crystalline L-alanine shows unusual features tentatively assigned to a localization of vibrational energy. However, other properties alternatively suggest the existence of a second order phase transition undetected in previous crystallographic work. In this paper, we present the results of a high resolution X-ray diffraction study down to 10 K, together with new structure determinations at intermediate temperatures. The data rule out the hypothesis of a conventional structural phase transition. No change in the space group symmetry is observed and an anomalous decrease of the lattice parameter c in discrete steps is discovered when heating the crystal from 10 K to room temperature. It could be ascribed to a progressive conformational change of the NH3 + group of the zwitterionic molecule. An analysis of the physical properties of crystalline L-alanine suggests the existence of a strong dynamic Jahn-Teller-like effect owing to the NH3 + charge-lattice coupling. This would explain both the splitting of some vibrational states and properties related to a microscopic lattice instability like the onset of depolarization in the transmitted light below ~250 K.

We present cryo x-ray diffraction microscopy of high-pressure-cryofixed bacteria and report high-convergence imaging with multiple image reconstructions. Hydrated D. radiodurans cells were cryofixed at 200 MPa pressure into ∼10-μm-thick water layers and their unstained, hydrated cellular environments were imaged by phasing diffraction patterns, reaching sub-30-nm resolutions with hard x-rays. Comparisons were made with conventional ambient-pressure-cryofixed samples, with respect to both coherent small-angle x-ray scattering and the image reconstruction. The results show a correlation between the level of background ice signal and phasing convergence, suggesting that phasing difficulties with frozen-hydrated specimens may be caused by high-background ice scattering.

The gelation of methylcellulose in water has been studied by X-ray photon correlation spectroscopy, electrophoresis and rheological measurements by looking into the dynamics of silica nanoparticles as tracers in the polymer matrix. The temperature and scattering vector dependence of the structural relaxation time is investigated at the nanometric length scale during the formation of the strong gel state. We find a stress-dominated dynamics on approaching the gel state, characterized by a hyper-diffusive motion of the silica particles. These results support the idea of a unifying scenario for the dynamics of complex out of equilibrium soft materials.

Silica glass containing metal clusters is studied for both basic and applied aspects, related to the physics of cluster formation and to the optical properties of these materials. To obtain such composite structure, Cu+ Ni, Au+ Cu, Au+ Ag, Cu+ Co, and Cu+ Ag sequential implantations in fused silica were realized. The resulting systems, after possible annealing in various atmospheres, were studied by synchrotron radiation-based techniques, namely, extended X-ray absorption fine structure (EXAFS) spectroscopy, grazing incidence X-ray diffraction (GIXRD), and grazing incidence small angle X-ray scattering (GISAXS). The unique potential of these techniques is the capability to investigate dilute (volume fraction of clusters greater than or equal to 0.01) and very thin (50 nm) systems. In the presented experiment, both pure and alloy clusters in the nanometer range of size were observed to form, pointing out the complexity of the cluster formation process in terms of physical and chemical driving forces.

We report on the formation and detection of a compressed fluid phase of Xe clusters in as-implanted Si, at room temperature. The simultaneous structural characterization of the Xe clusters and of the Si matrix was performed by X-ray diffraction at grazing incidence coupled with two-dimensional detection; in both cases, the nearest-neighbor distance and the coordination were obtained. In order to investigate the early stage of the atomic inclusion and the cluster segregation, the average compression and size of Xe fluid clusters: within the amorphous Si matrix were explained within the simple Hard Sphere model.

Sequential ion implantation (copper and nickel) in silica and soda-lime glasses has been performed. The formation of copper-nickel alloy nanocluster in the glass host has been evidenced by synchrotron radiation-based techniques, namely X-ray diffraction and absorption spectroscopy. The nanocrystals' lattice parameter value was estimated, indicating the formation of CU55Ni45 alloy particles. Optical absorption spectra are also discussed.

The switchable mirror compound YH 3 has a high-pressure behavior at variance with current band-structure models. It remains transparent at least up to 25 GPa. At high pressure, the optical gap decreases linearly extrapolating to zero for 55±8 GPa, above which pressure a metallic state is expected. This is in disagreement with a theoretically predicted insulator-to-metal phase transition at 1.5 GPa. In-situ structural studies using synchrotron radiation reveal a 2% drop in the c -lattice vector at 4 GPa, while both above and below the phase transition, the spectra are consistent with a hcp structure. Hence this phase transition is probably due to a rearrangement of the hydrogen lattice positions only and the predicted hcp to fcc transition is not observed.

A novel X-ray technique is described for carrying out structural investigations of metallic nanoparticles buried in glass obtained by ion implantation. The method consists of maximizing the scattering contribution of the cluster-rich layer by working at the critical angle for total external reflection at the implanted-layer–substrate interface. By using the refracted beam as a probe, the diffraction profile of the metallic clusters in very dilute samples can be extracted by a simple subtraction procedure. The new procedure is applied to SiO2glasses implanted with Ag ions. The study was performed at the European Synchrotron Radiation Facility. The results indicate that a complete structural investigation can be performed by using highly collimated, very intense synchrotron radiation beams, a grazing-incidence geometry and two-dimensional detectors. The procedure is shown to be very useful for complementing the information from electron techniques (transmission electron microscopy, micro-beam electron diffraction) and X-ray spectroscopic (EXAFS) methods. In particular, the accuracy of the lattice-parameter determination is shown to be a factor of nine better than the accuracy of EXAFS results.