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We present an in situ nanobeam grazing-incidence X-ray diffraction (nanoGIXD) study of real-sized organic field effect transistors (OFET) under applied voltage. The nano-sized beam allows for spatially resolved monitoring of the structural behavior across the poly(3-hexylthiophene) (P3HT) polymer channel and the interfacial regions of the source and drain gold electrodes before and after the operation cycle. We observe major alterations of the gold contacts, in particular diffusion of Au atoms into the polymer channel and a local reorientation of the recrystallized Au nanocrystallites quantified by Hermans’ orientation factors. Therefore, the initially sharp electrode-polymer interfaces are significantly modified as a result of device operation. Our findings demonstrate that nanoGIXD has a high potential to probe functionality and reliability of working organic devices.

X-ray reflectivity studies of the structure of liquid–vapour and liquid–liquid interfaces at modern sources, such as free-electron lasers, are currently impeded by the lack of dedicated liquid surface diffractometers. It is shown that this obstacle can be overcome by an alternative experimental approach that uses the natural curvature of a liquid drop for variation of the angle of incidence. Two modes of operation are shown: (i) sequential reflectivity measurements by a nanometre beam and (ii) parallel acquisition of large ranges of a reflectivity curve by micrometre beams. The feasibility of the two methods is demonstrated by studies of the Hg/vapour, H2O/vapour and Hg/0.1 MNaF interface. The obtained reflectivity curves match the data obtained by conventional techniques up to 5αcin micro-beam mode and up to 35αcin nano-beam mode, allowing observation of the Hg layering peak.

Surface structures with tailored morphologies can be readily delivered by the evaporation-induced self-assembly process. It has been recently demonstrated that ZnO nanorods could undergo rapid chemical and morphological transformation into 3D complex structures of Zn(OH)2 nanofibers as a droplet of ZnO nanofluid dries on the substrate via a mechanism very different from that observed in the coffee ring effect. Here, we have investigated how the crystallinity and morphology of ZnO nanoparticles would affect the ultimate pattern formation. Three ZnO particles differing in size and shape were used, and their crystal structures were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Their dispersions were prepared by sonication in a mixture of isobutylamine and cyclohexane. Residual surface patterns were created by drop casting a droplet of the nanofluid on a silicon substrate. The residual surface patterns were analyzed by scanning electron microscopy (SEM) and microfocus grazing incidence X-ray diffraction (µGIXRD). Nanofluid droplets of the in-house synthesized ZnO nanoparticles resulted in residual surface patterns consisting of Zn(OH)2 nanofibers. However, when commercially acquired ZnO powders composed of crystals with various shapes and sizes were used as the starting material, Zn(OH)2 fibers were found covered by ZnO crystal residues that did not fully undergo the dissolution and recrystallization process during evaporation. The difference in the solubility of ZnO nanoparticles was linked to the difference in their crystallinity, as assessed using the Scherrer equation analysis of their XRD Bragg peaks. Our results show that the morphology of the ultimate residual pattern from evaporation of ZnO nanofluids can be controlled by varying the crystallinity of the starting ZnO nanoparticles which affects the nanoparticle dissolution process during evaporation.

The intrinsic strain at coupled components in magnetoelectric composites plays an important role for the properties and function of these materials. In this in situ X-ray nanodiffraction experiment, the coating-induced as well as the magnetic-field-induced strain at the coupled interface of complex magnetoelectric microcomposites were investigated. These consist of piezoelectric ZnO microrods coated with an amorphous layer of magnetostrictive (Fe90Co10)78Si12B10. While the intrinsic strain is in the range of 10–4, the magnetic-field-induced strain is within 10–5, one order of magnitude smaller. Additionally, the strain relaxation distance of around 5 μm for both kinds of strain superposes indicating a correlation. The value of both intrinsic and magnetic-field-induced strain can be manipulated by the diameter of the rodlike composite. The intrinsic interface strain within the ZnO increases exponentially by decreasing the rod diameter while the magnetic-field-induced strain increases linearly within the gi...

International audience; Amyloid fibres attract considerable interest due to their biological role in neurodegenerative diseases and their potential as functional biomaterials. Here, we describe an intrinsic signal of amyloid fibres in the near-infrared range. When combined with their recently reported blue luminescence, it paves the way towards new blueprints for the label-free detection of amyloid deposits in in vitro and in vivo contexts. The blue luminescence allows for staining-free characterization of amyloid deposits in human samples. The near-infrared signal offers promising prospects for innovative diagnostic strategies for neurodegenerative diseases—to improve medical care and for the development of new therapies. As a proof of concept, we demonstrate direct detection of amyloid deposits within brains of living, aged mice with Alzheimer’s disease using non-invasive and contrast-agent-free imaging. Ultraviolet–visible–near-infrared optical properties of amyloids open new research avenues for amyloidosis as well as for next-generation biophotonic devices.

International audience; Scanning nanofocus X-ray diffraction (nXRD) performed at a synchrotron is used to simultaneously probe the morphology and the structural properties of spin-coated CH3NH3PbI3 (MAPI) perovskite films for photovoltaic devices. MAPI films are spin-coated on a Si/SiO2/poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) substrate held at different temperatures during the deposition in order to tune the perovskite film coverage. The films are then investigated using nXRD and scanning electron microscopy (SEM). The advantages of nXRD over SEM and other techniques are discussed. A method to visualize, selectively isolate, and structurally characterize single perovskite grains buried within a complex, polycrystalline film is developed. The results of nXRD measurements are correlated with solar cell device measurements, and it is shown that spin-coating the perovskite precursor solution at elevated temperatures leads to improved surface coverage and enhanced solar cell performance

The influence of processing conditions on the thin film microstructure is a fundamental question that must be understood to improve the performance of solution-processed organic electronic materials. Using grazing-incidence X-ray diffraction, we have studied the structure of thin films of a tetra(aniline)-surfactant complex prepared by drop-casting from five solvents (hexane, chloroform, tetrahydrofuran, dichloromethane and ethanol), selected to cover a range of polarities. We found that the structure, level of order and degree of orientation relative to the substrate were extremely sensitive to the solvent used. We have attempted to correlate such solvent sensitivity with a variety of solvent physical parameters. Of particular significance is the observation of a sharp structural transition in the thin films cast from more polar solvents; such films presented significantly greater crystallinity as measured by the coherence length and paracrystalline disorder parameter. We attribute this higher structural order to enhanced dissociation of the acid surfactant in the more polar solvents, which in turn promotes complex formation. Furthermore, the more polar solvents provide more effective screening of (i) the attractive ionic interaction between oppositely charged molecules, providing greater opportunity for dynamic reorganisation of the supramolecular aggregates into more perfect structures; and (ii) the repulsive interaction between the positively charged blocks permitting a solvophobic-driven aggregation of the aromatic surfaces during solvent evaporation.

Micelles formed by the self-assembly of block copolymers in selective solvents have attracted widespread attention and have uses in a wide variety of fields, whereas applications based on their electronic properties are virtually unexplored. Herein we describe studies of solution-processable, low-dispersity, electroactive fibre-like micelles of controlled length from π-conjugated diblock copolymers containing a crystalline regioregular poly(3-hexylthiophene) core and a solubilizing, amorphous regiosymmetric poly(3-hexylthiophene) or polystyrene corona. Tunnelling atomic force microscopy measurements demonstrate that the individual fibres exhibit appreciable conductivity. The fibres were subsequently incorporated as the active layer in field-effect transistors. The resulting charge carrier mobility strongly depends on both the degree of polymerization of the core-forming block and the fibre length, and is independent of corona composition. The use of uniform, colloidally stable electroactive fibre-like micelles based on common π-conjugated block copolymers highlights their significant potential to provide fundamental insight into charge carrier processes in devices, and to enable future electronic applications.

Spider major ampullate silk is often schematically represented as a two-phase material composed of crystalline nanodomains in an amorphous matrix. Here we are interested in revealing its more complex nanoscale organization by probing Argiope bruennichi dragline-type fibers using scanning X-ray nanodiffraction. This allows resolving transversal structural features such as an about 1 μm skin layer composed of around 100 nm diameter nanofibrils serving presumably as an elastic sheath. The core consists of a composite of several nm size crystalline nanodomains with poly(l-alanine) microstructure, embedded in a polypeptide network with short-range order. Stacks of nanodomains separated by less ordered nanosegments form nanofibrils with a periodic axial density modulation which is particularly sensitive to radiation damage. The precipitation of larger β-type nanocrystallites in the outer core–shell is attributed to MaSp1 protein molecules.

The convection or settling of matter in the deep Earth's interior is mostly constrained by density variations between the different reservoirs. Knowledge of the density contrast between solid and molten silicates is thus of prime importance to understand and model the dynamic behavior of the past and present Earth. SiO2 is the main constituent of Earth's mantle and is the reference model system for the behavior of silicate melts at high pressure. Here, we apply our recently developed x-ray absorption technique to the density of SiO2 glass up to 110 GPa, doubling the pressure range for such measurements. Our density data validate recent molecular dynamics simulations and are in good agreement with previous experimental studies conducted at lower pressure. Silica glass rapidly densifies up to 40 GPa, but the density trend then flattens to become asymptotic to the density of SiO2 minerals above 60 GPa. The density data present two discontinuities at similar to 17 and similar to 60 GPa that can be related to a silicon coordination increase from 4 to a mixed 5/6 coordination and from 5/6 to sixfold, respectively. SiO2 glass becomes denser than MgSiO3 glass at similar to 40 GPa, and its density becomes identical to that of MgSiO3 glass above 80 GPa. Our results on SiO2 glass may suggest that a variation of SiO2 content in a basaltic or pyrolitic melt with pressure has at most a minor effect on the final melt density, and iron partitioning between the melts and residual solids is the predominant factor that controls melt buoyancy in the lowermost mantle.

Solution-processed mixed lead halide perovskites are promising1-4 candidates for opto-electronic devices5-7. When deposited from a precursor solution and annealed,5,8 perovskite films adopt a multi-grain or polycrystalline morphology9,10 which can be described in terms of the spatial distribution of the ensemble of crystallite grains (film ‘texture’). Achieving a fine control over the perovskite texture11 is crucial to improve device performance. Grain rotation has previously been observed in-situ in a variety of materials, but on a limited number of grains11-13 and never on perovskites. Here we present a method for investigating texture evolution during the thermal annealing of mixed lead halide perovskites. Our method is based on in-situ 2D grazing incidence wide-angle x-ray scattering (GI-WAXS) and employs a 10 keV wide-focussed X-ray beam to simultaneously probe a large number of grains. The ability to track the texture dynamics from a statistically relevant number of spots diffracting from single grains during thermal annealing and in grazing incidence geometry is likely to have applications understanding the structure of a range of new materials.

International audience; One key for understanding the stratification in the deep mantle lies in the determination of the density and structure of matter at high pressures, as well as the density contrast between solid and liquid silicate phases. Indeed, the density contrast is the main control on the entrainment or settlement of matter and is of fundamental importance for understanding the past and present dynamic behavior of the deepest part of the Earth's mantle. Here, we adapted the X-ray absorption method to the small dimensions of the diamond anvil cell, enabling density measurements of amorphous materials to unprecedented conditions of pressure. Our density data for MgSiO3 glass up to 127 GPa are considerably higher than those previously derived from Brillouin spectroscopy but validate recent ab initio molecular dynamics simulations. A fourth-order Birch-Murnaghan equation of state reproduces our experimental data over the entire pressure regime of the mantle. At the core-mantle boundary (CMB) pressure, the density of MgSiO3 glass is 5.48 +/- 0.18 g/cm(3), which is only 1.6% lower than that of MgSiO3 bridgmanite at 5.57 g/cm(3), i.e., they are the same within the uncertainty. Taking into account the partitioning of iron into the melt, we conclude that melts are denser than the surrounding solid phases in the lowermost mantle and that melts will be trapped above the CMB

International audience; We developed a new generation of superhydrophobic chips optimized for probing ultrasmall sample quantities by X-ray scattering and fluorescence techniques. The chips are based on thin Si3N4 membranes with a tailored pattern of SU-8 photoresist pillars. Indeed, aqueous solution droplets can be evaporated and concentrated at predefined positions using a non-periodic pillar pattern. We demonstrated quantitatively the deposition and aggregation of gold glyconanoparticles from the evaporation of a nanomolar droplet in a small spot by raster X-ray nanofluorescence. Further, raster nanocrystallography of biological objects such as rod-like tobacco mosaic virus nanoparticles reveals crystalline macro-domain formation composed of highly oriented nanorods

Despite extensive studies with many experimental techniques, the morphology and structure of the self-assembled aggregates of quaternary alkyl ammonium bromides (CnTABs; where n denotes the number of hydrocarbons in the surfactant tail) at the solid-liquid interface remains controversial, with results from atomic force microscopy (AFM) imaging pointing to a variety of surface aggregates such as cylinders and surface micelles, whilst surface force measurements and neutron reflectivity (NR) measurements reporting bilayer structures. Using a home-built liquid cell that employs the "bending mica" method, we have performed unprecedented synchrotron X-ray reflectometry (XRR) measurements to study the adsorption behaviour of a C nTAB series (n = 10, 12, 14, 16 and 18) at the mica-water interface at different surfactant concentrations. We find that our XRR data cannot be described by surface aggregates such as cylindrical and spherical structures reported by AFM studies. In addition we have observed that the bilayer thickness, surface coverage and the tilt angle all depend on the surfactant concentration and surfactant hydrocarbon chain length n, and that the bilayer thickness reaches a maximum value at approximately the critical micellisation concentration (∼1 cmc) for all the CnTABs investigated. We propose that CnTABs form disordered bilayer structures on mica at concentrations below cmc, whilst at ∼1 cmc they form more densely packed bilayers with the tails possibly tilted at an angle θt ranging from ∼40 to 60° with respect to the surface normal in order to satisfy the packing constraints due to the mica lattice charge, i.e. so that the cross-section area of the tilted chain would match that of the area of the lattice charge (As ≅ 46.8 Å2). As the surfactant concentration further increases, we find that the bilayer thickness decreases, and we ascribe this to the desorption of surfactant molecules, which recovers certain disorder and fluidity in the chain and thus leads to interdigitated bilayers again. In light of our XRR results, previously unattainable at the mica-water interface, we suggest that the surface aggregates observed by AFM could be induced by the interaction between the scanning probe and the surfactant layer, thus representing transient surface aggregation morphologies; whereas the CnTAB bilayers we observe with XRR are intrinsic structures under quiescent conditions. The suggestion of such quiescent bilayers will have fundamental implications to processes such as lubrication, self-assembly under confinement, detergency and wetting, where the morphology and structure of surfactant layers at the solid-liquid interface is an important consideration. © 2013 The Royal Society of Chemistry.

Conducting polymers have shown great potential for application in electronic devices. A major challenge in such applications is to control the supramolecular structures these materials form to optimise the functionality. In this work we probe the structure of oligo(aniline) thin films (of sub-μm thickness) drop cast on a silicon substrate using synchrotron surface diffraction. Self-assembly was induced through doping with an acid surfactant, bis(ethyl hexyl) phosphate (BEHP), resulting in the formation of well-ordered lamellae with the d-spacing ranging from 2.15 nm to 2.35 nm. The exact structural characteristics depended both on the oligomer chain length and film thickness, as well as the doping ratio. Complementary UV/Vis spectroscopy measurements confirm that such thin films retain their bulk electronic properties. Our results point to a simple and effective ionic self-assembly approach to prepare thin films with well-defined structures by tailoring parameters such as the oligomer molecular architecture, the nanofilm composition and the interfacial roughness.

The self-assembly behaviour, structure, and consequently the electronic properties of electroactive organic molecules can differ significantly from those of the bulk material when confined to thin films. Here we have examined the self-organised in-plane and out-of-plane structures of aniline oligomers in thin films using surface-sensitive grazing-incidence X-ray scattering (GIXS). Thin films of the aniline tetramer (TANI) and octamer (OANI) were prepared both in their native emeraldine base (EB) oxidation state and in the doped emeraldine salt (ES) state (combined with the acid surfactant bis(ethyl hexyl)phosphate (BEHP)), using a simple drop-casting and solvent annealing process. It was found that the presence of the acid surfactant induced self-organisation into highly ordered structures. The details of these structures, such as the morphology, orientation relative to the underlying substrate and the degree of orientation were found to depend on the molecular architecture of the oligomer. The BEHP-doped TANI system formed a highly oriented hexagonal unit cell (lattice parameters: a = b = 2.53 nm, c = 2.91 nm, γ = 120°), whereas the BEHP-doped OANI complex adopted a randomly oriented lamellar structure (d-spacing = 2.25 nm). Such detailed structural information reveals that the self-assembly behaviour and the packing of oligomer–BEHP complexes, when confined to thin films, are indeed different to that of the bulk phase materials. Furthermore, the molecular architecture of the oligomers directly influenced the structural changes of the doped films in response to in situ thermal treatment. These results demonstrate that through a simple processing route the morphology of electroactive oligomer films can be tailored by molecular design. These findings are important to future applications where thin film structure is a crucial consideration for device function and performance.