Knowledge of the sequence of different conformational states of a protein molecule is key to better understanding its biological function. A diffraction pattern from a single conformational state can ...be captured with an ultrafast X-ray Free-Electron Laser (XFEL) before the target is completely annihilated by the radiation. In this paper, we report the first experimental demonstration of conformation sequence recovery using diffraction patterns from randomly ordered conformations of a non-periodic object using the dimensional reduction technique Isomap and coherent diffraction imaging.
Scanning photoelectron microscopy (SPEM) is a powerful technique to image and probe micro and nano-structures. Recent achievements on imaging the sub-micro objects will be present in this report. For ...the first time, SPEM is used to explore and probe the chemical state and chemical composition of individual ZnO nanostructures. The capability of SPEM on imaging an individual MWCNT is shown which is down to 50 nm in diameter. The MWCNTs, partially covered with a metal, successfully are fabricated and presence of a sharp interface between CNT and metal is confirmed by SPEM. The morphology, composition and oxidation/reduction of isolated supported PtRh micro- and nano- particles produced by pulsed-laser deposition (PLD) have been investigated by SPEM. DOI: 10.1380/ejssnt.2011.158
The present in situ study of electrochemically induced processes occurring in Cr/Ni bilayers in contact with a YSZ electrolyte aims at a molecular‐level understanding of the fundamental aspects ...related to the durability of metallic interconnects in solid oxide fuel cells (SOFCs). The results demonstrate the potential of scanning photoelectron microspectroscopy and imaging to follow in situ the evolution of the chemical states and lateral distributions of the constituent elements (Ni, Cr, Zr, and Y) as a function of applied cathodic potential in a cell working at 650 °C in 10−6 mbar O2 ambient conditions. The most interesting findings are the temperature‐induced and potential‐dependent diffusion of Ni and Cr, and the oxidation–reduction processes resulting in specific morphology–composition changes in the Ni, Cr, and YSZ areas.
Back to basics: In situ scanning photoelectron microscopy study of electrochemically induced processes, occurring in a model SOFC Cr/Ni/YSZ/Ni/Cr system (see figure), reveals the effect of reaction temperature and applied potentials on the lateral distribution of Cr and Ni across the cell and on the evolution of the chemical state of the cell constituents.
In this paper we report an investigation of the degradation of the Pt/C electrocatalyst of an anodic membrane-electrode assembly (MEA) after 1000h of operation in a laboratory single-cell PEMFC, ...using synchrotron-based space-resolved photoelectron spectroscopy. This study is complemented by the analysis of a pristine MEA and reference materials, as well as by electrochemical measurements, SEM imaging and energy-dispersive X-ray fluorescence spectroscopy (EDX). Catalyst ageing correlates with a corrugation of morphology, as observed by SEM and scanning photoelectron microscopy (SPEM), corresponding to Pt nanoparticle agglomeration. Moreover – on the basis of high lateral resolution SPEM, X-ray photoelectron spectroscopy (XPS) and EDX analyses, – we found that, after operation, Pt is transported onto the fibres of the gas-diffusion layer (GDL). Space-resolved XPS shows a peak shift of the Pt 4f7/2 level to higher and lower binding energies with respect to Pt(111) and pristine Pt black, respectively, corresponding to nanocrystallinity in the first case and agglomeration in the second one. No oxidised Pt was found in any location of the anodically used MEA.
Sustainability, environmental and safety concerns raised by the increasing demand of batteries are driving research towards post-lithium technologies. Rechargeable Zn batteries are strong candidates, ...but still not practically viable, owing to the extensively studied, but poorly understood unstable behavior of Zn metal upon discharge-charge cycling. This limiting factor warrants more fundamental investigations and the present report provides the lacking molecular-level information on the Zn-based compounds forming at the electrode/electrolyte interface as a result of electrochemical cyclic in weakly acidic aqueous electrolyte. The results are obtained using ex situ X-ray absorption spectromicroscopy maps, modelled mathematically and complemented with cyclic voltammetry, symmetric-cell tests and electron microscopy. We have identified the role of the zincate precipitation resulting from local alkalinization during recharge, combined with additional zincate formation and decomposition to zinc oxide during discharge. The mathematical model allowed a transparent interpretation of morphochemical changes observed. The synergy of these processes leads to electrochemical localization effects, resulting in the formation of a complexly structured and low conductive ZnO-based template, that might play a role in driving shape changes.
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•Soft X-ray absorption spectromicroscopy (XAS) gives insight for Zn electrochemistry.•Zn anode cycling in mildly acidic aqueous electrolyte can generate zincates.•Parasitic HER yields space distribution of Zn species in mildly acidic electrolyte.•Chemical-state distribution of discharged and cycled Zn anodes, disclosed by XAS.•Homogeneous primary current distribution cannot avoid mesoscopic heterogeneities.
The potential of the two-color mode implemented at the FERMI free-electron laser (FEL) source for pumping and probing selectively different atomic species has been demonstrated by time-resolved ...scattering experiments with permalloy (FeNi alloy) and NiFe2O4 samples. We monitored the ultra-fast demagnetization of Ni induced by the pump FEL pulse, by tuning the linearly-polarized FEL probe pulse to the Ni-3p resonance and measuring the scattered intensity in the transverse magneto-optical Kerr effect geometry. The measurements were performed by varying the intensity of the FEL pump pulse, tuning its wavelength to and off of the Fe-3p resonance, and by spanning the FEL probe pulse delays across the 300-900 fs range. The obtained results have evidenced that for the case of NiFe2O4, there is a sensible difference in the magnetic response at the Ni site when the pump pulse causes electronic excitations at the Fe site.
The compositional and structural rearrangements at the catalyst surface during chemical reactions are issues of great importance for understanding and modeling the catalytic processes. Low-energy ...electron microscopy and photoelectron spectromicroscopy studies of the real-space structure and composition of a Au-modified Rh(110) surface during water formation reveal reorganization processes due to Au mass transport triggered by the propagating reaction fronts. The temporal evolution of the surface reaction results in a ‘patterned' surface consisting of separated Au-rich and Au-poor phases with different oxygen coverage, Rh surface structure, and reactivity. The experimental results are complemented by ab initio electronic-structure calculations of the O and Au adsorption phases, which demonstrate that the reorganization of the Au adlayer by the propagating reaction fronts is an energetically driven process. Our findings suggest that reaction-induced spatial inhomogeneity in the surface composition and structure is a common feature of metal catalysts modified with adatoms which become mobile under reaction conditions.
With size reduction of active elements in microelectronics to tens of nanometers and below, the effect of surface and interface properties on overall device performance becomes crucial. High ...resolution spectroscopic and imaging techniques provide a metrological route for characterization of these properties relevant to device diagnostics and failure analysis. With its roughly 100 nm spatial resolution, superior surface sensitivity, and approximately 200 meV spectral resolution, scanning photoelectron microscopy (SPEM) stands out as a comprehensive tool to access the surface/interface composition of nanodevices, as well to provide chemical state designations and materials property evolutions upon treatment by thermal, electrical, chemical, radiative and other stimuli. Here we present a SPEM-on-device setup that combines X-ray spectromicroscopy with advanced NIST microhotplate technology to demonstrate new combined analytical and electrical measurements capabilities of this metrology platform for operando nanodevice characterization. Using model integrated SnO2 nanowire (NW) chemiresistor devices, the chemically induced alterations in the chemical state of the nanowire surface are correlated to the observed conductance changes, thus directly testing the receptor and transduction mechanisms for SnO2 NW conductometric chemical sensors.
•SPEM-on-device setup combines X-ray spectromicroscopy with NIST microhotplate technology.•SnO2 nanowire chemiresistor used as a model system for operando nanodevice characterization.•Chemical state of the nanowire surface is correlated to the observed conductance changes.•Combined XBIC and SPEM mapping locate electroactive and chemical defects in nanodevice.
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