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We present an overview of the Elettra-Sincrotrone Trieste research center, which hosts synchrotron and free-electron laser light sources. We review the current status, provide examples of recent achievements in basic and applied research and discuss the upgrade programs of the facility.

Ultrashort and intense extreme ultraviolet (XUV) and X-ray pulses readily available at free-electron lasers (FELs) enable studying non-linear light−matter interactions on femtosecond timescales. Here, we report on the non-linear fluence dependence of magnetic scattering of Co/Pt multilayers, using FERMI FEL’s 70-fs-long single and double XUV pulses, the latter with a temporal separation of 200 fs, with a photon energy slightly detuned to the Co M2,3 absorption edge. We observe a quenching in magnetic scattering that sets-in already in the non-destructive fluence regime of a few mJ/cm² typically used for FEL-probe experiments on magnetic materials. Calculations of the transient electronic structure in tandem with a phenomenological modeling of the experimental data by means of ultrafast demagnetization unambiguously show that XUV-radiation-induced demagnetization is the dominant mechanism for the quenching in the investigated fluence regime of

Understanding and controlling the thermal transport at nanoscale is a key ingredient for the development of future nanoelectronical devices. In this study of thin silicon carbide (SiC) membrane we demonstrate the potential of free electron laser extreme ultraviolet (EUV) transient grating (TG) technique as contactless probe for thermoelastic response at length scales of 84 nm, where the Fourier heat diffusion law is no longer valid. The results have revealed that the mechanical behavior of the system can be fully described in the framework of Lamb waves. Moreover, by use of a bidimensional spatial detector to measure the TG signal, a new feature is the observed, time dependence in the emission angle of the transient diffraction, correlated to the transient grating signal intensity.

The non-IPR fulleride compound CsxC68 was investigated in analogy to previous experiments on CsxC58. While the vibrational properties as well as the electronic structure in the valence band range appear to be pretty similar to CsxC58, a striking difference could be observed by XPS and Photoemission Microscopy analysis: apparently, C68 forms different phases within a thick film including islands in which it is able to store more than 70 Cs atoms per fullerene cage and to keep these amounts even after annealing over 1100 K. This means that CsxC68 constitutes the highest alkali metal doping degree of any Fullerene species known so far. Spatially resolved photoemission analysis also revealed that the Cs-rich fulleride phases constitute a unique chemical state that has never been observed before.

The development of ultra-bright extreme ultraviolet (EUV) and X-ray free electron laser (FEL) sources has enabled the extension of wave-mixing approaches into the short wavelength regime. Such a class of experiments relies upon nonlinear interactions among multiple light pulses offering a unique tool for exploring the dynamics of ultrafast processes and correlations between selected excitations at relevant length and time scales adding elemental and site selectivity as well. Besides the availability of a suitable photon source, the implementation of wave mixing methodology requires efforts in developing the instrumental set-up. We have realized at the FERMI FEL two dedicated set-ups to handle multiple FEL beams with preselected parameters in a non-collinear fashion and control their interaction sequence at the target. These unique apparatuses, combined with the exceptional characteristics of the seeded FERMI FEL, have allowed us to make the first steps into this field and further advances are foreseen in the near future.

Adding submicrometer lateral resolution to the analytic capabilities of photoelectron spectroscopy was a milestone that opened up new opportunities to access lateral fluctuations in the chemical composition and electronic and magnetic structure of surfaces and interfaces and to explore exotic properties of nanostructured matter. To achieve a high spatial resolution while preserving the spectral resolution of this technique requires the very intense photon flux that has become available with the advent of third-generation synchrotron storage rings. The high spatial resolution of x-ray photoelectron microscopes, operated at synchrotron facilities, is achieved by either: (i) magnifying the image of the irradiated surface area using a suitable electron optical imaging system; or (ii) demagnifying the incident photon beam using x-ray photon optics. The contrast mechanisms in both instruments are based on photon absorption and the photon-induced electron emission is used to obtain spectroscopic information encoding the composition and electronic structure of the sample under investigation.

The complementary capabilities of the Scanning PhotoElectron Microscopes (SPEM) and X-ray PhotoEmission Electron Microscopes (XPEEM), operated at Elettra, in terms of imaging and micro-spectroscopy have opened unique opportunities to explore properties of functional materials as a function of their morphology and dimensions and to follow modifications in their properties during their operation. This paper describes the present performance of SPEMs and XPEEMs at Elettra, illustrated by selected recent studies relevant to graphene science. Ongoing efforts for implementing SPEM set-ups allowing for in-situ investigations under realistic operating conditions and PEEM set-up for spin-filtered momentum microscopy are outlined and discussed as well.

Highlights • Pulse-plating of Mn-oxide/polypyrrole nanocomposite studied in situ by ptychography. • Electrocrystallization followed in operando by dynamic coherent diffractive imaging. • Morphology and chemical state evolutions monitored in situ during electrodeposition. • Spectroscopic ptychography reveals valence distribution with nanometric resolution. • Local magnitude and phase spectra extracted from recostructued ptychographic images. Abstract Crucial for the advancement of electrochemical materials science is understanding the lateral variations in the elemental and chemical state of constituents induced by electrochemical reactions at nanoscales. This requires in situ studies to provide observables that contribute to both modeling beyond the phenomenological level and transducing exactly the functionally relevant quantities A range of X-ray coherent diffraction imaging (CDI) approaches has recently been proposed for imaging beyond the diffraction limit with potentially dramatic improvements of time resolution with chemical sensitivity. In this paper we report a selection of ptychography results obtained in situ after successive steps of electrochemically driven growth, complemented with absorption and phase spectroscopy at high lateral resolution. We demonstrate the onset of morphological instability feature formation and correlate the chemical state of Mn with local growth rate controlled by the current density distribution resulting from morphological evolution.

The rapid development of extreme ultraviolet (EUV) and x-ray ultrafast coherent light sources such as free electron lasers (FELs) has triggered the extension of wave-mixing techniques to short wavelengths. This class of experiments, based on the interaction of matter with multiple light pulses through the Nth order susceptibility, holds the promise of combining intrinsic ultrafast time resolution and background-free signal detection with nanometer spatial resolution and chemical specificity. A successful approach in this direction has been the combination of the unique characteristics of the seeded FEL FERMI with dedicated four-wave-mixing (FWM) setups, which leads to the demonstration of EUV-based transient grating (TG) spectroscopy. In this perspective paper, we discuss how the TG approach can be extended toward more general FWM spectroscopies by exploring the intrinsic multiparameter nature of nonlinear processes, which derives from the ability of controlling the properties of each field independently.

Nature Communications 10(1), 5217 (2019). doi:10.1038/s41467-019-13249-4, The invention of optical lasers led to a revolution in the field of optics and to the creation of such fields of research as quantum optics. The reason was their unique statistical and coherence properties. The emerging, short-wavelength free-electron lasers (FELs) are sources of very bright coherent extreme-ultraviolet and X-ray radiation with pulse durations on the order of femtoseconds, and are presently considered to be laser sources at these energies. FELs are highly spatially coherent to the first-order but in spite of their name, behave statistically as chaotic sources. Here, we demonstrate experimentally, by combining Hanbury Brown and Twiss interferometry with spectral measurements that the seeded XUV FERMI FEL-2 source does indeed behave statistically as a laser. The results may be useful for quantum optics experiments and for the design and operation of next generation FEL sources., Published by Nature Publishing Group UK, [London]

FERMI is the first and only seeded EUV-SXR free-electron laser (FEL) facility available to users; it operates at Elettra – Sincrotrone Trieste (Italy) and it presents five operating endstations. Three of them, namely LDM (Low Density Matter), DiProI (Diffraction and Projection Imaging) and MagneDyn (Magneto-Dynamical studies), use a Kirkpatrick–Baez (KB) active X-ray optics system to focus the FEL pulses into the experimental chambers. The present work reports on the final results of the upgraded KB Active Optics Systems (KAOS), which have been mechanically modified in order to improve stability and repeatability with respect to the original design. The results have been obtained on both the FERMI FEL lines, FEL1 and FEL2, and are particularly relevant for the latter as it is the low-wavelength line recently opened to users. After a thorough description of the new mechanical layout of the system and the aspects that have been improved after the refurbishment, a set of simulations of the optical performances are presented. The code used to simulate the behavior of KAOS is WISEr, a physical-optics-based tool, which is freely accessible, and integrated into the Oasys platform, that takes into account the specific surface metrology characterization of the beamline mirrors, including figure errors and microroughness power spectral density. The results of WISEr are then used as a reference for the actual optimization of the optical system. This procedure relies heavily on a wavefront sensor (WFS) mounted out of focus to optimize the refocusing mirrors alignment as well as their curvature bending (by minimization of the coefficients of the Zernike wavefront expansion). Moreover, the WFS data are used to reconstruct the focal spot parameters by means of a back-propagation of the electric field. Finally, these results are compared with those obtained after the FEL ablation of a PMMA layer positioned on the focal plane, and analyzed ex situ in a post-mortem fashion. The mechanically refurbished optical system and the multi-technique alignment approach, aimed at optimizing the mirrors' curvature, pitch and roll angles, allowed a focal spot of 1.8 µm × 2.4 µm at 4.14 nm wavelength (FEL2) to be inferred, confirmed by the PMMA ablation imprints.

This paper reports on the electrodeposition of Mn–Cu–ZnO for hybrid supercapacitors. This material exhibits a dual structure consisting of Mn-rich highly active, but poorly electronically conducting, grains, which are locked by a Cu-rich highly conductive network that also possesses some degree of charge-storage capacity. This work focuses on morphological, compositional, and chemical-state distributions with submicrometer lateral resolution. This information, which is crucial because doping distribution controls supercapacitor performance, has been obtained by combining electrochemical and in situ Raman measurements with synchrotron-based X-ray fluorescence and absorption microspectroscopy. Using a microfabricated thin-layer three-electrode microcell, we followed the morphochemical changes at different electrodeposition stages and found that pulse-plating allows the growth of Mn- and Cu-doped ZnO as self-organized structures with a consistent spatially stable composition distribution.

Synchrotron-based scanning photoelectron microscopy has opened unique opportunities for exploiting processes occurring at surfaces and interfaces, which control the properties of functional materials where issues of complexity at microscopic length scales should be faced and understood. The present article aims at demonstrating the present capabilities of this microscopic method to explore the surface composition of micro- and nano-structured materials, focused on cases relevant to catalysis. We report and discuss some recent results about the chemical state of supported PtRh alloy microparticles under oxidation conditions and the changes in the status of a Co/polypyrrole electrocatalyst due to ageing in the course of the oxygen reduction reaction. Monitoring the lateral inhomogeneity in the chemical state at sub-micrometer length scales by combining chemical imaging and micro-spectroscopy has provided comprehension of events occurring at the catalyst surface, which determine the performance of the morphologically complex catalytic systems. Ongoing efforts for development and implementing of new set-ups that allow working closer to the realistic conditions of catalytic reactions are also outlined and briefly discussed.

This work reports recent advances in characterization of the composition at submicron length scales of Al-based rapidly solidified alloys, which are correlated to their interactions with hydrogen. The hydrogen desorption kinetics and the evolution of the surface and subsurface structure and chemical state of high-purity Al and Al-3.0 at.% Cr alloy have been studied by thermal desorption analysis and scanning photoelectron microscopy. The alloy foil structure consisted of Cr-rich and Cr-depleted surface regions exhibits Cr segregation beneath the surface. The obtained results reveal how inclusions of aluminum oxide species can become very strong hydrogen traps at the highest temperatures of 600–630 °C, representing irreversible trapping in Al and its alloy. The effect of strong reversible and irreversible hydrogen traps on hydrogen desorption from aluminum alloys is discussed, suggesting that their direct identification in the microstructure provides further insights into hydrogen embrittlement mechanisms for aluminum materials in energy technologies.

We hereby report on a set of transient optical reflectivity and transmissivity measurements performed on silicon nitride thin membranes excited by extreme ultraviolet (EUV) radiation from a free electron laser (FEL). Experimental data were acquired as a function of the membrane thickness, FEL fluence and probe polarization. The time dependence of the refractive index, retrieved using Jones matrix formalism, encodes the dynamics of electron and lattice excitation following the FEL interaction. The observed dynamics are interpreted in the framework of a two temperature model, which permits to extract the relevant time scales and magnitudes of the processes. We also found that in order to explain the experimental data thermo-optical effects and inter-band filling must be phenomenologically added to the model.

Experimental approaches based on nonlinear optical processes (wave-mixing) have allowed major breakthroughs in diverse fields of science and technology. Nevertheless, these concepts were restricted to the optical regime due to the lack of coherent photon sources of sufficient peak brightness at sub-optical wavelengths. Nowadays, while the development of free electron lasers (FELs) potentially allows extreme ultraviolet (EUV) and X-ray wave-mixing, their full exploitation still requires efforts in instrumentation developments. The need to control (both in the spatial and temporal coordinates) multiple FEL input pulses, which may have different photon frequencies and polarizations, calls for the developments of instruments with a higher degree of complexity with respect to those typically used at synchrotron and FEL beamlines. Here we report on the progresses in the development of such kind of instrumentation at the FERMI FEL facility. Our FEL-based wave-mixing setups rely upon the transient grating (TG) approach, which represents a relevant benchmark for the development of advanced EUV/soft x-ray four-wave-mixing (FWM) experiments, as for instance coherent Raman scattering and multi-dimensional spectroscopy. © 2018 Elsevier B.V.

Fascinating spatiotemporal patterns forming during the electrodeposition of some alloys have attracted the interest of the scientific communities dealing with electrochemical materials science and dynamic processes. Notwithstanding extensive experimental work and recently achieved theoretical insights, several aspects of the physical chemistry of these dynamic structures are still elusive. In particular, the analytical methods employed so far to characterize these structures invariably failed to pinpoint any chemical or structural patterns correlated to those perceived by the naked eye or with a light microscope. In this work, we have made systematic use of the extreme surface sensitivity provided by synchrotron-based scanning photoelectron microspectroscopy, combined with progressive erosion by precisely controlled Ar+ sputtering, to achieve quantitative 3D understanding of the compositional and chemical-state distribution of an Ag−In electrodeposited layer, following the key elements Ag, In, and O. The results revealed that the pattern is present only in the topmost region (ca. 100 nm) of the layer and exhibits a regular distribution of the alloying elements in certain chemical states. Specifically, pattern formation in Ag−In electrodeposits is crucially controlled by the space distribution of surface In3+ oxi-/ hydroxides, deriving from reaction-diffusion processes taking place during alloy growth, and this pattern disappears in depth because of the delayed reduction of In3+ present in this film to elemental In, followed by intermetallic formation.

Electrodeposition and ageing under oxygen reduction reaction (ORR) of Mn-X/PPy (X=Co, Mg, Ni; PPy=polypyrrole) and Mn-Ag/G (G=graphene) composite electrocatalysts have been studied by quasi-in-situ soft X-ray absorption and fluorescence microspectroscopy. The fabricated materials exhibit micro-grained morphologies in which Mn is present mainly as Mn2+, accompanied by combinations of Co0/Co2+ and Ni0/Ni2+. Ageing leads to the formation of progressively larger mesoscopic aggregates. Initial ageing yields more active Mn3+ and Mn4+, in agreement with an improved ORR behaviour. Prolonged ageing causes the loss of Mn3+ and Mn4+ from the surface, in correlation with a degradation of the ORR response. In the investigated ageing period, Mn-Mg/PPy exhibits the best durability, with about half of the catalyst grains still showing the presence of Mn3+/Mn4+, while the others consist mainly of Mn2+. In Mn-Ni/PPy, the Ni2+ content tends to increase with ageing whereas Co3+ forms in the Mn-Co/PPy composites.

Four-wave mixing processes are achieved at suboptical wavelengths by using a free-electron laser as a source to generate extreme ultraviolet pulses that produce transient gratings. The phenomenon of four-wave mixing (FWM) occurs when two wavelengths of light interact to produce two extra wavelengths in the signal. It has been exploited in many optics technologies, from optical fibre communication to spectroscopy. Until now FWM has been limited to optical wavelengths. Here Filippo Bencivenga et al. show how to stimulate four-wave mixing processes at suboptical wavelengths using the FERMI free-electron laser as a source to generate extreme ultraviolet pulses that produce transient gratings. The extension of FWM to shorter wavelengths — combined with new developments in free-electron lasers — promises higher resolution for many techniques and the possibility of probe excitations to higher energies. Four-wave mixing (FWM) processes, based on third-order nonlinear light–matter interactions, can combine ultrafast time resolution with energy and wavevector selectivity, and enable the exploration of dynamics inaccessible by linear methods1,2,3,4,5,6,7. The coherent and multi-wave nature of the FWM approach has been crucial in the development of advanced technologies, such as silicon photonics8, subwavelength imaging9 and quantum communications10. All these technologies operate at optical wavelengths, which limits the spatial resolution and does not allow the probing of excitations with energy in the electronvolt range. Extension to shorter wavelengths—that is, the extreme ultraviolet and soft-X-ray ranges—would allow the spatial resolution to be improved and the excitation energy range to be expanded, as well as enabling elemental selectivity to be achieved by exploiting core resonances5,6,7,11,12,13,14. So far, FWM applications at such wavelengths have been prevented by the absence of coherent sources of sufficient brightness and of suitable experimental set-ups. Here we show how transient gratings, generated by the interference of coherent extreme-ultraviolet pulses delivered by the FERMI free-electron laser15, can be used to stimulate FWM processes at suboptical wavelengths. Furthermore, we have demonstrated the possibility of observing the time evolution of the FWM signal, which shows the dynamics of coherent excitations as molecular vibrations. This result opens the way to FWM with nanometre spatial resolution and elemental selectivity, which, for example, would enable the investigation of charge-transfer dynamics5,6,7. The theoretical possibility of realizing these applications has already stimulated ongoing developments of free-electron lasers16,17,18,19,20: our results show that FWM at suboptical wavelengths is feasible, and we hope that they will enable advances in present and future photon sources.

Refraction and absorption properties of soft X-rays provide distinct advantages for ‘fast’ imaging of matter consisting of light elements, as biological samples, with sensitivity better than conventional light microscopy. This is very attractive for nanotoxicology, in particular for rapid screening of nanoparticle distribution and their effects on exposed cells at submicrometer length scales. In this paper, we report on the first trials demonstrating the potential of scanning transmission X-ray microscopy to monitor morphological and chemical changes induced in Balb 3T3 mouse fibroblast cells exposed to CoFe2O4 nanoparticles. This research uses the complementary imaging methods of an advanced synchrotron soft X-ray microscopy instrument implementing a novel approach based on high-resolution absorption and phase contrast imaging for the identification of important cellular changes induced by the presence of nanoparticles. Copyright © 2015 John Wiley & Sons, Ltd.

Electrodeposition of manganese/polypyrrole (Mn/PPy) nanocomposites has been recently shown to be a technologically relevant synthesis method for the fabrication of Oxygen Reduction Reaction (ORR) electrocatalysts. In this study we have grown such composites with a potentiostatic anodic/cathodic pulse-plating procedure and characterised them by a multi-technique approach, combining a suite of in situ and ex situ spectroscopic methods with electrochemical measurements. We have thus achieved a sound degree of molecular-level understanding of the hybrid co-electrodeposition process consisting of electropolymerisation of polypyrrole with incorporation of Mn. By in situ Raman spectroscopy we followed the formation of MnOx and the polymer by monitoring the build-up and development of the relevant vibrational bands. The compositional and chemical-state distribution of the as-deposited material has been investigated ex situ by soft X-ray fluorescence (XRF) mapping and micro-absorption spectroscopy (micro-XAS). XRF shows that the spatial distribution of Mn is consistent in a rather wide range of current densities (c.d.s), while micro-XAS reveals a mixture of Mn valencies, with higher oxidation states prevailing at higher c.d.s. Pyrolysis of electrodeposits, desirable for obtaining more durable and active catalysts, has been followed in situ by photoelectron microspectroscopy, allowing to assess the evolution of: (i) the electrodeposit morphology, resulting in a uniform distribution of nanoparticles; (ii) the chemical state of manganese, changing from a mixture of valences to a final state consisting of Mn(III) and Mn(IV) oxides and (iii) the bonding nature of nitrogen, from initially N-pyrrolic to a combination of pyridinic and Mn–N/graphitic.

The characterization of the time structure of ultrafast photon pulses in the extreme-ultraviolet (EUV) and soft X-ray spectral ranges is of high relevance for a number of scientific applications and photon diagnostics. Such measurements can be performed following different strategies and often require large setups and rather high pulse energies. Here, high-quality measurements carried out by exploiting the transient grating process, i.e. a third-order non-linear process sensitive to the time-overlap between two crossed EUV pulses, is reported. From such measurements it is possible to obtain information on both the second-order intensity autocorrelation function and on the coherence length of the pulses. It was found that the pulse energy density needed to carry out such measurements on solid state samples can be as low as a few mJ cm−2. Furthermore, the possibility to control the arrival time of the crossed pulses independently might permit the development of a number of coherent spectroscopies in the EUV and soft X-ray regime, such as, for example, photon echo and two-dimensional spectroscopy.

Revealing the structure of complex biological macromolecules, such as proteins, is an essential step for understanding the chemical mechanisms that determine the diversity of their functions. Synchrotron based X-ray crystallography and cryo-electron microscopy have made major contributions in determining thousands of protein structures even from micro-sized crystals. They suffer from some limitations that have not been overcome, such as radiation damage, the natural inability to crystallize a number of proteins, and experimental conditions for structure determination that are incompatible with the physiological environment. Today, the ultra-short and ultra-bright pulses of X-ray free-electron lasers have made attainable the dream to determine protein structures before radiation damage starts to destroy the samples. However, the signal-to-noise ratio remains a great challenge to obtain usable diffraction patterns from a single protein molecule. With the perspective to overcome these challenges, we describe here a new methodology that has the potential to overcome the signal-to-noise-ratio and protein crystallization limits. Using a multidisciplinary approach, we propose to create ordered, two dimensional protein arrays with defined orientation attached on a self-assembled-monolayer. We develop a literature-based flexible toolbox capable of assembling different kinds of proteins on a functionalized surface and consider using a graphene cover layer that will allow performing experiments with proteins in physiological conditions.

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 NiFe 2 O 4 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 Photonics 2017, 4, 6 2 of 10 evidenced that for the case of NiFe 2 O 4 , 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 most recent light sources, extreme ultraviolet (EUV) and X-ray free electron lasers (FELs), have extended tabletop laser experiments to shorter wavelengths, adding element and chemical state specificity by exciting and probing electronic transitions from core levels. Through their unique properties, combining femtosecond X-ray pulses with coherence and enormous peak brightness, the FELs have enabled studies of a broad class of dynamic phenomena in matter that crosses many scientific disciplines and have led to major breakthroughs in the last few years. In this article, we review how the advances in the performance of the FELs, with respect to coherence, polarization and multi-color pulse production, have pushed the development of original experimental strategies to study non-equilibrium behavior of matter at the femtosecond–nanometer time–length scales. In this review, the emphasis is placed on the contribution of the EUV and soft X-ray FELs on three important subjects: (i) the new regime of X-ray mat...

This paper reports the development and application of a novel thin-layer electrochemical microcell for in situ soft x-ray fluorescence and absorption microspectroscopy. The microcell, fabricated using ultraviolet lithography, is an improved version of concepts previously developed in our group, featuring a wide optical window that allows the extension of the range of accessible in situ microspectroscopy and imaging methods, including those requiring small emission take-off angles. The three-electrode design implemented in the cell enables optimal electrochemical control. The first in situ experiment employing this new cell explores the electrochemical growth of a novel Mn-Co/polypyrrole composite that is a prospective electrocatalyst for Pt replacement in air cathodes. Morphological, compositional, and chemical-state distributions of Mn and Co codeposited with polypyrrole are subsequently performed in situ as a function of time and position, yielding otherwise unachievable information regarding the electrodeposition process.

A model membrane-electrode assembly of a high-temperature polymer-exchange membrane fuel cell based on a phosphoric-acid-imbibed membrane is studied under polarization by using scanning photoelectron microscopy (SPEM). The ability of SPEM to simultaneously probe the morphology, surface composition, and chemical state of cell constituents provides essential information on processes relevant to fuel cells. Despite the low ambient pressure of 1×10−5 mbar, by utilizing a dynamic high-pressure system, it is possible to monitor the Pt-catalyzed reduction of phosphoric acid with hydrogen and unveil the long-disputed nature of the ensuing products.

Synchrotron-based soft-X-ray imaging and microspectroscopy with sub-micrometer spatial resolution are used to investigate the electrodeposition of Mn–Cu–ZnO, a prospective active material for supercapacitors. This study is focused on the correlation of the local current density and the spatial distribution of the composition and chemical-state in electrodeposits grown potentiostatically at −0.7 V (vs a saturated calomel electrode), as well as the optimal potential for the achievement of high specific capacitance and cycling stability. The morphology, elemental distribution, and the local chemical state of both the electrode deposits and the grown dendrite structures are followed by using X-ray imaging, X-ray fluorescence mapping, and X-ray absorption microspectroscopy. For transmission soft-X-ray measurements, a thin-layer Hull-type microcell is developed and fabricated by using electron-beam lithography. The information obtained for the spatial distribution of the deposit is complemented by using electrochemical measurements and numerical simulations.

Synchrotron radiation news 26(6), 27 - 32 (2013). doi:10.1080/08940886.2013.850384, The free-electron laser (FEL) sources FLASH in Hamburg, LCLS at Stanford, and FERMI in Trieste provide XUV to soft X-ray radiation (FLASH and FERMI) or soft to hard X-ray radiation (LCLS) with unprecedented parameters in terms of ultrashort pulse length, high photon flux, and coherence. These properties make FELs ideal tools for studying ultrafast dynamics in matter on a previously unaccessible level. This paper first reviews results obtained at FEL sources during the last few years in the field of magnetism research. We start with pioneering experiments at FLASH demonstrating the feasibility of magnetic scattering at FELs [1, 2], then present pump–probe scattering experiments [3, 4] as well as the first FEL magnetic imaging experiments [5], and finally discuss a limitation of the scattering methods due to a quenching of the magnetic scattering signal by high-fluence FEL pulses [6]. All of the presented experiments exploit the X-ray magnetic circular dichroism effect [7, 8] to obtain element-specific magnetic scattering contrast, as known from synchrotron experiments [9–12]., Published by Taylor & Francis, Philadelphia, Pa.

Synchrotron radiation (SR) X-ray microscopy combined with X-ray fluorescence (XRF) microspectroscopy provides unique information that have pushed the frontiers of biological research, particularly when investigating intracellular mechanisms. This work reports an SR-XRF microspectroscopy investigation on the distribution and the potential toxicity of Fe2O3 and CoFe2O4 nanoparticles (NPs) in U87MG glioblastoma-astrocytoma cells. The U87MG cells exposed to NPs concentrations ranging from 5 to 250 µg/ml for 24 h were analyzed in order to monitor both morphological and chemical changes. The SR-XRF maps complemented with XRM absorption and phase contrast images have revealed different intracellular distribution patterns for the two nanoparticles types allowing different mechanism of toxicity to be deduced. Copyright © 2013 John Wiley & Sons, Ltd.

With a model invertebrate animal, we have assessed the fate of magnetic nanoparticles in biologically relevant media, i.e., digestive juices. The toxic potential and the internalization of such nanoparticles by nontarget cells were also examined. The aim of this study was to provide experimental evidence on the formation of Co2+, Fe2+, and Fe3+ ions from CoFe2O4 nanoparticles in the digestive juices of a model organism. Standard toxicological parameters were assessed. Cell membrane stability was tested with a modified method for measurement of its quality. Proton-induced X-ray emission and low energy synchrotron radiation X-ray fluorescence were used to study internalization and distribution of Co and Fe. Co2+ ions were found to be more toxic than nanoparticles. We confirmed that Co2+ ions accumulate in the hepatopancreas, but Fen+ ions or CoFe2O4 nanoparticles are not retained in vivo. A model biological system with a terrestrial isopod is suited to studies of the potential dissolution of ions and other ...

This paper reports an investigation into the aging of pyrolyzed cobalt/polypyrrole (Co/PPy) oxygen reduction reaction (ORR) electrocatalysts, based on quasi-in-situ photoelectron microspectroscopy. The catalyst precursor was prepared by potentiostatic reverse-pulse coelectrodeposition from an acetonitrile solution on graphite. Accelerated aging was obtained by quasi-in-situ voltammetric cycling in an acidic electrolyte. Using photoelectron imaging and microspectroscopy of single Co/PPy grains at a resolution of 100 nm, we tracked the ORR-induced changes in the morphology and chemical state of the pristine material, consisting of uniformly distributed similar to 20 nm nanoparticles, initially consisting of a mixture of Co(II) and Co(III) oxidation states in almost equal amounts. The evolution of the Co 2p, O 1s, and N 1s spectra revealed that the main effects of aging are a gradual loss of the Co present at the surface and the reduction of Co(III) to Co(II), accompanied by the emergence and growth of a N 1s signal, corresponding to electrocatalytically active C-N sites.

FERMI is the first seeded EUV-SXR free electron laser (FEL) user facility, and it is operated at Elettra Sincrotrone Trieste. Two of the four already operating beamlines, namely LDM (Low Density Matter) and DiProI (Diffraction and Projection Imaging), use a Kirkpatrick-Baez (K-B) active X-ray optics system for focusing the FEL pulses onto the target under investigation. A wafefront sensor is used as diagnostic for the characterization of the focused spot and for the optimization of the parameters of these active optical systems as well. The aim of this work is, first, to describe in detail the optimization procedure using the wavefront sensor through the minimization of the Zernike coefficients, and second, report on the final results obtained on the K-B optical system at the DiProI endstation. The wavefront sensor, mounted out of focus behind the DiProI chamber, allows to compute the intensity distribution of the FEL beam, typically a mix between several modes resulting in a ”noisy hyper-Gaussian” intensity profile, and the wavefront residual from ideal propagation shape and after tilt correction. Combining these two measures we can obtain the electric field of the wave out of focus. Propagating back the electric field we reconstruct the focal spot in far field approximation. In this way the sensor works as a diagnostic reconstructing the focal spot. On the other hand, after modelling the electric field with a Zernike polynomial it is easy and fast to optimize the mirror bending and the optical system angles by minimizing the aberrations, quantified in terms of Zernike coefficients. Since each coefficient corresponds to a single parameter, they can be minimized one at the time. Online wavefront measurements have made possible the optimization of the bending acting on the mirror curvature, and of the (pitch and roll) angle positions of the K-B system. From the wavefront measurements we have inferred a focal spot for DiProI of 5.5 μm x 6.2 μm at 32 nm wavelength, confirmed by the PMMA ablation imprints. The experimental results were compared with the predictions from simulations obtained using the WISE code, starting from the characterization of the actual mirror surface metrology. The results from simulations were found to be in agreement with the experimental measurements.

Ambient-pressure photoelectron spectroscopy (APPES) and microscopy are at the frontier of modern chemical analysis at liquid–gas, solid–liquid and solid–gas interfaces, bridging science and engineering of functional materials. Complementing the current state-of-the art of the instruments using differentially pumped analyzers, we survey in this short review several alternative APPES approaches, developed recently in the scanning photoelectron microscope (SPEM) at the Elettra laboratory. The reported set-ups allow for performing dynamic near-ambient pressure experiments without introducing additional differential pumping stages. They include implementation of pulsed-gas injection in the vicinity of samples or placing the sample inside reaction cells with very small apertures. The major part of the review is dedicated to construction and performance of novel environmental cells, where ultrathin electron-transparent but molecularly impermeable membranes are used to isolate the gas or liquid ambient from the electron detector operated in ultra-high vacuum (UHV). We demonstrate that two-dimensional materials, such as graphene and derivatives, are mechanically robust to withstand atmospheric—UHV pressure differences and are sufficiently transparent for the photoelectrons emitted from samples immersed in liquid or gaseous media. Representative results illustrate the performance of reported APPES approaches using tunable synchrotron X-rays, combined with the sub-micrometer lateral resolution of SPEM. They demonstrate the unique opportunities for addressing the chemical composition and electronic structure of surfaces and interfaces under realistic operation conditions with unprecedented lateral and spectral resolution.

The stability of pyrolyzed Mn–Co/polypyrrole (PPy) nanocomposites towards the Oxygen Reduction Reaction (ORR) in alkaline solution, was studied with a close-knit group of complementary microscopic and space-resolved spectroscopic approaches: Atomic Force Microscopy (AFM), Scanning and High-Resolution Transmission Electron Microscopy (SEM, HRTEM) and identical-location Scanning PhotoElectron Microscopy (SPEM). Tracking quasi-in situ the morphochemical evolution of the Mn–Co/PPy catalyst upon electrochemical aging under ORR conditions by this multi-technique approach, has allowed to clarify the key physico-chemical processes underlying the dramatic impact of Co additions to stability improvement. Keywords: Mixed manganese oxides, Polypyrrole, Oxygen reduction, Electrocatalysis, Nanocomposites, X-ray photoelectron microspectroscopy

Ambient-pressure photoelectron spectroscopy (APPES) and microscopy are at the frontier of modern chemical analysis at liquid-gas, solid-liquid and solid-gas interfaces, bridging science and engineering of functional materials. Complementing the current state-of-the art of the instruments, we survey in this short review several alternative APPES approaches, developed recently in the scanning photoelectron microscope (SPEM) at the Elettra laboratory. In particular, we report on experimental setups for dynamic near-ambient pressure environment, using pulsed-gas injection in the vicinity of samples or reaction cells with very small apertures, allowing for experiments without introducing additional differential pumping stages. The major part of the review is dedicated to the construction and performance of novel environmental cells using ultrathin electron-transparent but molecularly impermeable membranes to isolate the gas or liquid ambient from the electron detector operating in ultra-high vacuum (UHV). We demonstrate that two dimensional materials, such as graphene and derivatives, are mechanically robust to withstand atmospheric - UHV pressure differences and are sufficiently transparent for the photoelectrons emitted from samples immersed in the liquid or gaseous media. There are many unique opportunities for APPES using X-rays over a wide energy range. We show representative results that illustrate the potential of these ‘ambient-pressure’ approaches. Combined with the ca 100 nm lateral resolution of SPEM, they can overcome the pressure gap challenges and address the evolution of chemical composition and electronic structure at surface and interfaces under realistic operation conditions with unprecedented lateral and spectral resolution.

The FERMI Free Electron Laser (FEL) in Trieste, Italy operates in the extreme ultraviolet and soft x rays (EUV-SXR) wavelength range delivering high-fluence, stable, ultra-short pulses. Its unique design based on a seeded scheme and on tunable undulators allows unprecedented control of pulse parameters such as wavelength, phase, polarization, synchronization, pulse duration and implementation of multi-color FEL schemes. Both FEL-1 and FEL-2 lines with nominal wavelength range 100-20 nm and 20-4 nm, respectively, are open to users. We report on the unique features of FERMI, in particular those that have evolved beyond the original design, and on their application to pioneering experiments. We also present the upgrades that are planned to further expand the capabilities of this unique light source.

This paper reports the first in-situ synchrotron-based scanning photoelectron microscopy study of an operating YSZ-supported single-chamber SOFC with Au–MnO2 composite cathode and NiO anode, fed with 10−5 mbar 1:1 mixture of CH4 fuel and O2 at 650 °C. We employed a YSZ-supported cell with Au–MnO2 composite cathode and NiO anode. The chemical imaging and micro-XPS results were complemented with simultaneous electrochemical measurements, open circuit potential, potentiostatic and impedance spectrometry. The cell was operated under two conditions: (i) with fully oxidized electrodes and (ii) after in-situ reductive activation of the anode. The current delivered by the cell after in-situ reduction was about one order of magnitude higher. The chemical states of Ni and Mn were affected by the in-situ reduction process but they were not modified by the fuel-cell operation. Notwithstanding the absence of chemical state transformations of the electrode materials during the prolonged fuel-cell operation, cell aging brings about morphological change, accompanied by a decrease of the extracted current. Keywords: SOFC, Single-chamber SOFC, Hydrocarbon-fuelled SOFC, SPEM, XPS, X-ray microscopy

The effect of the concentration of cobalt ferrite (CoFe 2 O 4 ) nanoparticles (NPs) on their intracellular location and distribution has been explored by synchrotron radiation X-ray and fluorescence microscopy (SR-XRF) monitoring the evolution of NPs elemental composition as well. In cells exposed to low concentrations of CoFe 2 O 4 NPs, the NPs preferentially segregate in the perinuclear region preserving their initial chemical content. At concentrations exceeding 500 μM the XRF spectra indicate the presence of Co and Fe also in the nuclear region, accompanied by sensible changes in the cellular morphology. The increase of the Co/Fe ratio measured in the nuclear compartment indicates that above certain concentrations the CoFe 2 O 4 NPs intracellular distribution could be accompanied by biodegradation resulting in Co accumulation in the nucleus.

The performance of new materials and devices often depends on processes taking place at the interface between an active solid element and the environment (such as air, water or other fluids). Understanding and controlling such interfacial processes require surface-specific spectroscopic information acquired under real-world operating conditions, which can be challenging because standard approaches such as X-ray photoelectron spectroscopy generally require high-vacuum conditions. The state-of-the-art approach to this problem relies on unique and expensive apparatus including electron analysers coupled with sophisticated differentially pumped lenses. Here, we develop a simple environmental cell with graphene oxide windows that are transparent to low-energy electrons (down to 400 eV), and demonstrate the feasibility of X-ray photoelectron spectroscopy measurements on model samples such as gold nanoparticles and aqueous salt solution placed on the back side of a window. These proof-of-principle results show the potential of using graphene oxide, graphene and other emerging ultrathin membrane windows for the fabrication of low-cost, single-use environmental cells compatible with commercial X-ray and Auger microprobes as well as scanning or transmission electron microscopes.