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1.
J Synchrotron Radiat ; 26(Pt 5): 1462-1472, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31490133

RESUMO

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.

2.
J Synchrotron Radiat ; 23(1): 132-40, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26698055

RESUMO

The recent advent of free-electron laser (FEL) sources is driving the scientific community to extend table-top laser research to shorter wavelengths adding elemental selectivity and chemical state specificity. Both a compact setup (mini-TIMER) and a separate instrument (EIS-TIMER) dedicated to four-wave-mixing (FWM) experiments has been designed and constructed, to be operated as a branch of the Elastic and Inelastic Scattering beamline: EIS. The FWM experiments that are planned at EIS-TIMER are based on the transient grating approach, where two crossed FEL pulses create a controlled modulation of the sample excitations while a third time-delayed pulse is used to monitor the dynamics of the excited state. This manuscript describes such experimental facilities, showing the preliminary results of the commissioning of the EIS-TIMER beamline, and discusses original experimental strategies being developed to study the dynamics of matter at the fs-nm time-length scales. In the near future such experimental tools will allow more sophisticated FEL-based FWM applications, that also include the use of multiple and multi-color FEL pulses.

3.
J Synchrotron Radiat ; 22(3): 544-52, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25931067

RESUMO

The Diffraction and Projection Imaging (DiProI) beamline at FERMI, the Elettra free-electron laser (FEL), hosts a multi-purpose station that has been opened to users since the end of 2012. This paper describes the core capabilities of the station, designed to make use of the unique features of the FERMI-FEL for performing a wide range of static and dynamic scattering experiments. The various schemes for time-resolved experiments, employing both soft X-ray FEL and seed laser IR radiation are presented by using selected recent results. The ongoing upgrade is adding a reflection geometry setup for scattering experiments, expanding the application fields by providing both high lateral and depth resolution.

4.
Opt Express ; 22(11): 12869-79, 2014 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-24921484

RESUMO

X-ray free electron lasers (FEL) coupled with optical lasers have opened unprecedented opportunities for studying ultrafast dynamics in matter. The major challenge in pump-probe experiments using FEL and optical lasers is synchronizing the arrival time of the two pulses. Here we report a technique that benefits from the seeded-FEL scheme and uses the optical seed laser for nearly jitter-free pump-probe experiments. Timing jitter as small as 6 fs has been achieved and confirmed by measurements of FEL-induced transient reflectivity changes of Si3N4 using both collinear and non-collinear geometries. Planned improvements of the experimental set-up are expected to further reduce the timing jitter between the two pulses down to fs level.

5.
Opt Express ; 22(7): 8085-93, 2014 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-24718184

RESUMO

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.

6.
Acta Chim Slov ; 61(2): 263-71, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25125109

RESUMO

Electrodeposition of graphene-supported Co for ORR electrocatalysts from an acetonitrile solution has been studied by a multi-technique approach, combining a suite of spectroscopic methods with electrochemical measurements, allowing a molecular-level understanding of potentiostatic and pulsed-potential plating processes from the organic solvent onto a freestanding graphene film. The formation of the graphene film by the light-scribe approach has been monitored by Raman spectroscopy; the electrodeposition process has been clarified by cyclic voltammetry and the compositional and chemical-state distribution of Co have been investigated ex situ by soft X-ray absorption spectroscopy and fluorescence mapping, showing that both spatial distribution and valence state are homogeneous and independent of the local current density. The deposit consists in micrometric aggregates of Co/CoO nanoparticles with diameter ca. 30 nm (pulsed) and 200 nm (potentiostatic deposition). Potentiostatic deposition allows to obtain better ORR electrocatalytic perfomance in terms of nnumber of transferred electrons, onset/ half-wave potential and current density.

7.
Environ Sci Technol ; 47(19): 11284-92, 2013 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-23952740

RESUMO

Tungsten nanofibers are recognized as biologically potent. We study deviations in molecular composition between normal and digestive gland tissue of WOx nanofibers (nano-WOx) fed invertebrate Porcellio scaber (Iosopda, Crustacea) and revealed mechanisms of nano-WOx effect in vivo. Fourier Transform Infrared (FTIR) imaging performed on digestive gland epithelium was supplemented by toxicity and cytotoxicity analyses as well as scanning electron microscopy (SEM) of the surface of the epithelium. The difference in the spectra of the Nano-WOx treated and control cells showed up in the central region of the cells and were related to lipid peroxidation, and structural changes of nucleic acids. The conventional toxicity parameters failed to show toxic effects of nano-WOx, whereas the cytotoxicity biomarkers and SEM investigation of digestive gland epithelium indicated sporadic effects of nanofibers. Since toxicological and cytological measurements did not highlight severe effects, the biochemical alterations evidenced by FTIR imaging have been explained as the result of cell protection (acclimation) mechanisms to unfavorable conditions and indication of a nonhomeostatic state, which can lead to toxic effects.


Assuntos
Sistema Digestório/efeitos dos fármacos , Nanofibras/toxicidade , Óxidos/toxicidade , Tungstênio/toxicidade , Animais , Membrana Celular/efeitos dos fármacos , Sistema Digestório/citologia , Comportamento Alimentar/efeitos dos fármacos , Isópodes , Espectroscopia de Infravermelho com Transformada de Fourier
8.
Environ Sci Technol ; 47(10): 5400-8, 2013 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-23578201

RESUMO

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 Co(2+), Fe(2+), and Fe(3+) 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. Co(2+) ions were found to be more toxic than nanoparticles. We confirmed that Co(2+) ions accumulate in the hepatopancreas, but Fe(n+) 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 products from metal-containing nanoparticles in biologically complex media.


Assuntos
Cobalto/metabolismo , Crustáceos/metabolismo , Compostos Férricos/metabolismo , Nanopartículas Metálicas/toxicidade , Administração Oral , Animais , Cátions , Espectrofotometria Atômica
9.
Eur Phys J Plus ; 138(1): 79, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36712550

RESUMO

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.

10.
Chemistry ; 18(33): 10196-210, 2012 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-22836392

RESUMO

Fuel cells are one of the most appealing environmentally friendly devices for the effective conversion of chemical energy into electricity and heat, but still there are key barriers to their broad commercialization. In addition to efficiency, a major challenge of fuel-cell technology is the durability of the key components (interconnects, electrodes, and electrolytes) that can be subject to corrosion or undesired morphology and chemical changes occurring under operating conditions. The complementary capabilities of synchrotron-based soft X-ray microscopes in terms of imaging, spectroscopy, spatial and time resolution, and variable probing depths are opening unique opportunities to shed light on the multiple processes occurring in these complex systems at microscopic length scales. This type of information is prerequisite for understanding and controlling the performance and durability of such devices. This paper reviews the most recent efforts in the implementation of these methods for exploring the evolving structure and chemical composition of some key fuel cell components. Recent achievements are illustrated by selected results obtained with simplified versions of proton-exchange fuel-cells (PEFC) and solid-oxide fuel-cells (SOFC), which allow in situ monitoring of the redox reactions resulting in: 1) undesired deposits at interconnects and electrodes (PEFC); 2) material interactions at the electrode-electrolyte interface (PEFC); 3) release of corrosion products to the electrolyte phase (PEFC, and 4) mass-transport processes and structural changes occurring at the high operation temperatures of SOFC and promoted by the polarization.

11.
Opt Express ; 19(17): 16542-9, 2011 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-21935018

RESUMO

Single-particle experiments using X-ray Free Electron Lasers produce more than 10(5) snapshots per hour, consisting of an admixture of blank shots (no particle intercepted), and exposures of one or more particles. Experimental data sets also often contain unintentional contamination with different species. We present an unsupervised method able to sort experimental snapshots without recourse to templates, specific noise models, or user-directed learning. The results show 90% agreement with manual classification.

12.
Phys Chem Chem Phys ; 13(17): 7968-74, 2011 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-21437296

RESUMO

This paper reports a pioneering application of soft X-ray scanning transmission microscopy (STXM), combined with micro-spot X-ray absorption spectroscopy (XAS) and X-ray fluorescence spectroscopy (XRF), for the investigation of the corrosion of metal electrodes in contact with room-temperature ionic liquids (RTIL). Using an open electrochemical cell in vacuo we explore some fundamental aspects of the aggressiveness of the 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMP][TFSA]) RTIL towards Ni under in situ electrochemical polarisation. The possibility of imaging electrochemically-induced morphological features in conjunction with micro-XAS and XRF spectroscopies has provided unprecedented details regarding the space distribution and chemical state of corrosion products.

13.
Part Fibre Toxicol ; 8(1): 7, 2011 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-21299853

RESUMO

BACKGROUND: Occupational or environmental exposure to asbestos fibres is associated with pleural and parenchymal lung diseases. A histopathologic hallmark of exposure to asbestos is the presence in lung parenchyma of the so-called asbestos bodies. They are the final product of biomineralization processes resulting in deposition of endogenous iron and organic matter (mainly proteins) around the inhaled asbestos fibres. For shedding light on the formation mechanisms of asbestos bodies it is of fundamental importance to characterize at the same length scales not only their structural morphology and chemical composition but also to correlate them to the possible alterations in the local composition of the surrounding tissues. Here we report the first correlative morphological and chemical characterization of untreated paraffinated histological lung tissue samples with asbestos bodies by means of soft X-ray imaging and X-Ray Fluorescence (XRF) microscopy, which reveals new features in the elemental lateral distribution. RESULTS: The X-ray absorption and phase contrast images and the simultaneously monitored XRF maps of tissue samples have revealed the location, distribution and elemental composition of asbestos bodies and associated nanometric structures. The observed specific morphology and differences in the local Si, Fe, O and Mg content provide distinct fingerprints characteristic for the core asbestos fibre and the ferruginous body. The highest Si content is found in the asbestos fibre, while the shell and ferruginous bodies are characterized by strongly increased content of Mg, Fe and O compared to the adjacent tissue. The XRF and SEM-EDX analyses of the extracted asbestos bodies confirmed an enhanced Mg deposition in the organic asbestos coating. CONCLUSIONS: The present report demonstrates the potential of the advanced synchrotron-based X-ray imaging and microspectroscopy techniques for studying the response of the lung tissue to the presence of asbestos fibres. The new results obtained by simultaneous structural and chemical analysis of tissue specimen have provided clear evidence that Mg, in addition to Fe, is also involved in the formation mechanisms of asbestos bodies. This is the first important step to further thorough investigations that will shed light on the physiopathological role of Mg in tissue response to the asbestos toxicity.


Assuntos
Amianto/análise , Asbestose/patologia , Pulmão/química , Pulmão/diagnóstico por imagem , Pulmão/patologia , Microscopia de Fluorescência/métodos , Síncrotrons , Amianto/efeitos adversos , Humanos , Nanopartículas , Radiografia , Espectrometria por Raios X , Raios X
15.
Nat Commun ; 9(1): 4498, 2018 10 29.
Artigo em Inglês | MEDLINE | ID: mdl-30374062

RESUMO

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.

16.
Phys Rev Lett ; 99(4): 046803, 2007 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-17678388

RESUMO

The diffusion mechanism of indium atoms along multiwalled carbon nanotubes is studied by means of photoemission spectromicroscopy and density functional theory calculations. The unusually high activation temperature for diffusion (approximately 700 K), the complex C 1s and In 3d5/2 spectra, and the calculated adsorption energies and diffusion barriers suggest that the indium transport is controlled by the concentration of defects in the C network and proceeds via hopping of indium adatoms between C vacancies.

17.
Catal Letters ; 59(5): 448-468, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28008215

RESUMO

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.

18.
J Phys Chem B ; 109(24): 11980-5, 2005 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-16852477

RESUMO

Using scanning tunneling microscopy, low-energy electron diffraction, and X-ray photoelectron spectroscopy, we studied the evolution of the structure and chemical state of a Rh(110) surface, modified by K adlayers and exposed to high O2 doses at elevated temperatures. We find that oxygen coadsorption on the K-covered Rh(110) leads to massive reconstruction of the Rh(110) surface. Stable reconstructed (10 x 2) and (8 x 2) segmented phases with a local coverage of more than two oxygen atoms per surface Rh atom were observed. Formation of surface oxide, which coexists with the (10 x 2) and (8 x 2) segmented adsorption phases, is evidenced at the highest O2 doses. The development of strongly reconstructed adsorption phases with oxide-like stoichiometry and surface oxide under UHV conditions is explained in terms of the stabilization of the (1 x 2) reconstruction and promotion of O2 dissociation by the K adatoms.

19.
J Phys Chem B ; 109(29): 14052-8, 2005 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-16852764

RESUMO

The oxidation states formed during low-temperature oxidation (T < 500 K) of a Ru(0001) surface are identified with photoelectron spectromicroscopy and thermal desorption (TD) spectroscopy. Adsorption and consecutive incorporation of oxygen are studied following the distinct chemical shifts of the Ru 3d(5/2) core levels of the two topmost Ru layers. The evolution of the Ru 3d(5/2) spectra with oxygen exposure at 475 K and the corresponding O2 desorption spectra reveal that about 2 ML of oxygen incorporate into the subsurface region, residing between the first and second Ru layer. Our results suggest that the subsurface oxygen binds to the first and second layer Ru atoms, yielding a metastable surface "oxide", which represents the oxidation state of an atomically well ordered Ru(0001) surface under low-temperature oxidation conditions. Accumulation of more than 3 ML of oxygen is possible via defect-promoted penetration below the second layer when the initial Ru(0001) surface is disordered. Despite its higher capacity for oxygen accumulation, also the disordered Ru surface does not show features characteristic for the crystalline RuO2 islands. Development of lateral heterogeneity in the oxygen concentration is evidenced by the Ru 3d(5/2) images and microspot spectra after the onset of oxygen incorporation, which becomes very pronounced when the oxidation is carried out at T > 550 K. This is attributed to facilitated O incorporation and oxide nucleation in microregions with a high density of defects.

20.
ACS Appl Mater Interfaces ; 6(22): 19621-9, 2014 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-25369153

RESUMO

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 ∼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.

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