Cerdanyola del Vallès, Spain
Cerdanyola del Vallès, Spain

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Garcia-Simon C.,University of Girona | Garcia-Borras M.,University of Girona | Gomez L.,University of Girona | Gomez L.,Autonomous University of Barcelona | And 8 more authors.
Nature Communications | Year: 2014

Since fullerenes are available in macroscopic quantities from fullerene soot, large efforts have been geared toward designing efficient strategies to obtain highly pure fullerenes, which can be subsequently applied in multiple research fields. Here we present a supramolecular nanocage synthesized by metal-directed self-assembly, which encapsulates fullerenes of different sizes. Direct experimental evidence is provided for the 1:1 encapsulation of C 60, C 70, C 76, C 78 and C 84, and solid state structures for the host-guest adducts with C 60 and C 70 have been obtained using X-ray synchrotron radiation. Furthermore, we design a washing-based strategy to exclusively extract pure C 60 from a solid sample of cage charged with a mixture of fullerenes. These results showcase an attractive methodology to selectively extract C 60 from fullerene mixtures, providing a platform to design tuned cages for selective extraction of higher fullerenes. The solid-phase fullerene encapsulation and liberation represent a twist in host-guest chemistry for molecular nanocage structures. © 2014 Macmillan Publishers Limited. All rights reserved.

Owen R.L.,Diamond Light Source | Juanhuix J.,Alba Synchrotron | Fuchs M.,Brookhaven National Laboratory
Archives of Biochemistry and Biophysics | Year: 2016

Following pioneering work 40 years ago, synchrotron beamlines dedicated to macromolecular crystallography (MX) have improved in almost every aspect as instrumentation has evolved. Beam sizes and crystal dimensions are now on the single micron scale while data can be collected from proteins with molecular weights over 10 MDa and from crystals with unit cell dimensions over 1000 Å. Furthermore it is possible to collect a complete data set in seconds, and obtain the resulting structure in minutes. The impact of MX synchrotron beamlines and their evolution is reflected in their scientific output, and MX is now the method of choice for a variety of aims from ligand binding to structure determination of membrane proteins, viruses and ribosomes, resulting in a much deeper understanding of the machinery of life. A main driving force of beamline evolution have been advances in almost every aspect of the instrumentation comprising a synchrotron beamline. In this review we aim to provide an overview of the current status of instrumentation at modern MX experiments. The most critical optical components are discussed, as are aspects of endstation design, sample delivery, visualisation and positioning, the sample environment, beam shaping, detectors and data acquisition and processing. © 2016 Published by Elsevier Inc.

Leon-Reina L.,University of Malaga | Garcia-Mate M.,University of Malaga | Garcia-Mate M.,X Ray Data Services S.L | Alvarez-Pinazo G.,University of Malaga | And 5 more authors.
Journal of Applied Crystallography | Year: 2016

This study reports 78 Rietveld quantitative phase analyses using Cu Kα1, Mo Kα1 and synchrotron radiations. Synchrotron powder diffraction has been used to validate the most challenging analyses. From the results for three series with increasing contents of an analyte (an inorganic crystalline phase, an organic crystalline phase and a glass), it is inferred that Rietveld analyses from high-energy Mo Kα1 radiation have slightly better accuracies than those obtained from Cu Kα1 radiation. This behaviour has been established from the results of the calibration graphics obtained through the spiking method and also from Kullback-Leibler distance statistic studies. This outcome is explained, in spite of the lower diffraction power for Mo radiation when compared to Cu radiation, as arising because of the larger volume tested with Mo and also because higher energy allows one to record patterns with fewer systematic errors. The limit of detection (LoD) and limit of quantification (LoQ) have also been established for the studied series. For similar recording times, the LoDs in Cu patterns, ∼0.2 wt%, are slightly lower than those derived from Mo patterns, ∼0.3 wt%. The LoQ for a well crystallized inorganic phase using laboratory powder diffraction was established to be close to 0.10 in stable fits with good precision. However, the accuracy of these analyses was poor with relative errors near to 100%. Only contents higher than 1.0 wt% yielded analyses with relative errors lower than 20%.

Corma A.,Technical University Valencia Consejo Superior Of Investigaciones Cientificas | Concepcion P.,Technical University Valencia Consejo Superior Of Investigaciones Cientificas | Boronat M.,Technical University Valencia Consejo Superior Of Investigaciones Cientificas | Sabater M.J.,Technical University Valencia Consejo Superior Of Investigaciones Cientificas | And 10 more authors.
Nature Chemistry | Year: 2013

The catalytic activity of gold depends on particle size, with the reactivity increasing as the particle diameter decreases. However, investigations into behaviour in the subnanometre regime (where gold exists as small clusters of a few atoms) began only recently with advances in synthesis and characterization techniques. Here we report an easy method to prepare isolated gold atoms supported on functionalized carbon nanotubes and their performance in the oxidation of thiophenol with O 2. We show that single gold atoms are not active, but they aggregate under reaction conditions into gold clusters of low atomicity that exhibit a catalytic activity comparable to that of sulfhydryl oxidase enzymes. When clusters grow into larger nanoparticles, catalyst activity drops to zero. Theoretical calculations show that gold clusters are able to activate thiophenol and O 2 simultaneously, and larger nanoparticles are passivated by strongly adsorbed thiolates. The combination of both reactants activation and facile product desorption makes gold clusters excellent catalysts. © 2013 Macmillan Publishers Limited. All rights reserved.


PubMed | CSIC - Institute of Materials Science, Coventry University, French National Center for Scientific Research and Alba synchrotron
Type: | Journal: Dalton transactions (Cambridge, England : 2003) | Year: 2017


Juanhuix J.,ALBA Synchrotron | Gil-Ortiz F.,ALBA Synchrotron | Cuni G.,ALBA Synchrotron | Colldelram C.,ALBA Synchrotron | And 8 more authors.
Journal of Synchrotron Radiation | Year: 2014

BL13-XALOC is currently the only macromolecular crystallography beamline at the 3 GeV ALBA synchrotron near Barcelona, Spain. The optics design is based on an in-vacuum undulator, a Si(111) channel-cut crystal monochromator and a pair of KB mirrors. It allows three main operation modes: a focused configuration, where both mirrors can focus the beam at the sample position to 52 μm × 5.5 μm FWHM (H × V); a defocused configuration that can match the size of the beam to the dimensions of the crystals or to focus the beam at the detector; and an unfocused configuration, where one or both mirrors are removed from the photon beam path. To achieve a uniform defocused beam, the slope errors of the mirrors were reduced down to 55 nrad RMS by employing a novel method that has been developed at the ALBA high-accuracy metrology laboratory. Thorough commissioning with X-ray beam and user operation has demonstrated an excellent energy and spatial stability of the beamline. The end-station includes a high-accuracy single-axis diffractometer, a removable mini-kappa stage, an automated sample-mounting robot and a photon-counting detector that allows shutterless operation. The positioning tables of the diffractometer and the detector are based on a novel and highly stable design. This equipment, together with the operation flexibility of the beamline, allows a large variety of types of crystals to be tackled, from medium-sized crystals with large unit-cell parameters to microcrystals. Several examples of data collections measured during beamline commissioning are described. The beamline started user operation on 18 July 2012. © 2014 International Union of Crystallography.

Nicolas J.,ALBA Synchrotron | Martinez J.C.,ALBA Synchrotron
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2013

The Alba-NOM instrument is a high accuracy scanning machine capable of measuring the slope profile of long mirrors with resolution below the nanometer scale and for a wide range of curvatures. We present the characterization of different sources of errors that limit the uncertainty of the instrument. We have investigated three main contributions to the uncertainty of the measurements: errors introduced by the scanning system and the pentaprism, errors due to environmental conditions, and optical errors of the autocollimator. These sources of error have been investigated by measuring the corresponding motion errors with a high accuracy differential interferometer and by simulating their impact on the measurements by means of ray-tracing. Optical error contributions have been extracted from the analysis of redundant measurements of test surfaces. The methods and results are presented, as well as an example of application that has benefited from the achieved accuracy. © 2012 Elsevier B.V. All rights reserved.

Nicolas J.,ALBA Synchrotron | Campos J.,Autonomous University of Barcelona
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

The use of linear methods to obtain both the error surface and the instrument error from redundant-independent datasets has been proposed to improve the accuracy of angle measuring scanning devices such as the long trace profilometer (LTP) or the nanometer optical measuring machine (NOM). In this work we propose to extend the method to measurements obtained during the calibration of mechanical benders. The proposed method allows determining an error-free measure of the slope error, the curvature and the cubic component of the mirror, as well as the instrument error. The description of the method, simulations and practical works are presented. © 2013 SPIE.

Nicolas J.,ALBA Synchrotron | Garcia G.,ALBA Synchrotron
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

Many synchrotron experimental techniques require a variable size x-ray photon beam on the sample or on the detector. The easiest way to achieve this, with the minimum set of optical elements, is to defocus the beam, typically by changing the bending radius of the focusing mirrors. Nevertheless, to defocus the beam from sample has the problem that the beam profile is heavily modulated by striations caused by the surface error of the focusing optics. To our knowledge, a relationship between these modulations of the beam and the surface errors that originates them has not been properly established. In this work we show that beam modulation of a defocused beam has a nonlinear dependence on the slope profile of the mirror. From the derived relationships it follows that the relative contributions to beam striations of slope error lower and higher spatial frequencies vary depending on how far away the measurement plane is from the image plane. We explore the relationship between the amplitude of the striations and the power spectral density of the slope errors. © 2013 SPIE.

Nicolas J.,Alba Synchrotron | Ruget C.,Alba Synchrotron | Juanhuix J.,Alba Synchrotron | Benach J.,Alba Synchrotron | Ferrer S.,Alba Synchrotron
Journal of Physics: Conference Series | Year: 2013

A practical limitation of X-ray focusing mirrors is that, while providing nice gaussian photon distributions at the focal plane, they usually produce inhomogeneous beam profiles upon defocusing that are caused by the mirror polishing errors. This can become a limitation in order to match the beam size with the sample dimensions, as the sample is not uniformly illuminated. We outline a method to achieve well shaped unfocused beams that has been successfully proven at BL13-XALOC, the macromolecular crystallography beamline at the ALBA synchrotron. As received from the manufacturer, the mirrors had rms slope errors of 180 nrad rms (vertically focusing mirror, VFM) and 210 nrad rms (horizontally focusing mirror, HFM). Ray tracing simulations suggested that pronounced stripes arising from the surface waviness would appear upon defocusing. By using the elastic beam theory to model the deformations and calculating the necessary correcting forces exerted by a few mechanical actuators that were installed in the mirror mechanical holders, we were able to reduce the slope errors of the mirrors to 55 nrad rms (VFM) and 83 nrad rms (HFM). The corrected mirrors were installed at the beamline and they were tested with the X-ray beam from the undulator source. © 2013 IOP Publishing Ltd.

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