Destacats

Cada any, un comitè d'experts s'ha d'enfrontar a la difícil tasca d'escolllir, d'entre totes les publicacions ICREA, unes poques que destaquin sobre la resta. És tot un repte: de vegades els debats s'acaloren, i sempre són difícils, però acaba sortint-ne una llista amb les millors publicacions de l'any. No es concedeix cap premi, i l'únic reconeixement addicional és l'honor d'ésser presentat com a Highlight. Cada publicació té alguna cosa especial, sia una solució especialment elegant a un vell problema, un resó espectacular als mitjans de comunicació o simplement, la fascinació d'una idea revolucionària. Independentment del motiu, es tracta dels millors dels millors i, com a tals, ens plau compartir-los aquí.

LIST OF SCIENTIFIC HIGHLIGHTS

Format: yyyy

  • Architecting Graphene Micromotors: A Simple Paper-Based Manufacturing Technology (2018)

    Merkoçi, Arben (ICN2)

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    Architecting Graphene Micromotors: A Simple Paper-Based Manufacturing Technology

    The group led by Prof. Merkoçi developed a graphene oxide rolled-up tube production process that uses wax-printed membranes for the fabrication of on-demand engineered micromotors at different levels of oxidation, thickness, and lateral dimensions. Using this technology the graphene oxide rolled-up tubes have shown magnetic and catalytic movement within the addition of magnetic nanoparticles or sputtered platinum in the surface of graphene-oxide-modified wax-printed membranes prior to the scrolling process. As a proof of concept, the authors have shown that the as-prepared catalytic graphene oxide rolled-up micromotors are successfully exploited for oil removal from water. This micromotor production technology relies on an easy, operator-friendly, fast, and cost-efficient wax-printed paper-based method and may offer a myriad of hybrid devices and applications. The developed technology may open the way of simple micromotors fabrication using other 2D materials for various applications.

  • The most precise measurement of the (dark) matter distribution in the universe (2018)

    Miquel Pascual, Ramon (IFAE)

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    The most precise measurement of the (dark) matter distribution in the universe

    There is overwhelming evidence that most of the matter in the universe is in a "dark" form that neither emits nor blocks light, and is therefore invisible to even the largest telescopes. While the detailed nature of this "dark matter" remains unknown, its gravitational interactions can be used to detect it and study its spatial distribution as a function of cosmic time, which, in turn, depends on the nature of the mysterious "dark energy" responsible for the current accelerated expansion of the universe. Particularly relevant is the so-called "weak gravitational lensing" effect, in which the observed shapes of distant galaxies are slightly modified by the gravitational pull of the masses between them and us. Then, the statistical properties of a large set of images of distant galaxies can be studied to determine the distribution of the intervening matter, which is mostly dark.

    The Dark Energy Survey (DES) is an international collaboration of 350 scientists from 28 institutions in 8 countries that is surveying an eighth of the sky using DECam, a 570-megapixel camera installed at the Blanco 4-meter telescope in the Cerro Tololo Inter-American Observatory in Chile. Looking at the data from the first season of observations (2013/14), DES has measured the shapes of about 35 million distant galaxies. Combining the measurement of the correlations between the shapes of these distant galaxies (sources) with the correlations in the positions of closer galaxies (lenses) and with the cross-correlations between the shapes of the sources and the positions of the lenses (a measurement led by IFAE), DES has produced the most precise determination of the clustering of the (mostly dark) matter (fig. 2). This is the first direct measurement that is as precise as those coming from the cosmic microwave background radiation, which is sensitive to the tiny inhomogeneities when the universe was 380000 years old, which can then be extrapolated to predict the large inhomogeneities we see today. The agreement between this extrapolation and the DES direct measurement provides a stringent test of the current cosmological model, with a cosmological constant as the dark energy.

  • A five-continent, 100,000-participant experiment to test Einstein's theory of local realism (2018)

    Mitchell, Morgan W. (ICFO)
    Acín Dal Maschio, Antonio (ICFO)

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    A five-continent, 100,000-participant experiment to test Einstein's theory of local realism

    A Bell test is a randomized trial that compares experimental observations against the philosophical worldview of local realism, in which the properties of the physical world are independent of our observation of them and no signal travels faster than light. A Bell test requires spatially distributed entanglement, fast and high-efficiency detection and unpredictable measurement settings. Although technology can satisfy the first two of these requirements, the use of physical devices to choose settings in a Bell test requires seemingly circular arguments that make assumptions about the same physics one aims to test. Bell himself noted this weakness in using physical setting choices and argued that human ‘free will’ could be used rigorously to ensure unpredictability in Bell tests. We led and coordinated a set of local-realism tests using human choices, valid without assumptions about predictability in physics. We recruited about 100,000 human participants to play an online video game that incentivizes fast, sustained input of unpredictable selections and illustrates Bell-test methodology. The participants generated 97,347,490 binary choices, which were directed via a scalable web platform to 12 laboratories on five continents, where 13 experiments tested local realism using photons, single atoms, atomic ensembles and superconducting devices. Over a 12-hour period on 30 November 2016, participants worldwide provided a sustained data flow of over 1,000 bits per second to the experiments, which used different human-generated data to choose each measurement setting. The observed correlations strongly contradict local realism and other realistic positions in bipartite and tripartite scenarios. Project outcomes include closing the ‘freedom-of-choice loophole’ (the possibility that the setting choices are influenced by hidden variables to correlate with the particle properties), the utilization of video-game methods for rapid collection of human-generated randomness, and networking techniques enabling global participation in experimental science.

  • Tailoring graphene with atomic precision (2018)

    Mugarza Ezpeleta, Aitor (ICN2)
    Valenzuela, Sergio O. (ICN2)

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    Tailoring graphene with atomic precision

    Nanosize pores can turn semimetallic graphene into a semiconductor, and from being impermeable into the most efficient molecular-sieve membrane. These emerging properties places nanoporous graphene at the focus of different fields of science and technology due to its potential application as active component of electronic and photonic devices, or as an atom-thick selective nanosieve for sequencing, ion transport, gas separation, and water purification.

    The challenge is to nanostructure graphene with the right dimensions and the required precision. Room temperature semiconducting applications require gaps that can only be achieved by narrowing the graphene stripes between pores below ~3 nm. Likewise, selectivity in molecular sieving requires pores of similar size. At this scale, gap homogeneity and sieving selectivity can only be achieved with atomic scale structural homogeneity, a resolution that is not accessible to top-down nanofabrication techniques (a fluctuation of a single carbon atom in the width of a graphene stripe of this scale can lead to gap variations as large as 50%).

    Inspired by on-surface routes to synthesize covalent carbon-based nanostructures, we have devised a bottom-up strategy for the formation of nanoporous graphene that exhibits both semiconducting and nanosieving functionalities. The hierarchical method consists on a series of thermally activated reaction steps that lead first to parallel arrays of nanoribbons that later couple to form the nanoporous material. Using this holey graphene, we have fabricated field-effect transistors with on/off ratios 3 orders of magnitude larger than those achieved with standard, continuous graphene.

  • Enabling catalysts to better clean car polluted air (2018)

    Neyman, Konstantin M (UB)

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    Enabling catalysts to better clean car polluted air

    The taste of the chocolate cake’s icing should not depend on whether it is served on a porcelain or silver plate. Similarly, for chemical reactions on large metal particles the support on which the particles are deposited should not play a crucial role, because atoms noticeably affect only their immediate vicinity. It was believed that for catalytic particles containing thousands of atoms the support should not affect chemical reactions occurring far away from it. However, an astonishing long-range effect of supports has been discovered, which can make car exhaust catalytic converters more efficient, in particular, for decreasing emissions of toxic carbon monoxide (CO).

    The results published in Nature Materials magazine were obtained from experiments performed by Prof. G. Rupprechter and co-workers (TU Vienna, Austria) and understood by computational modelling led by team of ICREA Professor K. Neyman (Universitat de Barcelona). Surprisingly, chemical processes on palladium microcrystalline particles used as exhaust gas catalysts changed significantly when such particles were supported on chemically inactive metal oxides.

    CO produced by combustion engines must be converted into CO2. This is achieved by catalysts containing palladium and platinum. The present study dealt with chemical reactions on micrometre-size palladium grains. For grains supported on oxides of aluminium or zirconium the resulting catalysts remained active at notably higher CO presure. Remarkably, less than a nanometre wide contact line between grains and support influenced CO oxidation reactions on the surface of the entire palladium grains that are hundred thousand times larger. Visualisations by a photoemission electron microscope revealed that catalyst deactivation always starts where a grain contacts the support and from there deactivation spreads like a tsunami wave over the whole grain. Hence, the contact line with the supports is pivotal for modifying chemical properties of supported grains. These observations are rationalized by calculated stronger binding of oxygen on palladium atoms in direct contact with the support.

  • Hide-and-seek enzyme conformations for new function! (2018)

    Osuna Oliveras, Sílvia (UdG)

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    Hide-and-seek enzyme conformations for new function!

    Each chemical reaction that happens in our body would not take place in a timescale compatible with life without the presence of substances called enzymes. Enzymes therefore make life possible. These molecules able to accelerate the chemical reactions are called catalysts. Among all existing catalysts, enzymes are the best ones, as they are capable of accelerating the chemical reactions that take place in our body by many orders of magnitude. 

    The use of enzymes in industry is, however, still quite limited as they were not optimized for the industrial conditions. Thus, modifying natural enzymes for broadening their scope and applicability in industry is highly appealing given their high potential. Much fundamental and applied research is being carried out to understand the mechanism of action of catalysts and propose modifications to the enzyme structure to improve their efficiency. 

    Although it was originally thought that enzymes present a single conformation of their structure, experimental and computational evidences have demonstrated that they can adopt multiple conformations in solution. In fact, enzymes are highly dynamic and can be described as ensembles of differently populated conformations. In the group, we have demonstrated that by introducing mutations to the enzyme, the populations of the accessible conformational states can be tuned, thus enabling emergence of novel function. 

    We found that careful analysis of the conformational ensemble of enzymes is key for modifying the enzyme ability to accommodate alternative industrially-relevant substrates, and even increase the activity towards some residual promiscuous reactions of interest. We have also developed a new computational tool, that we call Shortest Path Map (SPM), which analyzes the different conformations that the enzyme can adopt and identifies which positions of the enzyme are more important for favoring a desired conformation and enable novel function. Our new developed approach provides the enzyme (re)design field with a rational strategy to determine promising sites for enhancing novel activity through mutation.

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