Spraying nanopaper

New process produces extremely smooth cellulose layers on an industrial scale

With a new spray coating process, very uniform layers of cellulose nanofibers (CNF) can be produced on an industrial scale. X-ray investigations at DESY’s research light source PETRA III as well as investigations with an atomic force microscope and neutron scattering show how the layer is structured and can be tailored for different purposes like extremely thin, smooth and tough nanopaper. A Swedish-German research team led by DESY scientist Stephan Roth presents its structural analyses in the journal Macromolecules.
“Porous, nanostructured cellulose films have a number of advantageous properties that make them interesting for various applications from ultrastrong bio-active fibres to transparent conductive nanopaper,” explains the main author of the study, Calvin Brett from DESY and the Royal Institute of Technology (KTH) in Stockholm. “They are lightweight and temperature stable, have excellent mechanical properties, a low density and are made from renewable raw materials – cellulose nanofibers are usually made from wood.”

> Read more on the PETRA III at DESY website

Image: A silicon wafer without (top) and with (bottom) nano-cellulose coating. Each wafer is two centimetres wide and ten centimetres long. The coating is just 200 nanometres thin. Credit: DESY/KTH Stockholm, Calvin Brett.

Beryllium configuration with neighbouring oxygen atoms revealed

High-pressure experiments prove 50-year-old theoretical prediction.

In high-pressure experiments at DESY’s X-ray light source PETRA III, scientists have observed a unique configuration of beryllium for the first time: At pressures nearly a million times the average atmospheric pressure, beryllium in a phosphate crystal acquires six neighbouring atoms instead of the usual four. This six-fold coordination had been predicted by theory more than 50 ago, but could not be observed until now in inorganic compounds. DESY scientist Anna Pakhomova and her collaborators report their results in the journal Nature Communications.
“Originally, chemistry textbooks stated that elements like beryllium from the second period of the periodic table could never have more than four neighbours, due to their electron configuration”, explains Pakhomova. “Then around 50 years ago theorists discovered that higher coordinations could actually be possible, but these have adamantly evaded experimental proof in inorganic compounds.” Inorganic compounds are typically those without carbon – apart from a few exceptions like carbon dioxide and carbon monoxide.

>Read more on the PETRA III at DESY website

Image: Transformation of the usual fourfold coordination of beryllium to five- and sixfold with increasing pressure. (Credit: DESY, Anna Pakhomova)

Simulating earthquakes and meteorite impacts in the lab

New device squeezes samples with 1.6 billion atmospheres per second.

A new super-fast high-pressure device at DESY’s X-ray light source PETRA III allows scientists to simulate and study earthquakes and meteorite impacts more realistically in the lab. The new-generation dynamic diamond anvil cell (dDAC), developed by scientists from Lawrence Livermore National Laboratory (LLNL), DESY, the European Synchrotron Radiation Source ESRF, and the universities of Oxford, Bayreuth and Frankfurt/Main, compresses samples faster than any similar device before. The instrument can turn up the pressure at a record rate of 1.6 billion atmospheres per second (160 terapascals per second, TPa/s) and can be used for a wide range of dynamic high-pressure studies. The developers present their new device, that has already proven its capabilities in various materials experiments, in the journal Review of Scientific Instruments.
“For more than half a century the diamond anvil cell or DAC has been the primary tool to create static high pressures to study the physics and chemistry of materials under those extreme conditions, for example to explore the physical properties of materials at the center of the Earth at 3.5 million atmospheres,” said lead author Zsolt Jenei from LLNL. To simulate fast dynamic processes like earthquakes and asteroid impacts more realistically with high compression rates in the lab, Jenei’s team, in collaboration with DESY scientists, now developed a new generation of dynamically driven diamond anvil cell (dDAC), inspired by the pioneering original LLNL design, and coupled it with the new fast X-ray diffraction setup of the Extreme Conditions Beamline P02.2 at PETRA III.

>Read more on the PETRA III at DESY website

Image: Artist’s impression of a meteorite impact.
Credit: NASA

3D X-ray view of an amber fossil

Research team unravels secrets of 50-million-year-old parasite larvae

With the intense X-ray light from DESY’s particle accelerator PETRA III, researchers have investigated an unusual find: a 50-million-year-old insect larva from the era of the Palaeogene. The results offer a unique insight into the development of the extinct insect, as the team reports in the journal Arthropod Systematics & Phylogeny.
When the biologist Hans Pohl from the Friedrich Schiller University in Jena tracked down an insect fossil trapped in amber on eBay, the joy of discovery was great: it was a special specimen, a 50-million-year-old larva of an extinct twisted-wing insect from the order of Strepsiptera. But in order to be able to investigate it in detail, he needed the help of materials researchers from the Helmholtz Centre in Geesthacht, which operates a beamline at DESY’s X-ray source PETRA III.
Strepsiptera are parasites that infest other insects, such as bees and wasps, but also silverfish. “In most of the approximately 600 known species, the females remain in their host throughout their lives,” says Pohl. “Only the males leave it for the wedding flight, but then live only a few hours.” But there are exceptions: In species that infest silverfish, the wingless females also leave their host.

>Read more on the PETRA III at DESY website

Image: The fossil in amber. Its age lies between 42 to 54 million years. This fossil was scientifically examined at the Institute for Zoology and Evolutionary Research at the University of Jena.
Credit: FSU, Hans Pohl 

Nanometre gaps can crystallise liquids

X-ray examination shows surprising coexistence of liquid and crystalline form.

Very narrow gaps make liquids crystallise partially. X-ray investigations at DESY show that in gaps just a few molecule diameters wide both, liquid and crystal properties of a material can exist at the same time. The observation of this coexistence is important for all liquids in very small cavities and thus also for the study of friction (tribology). The team led by DESY researchers Milena Lippmann and Oliver Seeck presents the research in The Journal of Physical Chemistry Letters.
It was already known that liquids form atomically thin layers at an interface, such as the bottom or wall of a vessel. At the interface, the liquid is therefore not as disordered as in the volume. A relatively well-ordered layer of molecules of the liquid forms directly on the wall, on top of which a further layer is formed that is somewhat less orderly, on top of which a layer is even less orderly, until after about four to five layers the liquid is disordered.
“Despite this layering, the liquid remains liquid – the chemistry and physics of the layer do not change fundamentally,” explains Seeck. “An interesting situation arises if two smooth interfaces are brought together to a nanometre distance with a liquid between them.” One nanometre is one millionth of a millimetre. This brings the distance into the realm of molecule sizes. Depending on the specific liquid, its molecules can have a diameter of half a nanometre, for example.

>Read more on the PETRA III at DESY website

Image: Experimental set-up: In a diamond anvil cell, liquid is confined to a few nanometres narrow gap (centre). In this environment, layers and crystallisation coexist, as the X-ray investigation has shown.
Credit: DESY, Milena Lippmann

Exotic properties of iridium compounds

Scientists at DESY’s X-ray source PETRA III and the London Centre for Nanotechnology, at University College London, have developed a new method for examining the astonishing properties of a special class of iridium oxides known as iridates. The team of principal author Pavel Alexeev, from the Dynamics Beamline P01 at PETRA III, is presenting the procedure in the journal Scientific Reports.

Many oxides belonging to certain groups of transition metals (chemical elements with an incomplete d electron shell) are known for their exotic magnetic and electronic properties. These can be attributed qualitatively to a range of interactions between the charge of the electrons, their magnetic moment, their localization within the crystals and their atomic orbitals. The relative strengths of the various interactions determine whether an oxide is magnetic, an insulator, an electrical conductor or even a superconductor. The so-called 4d and 5d transitions metals are particularly interesting in this respect.

The properties of many of these oxides can be specifically adjusted by applying external electric or magnetic fields, or exerting pressure on the material. This makes them interesting for numerous applications in micro- and nanoelectronics, for data storage and information processing. Such behaviour is particularly pronounced in the oxides of 5d transition metals, such as tantalum, tungsten, osmium and iridium. The oxides of iridium are especially remarkable because they lose their magnetisation when subjected to pressure, and even under normal conditions develop unexpected magnetic structures. Although some of their properties have been known for quite a while, efforts to explain this behaviour are still in their infancy. This makes it all the more important to develop methods that provide detailed insights into such materials.

A particularly suitable and extremely sensitive method of studying the electronic and magnetic properties of solids is nuclear resonant scattering (NRS) using synchrotron radiation. This method uses the nuclei of the atoms of certain isotopes as local probes for the material’s properties. In view of its numerous possible applications, specialised measuring stations have been set up for this purpose on the P01 beamline at PETRA III, which are used by many scientists from all over the world every year. Among other things, the method allows the orientation of atomic magnetic moments to be determined with great accuracy. NRS therefore complements other X-ray techniques and – in contrast to neutron techniques – makes it possible to study small samples, for example when used on samples subject to high pressure.

>Read more on the PETRA III at DESY website

Image: Samples of strontium-iridium-trioxid crystals.
Credit: University College London, James Vale/Emily Hunter

New method for imaging electronic orbitals in solids

Orbital states are quantum mechanical constructions that describe the probability to find an electron in an atom, molecule or solid.  We know from atomic physics that an s-orbital is spherical or that a p-orbital is dumbbell-shaped, but how do the complicated distributions of the electrons that contribute to chemical bonds in solids look like?  Knowledge of these orbital states or electron distributions is the basis for our understanding of chemical bonds and related physical properties, which is a crucial step towards tailoring materials with specific characteristics. Here X-ray spectroscopy has contributed tremendously, however, the interpretation of the spectra is not easy and is often based on some assumptions for the analysis of the data.  Hence it would be very important to have an experimental method that gives a direct image of the local electron density.

Image: (a) (b) Integrated intensities of the M1 transition 3s→3d in the Fig. above plotted on the respective projections of the 3A2 3d(x2-y2/3z2-r2) orbital of Ni2+. (c) The three dimensional plot of the 3A2 3d(x2-y2/3z2-r2) orbital (more specific: the hole density) with the projections as in (a) and (b), respectively.
Credit: © MPI CPfS

How virtual photons alter atomic X-ray spectra

Control out of the vacuum, virtually

Certain X-ray optical properties of metal atoms can be controlled with the help of virtual photons. This has been demonstrated for the first time by a DESY research team at PETRA III, by using the highly brilliant radiation from this X-ray light source at DESY. In the journal Physical Review Letters they report on how the X-ray spectra of metal atoms can be controlled by virtual photons. This opens up new possibilities for specifically modifying the X-ray optical properties of materials.
So-called virtual photons play an important role in the interaction of light and matter. This is quite remarkable because they do not exist in the classical sense. Virtual photons are created in the vacuum out of nothing and then disappear again after an extremely short time. If these photons interact during their short existence with the electrons of an atom, the binding energies of the electrons shift ever so slightly.

>Read more on the PETRA III website at DESY

Image: Experimental setup to measure the collective Lamb shift at tantalum.
Credit: DESY, Haber et al.

Scientists develop printable water sensor

X-ray investigation reveals functioning of highly versatile copper-based compound

A new, versatile plastic-composite sensor can detect tiny amounts of water. The 3d printable material, developed by a Spanish-Israeli team of scientists, is cheap, flexible and non-toxic and changes its colour from purple to blue in wet conditions. The researchers lead by Pilar Amo-Ochoa from the Autonomous University of Madrid (UAM) used DESY’s X-ray light source PETRA III to understand the structural changes within the material that are triggered by water and lead to the observed colour change. The development opens the door to the generation of a family of new 3D printable functional materials, as the scientists write in the journal Advanced Functional Materials (early online view).

>Read more on the PETRA III at DESY website

Image: When dried, for example in a water-free solvent, the sensor material turns purple.
Credit: UAM, Verónica García Vegas

Simulating meteorite impacts in the lab

Scientists monitor the response of feldspar minerals to rapid compression

A US-German research team has simulated meteorite impacts in the lab and followed the resulting structural changes in two feldspar minerals with X-rays as they happened. The results of the experiments at DESY and at Argonne National Laboratory in the US show that structural changes can occur at very different pressures, depending on the compression rate. The findings, published in the 1 February issue of the scientific journal Earth and Planetary Science Letters (published online in advance), will aid other scientist to reconstruct the conditions leading to impact craters on Earth and other terrestrial planets.

>Read more on the PETRA III at DESY website

Image: Scanning electron microscopy image of the micro-structure of albite prior to the rapid compression experiments.
Credit: Stony Brook University, Lars Ehm

What keeps spiders on the ceiling?

DESYs X-ray source PETRA III reveals details of adhesive structures of spider legs

Hunting spiders easily climb vertical surfaces or move upside down on the ceiling. A thousand tiny hairs at the ends of their legs make sure they do not fall off. Like the spider’s exoskeleton, these bristle-like hairs (so-called setae) mainly consist of proteins and chitin, which is a polysaccharide. To find out more about their fine structure, an interdisciplinary research team from the Biology and Physics departments at Kiel University and the Helmholtz-Zentrum Geesthacht (HZG) examined the molecular structure of these hairs in closer detail at DESY’s X-ray light source PETRA III and at the European Synchrotron Radiation Facility ESRF. Thanks to the highly energetic X-ray light, the researchers discovered that the chitin molecules of the setae are specifically arranged to withstand the stresses of constant attachment and detachment. Their findings could be the basis for highly resilient future materials. They have been published in the current issue of the Journal of the Royal Society Interface.

>Read more on the PETRA III at DESY website

Image: In order to find out why the hunting spider Cupiennius salei adheres so well to vertical surfaces, the interdisciplinary research team investigates the tiny adhesive hairs on the spider legs.
Credit: Universität Kiel, Julia Siekmann

Platinum forms nano-bubbles

Technologically important noble metal oxidises more readily than expected.

Platinum, a noble metal, is oxidised more quickly than expected under conditions that are technologically relevant. This has emerged from a study jointly conducted by the DESY NanoLab and the Vienna University of Technology. Devices that contain platinum, such as the catalytic converters used to reduce exhaust emissions in cars, can suffer a loss in efficacy as a result of this reaction. The team around principal author Thomas Keller, from DESY and the University of Hamburg, is presenting its findings in the journal Solid State Ionics. The result is also a topic at the users’ meeting of DESY’s X-ray light sources with more than 1000 participants currently taking place in Hamburg.
“Platinum is an extremely important material in technological terms,” says Keller. “The conditions under which platinum undergoes oxidation have not yet been fully established. Examining those conditions is important for a large number of applications.”
The scientists studied a thin layer of platinum which had been applied to an yttria-stabilised zirconia crystal (YSZ crystal), the same combination that is used in the lambda sensor of automotive exhaust emission systems. The YSZ crystal is a so-called ion conductor, meaning that it conducts electrically charged atoms (ions), in this case oxygen ions. The vapour-deposited layer of platinum serves as an electrode. The lambda sensor measures the oxygen content of the exhaust fumes in the car and converts this into an electrical signal which in turn controls the combustion process electronically to minimize toxic exhausts.

>Read more on the DESY (PETRA III) website

Image: Electron microscope view into the interior of a platinum bubble. The cross-section was exposed with a focused ion beam. Below the hollow Pt bubble the angular YSZ crystal can be seen.
Credit: DESY, Satishkumar Kulkarni

LEAPS holds its first plenary meeting

Synchrotron radiation source SESAME welcomed as associated partner

On 12 and 13 November, the League of European Accelerator-based Photon Sources (LEAPS), the association of European research lightsources, met at DESY for its first plenary meeting. More than 150 scientists from the 16 accelerator-based lightsources in Europe, which are members of LEAPS, travelled to Hamburg to do so. Among them were the directors of all institutions, representatives of eight national science ministries and research funding agencies as well as Philippe Froissard from the European Commission.
“The League of European Accelerator-based Photon Sources has made great progress since its foundation a year ago, and I am convinced that this is the way to make our science with European lightsources shine even brighter in the future,” said Helmut Dosch, Chairperson of LEAPS, who opened the meeting together with LEAPS Vice-Chairperson Caterina Biscari from the Spanish synchrotron radiation source ALBA. The LEAPS consortium represents the interests of more than 25 000 users in total.
>Read more on the DESY website
and another article on the ALBA website. Please find here all news about the LEAPS initiative.

X-ray fluorescence imaging could open up new diagnostic possibilities in medicine

Using gold to track down diseases

A high-precision X-ray technique, tested at PETRA III, could catch cancer at an earlier stage and facilitate the development and control of pharmaceutical drugs. The test at DESY’s synchrotron radiation source, which used so-called X-ray fluorescence for that purpose, has proved very promising, as is now being reported in the journal Scientific Reports by a research team headed by Florian Grüner from the University of Hamburg. The technique is said to offer the prospect of carrying out such X-ray studies not only with higher precision than existing methods but also with less of a dose impact. However, before the method can be used in a clinical setting, it still has to undergo numerous stages of development.

The idea behind the procedure is simple: tiny nanoparticles of gold having a diameter of twelve nanometres (millionths of a millimetre) are functionalised with antibodies using biochemical methods. “A solution containing such nanoparticles is injected into the patient,” explains Grüner, a professor of physics at the Centre for Free-Electron Laser Science (CFEL), a cooperative venture between DESY, the University of Hamburg and the Max Planck Society. “The particles migrate through the body, where the antibodies can latch onto a tumour that may be present.” When the corresponding parts of the patient’s body are scanned using a pencil X-ray beam, the gold particles emit characteristic X-ray fluorescence signals, which are recorded by a special detector. The hope is that this will permit the detection of tiny tumours that cannot be found using current methods.

>Read more on the PETRA III at DESY website

Image: Gold nanoparticles spiked with antibodies can specifically attach to tumors or other targets in the organism and can be detected there by X-ray fluorescence.
Credit: Meletios Verras [Source]

Extremely small magnetic nanostructures with invisibility cloak

Future data storage technology

In novel concepts of magnetic data storage, it is intended to send small magnetic bits back and forth in a chip structure, store them densely packed and read them out later. The magnetic stray field generates problems when trying to generate particularly tiny bits. Now, researchers at the Max Born Institute (MBI), the Massachusetts Institute of Technology (MIT) and DESY were able to put an “invisibility cloak” over the magnetic structures. In this fashion, the magnetic stray field can be reduced, allowing for small yet mobile bits. The results were published in Nature Nanotechnology.

For physicists, magnetism is intimately coupled to rotating motion of electrons in atoms. Orbiting around the atomic nucleus as well as around their own axis, electrons generate the magnetic moment of the atom. The magnetic stray field associated with that magnetic moment is the property we know from e.g. a bar magnet we use to fix notes on pinboard. It is also the magnetic stray field that is used to read the information from a magnetic hard disk drive. In today’s hard disks, a single magnetic bit has a size of about 15 x 45 nanometer, about 1.000.000.000.000 of those would fit on a stamp.

One vision for a novel concept to store data magnetically is to send the magnetic bits back and forth in a memory chip via current pulses, in order to store them at a suitable place in the chip and retrieve them later. Here, the magnetic stray field is a bit of a curse, as it prevents that the bits can be made smaller for even denser packing of the information. On the other hand, the magnetic moment underlying the stray field is required to be able to move the structures around.

>Read more on the PETRA III at DESY website

Credit: MIT, L. Caretta/M. Huang [Source]

X-rays reveal L-shape of scaffolding protein

Structural biologists discover unexpected results at PETRA III at DESY in Germany.

An investigation at DESY’s X-ray light source PETRA III has revealed a surprising shape of an important scaffolding protein for biological cells. The scaffolding protein PDZK1 is comprised of four so-called PDZ domains, three linkers and a C-terminal tail. While bioinformatics tools had suggested that PDZK1’s PDZ domains and linkers would behave like beads on a string moving around in a highly flexible manner, the X-ray experiments showed that PDZK1 has a relatively defined L-shaped conformation with only moderate flexibility. The team led by Christian Löw from the Centre for Structural Systems Biology CSSB at DESY and Dmitri Svergun from the Hamburg branch of the European Molecular Biology Laboratory EMBL report their results in the journal Structure.

Similar to metal scaffolding which provides construction workers with access points to a building, scaffolding proteins mediate interactions between proteins situated on the membrane of the human cell. While the molecular structure of each of PDZK1’s four individual PDZ domains has been solved using X-ray crystallography and NMR spectroscopy, the overall arrangement of the domains in the protein as well as their interactions was not yet understood.

>Read more on the PETRA III at DESY website

Image: Artistic shape interpretation of the scaffolding protein PDZK1. (Credit: Manon Boschard)tistic shape interpretation of the scaffolding protein PDZK1.
Credit: Manon Boschard