[aplicacoes] estrutura cristalina de solidos

EstruturalCristalinadeSólidos:Aplicações

Prof.AnaMaliska

DaphinyPo?maier,posdoc

21‐set‐2011.

NucleaçãoecristalizaçãodaSiO2

D.J.Tobler,S.Shaw,L.G.Benning“QuanTficaTonofiniTalstepsofnucleaTonandgrowthofsilicananoparTcles:Anin‐situSAXSandDLSstudy”GeochimicaetCosmochimicaActa73(2009)5377–5393

proaches, cryo- T E M photomicrographs of silica particlesthat were flash-frozen in solution in their native state froman experiment with 1600 ppm Si O 2 and IS = 0.05 were eval-uated ( F ig. 7C). T he particle diameters obtained from cryo-T E M matched those derived from the S A X S measurementsbetter than the results from conventional T E M ( T able 2).

4.5. K inetic analysis of S A X S data

T he evaluation of the reaction k inetics of silica nanopar-ticle nucleation and growth was carried out with the time-resolved S A X S data from the experiments with 640 ppmSi O 2 and all three IS studied. T he growth profiles of parti-cles forming in higher concentrated solutions (1600 pmSi O 2) did not provide enough data points for a thorough k i-netic analysis but they could be used for comparative qual-itative analyses.

4.5.1. NucleationT he fast decrease in monosilicic acid concentration

(< 5 min) when the p H of the experimental solutions wasadjusted to 7 ( F ig. 2) showed that silica polymerizationwas instantaneous. In addition, the lack of induction peri-ods in S A X S data (i.e., particles were detected from the

beginning of data collection) suggests that particle nucle-ation was instantaneous within the resolution of our study.T his fits well with the goodness of fit of the S A X S data tothe C hronomal k inetic model which assumes instantaneous,homogenous nucleation ( F ig. 8).

Information on the radii of the critical nuclei, R0, form-ing within the polymerizing solutions were obtained byextrapolation the particle growth profiles to t = 0 usingthe C hronomal analysis approach. R0 values for all640 ppm Si O 2 experiments are listed in T able 3 and vary be-tween 1.09 and 1.00 nm with no apparent dependence onIS.

F or comparison, critical nuclei sizes were also deter-mined using the G ibbs– K elvin equation ( G ibbs, 1961, T a-ble 3):

R þ0 ¼ 2v r =Rc T lnðS þ 1Þ ð9Þ

where m is the molar volume (27.2 cm3; I ler, 1979), r is thesurface energy (for amorphous silica, 80 erg cm–2; I ler,1973), Rc, the gas constant, and S is the supersaturation de-fined as S ¼ ðC C sÞ=C s with C being the actual concentra-tion and C s the solubility (116 ppm Si O 2 at 25 C ;G unnarsson and A rnorsson, 2000). In all 640 ppm Si O 2

experiments, the calculated R0+ values varied between

F ig. 7. ( A ) F E G –S E M and (B) T E M photomicrograph of silica nanoparticles grown for 30 min in a solution with 1600 ppm Si O 2 and IS of0.22. (C) C ryo-T E M photomicrograph of silica nanoparticles quenched after 1.5 h from a solution with 1600 ppm Si O 2 and IS of 0.05.

T able 2C omparison of particle diameters obtained from S A X S, D L S and T E M .

[Si02] (ppm) IS T ime (h) Particle diameter (nm)

S A X Sa D L S T E M

640 0.02 1 5.8 4.6 ± 1.0 3.1 ± 0.42 6.7 4.7 ± 1.1 3.3 ± 0.4

0.11 1 7.0 — —2 7.7 — 4.5 ± 0.7

0.22 1 7.2 5.8 ± 1.9 5.2 ± 0.92 8.0 8.0 ± 5.0 3.6 ± 0.5

1600 0.05 1 6.9 8.7 ± 2.2 —1.5 7.2b 10.1 ± 3.1 6.1 ± 1.1c

2 7.5b 9.6 ± 1.8 —0.11 1 7.6 9.9 ± 3.5 5.4 ± 0.5

2 7.9 A ggregation —0.22 0.5 7.5 8.0 ± 1.0 5.1 ± 0.6

1 7.9 A ggregation 6.7 ± 0.92 7.9 A ggregation —

a E rror of S A X S < 3%.b Estimates based on the progression of growth curves obtained from S A X S.c R esult from cryo-T E M .

S A X S and D L S study of silica nanoparticle formation 5385

the time-dependent change in the apparent mean hydrody-namic diameter of the growing particles via changes in thescattering of laser light caused by the Brownian motion ofthe particles. In contrast to the S A X S measurements, thedata showed large variations between single data points.F urthermore, due to the lower resolution of D L S at smallparticle sizes the average% error of the individual D L S datapoints ranged between 27 and 40 ( F ig. 6). D espite these lar-ger errors, overall, the trends between particle growth pro-files and [Si O 2]/ IS were similar to those observed withS A X S. H owever, the D L S growth curves di ered fromthe S A X S results in two ways: (i) the appearance of the firstdetectable particle was delayed at lower [Si O 2] ( 30 min;F ig. 6, full symbols) and (ii) following an initial steadygrowth a sudden increase in particle size was observed forhigher concentrated solutions ( F ig. 6; after 30 min for1600 ppm Si O 2/0.22 IS). T he observed delay at low concen-trations probably represents an artefact of the lower detec-tion limits of the D L S as compared to synchrotron-basedS A X S measurements ( 1 vs. 0.1 nm). C onversely, the dra-matic increase in growth probably indicates aggregationas even a small percentage (1–2 vol%) of larger particlesin a particle suspension would dramatically increase theoverall particle diameter derived by D L S (www.mal-vern.com, technical note).

4.4. E lectron microscopy

T o image and verify the size of silica nanoparticles eval-uated with S A X S and D L S, samples of the reacting solu-tions were removed after specific time steps (between10 min and 3 h) for S E M and T E M analysis. F ig. 7 A showsa F E G –S E M photomicrograph of silica nanoparticles after30 min of polymerization in a solution with 1600 ppm Si O 2

and IS = 0.22. T he particles are all aggregated but from im-age analyses an approximate particle diameter of 4–8 nmcould be estimated for the individual particles within theaggregates.

A more accurate estimate of the particle size distribu-tions was derived from the T E M photomicrographs( F ig. 7B) where the individual particles could be distin-guished. T he micrographs supported that the particles areapproximately spherical and monodisperse. U sing theT E M photomicrographs, the average particle diameterand the standard deviations (i.e., polydispersity) were deter-mined for a variety of experimental conditions. T he resultsare listed in T able 2 along with the results from D L S andS A X S (R values from S A X S were converted to particlediameter).

T o test for artefacts caused by sample dehydration andthe high vacuum of standard S E M and T E M analytical ap-

F ig. 5. ( A ) T ime evolution of the normalized scattering intensity, ar, in solutions with 640 and 1600 ppm Si O 2 at two di erent IS each. (B)P(R) of scattered silica nanoparticles as a function of R and time (t = 10–55 min with time steps of 5 min) evaluated with G N O M and E q. (8)(1600 ppm Si O 2, IS = 0.05).

F ig. 6. G rowth of silica nanoparticles in solutions with varying [Si O 2] and IS as determined by D L S. T he arrow indicates the start of particleaggregation for solutions with 1600 ppm Si O 2 and IS of 0.22 (% errors are average values).

5384 D .J. T obler et al. / G eochimica et C osmochimica A cta 73 (2009) 5377–5393

AprocuradamelhorcoisadepoisdosDiamantes

9September 2009 ESRFnews

Focus on: extreme conditions

Most people associate diamonds w ith jewellery, but these gemstones go beyond beauty. They are the hardest natural material known and are highly valued by industry for this property. Industrial uses include cutting, drilling, grinding and polishing. However, there are a few drawbacks: diamonds strongly resist heating and as soon as they are in contact w ith a metal, they ally w ith it. This is why researchers are in pursuit of substitutes for diamonds w ith a better conductivity and more resistance to temperature and corrosion.

To create new materials, scientists focus on the periodic table. Carbon, the source of diamonds, is not the only element that is linked to hardness. Boron and nitrogen also form strong, short chemical bonds. In 1956 scientists combined boron and nitrogen to create cubic boron nitride (cBN), which has been used as an alternative for synthetic diamonds. However, it only has half of the hardness of diamond.

A team from the Inst itute for Superhard Materia ls in Ukra ine, together w ith scient ists from the University of Paris, the University of Bayreuth (Germany) and the ESRF, managed to comb ine carbon, boron and nitrogen in one materia l in 2001. The result , cub ic BC2N , is a compound that is ha lf way bet ween d iamond and boron nitride in composit ion. The team app lied a pressure of 18 GPa and temperatures above 2200 K , which triggered the appearance of a new phase. A lthough the new compound is not as hard as d iamond, it is harder than its predecessor, cBN . Desp ite the fac t that it was synthesised e ight years ago, the paper on BC2N is st ill in the lime light (So lozhenko et al. 2001). Proof of this are the 150 citat ions that it has had – 80 of which were in 2008 .

A cheap, super-hard materialThe financial cost of developing these new materials at a mass-production rate w ill determine whether they w ill be used in industry. A potentially cheap solution for an ultrahard material is the result of research done by the University of Bordeaux and the University of Clermont-Ferrand (France).

The team studied a carbon nitride under

high pressure and temperature, but the first experiments failed. The scientists soon noticed that there was a small portion of the structure that was already surprisingly super-hard at ambient conditions. The team then decided to isolate the small particle, compress it and characterise it.

The results proved that, in accordance w ith previous theoretical predictions, crystalline carbon nitrides exhibit exceptional compressibility behaviour. In addition, despite the usual considerations, the team demonstrated that there is no need for severe and expensive pressure and temperature conditions to elaborate low-compressibility, covalent materials (Goglio et al. 2009).

The downside of this story, and most of the stories linked to creating new materials, is that their produc tion is still at a very small scale. In most cases, when scientists try to increase the produc tion, the material decomposes, which means that the phases are very fragile. However, the creation of new hard materials is progressing sw if tly and researchers generally comment that it is only a question of time until new materials can be synthesised in large quantities.

Industrial interestA team from the University of Bayreuth has already managed to raise the interest of industry in their patented Aggregated Diamond Nanorods (ADNRs), a new material synthesised in 2005 based on bulk samples of nanocrystalline diamond and identified

at the ESRF as the densest form of carbon (Dubrovinskaia et al. 2005).

Results showed that the ADNRs’ density is greater than that of diamond by 0.2–0.4% and is 11% less compressible. The combination of the hardness of the ADNRs and its chemical stability could make it a potential material for machining hard materials, grinding and polishing, as well as for use as anvils in scientific devices like diamond anvil cells and multi-anvil presses.

Another new material that is attracting the interest of industry is the super-hard aggregated boron nitride nanocomposite (ABNNC), synthesised by the same team and tested at the Sw iss Norwegian Beamline at the ESRF (Dubrovinskaia et al. 2007). ABNNC is the first non-carbon-based bulk material w ith a value of hardness approaching that of single crystal and polycrystalline diamond and ADNRs. ABNNC also has unusually high fracture toughness and wear resistance, as well as high thermal stability (above 1600 K in air), making it an exceptional superabrasive.M Capellas

ReferencesN Dubrovinskaia et al. 2005 Appl. Phys. Lett. 87 083106.N Dubrovinskaia et al. 2007 Appl. Phys. Lett. 90 101912.G Goglio et al. 2009 D iamond & Related Materials 18 627–631.V L Solozhenko et al. 2001 Appl. Phys. Lett. 78 1385–1387.

New materials with better properties than diamond have come to light after testing them at the ESRF.

Finding the next best thing after diamonds

Apart from its use in jewellery, diamond is highly valued and widely used in industry.

ISTO

CKP

HO

TO.C

OM

ESRFSep09FOCUS_NewMaterials_p09.indd 9 4/9/09 11:52:06



















ISTO

CKP

HO

TO.C

OM




















ISTO

CKP

HO

TO.C

OM


O2,NaeLi,Isolante‐Condutor?

10


September 2009 ESRFnews

Oxygen is the third most abundant element in the universe by mass, after hydrogen and helium. More than 20% of the volume of air consists of oxygen. Despite its predominance, its behaviour under pressure is still not clear to researchers. Above a pressure of 96 GPa (about a quarter of the pressure inside the Earth’s core), oxygen has shown a metallic phase, but scientists have only recently determined the changes in its crystalline structure.

A team from the Commissariat à l’Energie Atomique (France), the University of Ottawa (Canada) and the ESRF, clarified a standing debate on the transition of the element from the insulator to the metallic phase (Weck et al. 2009). They used angle-dispersive X-ray diffraction on three single-crystal samples of oxygen embedded in helium at ID27 – the high-pressure beamline. The results showed the atomic displacements leading to the new structure. Metallisation takes place due to the closure of the band gap that occurs w ith an instability of the lattice, which evolves into a denser structure w ith the dissociation of molecular entities.

The metallic oxygen can transform even further. Above 250 GPa, theoreticians predict that it transitions to an atomic metal. “This is the next challenge for ID27, providing that the users grow good quality single crystals at these conditions,” explains Mohamed Mezouar, the scientist in charge of the beamline.

Weird metalsThe opposite effect from oxygen under pressure takes place when metals, such as sodium and lithium, become compressed. They both belong to the group of lighter elements classified as “simple metals”, meaning that they have simple crystal and electronic structures. However, under pressure they adopt different physical states. Recently, two separate teams (Ma et al. 2009 and Matsuoka et al. 2009) discovered that sodium and lithium are actually insulating when under pressure and that sodium becomes transparent, using Raman spectrometry and the Advanced Photon Source in Chicago (US) (Ma et al. 2009).

The pioneering experimental work on lithium and sodium under high pressure was started at the ESRF on the beamline ID9A several years ago. It was known that

under ordinary conditions sodium adopts a straightforward crystal structure, but under high pressure, and therefore high density of the metal, things change. For starters, the melting temperature of sodium is lower at high pressure (118 GPa) than at ambient conditions. Today, a team from the University of Edinburgh (Gregoryanz et al. 2008) and the ESRF found that seven different crystalline

phases are reached in a very small region of pressure–temperature domain, in the vicinity of the sodium’s melting curve minimum. Slight changes in pressure or temperature set off new transitions, some of which are very complex and had never been observed in any other element before. One of these structures contains more than 500 atoms in the unit cell.

The team carried out their experiments on ID27 using single-crystal diffraction. They identified the lattice parameters and the number of atoms of all seven phases. The results for sodium shed light on theoretical models that predict bizarre states for other materials, such as hydrogen.M Capellas

ReferencesE Gregoryanz et al. 2008 Science 320 1054 .Y Ma et al. 2009 Nature 458 182–185.T Matsuoka et al. 2009 Nature 458 186–189.G Weck et al. 2009 PRL 102 255503.

L LU

ND

EGA

ARD

Composite diffraction image: data from the one of the phases of sodium with 90 atoms in unit cell.

Elements change from insulator to conductor, and vice versaMany elements, such as oxygen, are insulating at room temperature, but if you put them under pressure you get materials that don’t have electrical resistance. The other way round, which is a more exotic event, takes place with elements such as lithium or sodium. Scientists are slowly managing to understand why and how these events happen.

“Sodium and lithium are actually insulating when under pressure”

ESRFSep09FOCUS_Sodium_p10.indd 10 4/9/09 11:52:25

10




A team from the Commissariat à l’Energie Atomique (France), the University of Ottawa (Canada) and the ESRF, clarified a standing debate on the transition of the element from the insulator to the metallic phase (Weck et al. 2009). They used angle-dispersive X-ray diffraction on three single-crystal samples of oxygen embedded in helium at ID27 – the high-pressure beamline. The results showed the atomic displacements leading to the new structure. Metallisation takes place due to the closure of the band gap that occurs with an instability of the lattice, which evolves into a denser structure with the dissociation of molecular entities.







ReferencesE Gregoryanz et al. 2008 Science 320 1054.Y Ma et al. 2009 Nature 458 182–185.T Matsuoka et al. 2009 Nature 458 186–189.G Weck et al. 2009 PRL 102 255503.

L LU

ND

EGA

ARD





10




A team from the Commissariat à l’Energie Atomique (France), the University of Ottawa (Canada) and the ESRF, clarified a standing debate on the transition of the element from the insulator to the metallic phase (Weck et al. 2009). They used angle-dispersive X-ray diffraction on three single-crystal samples of oxygen embedded in helium at ID27 – the high-pressure beamline. The results showed the atomic displacements leading to the new structure. Metallisation takes place due to the closure of the band gap that occurs w ith an instability of the lattice, which evolves into a denser structure w ith the dissociation of molecular entities.







ReferencesE Gregoryanz et al. 2008 Science 320 1054 .Y Ma et al. 2009 Nature 458 182–185.T Matsuoka et al. 2009 Nature 458 186–189.G Weck et al. 2009 PRL 102 255503.

L LU

ND

EGA

ARD





Na‐7fases!‐pressao/temperatura


Take a trip from the centre of the Earth to its surface

The Earth as it is viewed from space. Earth ranks fifth in size among the nine planets that make up our solar system. It has a diameter of about 13 000 km.

that “sulphur cannot be rejected in sufficient quantities to match the seismological data, so we have to look for other elements – silicon and oxygen being the best candidates”.

Silicon and oxygenObserving the speed at which seismic waves pass through the Earth allows geophysicists to determine the density and stiffness of rocks at inaccessible depths. If they can match those properties w ith those of known substances at elevated temperatures and pressures, they can

subsequently infer what the conditions must be deep in the Earth.

At the ESRF, a team from the Institut de M inéralogie et de Physique des M ilieux Condensés at the University of Paris studied the sound velocity in solid iron alloyed w ith light elements using high-resolution inelastic X-ray scattering on ID28 (Badro et al. 2007). It ruled out sulphur as a possible light element in the core and proposed that the inner core is made of iron, silicon (2.3% wt) and traces of oxygen. If extrapolated to the liquid state, the team suggests that the outer core could contain 2.8% wt silicon and 5.3% wt oxygen. Silicon and oxygen can be partly dissolved in iron, so the total amount of light elements in the inner core would be 2.5% wt, and 8% wt in the outer core.

More recently, the team studied silicon bearing iron–nickel alloys and compared them w ith pure iron. The results, which have been submitted for publication, show a model for the contribution of silicon and nickel to the Earth’s inner core.

On the boundaries between the core and the mantle: the weird D’’ layerThe core still has many surprises in store, as does the mantle surrounding it. At the boundary between the two zones there is the so-called D’’ layer. This heterogeneous layer can have from no thickness to about 250 km.

The bizarreness of the D’’ layer is the subject of debate among geologists. Some link it to the fact that supposedly there are expelled elements from the core that reach the mantle, where they w ill create hotspots, plumes, etc. Others blame the partial fusion of the material present, which mixes w ith other materials like water and the phase transition of silicate-perovskite (analogue to the calcium titanium oxide mineral found in the Earth’s crust) to post-perovskites. Finally, there is another point of view that states that the culprit is the slabs in the subduction zone, which sink onto the D’’ layer area, transforming it into a “slab graveyard”.

The quest to decipher the strangeness of the D’’ layer could provide the community w ith a lot of valuable information about the Earth’s dynamics. The team from the University of Clermont-Ferrand has recently tried to determine the density

and anisotropy of magnesium- and iron- containing silicate perovskites on ID24 and ID27. It also investigated post-perovskite of the same material, which occurs when pressure increases in the lower mantle. The idea was to determine whether the phase transitions in perovskite are at the origin of seismic discontinuities in the zone. The post-perovskite transition could also provide information about the temperature variations of the D’’ layer. At the time of ESRFnews going to press, a very promising paper addressing these questions was in the submission process (Andrault et al. 2009).

It is crucial to study perovskites w ith iron, even if it is technically more complicated, because iron is a transition element that can change its electronic structure under pressure and, as a consequence, the way that the Earth’s interior behaves. Researchers from the University of Bayreuth carried out nuclear resonance experiments on ID18 and ID27, as well as at the Advanced Photon Source, on lower-mantle perovskites. The goal was to measure the spin-state transitions of iron in the perovskite. Surprisingly, they found a stable intermediate spin state throughout the lower mantle (McCammon et al. 2008).

Closer to the surface: the subduction zone The lower mantle might be the destination of ocean plates when they become too cold and sink. The plates are taken from the subduction zones, from where they are driven back to the mantle, beneath another continental or oceanic plate. The reactions happening in the subduction zone are directly linked to earthquake and volcanic activity. The materials in this area react w ith the water present and take it back to the surface or send it down to the mantle. Dehydration of the rocks of the subduction slabs could trigger earthquakes. Scientists from the University of Lyon are trying to confirm this model by studying the materials present in the subduction zone, such as talc (a mineral resulting from the metamorphism of magnesian minerals such as serpentine, pyroxene, amphibole, olivine, in the presence of carbon dioxide and water) or antigorite (the high-pressure variety of serpentine, containing 13% wt of water).

Talc commonly hydrates ultramafic rocks

Layer Distance from surface (km) Pressure (GPa) Temperature (ºC) Crust 0–35 <1 200–600Upper mantle 35–660 1–25 600–1600Lower mantle 660–2890 25–136 1600–4000Outer core 2890–5150 136–330 4400–6100Inner core 5150–6360 330–360 6100K (±500K)

The Earth’s layers

NA

SA G

OD

DA

RD S

PACE

FLI

GH

T CE

NTE

R (N

ASA

-GSF

C)

ESRFSep09FOCUS_Earth_p12-13.indd 13 4/9/09 11:53:51

CondiçõesExtremas–centrodaterraFocus on: extreme conditions

12 September 2009 ESRFnews

Take a trip from the centre of the Earth to its surface

Geologists believe that Earth was struck by a planet the size of Mars about 4.5 billion years ago. The impact led to the formation of our satellite, the Moon and melted most of the planet’s rocks, creating its core, as the metallic iron between the rocks sank towards the centre. Therefore, iron is of major interest in the scientific community. Despite it being physically impossible to access the Earth’s core, high-pressure experiments at synchrotron sources can provide major clues about the role that iron and other materials play in the core.

The Earth’s core is divided into two zones: the outer core, which is liquid, and the inner core, which is solid. The main component of the core is iron, which is crystallised in the inner core. Scientists know this because the speed of sound through the core (the velocity at which seismic waves travel across it) and the density of the core are similar to those seen in iron at high pressures and temperatures. On top of that, iron is sufficiently abundant in the universe to make up for approximately 35% of the mass of the planet present in the core.

However, iron is not alone in the core. The core should contain ~10% wt of nickel and, more importantly, seismology shows that both parts of the core are too light to be pure, dense iron–nickel alloy. The outer core could have 6–10% wt of lighter elements, while the inner core would contain 2–3% wt. The candidates that could potentially mix w ith iron are sulphur, silicon, carbon and oxygen.

The case of sulphurIt is quite likely that sulphur is present in the deepest sector of the Earth because meteorites contain this element abundantly. A team from the University of Paris and the University of Clermont-Ferrand (France) is studying how sulphur fuses w ith iron at high pressure and temperature. It focuses on how it crystallises and what phases form when mixing it w ith iron. The team recently published the results of experiments on ID27 at the ESRF, where it studied the fusion temperature of an alloy of iron and sulphur (Fe-FeS) (Morard et al. 2008 and 2009). They discovered that when adding sulphur to iron the melting temperature decreases by almost 1000 K and at extreme pressures acts as an antifreeze. However, iron is not the first phase to crystallise below the melting temperature but Fe3S, implying that sulphur gets trapped in the solid phase (for

plausible sulphur contents). Researchers also point out that sulphur enters the structure of liquid iron as an impurity, w ithout disturbing the local structure.

The results contest the hypothesis that the crystallisation of the inner core, which still happens at a rate of 800 tonnes per second, rejects enough sulphur to the outer core to match the 6–10% wt density deficit. At the same time, seismological measurements state that there is a big difference in density between the inner and outer cores, so there

needs to be a rejection of elements. Those light elements, when rejected, facilitate the convection to the outer core and allow the magnetic fields to take place. A paper, mainly based on ab initio calculations (A lfe 2002), suggest that sulphur would become increasingly compatible w ith solid iron at increasing pressure and that sulphur would not be rejected to the outer core (so sulphur could not explain the density difference between the inner and outer cores). Chrystéle Sanloup, a scientist at the University of Paris, concludes

The Earth as it is viewed from space. Earth ranks fifth in size among the nine planets that make up our solar system. It has a diameter of about 13 000 km.

The Earth is still an enigma. But the ESRF is helping to demystify our planet, its composition and inner activity.

ESRFSep09FOCUS_Earth_p12-13.indd 12 4/9/09 11:53:28

Fe(35%)+Ni+S,Si,C,O

Fe‐FeS=Fe3S(1000K)

Fel‐2.8%Si+5.3%O2

silicate‐perovskites‐>post‐perovskites

Proteínaligadaàevoluçãodoesperma,bacteriaparaformarouro

In brief

6 December 2009 ESRFnews

Sperm are the only cells in our bodies that sw im and speed is crucial in their objective of fertility. These cells have developed the means to be exceptionally streamlined and an international team of researchers has used the ESRF structural biology beamlines to find out how. The presence of the Bromodomain testis-specific protein (Brdt) in developing sperm directs tight repackaging of sperm DNA .

Because it is such a long and unw ieldy molecule, our DNA is packaged for convenience into a complex structure called chromatin: long DNA strands are wound around proteins called histones. In sperm, however, this package has become even more compact, reducing the size of the sperm head and making it more hydrodynamic.

The nature of chromatin – how open or compact it is – is intricately regulated. Histones are marked w ith different chemical tags, often several per histone,

that act as a code to direct changes in chromatin structure. Different proteins bind to the tags, the combination of which deciphers the code. Until now, scientists thought that these proteins bind using one or more modular “domains”, w ith each domain docking to just one tag. However, this new study reports

the discovery of an extra level of sophistication. The researchers studied histone-binding of Brdt, finding that it binds most strongly to a histone w ith two tags of a particular kind (in this case, acetyl groups) and, contrary to expectations, uses just one protein domain to do so.

The key experiments took

place on ID23-1 and ID23-2. “ We could only obtain a few small crystals of Brdt bound to a doubly tagged ligand,” explains Carlo Petosa, researcher at the Institut de Biologie Structurale in Grenoble and member of the team. “ What’s more, the crystals initially appeared to be unusable because they were highly disordered internally. However, exposing the edges of a crystal to a grazing beam of X-rays revealed that the thinnest tips gave a well-ordered diffraction pattern. Using the microfocused beam at ID23-2, we could collect enough data from a single crystal to solve the structure.”

The researchers believe that their work w ill shed light on potential problems in sperm development and are now looking at the role that this protein plays in human male infertility.

ReferenceJ Morinière et al. 2009 Nature 461 664–668 .

Users’ corner

Follow ing the 1 September deadline , 985 proposals for ESRF beamtime allocation were rece ived. The next deadline for submission of standard proposals w ill be on 1 March 2010. The next deadline for submission of long-term proposals is 15 January 2010.

The plenary session of the 20th ESRF Users’ Meeting w ill take place on 10–11 February 2010. Two workshops and a school w ill be associated w ith the Users’ Meeting: – “Science w ith X-ray nano-

beams” workshop;– “Science at high pressure”

workshop;– “Getting the most from the MX

beamlines” Macromolecular Crystallography School.

The plenary session of the Users’ Meeting has been extended to one and a half days in order to include a w ider range of scientific talks as well as a discussion session. During this

session, feedback from the different parallel sessions can be exchanged and questions can be addressed to the ESRF management.

More information about the Users’ Meeting can be found at w w w.esrf.eu/events/conferences/usersmeeting2010/users-meeting-2010-associated-workshops.

News from the beamlines Shutdown of ID24 and BM29: one of the first upgrade projects concerns the renewal of the X AS beamlines ID24 and BM29. Scheduled interventions on both beamlines w ill become effective during or after the next scheduling period (2010/II from March to July 2010). The current planning includes:– the shutdown of BM29 on

26 May 2010 for relocation to BM23. The current plan is to reopen the beamline at the beginning of 2011.

– the shutdown of ID24 on

28 July 2010 for reconstruction on the same port. The renewed ID24 w ill comprise two stations, which w ill be commissioned in 2011. Current planning is to reopen the first branch of the renewed beamline in the second half of 2011.

At ID01 the in situ AFM and the nanodiffraction set-up were combined allow ing in situ coherent diffraction imaging while deforming a nano-object by the AFM-tip. The sample positioning stage was equipped w ith an additional piezo rotation stage to facilitate the sample alignment, in particular, for in-plane stress and strain studies of individual nanostructures. Moreover, the AFM tuning fork was mounted on a second positioning tower equipped w ith three piezo translation stages for x, y and z movement. A ll piezo stages of both the sample and the tuning fork positioning tower are now controllable by SPEC. Thus, the above-mentioned

improvements facilitate the alignment of the sample and the AFM-tip w ith respect to the X-ray beam. It enables the accurate positioning of a pre-chosen nanostructure in the focal beam spot that can currently be as small as 300 nm. A new wavelength-dispersive spectrometer is now available for the users at ID21 beamline. The new ly developed instrument can be operated for X-rays between 1.2 and 7.2 keV. Energy resolution, in the range of 10–30 eV, provides new possibilities for X-ray micro-fluorescence analysis at ID21 beamline. The wiki site presenting best practices to perform in situ measurement of electrical polarisation on multiferroics, announced in “Users’ Corner” in the September issue of ESRFnews, has been moved to http://interactive.npl.co.uk /multiferroics/index.php/Main_Page.

Macromolecular crystallography unveils protein linked to the evolution of sperm

XX

XX

X

Sperm (the only cell in our body that swims) racing to get to the egg.

ISTO

CKP

HO

TO.C

OM

ESRFDec09INBRIEF_p6,7.indd 6 30/11/09 14:50:31

In brief

6 December 2009 ESRFnews

Sperm are the only cells in our bodies that sw im and speed is crucial in their objective of fertility. These cells have developed the means to be exceptionally streamlined and an international team of researchers has used the ESRF structural biology beamlines to find out how. The presence of the Bromodomain testis-specific protein (Brdt) in developing sperm directs tight repackaging of sperm DNA .

Because it is such a long and unw ieldy molecule, our DNA is packaged for convenience into a complex structure called chromatin: long DNA strands are wound around proteins called histones. In sperm, however, this package has become even more compact, reducing the size of the sperm head and making it more hydrodynamic.

The nature of chromatin – how open or compact it is – is intricately regulated. Histones are marked w ith different chemical tags, often several per histone,

that act as a code to direct changes in chromatin structure. Different proteins bind to the tags, the combination of which deciphers the code. Until now, scientists thought that these proteins bind using one or more modular “domains”, w ith each domain docking to just one tag. However, this new study reports

the discovery of an extra level of sophistication. The researchers studied histone-binding of Brdt, finding that it binds most strongly to a histone w ith two tags of a particular kind (in this case, acetyl groups) and, contrary to expectations, uses just one protein domain to do so.

The key experiments took

place on ID23-1 and ID23-2. “ We could only obtain a few small crystals of Brdt bound to a doubly tagged ligand,” explains Carlo Petosa, researcher at the Institut de Biologie Structurale in Grenoble and member of the team. “ What’s more, the crystals initially appeared to be unusable because they were highly disordered internally. However, exposing the edges of a crystal to a grazing beam of X-rays revealed that the thinnest tips gave a well-ordered diffraction pattern. Using the microfocused beam at ID23-2, we could collect enough data from a single crystal to solve the structure.”

The researchers believe that their work w ill shed light on potential problems in sperm development and are now looking at the role that this protein plays in human male infertility.

ReferenceJ Morinière et al. 2009 Nature 461 664–668 .

Users’ corner

Follow ing the 1 September deadline , 985 proposals for ESRF beamtime allocation were rece ived. The next deadline for submission of standard proposals w ill be on 1 March 2010. The next deadline for submission of long-term proposals is 15 January 2010.

The plenary session of the 20th ESRF Users’ Meeting w ill take place on 10–11 February 2010. Two workshops and a school w ill be associated w ith the Users’ Meeting: – “Science w ith X-ray nano-

beams” workshop;– “Science at high pressure”

workshop;– “Getting the most from the MX

beamlines” Macromolecular Crystallography School.

The plenary session of the Users’ Meeting has been extended to one and a half days in order to include a w ider range of scientific talks as well as a discussion session. During this

session, feedback from the different parallel sessions can be exchanged and questions can be addressed to the ESRF management.

More information about the Users’ Meeting can be found at w w w.esrf.eu/events/conferences/usersmeeting2010/users-meeting-2010-associated-workshops.

News from the beamlines Shutdown of ID24 and BM29: one of the first upgrade projects concerns the renewal of the X AS beamlines ID24 and BM29. Scheduled interventions on both beamlines w ill become effective during or after the next scheduling period (2010/II from March to July 2010). The current planning includes:– the shutdown of BM29 on

26 May 2010 for relocation to BM23. The current plan is to reopen the beamline at the beginning of 2011.

– the shutdown of ID24 on

28 July 2010 for reconstruction on the same port. The renewed ID24 w ill comprise two stations, which w ill be commissioned in 2011. Current planning is to reopen the first branch of the renewed beamline in the second half of 2011.

At ID01 the in situ AFM and the nanodiffraction set-up were combined allow ing in situ coherent diffraction imaging while deforming a nano-object by the AFM-tip. The sample positioning stage was equipped w ith an additional piezo rotation stage to facilitate the sample alignment, in particular, for in-plane stress and strain studies of individual nanostructures. Moreover, the AFM tuning fork was mounted on a second positioning tower equipped w ith three piezo translation stages for x, y and z movement. A ll piezo stages of both the sample and the tuning fork positioning tower are now controllable by SPEC. Thus, the above-mentioned

improvements facilitate the alignment of the sample and the AFM-tip w ith respect to the X-ray beam. It enables the accurate positioning of a pre-chosen nanostructure in the focal beam spot that can currently be as small as 300 nm. A new wavelength-dispersive spectrometer is now available for the users at ID21 beamline. The new ly developed instrument can be operated for X-rays between 1.2 and 7.2 keV. Energy resolution, in the range of 10–30 eV, provides new possibilities for X-ray micro-fluorescence analysis at ID21 beamline. The wiki site presenting best practices to perform in situ measurement of electrical polarisation on multiferroics, announced in “Users’ Corner” in the September issue of ESRFnews, has been moved to http://interactive.npl.co.uk /multiferroics/index.php/Main_Page.

Macromolecular crystallography unveils protein linked to the evolution of sperm

XX

XX

X

Sperm (the only cell in our body that swims) racing to get to the egg.

ISTO

CKP

HO

TO.C

OM


In brief

7December 2009 ESRFnews

ESRF and SOLEIL host SRI in 2012

Australian scientists have found that the bacterium Cupriavidus metallidurans catalyses the biomineralisation of gold by transforming toxic gold compounds to their metallic form using active cellular mechanism.

Researchers reported the presence of bacteria on gold surfaces but have never clearly elucidated their role. Now, an international team of scientists has found that there may be a biological reason for the presence of these bacteria on gold grain surfaces. “A number of years ago we discovered that the metal-resistant bacterium C. metallidurans occurred on gold grains from two sites in Australia. The sites are 3500 km apart, in southern New South Wales and northern Queensland, so when we found the same organism on grains from both sites we thought that we were onto something. It made us wonder why these organisms live in this particular environment. The results of this study point to their involvement in the active detoxification of gold complexes leading to formation of gold biominerals”, explains Frank Reith, leader of the research and working at the University of Adelaide (Australia).

The experiments showed that C. metallidurans rapidly accumulates toxic gold complexes from a solution prepared in the lab. This process promotes

gold toxicity, which pushes the bacterium to induce oxidative stress and metal resistance clusters as well as an as yet uncharacterised gold-specific gene cluster in order to defend its cellular integrity. This leads to active biochemically mediated reduction of gold complexes to nano-particulate, metallic gold, which may contribute to the growth of gold nuggets.

For this study scientists combined synchrotron techniques at the ESRF and the Advanced Photon Source (APS), and molecular microbial techniques to understand the biomineralisation in bacteria.

It is the first time that these techniques have been used in the same study, so Reith brought together a multinational team of experts in both areas for the success of the experiment.

The team was made up of scientists from the University of Adelaide, the Commonwealth Scientific and Research Organization, the University of California (US), the University of Western Ontario and the University of Saskatchewan (both Canada), Martin-Luther-Universität (Germany), University of Nebraska-Lincoln (US), SCK .CEN (Belgium), the APS (US) and the ESRF (France).

This is the first direct evidence that bacteria are actively involved in the cycling of rare and precious metals, such as gold. These results open the door to the production of biosensors: “The discovery of a gold-specific operon means that we can now start to develop gold-specific biosensors, which w ill help mineral explorers to find new gold deposits. To achieve this we need to further characterise the gold-specific operon on a genomic as well as proteomic level. If funding for this research is granted I believe that we can produce a functioning biosensor w ithin 3–5 years,” concludes Reith.

ReferenceF Reith et al. 2009 PNAS.doi:10.1073/pnas.0904583106.

The American Physical Society has recently completed the study “Access to Major International X-ray and Neutron Scattering Facilities”, which explores how scientists’ access to light and neutron sources has been evolving not only in the US but also internationally. The final report has been posted on the APS website at w w w.aps.org/programs/international/resources/facilities.cfm. It positions the ESRF as the leader in synchrotron facilities for the next decade.

For the study, 32 facilities and user groups across the globe completed a questionnaire on access issues and policies. The authors based their report on these data and on discussions that they had w ith individuals in the US and abroad. In their findings, they put many aspects of interest to light source users in Europe into a global perspective. These include different ways to access beamtime, notably the relation between Collaborating Research Groups and facility beamlines, the role of the facilities’ scientists, support given to users technically and for travel and logistics, and effective availability of a facility for a user.

It is w ith great sadness that we have to report that Ruprecht Haensel passed away on 19 October after a long illness.

In 1986 he became the first director general at the ESRF where he stayed until the machine was running and the first beamlines were taking shape, in 1992. Haensel was the first synchrotron radiation user at DESY in Hamburg. In 1974 he became professor of physics at Kiel University, where he later became dean, and he stayed there until he retired in 2000. During this time he moved to Grenoble and became director of the Institut Laue Langevin (1985–1986).

ESRF gets good marks from study

Ruprecht Haensel (1935–2009)

The two lightsources based in France, the ESRF in Grenoble and SOLEIL in Paris, w ill welcome the next Synchrotron Radiation and Instrumentation (SRI) meeting in 2012. The decision was announced at this year’s SRI conference, which took place in Melbourne (Australia) in October.

The international committee of directors of synchrotron sources worldw ide voted for the ESRF and SOLEIL because of the excellence of the scientific programme presented, the scholarships and tutorials offered to young scientists and the push for more involvement of industry and other lightsources in the event.

As it ’s a joint collaboration, the meeting w ill take place in Lyon, a thriving French city in the heart

of Europe, one hour away from Grenoble and two hours from Paris by high-speed train.

Other European sources are welcome to participate at this event and some have already signed up for satellite workshops.

As well as the ESRF, the Spanish

synchrotron ALBA (currently under construction) also placed a bid to hold the event. Despite not w inning, the synchrotron, based in Barcelona, and due to be up and running from next year, w ill host a satellite workshop before or after the main conference.

Bacterium helps to form gold

REIT

H E

T A

L, P

NA

S 5–

9 O

CTO

BER

2009

A TEM image of a C. metallidurans ultrathin section containing a gold nanoparticle (in the middle).

1 µm

View of the Lyon Convention Centre (right), the venue for SRI 2012.

UM

R-C

NRS

MA

P-EN

SAL


In brief


ESRF and SOLEIL host SRI in 2012

Australian scientists have found that the bacterium Cupriavidus metallidurans catalyses the biomineralisation of gold by transforming toxic gold compounds to their metallic form using active cellular mechanism.

Researchers reported the presence of bacteria on gold surfaces but have never clearly elucidated their role. Now, an international team of scientists has found that there may be a biological reason for the presence of these bacteria on gold grain surfaces. “A number of years ago we discovered that the metal-resistant bacterium C. metallidurans occurred on gold grains from two sites in Australia. The sites are 3500 km apart, in southern New South Wales and northern Queensland, so when we found the same organism on grains from both sites we thought that we were onto something. It made us wonder why these organisms live in this particular environment. The results of this study point to their involvement in the active detoxification of gold complexes leading to formation of gold biominerals”, explains Frank Reith, leader of the research and working at the University of Adelaide (Australia).

The experiments showed that C. metallidurans rapidly accumulates toxic gold complexes from a solution prepared in the lab. This process promotes

gold toxicity, which pushes the bacterium to induce oxidative stress and metal resistance clusters as well as an as yet uncharacterised gold-specific gene cluster in order to defend its cellular integrity. This leads to active biochemically mediated reduction of gold complexes to nano-particulate, metallic gold, which may contribute to the growth of gold nuggets.

For this study scientists combined synchrotron techniques at the ESRF and the Advanced Photon Source (APS), and molecular microbial techniques to understand the biomineralisation in bacteria.

It is the first time that these techniques have been used in the same study, so Reith brought together a multinational team of experts in both areas for the success of the experiment.

The team was made up of scientists from the University of Adelaide, the Commonwealth Scientific and Research Organization, the University of California (US), the University of Western Ontario and the University of Saskatchewan (both Canada), Martin-Luther-Universität (Germany), University of Nebraska-Lincoln (US), SCK .CEN (Belgium), the APS (US) and the ESRF (France).

This is the first direct evidence that bacteria are actively involved in the cycling of rare and precious metals, such as gold. These results open the door to the production of biosensors: “The discovery of a gold-specific operon means that we can now start to develop gold-specific biosensors, which w ill help mineral explorers to find new gold deposits. To achieve this we need to further characterise the gold-specific operon on a genomic as well as proteomic level. If funding for this research is granted I believe that we can produce a functioning biosensor w ithin 3–5 years,” concludes Reith.

ReferenceF Reith et al. 2009 PNAS.doi:10.1073/pnas.0904583106.

The American Physical Society has recently completed the study “Access to Major International X-ray and Neutron Scattering Facilities”, which explores how scientists’ access to light and neutron sources has been evolving not only in the US but also internationally. The final report has been posted on the APS website at w w w.aps.org/programs/international/resources/facilities.cfm. It positions the ESRF as the leader in synchrotron facilities for the next decade.

For the study, 32 facilities and user groups across the globe completed a questionnaire on access issues and policies. The authors based their report on these data and on discussions that they had w ith individuals in the US and abroad. In their findings, they put many aspects of interest to light source users in Europe into a global perspective. These include different ways to access beamtime, notably the relation between Collaborating Research Groups and facility beamlines, the role of the facilities’ scientists, support given to users technically and for travel and logistics, and effective availability of a facility for a user.

It is w ith great sadness that we have to report that Ruprecht Haensel passed away on 19 October after a long illness.

In 1986 he became the first director general at the ESRF where he stayed until the machine was running and the first beamlines were taking shape, in 1992. Haensel was the first synchrotron radiation user at DESY in Hamburg. In 1974 he became professor of physics at Kiel University, where he later became dean, and he stayed there until he retired in 2000. During this time he moved to Grenoble and became director of the Institut Laue Langevin (1985–1986).

ESRF gets good marks from study

Ruprecht Haensel (1935–2009)

The two lightsources based in France, the ESRF in Grenoble and SOLEIL in Paris, w ill welcome the next Synchrotron Radiation and Instrumentation (SRI) meeting in 2012. The decision was announced at this year’s SRI conference, which took place in Melbourne (Australia) in October.

The international committee of directors of synchrotron sources worldw ide voted for the ESRF and SOLEIL because of the excellence of the scientific programme presented, the scholarships and tutorials offered to young scientists and the push for more involvement of industry and other lightsources in the event.

As it ’s a joint collaboration, the meeting w ill take place in Lyon, a thriving French city in the heart

of Europe, one hour away from Grenoble and two hours from Paris by high-speed train.

Other European sources are welcome to participate at this event and some have already signed up for satellite workshops.

As well as the ESRF, the Spanish

synchrotron ALBA (currently under construction) also placed a bid to hold the event. Despite not w inning, the synchrotron, based in Barcelona, and due to be up and running from next year, w ill host a satellite workshop before or after the main conference.

Bacterium helps to form gold

REIT

H E

T A

L, P

NA

S 5–

9 O

CTO

BER

2009

A TEM image of a C. metallidurans ultrathin section containing a gold nanoparticle (in the middle).

1 µm

View of the Lyon Convention Centre (right), the venue for SRI 2012.

UM

R-C

NRS

MA

P-EN

SAL


SíntesedeMateriais“NTE”


Focus on: time-resolved studies

A vast majority of materials expand on heating, which can have adverse consequences on their applications. Negative thermal expansion (NTE) materials, on the other hand, contract on heating. These materials are of great interest to industry, because they can potentially counteract the expansion of another material upon heating.

For instance, glass–ceramic stoves used in many households can resist dramatic changes of temperature w ithout cracking. The reason for this resistance is the crystalline component of thermal glass–ceramics, which has a negative coefficient of thermal expansion and contrasts w ith the positive coefficient of the glass. This is one example of a common use of NTE materials, but there are many others, such as dental composite fillings or substrates for high-precision optical applications.

Most NTE materials expand anisotropically, (differently in all dimensions). However, for materials w ith a cubic crystal structure the symmetry forces them to contract equally in all dimensions – isotropic contraction. This helps to minimise problems such as micro-cracking during repeated thermal cycling.

The most famous cubic NTE material is zirconium tungstate (ZrW2O8), which contracts over a temperature range of 0.3–1050 K . However, at about 450 K , it suffers a transition from an ordered structure to a disordered one, and above 0.2 GPa of pressure it becomes significantly denser and loses NTE properties. These transitions could limit the industrial uses for this material.

Researchers from Durham University (UK), the University of K iel (Germany) and the ESRF have now found a rapid synthesis of an alternative to this well studied material.

Cubic ZrMo2O8 had been thought to be metastable at all temperatures and, unlike cubic ZrW2O8, it had not been possible to synthesise it directly from the constituent oxides – until now.

The researchers noticed in their lab that they might be able to form the supposedly metastable cubic phase by firing the constituent oxides at high temperatures (~1450 K) for a few seconds followed by rapid quenching. The team used the ID11 beamline to carry out in situ experiments to monitor the evolution of the metal oxides as they reacted at high temperatures, using the technique of powder diffraction. They benefited from

the high flux and high-energy X-rays of the beamline, and the FRELON camera provided them w ith a unique real-time insight into the synthesis of the new material. This camera was particularly important due to the extremely short timescales over which the different phases appeared.

The reaction took place extremely quickly at elevated temperatures w ith ZrMo2O8 formation occurring w ithin seconds at ~1360–1400 K . Reaction occurs via the melting of MoO3, the formation of trigonal ZrMo2O8 and then the formation of cubic ZrMo2O8. The reaction is complete w ithin a few seconds and the material can be quenched from the reaction conditions, where it appears to be thermodynamically stable, to room temperature.

Because the researchers discovered that this NTE material can be synthesised in this way, it means that lengthy precursor routes requiring careful thermal transformations may no longer be necessary.

John Evans, leader of the team, from Durham University, comments that “ the use of extremely rapid quantitative powder diffraction at the ESRF was crucial to unravelling this chemistry and similar techniques could provide significant insight in other areas of materials synthesis”.M Capellas

ReferenceJ E Readman et al. 2009 J. Am. Chem. Soc. doi:10.1021/ja907648z.

A team of European scientists and the ESRF has, for the first time, enabled the rapid synthesis of a negative thermal expansion material that was thought to be metastable, from its component oxides.

Scientists follow the synthesis of an NTE material as it happens

Two views of ZrMo2O8 from different angles. Right: viewed from the three fold axis. ZrO6 octahedra is shown in green, MoO4 tetrahedra in yellow.

ESRFDec09FOCUS_FastDiff_p09.indd 9 30/11/09 14:55:08





































CélulasCombusoveisPoliméricas

C.C.deAraujo,K.D.Kreuer,M.Schuster,G.Portale,H.Mendil‐Jakani,G.GebelandJ.Maier”Poly(p‐phenylenesulfone)swithhighionexchangecapacity:ionomerswithuniquemicrostructuralandtransportfeatures”Phys.Chem.Chem.Phys.,2009,11,3305‐3312.

V.RossiAlberTni,B.Paci,F.Nobili,R.Marassi,M.DiMichiel“Time/Space‐ResolvedStudiesoftheNafionMembraneHydraTonProfileinaRunningFuelCell”AdvancedMaterialsVolume21,Issue5,pages578–583,February2,2009.

Focus on: materials for energy

8 M arch 2010 ESRFnews

Fifty years after their first application in aerospace, fuel cells are slow ly getting closer to being part of our everyday life. Many buses use fuel cells and this is intrinsically coupled w ith the use of hydrogen as a source of energy. Unlike a battery, a fuel cell does not store energy, it transforms it.

There are several types of fuel cells and they are defined by the type of electrolyte that they use to convert the chemical energy into electrical energy, the kind of fuel involved and their operating temperature. The best known fuel cell is that based on a proton exchange membrane fuel cell (PEMFC), which can be used in portable and stationary applications, as well as in transportation. The core of PEMFC is a polymeric electrolyte membrane able to conduct the protons from the anode to the cathode. Its commercial variant is based on Nafion, by DuPont, as the polymer electrolyte.

The current membranes are limited by different factors, such as the cost of the platinum-based catalyst, the cost of Nafion, the complex water management for the optimal ion conductivity and the permeability of these membranes to methanol, which could otherw ise be used directly as fuel. The fuel for PEMFC is hydrogen obtained from methanol or a hydrocarbon, such as methane or propane, or from electrolysis of water, possibly conducted by using solar panels.

The electricity production in a fuel cell involves the reaction between the supplying gases (hydrogen and oxygen) flow ing along the opposite faces of the membrane. Therefore, to meet oxygen, the hydrogen, in ionic form (protons), must migrate across the membrane from one surface to the other. The electrons produced on hydrogen oxidation are forced to pass outside the cell,

through an external circuit, and in this way provide the electric power. To effectively transport protons, the membrane needs to be humidified. However, an excess of water may produce cathode flooding and the consequent decrease of the cell performances.

Several groups are studying membranes like Nafion at the ESRF to monitor in situ the changes that it goes through during the oxidation and reduction processes, the aging of its nanostructure, or its hydration degree as a function of the operative electrochemical parameters. The scientists use beamlines such as ID02, ID13, ID15 and BM26.

Recently, a team from the Istituto di Struttura della Materia in Rome, University of Camerino (Italy), and the ESRF measured the water in a running fuel-cell membrane in real-life conditions. For this experiment, they used the high-energy beamline ID15B and determined the overall presence of water and the hydration degree in each layer of the membrane w ith the highest precision ever.

To observe the overall amount of water in the membrane, the team carried out the experiment by irradiating a Nafion 117 membrane, about 140 µm thick, w ith an X-ray beam w ith a cross-section equivalent to its

thickness. The researchers took a sequence of diffraction patterns that showed the water changes induced by changes of the working conditions. In this way, the variations in the degree of water could be correlated w ith the cell voltage.

The team also carried out spacially resolved experiments to determine the water distribution along the membrane thickness. This helped the scientists to elucidate in detail the complex water dynamics occurring in the active component of a running fuel cell. Valerio Rossi A lbertini, a member of the team, explains that: “ the water dynamics in the membrane of a fuel cell is one of the main aspects in the use of such devices for locomotion. The variable working conditions, for instance because of the request of rapid increase of power supply during the acceleration of a vehicle, may produce dysfunctions and electrochemical instabilities due to water overproduction. Conversely, an insufficient hydration of the supplying gases or the heat release due to the proton current in the membrane may result in its drying. The method developed at ID15 can help in understanding and describing such complex water dynamics.”

A Mercedes Benz Citaro London bus running on fuel cells. This kind of bus was first used in 2004 in the English capital. Several cities around the world already use fuel cells in their buses.

Low emissions, quiet performance and high energy efficiency are the biggest assets of fuel cells, currently used mostly in transportation. These cells are becoming an optimum way to gear ourselves to a more environmentally friendly world.

Take a look inside a fuel cellThe fuel cell uses hydrogen and oxygen to create electricity. The reaction occurs in a structure consisting of two electrodes (the anode and the cathode) separated by the electrolyte membrane, which lets the ions through. The electrodes activate the hydrogen oxidation as well as the oxygen reduction.

In the case of a proton-exchange membrane, the hydrogen at the anode is dissociated into protons and electrons. At the cathode, the oxygen, electrons and protons recombine to form water.

–

+

solid polymer electrolyte

cathode

anode

distributor plate

H2

current collector

electricity heat

MEAH2O

O2 (air)H+

A look into polymers in fuel cells

ESRFMar10FOCUS_Fuelcells_p8-9.indd 8 17/2/10 14:12:15

CO

MM

UN

ICA

TION

www.advmat.de

From this preliminary study, one can conclude that thismethod is able to detect the correlation between even minimalchanges in the voltage and the hydration degree, as can be seen inthe correspondence of the red circles in Figure 3.

The second part of this study consisted of a vertical scan of theNafion 1 117 membrane, executed collecting the diffractionpatterns produced by the primary X-ray beam with a transversalsection of 10 mm (vertical) 100 mm (horizontal).

After the cell reached steady conditions (after about 2 h, at theselected constant current of 100 m A), stratigraphy was accom-plished starting from the position at which the primary beamgrazed the membrane interface with the Pt catalyst at the anodeside. The cell was progressively vertically shifted, in steps of 7 mm ,until the opposite interface at the cathode side was reached, withdiffraction pattern collection at each step. Since the membranewas about 180 mm thick, such sampling allowed the water contentto be quantified in a stack of 21 different ‘‘slices’’. The mainchanges in the diffraction patterns of the collected sequence arelocalized between the q-values 0.5 and 5 A 1 (see the insert of Fig.4). Scanning the Nafion membrane layer by layer from the H 2

electrode towards the O2 electrode, the trend can be qualitativelydescribed as follows: a) the initial patterns of the sequence,corresponding to slices of the membrane close to the H 2 anode,exhibit a relatively steep increase of the main-peak height (at1.1 A 1), accompanied by a decrease of the intensity in the1.5–2.5 A 1 q-range; b) after the first five patterns, the trend isinverted, with the intensity of the main peak progressivelydecreasing, with a lower slope. The scanning sequence was thenreversed from the O2 to the H 2 electrode.

The two curves representing the amount of water contained ineach layer (namely, hd as a function of the vertical coordinate ofthe membrane), measured from the anode to cathode, and thenthe reverse, are shown in Figure 4. As can be seen, they overlapsatisfactorily, thus demonstrating that the results are reproducibleand that the membrane-hydration conditions are in a steady-state.

The maximum water content appears to beat the center of the membrane. This may beexplained assuming that, giving the lowcurrent flowing through the cell, the prevailingcontribution comes from the diffusion of watercarried by the gas streams. Such results confirmthose obtained by previous investigations,[22,23]

carried out on cells operating in similarconditions.

In addition, the present study provides amore accurate description of the time-dependent water distribution, due to boththe higher spatial resolution and the possibilityof observing the membrane-hydration changesthrough real-time stratified imaging (see thetime /space-resolved study below).

For the third part of this study, time /space-resolved measurements of the hydrationdegree were performed during a polarizationcurve (40 m A , 30 min duration steps) from 0 to1 A , as shown in the inset of Figure 5.

The membrane was scanned by a primaryX-ray beam whose cross section was 5 mm(vertical, corresponding to the spatial resolu-

tion) 100 mm (horizontal), which allowed the hydration degreeof 31 ‘‘slices’’ of the membrane to be independently investigated.Several scans were also executed at open circuit, after the end ofthe polarization, in order to follow the hydration behavior duringcell relaxation. The timing sequence (30 min at each current /potential value) was such that the hydration response of the singleslices of the membrane may be considered to be inquasi-equilibrium conditions.

Figure 4. Space-resolved study of the water distribution in the PEM insteady conditions: water content of the membrane as a function of thevertical scan, from anode to cathode, and reverse. The diffraction patternscorresponding to the two scanning sequences (from the H 2 to the O2electrode and reverse) are reported in the insert.

Figure 5. Space / time-resolved study of the water distribution in the PEM . 3D plot of thetime-dependent water amount in each ‘‘slice’’ of the membrane, carried out in real workingconditions (the polarization curve is shown in the inset). The isolevel projection of the surface onthe base plane is also reported.

Adv. Mater. 2009, 21, 578–583 2009 WILEY-VC H Verlag Gmb H & Co. KGaA, Weinheim 581

Armazenandogaseseenergia,projetandoasbateriasdeLidofuturo


12 M arch 2010 ESRFnews

Storing gases: a key for a greener future

Fossil fuels are becoming scarce and hydrogen is starting to be the next best thing for transport applications. Because hydrogen is the lightest element in the periodic table, it has the highest energy-to-mass ratio of any chemical, its main source is water and it does not pollute. Despite the great advantages, its use is still a challenge.

The mass production of hydrogen is the first obstacle that scientists face in the implementation of this element as a future fuel. Another drawback, and possibly the biggest, is that because hydrogen is a gas at ambient temperature, it takes up a lot of space. This is why the scientific community is trying to find the perfect formula to store it. Once stored, it could produce energy by combustion, or fuel cells could convert it into energy electrochemically.

There are many different approaches to the question of storing, and the subsequent release of, hydrogen. The fact that the future systems would have to store and deliver the gas to a fuel cell in mild conditions makes it more difficult for the community to find solutions.

Hydrogen-storage approaches can be divided into physical storage, where hydrogen molecules are captured by porous solids or pure hydrogen is compressed or liquefied, and chemical storage, where hydrogen atoms are chemically bound to other elements.

Hydrogen can be reversibly stored in certain solid materials. Today, scientists focus on compounds of light elements w ith hydrogen in order to discover the successor for petrol, which needs to have high hydrogen-storage capacity both by mass and volume. Three classes of the materials currently receive significant attention, namely the borohydrides, which contain boron and hydrogen, amides based on nitrogen and hydrogen, and alanates containing aluminium and hydrogen.

Several research groups come to the ESRF to study hydrogen-storage systems at different beamlines, such as BM1, ID31 and ID11. A team from BM1 has recently explored stable borohydrides, such as LiBH4 and Ca(BH4)2, which have very high hydrogen contents of 18 and 11.5 w t% , but, unfortunately high

hydrogen-release temperatures as well. More recently, together w ith a group at the University of Aarhus (Denmark), they prepared and characterised novel anion-substituted modifications of these materials.

The joint team also prepared novel materials by cation substitution, e.g. LiZn2(BH4)5 by a reaction of LiBH4 and ZnCl2. The idea was to introduce a less electropositive metal (Zn) in the structure of the borohydride. “ We discovered a much unexpected structural chemistry of these new compounds, which store large amounts of hydrogen and release it at low temperatures of some 80–100 °C,” explains Yaroslav Filinchuk, of BM1. He continues: “ We have already proven that the novel modified borohydrides show interesting structural, chemical and physical properties.” Scientists aim for unstable materials, as they can release the hydrogen in mild conditions, whereas if they are too stable, they require a lot of heat to release it.

Hydrogen-fuelled buses are already a reality, for example in Japan and Germany, but general application of hydrogen as a new fuel in cars is still some time away, despite the fact that the automobile industry is starting to associate itself w ith academic research.

Metal-organic frameworksAnother promising way of storing hydrogen, as well as capturing gases such as CO2, is the so-called metal-organic frameworks (M OF). M OFs are extended crystalline networks made of metal/oxide groups held together by organic linkers, w ith large, open pores that make them ideal for storing gases. Their pore size and shape can be easily tuned by changing either the organic ligands or the metallic clusters. They can potentially have other applications, such as sensors in nanotechnology, and they are already used in catalysis and ion-exchange processes. The advantages of these materials in comparison w ith the hydrides are that they have a low density and the hydrogen storage is governed by a physisorption process and not a redox reaction. Scientists come to the ESRF to study crystalline structures of different M OFs using mostly X-ray powder diffraction on beamlines such as ID31 and BM1, although they have also used microdiffraction at ID13.

An active group in this domain, and regular user of the ESRF, is the team from the Institut Lavoisier in Versailles (France). As if it was a Meccano, they have managed

The quest to become more environmentally friendly has driven scientists to develop materials to store hydrogen or greenhouse gases. The ESRF has proven a useful tool in this rapidly evolving field.

ESRFMar10FOCUS_Hydrogen_p12-13.indd 12 17/2/10 14:18:08

13M arch 2010 ESRFnews


to design and build different structures that could take up molecules of a different size. They have developed a variety of M ILs (for Material Institut Lavoisier), including the metal terephthalate M IL-101 back in 2005, a structure w ith very large internal pores (a diameter of 3.4 nm) and surface area (5900 m2g–1). This M IL is still studied today and tested for the purification of hydrogen using mixtures of greenhouse gases (CO2 and CH4).

Two years later, the team joined forces w ith the University of Rennes to publish its results on new hybrid frameworks: M IL-88 A , B, C and D. The peculiarity of these new structures is that they could sustain a reversible huge increase in volume. It ranged from 85% of their size up to an unprecedented 230% . Such a large expansion in crystalline materials had not been observed before. This reversible “breathing” action is similar to the function of lungs in humans: they grow in size when inhaling and go back to their original size when exhaling. The lungs only expand, however, by approximately 40% .

Various solvents (normally water, but also alcohols) entering the materials open their cavities. This makes the structures grow,

w ithout breaking bonds and retaining the crystallinity of the materials. The reverse process was achieved by heating the solvated form, which ended in the material closing pores w ith almost no accessible porosity. The scientists came to the ESRF to study the structure before and after the “breathing” process, using X-ray powder diffraction.

Today the team is working on the use of M OFs for their separation properties (gases, liquids) as well as to develop biomedical applications using non-toxic biodegradable iron M OFs.

Industrial applications on hydrogen storage are already under way. Researchers from the company BASF showed recently that, compared w ith pressurising an empty container w ith hydrogen, if the M OFs are added they increasingly take up higher amounts of hydrogen w ith less pressure.

Sequestration of toxic gasesCO2 and CH4 are two types of gases that are currently damaging our planet, so their elimination would be another step towards a cleaner environment. CH4 is not adsorbed by M OFs as well as CO2, but, on the other hand, both of these gases are adsorbed at room temperature, unlike hydrogen.

A team led by the University of A ix-Marse ille in co llaboration w ith the team from the Institut Lavo isier, together w ith IFP, the University of Caen, the University of Montpe llier and the ESRF (all in France), recently studied M IL-53 (Cr) for the separation of mixtures of CO2 and CH4 at amb ient temperatures. M IL-53 (Cr) changes its pore size and shape in response to adsorption of mo lecules such as CO2 and H2O , go ing from a narrow-pore to a large-pore form. However, apo lar mo lecules like CH4 don’t normally have any effec t. The breathing behaviour of the M O F in the presence of gas mixtures is not yet clear to scientists, especially when they contain a component that provokes breathing and another one that doesn’t , like CO2 and CH4.

It is necessary to separate the two gases as part of the capture, transportation and sequestration of CO2. For this it is required to obtain a pure CO2 (>95%) prior to its storage, either in former gas or oil reservoirs or other geological areas of interest. As CO2 is produced by industry w ithin a complex mixture of CO2, CH4, CO , H2S, CH4..., one has to capture CO2 w ith a high selectivity versus the other components. M OFs, w ith their tunable pore size, large sorption capacities, good selectivity and easy regeneration, offer a nice alternative to zeolites or amines.

Experiments at the ESRF allowed the team to study the breathing of the so lid upon adsorption. By combining dif frac tion w ith Raman spec troscopy and computer simulations, they evaluated the “breathing” pattern of the M ILs. They found that the coadsorption of CO2 and CH4 leads to a similar breathing pattern of M IL-53 (Cr) as w ith pure CO2.

For the future, scientists find potential in the flexibility of some M ILs: “One could imagine benefiting from the flexibility by applying a mechanical pressure to make the M IL-53 solid close its pores and desorb gas mixtures, for an easier regeneration w ithout the need for thermal or vacuum treatments,” explains Christian Serre of the Institut Lavoisier.M Capellas

ReferencesL M Arnbjerg et al. 2009 Chem. Mater. 21 5772–5782.T Devic et al. 2010 J. Am. Chem. Soc. 132 1127–1136.Y Filinchuk et al. 2008 Angew. Chem. Int. Ed. 47 529–532.Y Filinchuk et al. 2009 Acta Mater. 57 732–738.L Hamon et al. 2009 J. Am. Chem. Soc. 131 17490–17499.P L Llewellyn et al. 2006 Angew. Chem. Int. Ed. 45 7751–7754.D Ravnsbæk et al. 2009 Angew. Chem. Int. Ed. 48 6659–6663.C Serre et al. 2007 Science 315 1828–1831.

Left: hydrogen, a simple element that has given hope to scientists in the quest for a more environmentally friendly world. Above: The MIL-53 is a very flexible metal-organic framework. On the left, the dried form of the structure (large pore form); on the right, the structure (narrow pore form) after adsorption of various guests, such as carbon dioxide or water.

INST

ITU

T LA

VO

ISIE

R

ISTO

CKP

HO

TO.C

OM


14


M arch 2010 ESRFnews

In 1899 a Belgian electric car equipped w ith lead-acid batteries reached a speed of 108 km per hour. More than a century later, cars powered by batteries are just starting to become a reality but are still far from everyday use. Studies on batteries have not evolved as much as other fields of research. This is due to the lack of suitable electrode and electrolyte materials, in addition to the difficulties in mastering the interfaces between them (Armand et al. 2008).

Batteries have two elec trodes connec ted by an elec tro lyte that conduc ts ions. When an external device is connec ted to the battery elec trodes, elec trons go from more negative to more positive potential and provide elec trical energy to the external circuit. One of the most popular batteries today is the lithium-ion battery, which is w idely used in elec tronics and is expec ted to be a candidate for hybrid-elec tric car applications. This battery was first commercialised in 1991 and it stores about five times more energy per unit mass than the o ld lead-acid batteries.

The drawbacks of this battery include the limited amount of lithium available worldw ide if this was to be used, for example, in the automobile industry, as well as the risk of explosion due to the combination of combustible material and oxidising agent. The “rocking-chair” mechanism in lithium-ion batteries can invo lve large changes of the elec trode’s vo lume. These generally deteriorate and age the elec trical contac t and scientists are investigating how the struc ture of the elec trode changes over time.

Synchrotron X-rays offer scientists a way to obtain information about the battery elec trode’s struc ture and beamlines such as BM1 or ID31 are often used in this field. A team from the National Institute of Advanced Industrial Science and Techno logy in Osaka (Japan), as well as the ESRF and SPring-8 , studied in situ a single crystal system of a go ld model anode for lithium-ion batteries (Renner et al. 2008). The researchers went to ID32, where they used X-ray dif frac tion.

They studied a gold-lithium alloy because gold has many electrons and this provides a very strong diffraction signal. Thanks to their experiments they could follow the gold system’s structural degradation and

pulverisation under different electrochemical conditions. The team is now preparing new experiments at the ESRF: “ We’ll still use gold, but we w ill progressively focus more on silver and silicon as possible candidates for the anodes. Silicon is indeed a very promising candidate as a single-element anode in lithium-ion batteries, as it can increase the storage capacity of battery anodes,” explains Frank Renner, leader of the team and head of the Interface Structures and High-Temperature Reactions Group at Max Planck Institute for Iron Research in Düsseldorf (Germany).

Phosphate-based compounds are also of great interest as elec trodes for the community studying batteries due to their low cost. At the ESRF, several groups have studied the crystal struc ture of materials such as sodium pentamo lybdyl tetradiphosphate or dif ferent vanadium phosphates as cathodes for lithium batteries (Dubarri et al. 2008 , Filinchuk et al., 2008 , Caignaert et al. 2007). Synchrotron radiation sources have also been used for the study of lithium iron phosphate.

Batteries for microelectronics applicationsThin-film solid-state batteries are the best candidates for use in microelectronic devices, such as medical implants or smart sensors. Today, negative electrodes of existing solid-state thin-film, lithium-ion batteries are usually made up of pure metallic lithium. This element has a low melting point and, consequently, it is not adapted for microelectronic integration. Scientists from the Eindhoven University of Technology (the Netherlands) are studying the possibility of using germanium electrodes in thin-film microbatteries. A lthough germanium has not

been studied thoroughly for batteries due to its high cost, this would not be an issue in thin-film batteries. In addition, it has higher electrical conductivity than silicon.

The team characterised the material’s structural changes using in situ electrochemical X-ray diffraction (Baggetto et al. 2009) and recently used the DUBBLE beamline at the ESRF to carry out in situ X-ray absorption spectroscopy. This technique proved to be an efficient tool to track the material reaction mechanism and allowed them to derive the evolution of the short-range ordering of germanium thin-film electrodes as a function of lithium content. Their results are currently being submitted for publication.

Research on batteries using synchrotron radiation is experiencing a period of rapid grow th. “Batteries are becoming more important , especially in the framework of the new engines in the automobile industry. In Germany, at least , there is a real w ill by the government to fund this research intensively,” says Frank Renner. M Capellas

ReferencesM Armand et al. 2008 Nature 451 652–657. L Baggetto et al. submitted.L Baggetto et al. 2009 Journal of the Electrochemical Society 156 A169–175.V Caignaert et al. 2007 Journal of Solid State Chemistry 180 2437–2442.M Dubarri et al. 2008 Electrochimica Acta 53 4564–4572.Y Filinchuk et al. 2008 Journal of A lloys and Compounds 463 124–128 .F U Renner et al. 2008 Electrochimica Acta 53 6064–6069.

Lithium batteries are widely used in mobile communication devices, such as PDAs or smartphones.

Designing the lithium-ion batteries of the futureSynchrotron research is increasingly being used by scientists working on lithium-ion batteries.

ISTO

CKP

HO

TO.C

OM

ESRFMar10FOCUS_Batteries_p14.indd 10 17/2/10 14:19:07



to design and build different structures that could take up molecules of a different size. They have developed a variety of M ILs (for Material Institut Lavoisier), including the metal terephthalate M IL-101 back in 2005, a structure w ith very large internal pores (a diameter of 3.4 nm) and surface area (5900 m2g–1). This M IL is still studied today and tested for the purification of hydrogen using mixtures of greenhouse gases (CO2 and CH4).

Two years later, the team joined forces w ith the University of Rennes to publish its results on new hybrid frameworks: M IL-88 A , B, C and D. The peculiarity of these new structures is that they could sustain a reversible huge increase in volume. It ranged from 85% of their size up to an unprecedented 230% . Such a large expansion in crystalline materials had not been observed before. This reversible “breathing” action is similar to the function of lungs in humans: they grow in size when inhaling and go back to their original size when exhaling. The lungs only expand, however, by approximately 40% .

Various solvents (normally water, but also alcohols) entering the materials open their cavities. This makes the structures grow,

w ithout breaking bonds and retaining the crystallinity of the materials. The reverse process was achieved by heating the solvated form, which ended in the material closing pores w ith almost no accessible porosity. The scientists came to the ESRF to study the structure before and after the “breathing” process, using X-ray powder diffraction.

Today the team is working on the use of M OFs for their separation properties (gases, liquids) as well as to develop biomedical applications using non-toxic biodegradable iron M OFs.

Industrial applications on hydrogen storage are already under way. Researchers from the company BASF showed recently that, compared w ith pressurising an empty container w ith hydrogen, if the M OFs are added they increasingly take up higher amounts of hydrogen w ith less pressure.

Sequestration of toxic gasesCO2 and CH4 are two types of gases that are currently damaging our planet, so their elimination would be another step towards a cleaner environment. CH4 is not adsorbed by M OFs as well as CO2, but, on the other hand, both of these gases are adsorbed at room temperature, unlike hydrogen.

A team led by the University of A ix-Marse ille in co llaboration w ith the team from the Institut Lavo isier, together w ith IFP, the University of Caen, the University of Montpe llier and the ESRF (all in France), recently studied M IL-53 (Cr) for the separation of mixtures of CO2 and CH4 at amb ient temperatures. M IL-53 (Cr) changes its pore size and shape in response to adsorption of mo lecules such as CO2 and H2O , go ing from a narrow-pore to a large-pore form. However, apo lar mo lecules like CH4 don’t normally have any effec t. The breathing behaviour of the M O F in the presence of gas mixtures is not yet clear to scientists, especially when they contain a component that provokes breathing and another one that doesn’t , like CO2 and CH4.

It is necessary to separate the two gases as part of the capture, transportation and sequestration of CO2. For this it is required to obtain a pure CO2 (>95%) prior to its storage, either in former gas or oil reservoirs or other geological areas of interest. As CO2 is produced by industry w ithin a complex mixture of CO2, CH4, CO , H2S, CH4..., one has to capture CO2 w ith a high selectivity versus the other components. M OFs, w ith their tunable pore size, large sorption capacities, good selectivity and easy regeneration, offer a nice alternative to zeolites or amines.

Experiments at the ESRF allowed the team to study the breathing of the so lid upon adsorption. By combining dif frac tion w ith Raman spec troscopy and computer simulations, they evaluated the “breathing” pattern of the M ILs. They found that the coadsorption of CO2 and CH4 leads to a similar breathing pattern of M IL-53 (Cr) as w ith pure CO2.

For the future, scientists find potential in the flexibility of some M ILs: “One could imagine benefiting from the flexibility by applying a mechanical pressure to make the M IL-53 solid close its pores and desorb gas mixtures, for an easier regeneration w ithout the need for thermal or vacuum treatments,” explains Christian Serre of the Institut Lavoisier.M Capellas

ReferencesL M Arnbjerg et al. 2009 Chem. Mater. 21 5772–5782.T Devic et al. 2010 J. Am. Chem. Soc. 132 1127–1136.Y Filinchuk et al. 2008 Angew. Chem. Int. Ed. 47 529–532.Y Filinchuk et al. 2009 Acta Mater. 57 732–738.L Hamon et al. 2009 J. Am. Chem. Soc. 131 17490–17499.P L Llewellyn et al. 2006 Angew. Chem. Int. Ed. 45 7751–7754.D Ravnsbæk et al. 2009 Angew. Chem. Int. Ed. 48 6659–6663.C Serre et al. 2007 Science 315 1828–1831.

Left: hydrogen, a simple element that has given hope to scientists in the quest for a more environmentally friendly world. Above: The MIL-53 is a very flexible metal-organic framework. On the left, the dried form of the structure (large pore form); on the right, the structure (narrow pore form) after adsorption of various guests, such as carbon dioxide or water.

INST

ITU

T LA

VO

ISIE

R

ISTO

CKP

HO

TO.C

OM


Egipciostornaramosvidrosopacos


Feature

The Egyptian civilisation is one of the most interesting of the ancient world, mainly thanks to the advanced skills of its craftsmen. However, little is known about the first real production of glass objects, which appeared during the 18th Egyptian dynasty (1570–1292 BC). For this reason, a team from the Centre de Recherche et de Restauration des Musées de France, the Institut de M inéralogie et de Physique des M ilieux Condensés (IMPM C) and the ESRF, has studied ancient Egyptian opaque glasses from the Louvre Museum and the British Museum.

During the 18th dynasty, glass objects were opaque or translucent coloured glass and were dedicated to the upper classes, who used them as perfume or cosmetic containers. Opaque white, blue and turquoise glasses were opacified by calcium-antimonate crystals dispersed in a vitreous matrix. Among the different types of glass opacifiers, antimonate compounds have had a predominant role throughout history. They are found from the origins of glass technology in Mesopotamia until modern times. However, both their technology and provenance remain obscure.

To answer these questions, the researchers developed an original strategy focused on the investigation of the crystals and the vitreous matrices. For the first time they reproduced opacified glass by the addition of crystals in the laboratory under controlled conditions. They also compared these synthetic glasses to ancient Egyptian glasses using appropriate micro and nanoanalytical techniques never used before on this type of material: transmission electron microscopy at the IMPM C and micro X-ray absorption near-edge spectroscopy at ID21. The synchrotron-based measurements proved to be well suited to the selective measure of the antimony oxidation state in the vitreous matrix. Antimony, combined w ith the microstructure observations and the crystalline phases identification, is one of the key parameters used by the researchers as an indicator of the opacification process employed.

Until now, scientists thought that ancient Egyptian opaque glass was made from in situ crystallisation. This new study has refuted this assumption. Contrary to what was thought, the researchers demonstrated that Egyptian glassmakers were able to synthesise ex situ calcium-antimonate compounds, which do not exist in nature, and added them into the glass to opacify it. The results also show that

these opacifiers are nanocrystals.This outcome made the researchers

want to investigate further and try to reproduce the conditions of the preparation of calcium-antimonate crystals. The compounds were fired between 700 and 1100 °C for 1–18 hours, depending on the case. Subsequently, they studied the nature, crystallographic structure and oxidation of antimony on the crystals obtained, and the results were very close to the analysis on the Egyptian samples.

“Until now, Egyptian blue and green pigments were the only high-temperature compounds known to have been synthesised in ancient Egypt. Our results show that

calcium-antimonate glass opacifiers were also synthetic compounds. These findings provide further evidence for the sophisticated chemistry and remarkable know-how of this civilisation. We believe that this work is the starting point for a complete reassessment not only of ancient Egyptian glass studies but more generally of high-temperature technologies used throughout antiquity,” says Sophia Lahlil, the main correspondent of the research.M Capellas

ReferenceS Lahlil et al. 2010 Applied Physics A: Materials Science & Processing 98 1.

Research done at the ESRF has shown that craftsmen in ancient Egypt, contrary to belief, made opaque glass by adding synthesised calcium-antimonate crystals to a translucent glass. These compounds are nanocrystals and give the glass its non-transparent look.

Egyptians made opaque glasses using synthesised nanocrystals

Figure 1 (top and bottom left and centre): opaque, coloured glass from the 18th Egyptian dynasty. a) Small amphorae (inventory number AF2622). b) Shards (inventory numbers AF12707 and AF13175). c) Blue and turquoise necklace (inventory number E2341). These objects come from the Egyptian Antiquities Department of the Louvre Museum. Figure 2 (bottom right): micro X-ray fluorescence (µ-XRF) analysis of a polished fragment of Egyptian glass (sample c). µ-XRF elemental maps of antimony (red), calcium (green) and silicon (blue). The map size is 72 × 36 µm2, the pixel size is 0.5 × 0.5 µm2 and the probe size is 1.1 × 0.3 µm2.

D B

AG

AU

LT C

2RM

F

1a)

D V

IGEA

RS C

2RM

F

1b)

D B

AG

AU

LT C

2RM

F

Sb

devitrificat ion crystal

calcium ant imonate crystal

vitreous matrix

10 µmSi

Ca

1c)

2)

ID21

ESR

F

ESRFMar10FEATURE_EGYPTIAN_p15.indd 15 17/2/10 14:19:50


Feature













D B

AG

AU

LT C

2RM

F

1a)

D V

IGEA

RS C

2RM

F

1b)

D B

AG

AU

LT C

2RM

F

Sb



vitreous matrix

10 µmSi

Ca

1c)

2)

ID21

ESR

F



Feature













D B

AG

AU

LT C

2RM

F

1a)

D V

IGEA

RS C

2RM

F

1b)

D B

AG

AU

LT C

2RM

F

Sb



vitreous matrix

10 µmSi

Ca

1c)

2)

ID21

ESR

F



Feature













D B

AG

AU

LT C

2RM

F

1a)

D V

IGEA

RS C

2RM

F

1b)

D B

AG

AU

LT C

2RM

F

Sb



vitreous matrix

10 µmSi

Ca

1c)

2)

ID21

ESR

F



Feature













D B

AG

AU

LT C

2RM

F

1a)

D V

IGEA

RS C

2RM

F

1b)

D B

AG

AU

LT C

2RM

F

Sb



vitreous matrix

10 µmSi

Ca

1c)

2)

ID21

ESR

F


AumentandoaResistenciaaFadigadeumRolls‐RoyceedeumBoeing


Focus on: industry and academia

The initiation and propagation of fatigue cracks can be suppressed by the introduction of compressive residual stresses. The most commonly used method is to fire “shot” at the surface (Shot Peening), which generates compression to a depth of about 100–500 µm. In recent years, however, Rolls-Royce has introduced a new method called Laser Shock Peening (LSP). In LSP, a high-power laser pulse irradiates the surface of the material, producing plasma that generates shock waves. These induce compressive stresses on and beneath the surface. This method has the advantage that it improves the depth of compressive residual stress fields (up to several millimetres) in the material while maintaining a smooth surface finish.

Around 10 years ago Rolls-Royce was one of the first companies to use LSP commercially, applying it to aero-engine fan blades. “ It is absolutely critical that fan blades resist the effect of fatigue and fretting fatigue over many thousands of flying hours,” explains Phil W ithers, professor of materials science at the University of Manchester and leader of the collaboration w ith Rolls-Royce and the ESRF. “The University of Manchester supports Rolls-Royce in qualifying the LSP production process,” he says.

Lab X-rays require metal removal and measurement correction to determine stress profiles and are therefore destructive. The highly penetrating, non-invasive, hard X-ray beams of the ESRF come into the picture when the researchers try to understand the structural changes taking place in the fan blades during the service throughout their lives. Rolls-Royce has techniques that can simulate a very w ide range of extreme service conditions. “Synchrotron radiation is the only means of characterising the way that these protective stresses evolve over the life of the component w ithout destroying the part,” W ithers explains.

At the ESRF, scientists probe the samples

w ith a very high spatial resolution on beamlines like ID11, ID15 and ID31 where they carry out diffraction experiments using the poly-crystal structure as an atomic strain gauge. “ ID31 is especially convenient to investigate the material close to the surface,” says W ithers, “but then on ID11 and ID15 you have higher energies and we can study larger components.” Neutrons are a complementary tool in this research: they allow full-size engine assemblies due to their even higher penetrating power, although they provide less spatial resolution. In addition to the ESRF, the team also uses the Institut Laue-Langevin in Grenoble as well as the ISIS neutron source, and most recently Diamond (UK).

The benefits of this research go from underpinning the safety of the blades and their resistance to fretting fatigue and foreign object damage to extending the method to

other applications: so far, the team has tested titanium alloys (normally used in fan blades and biomaterials too), but also stainless steel for applications in power plants. “ In the case of aero engines, they are increasingly operating at higher temperatures and there is a continuous drive to make aircraft lighter. We need to find ways to make the materials and develop manufacturing processes that are up to the task and the ESRF helps us ensure that the science keeps up w ith technology,” says W ithers. M Capellas

ReferencesA K ing et al.2006 Mat. Sci. & Eng. 435–6 12–18 .A K ing et al. 2005 Materials Science Forum (ICRS7) 490–491 340–345.M Turski et al. 2010 Appl. Phys. A 99 549–556.

Rolls-Royce plc and the University of Manchester work together to improve the fatigue resistance of materials used in the aerospace industry. The ESRF has become an important tool in their research.

Increasing the fatigue resistance of fan blades

The unique titanium wide chord fan blades, seen here on a Trent 900.

Figure shows the in-plane (x and y) and out of plane (z) stresses with depth from the surface in the root of the fan blade a) as-laser peened and b) after in-service conditions. Fretting has reduced the near surface compression somewhat but a significant compressive stress is maintained.

© R

OLL

S-R

OY

CE P

LC 2

010

200

0

–200

–400

–600

–800

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0depth (mm)

xyz

(a)

stre

ss (M

Pa)

200

0

–200

–400

–600

–800

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0depth (mm)

xyz

(b)

stre

ss (M

Pa)

! " # $%&’ ( ) $* + , " - # . //0# . 1’ &- 23456778883 ) 9:( ; :; ) ( ) 888( <=; )



The initiation and propagation of fatigue cracks can be suppressed by the introduction of compressive residual stresses. The most commonly used method is to fire “shot” at the surface (Shot Peening), which generates compression to a depth of about 100–500 µm. In recent years, however, Rolls-Royce has introduced a new method called Laser Shock Peening (LSP). In LSP, a high-power laser pulse irradiates the surface of the material, producing plasma that generates shock waves. These induce compressive stresses on and beneath the surface. This method has the advantage that it improves the depth of compressive residual stress fields (up to several millimetres) in the material while maintaining a smooth surface finish.

Around 10 years ago Rolls-Royce was one of the first companies to use LSP commercially, applying it to aero-engine fan blades. “ It is absolutely critical that fan blades resist the effect of fatigue and fretting fatigue over many thousands of flying hours,” explains Phil W ithers, professor of materials science at the University of Manchester and leader of the collaboration w ith Rolls-Royce and the ESRF. “The University of Manchester supports Rolls-Royce in qualifying the LSP production process,” he says.

Lab X-rays require metal removal and measurement correction to determine stress profiles and are therefore destructive. The highly penetrating, non-invasive, hard X-ray beams of the ESRF come into the picture when the researchers try to understand the structural changes taking place in the fan blades during the service throughout their lives. Rolls-Royce has techniques that can simulate a very w ide range of extreme service conditions. “Synchrotron radiation is the only means of characterising the way that these protective stresses evolve over the life of the component w ithout destroying the part,” W ithers explains.

At the ESRF, scientists probe the samples

w ith a very high spatial resolution on beamlines like ID11, ID15 and ID31 where they carry out diffraction experiments using the poly-crystal structure as an atomic strain gauge. “ ID31 is especially convenient to investigate the material close to the surface,” says W ithers, “but then on ID11 and ID15 you have higher energies and we can study larger components.” Neutrons are a complementary tool in this research: they allow full-size engine assemblies due to their even higher penetrating power, although they provide less spatial resolution. In addition to the ESRF, the team also uses the Institut Laue-Langevin in Grenoble as well as the ISIS neutron source, and most recently Diamond (UK).

The benefits of this research go from underpinning the safety of the blades and their resistance to fretting fatigue and foreign object damage to extending the method to

other applications: so far, the team has tested titanium alloys (normally used in fan blades and biomaterials too), but also stainless steel for applications in power plants. “ In the case of aero engines, they are increasingly operating at higher temperatures and there is a continuous drive to make aircraft lighter. We need to find ways to make the materials and develop manufacturing processes that are up to the task and the ESRF helps us ensure that the science keeps up w ith technology,” says W ithers. M Capellas

ReferencesA K ing et al.2006 Mat. Sci. & Eng. 435–6 12–18 .A K ing et al. 2005 Materials Science Forum (ICRS7) 490–491 340–345.M Turski et al. 2010 Appl. Phys. A 99 549–556.

Rolls-Royce plc and the University of Manchester work together to improve the fatigue resistance of materials used in the aerospace industry. The ESRF has become an important tool in their research.

Increasing the fatigue resistance of fan blades

The unique titanium wide chord fan blades, seen here on a Trent 900.

Figure shows the in-plane (x and y) and out of plane (z) stresses with depth from the surface in the root of the fan blade a) as-laser peened and b) after in-service conditions. Fretting has reduced the near surface compression somewhat but a significant compressive stress is maintained.

© R

OLL

S-R

OY

CE P

LC 2

010

200

0

–200

–400

–600

–800

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0depth (mm)

xyz

(a)

stre

ss (M

Pa)

200

0

–200

–400

–600

–800

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0depth (mm)

xyz

(b)

stre

ss (M

Pa)

! " # $%&’ ( ) $* + , " - # . //0# . 1’ &- 23456778883 ) 9:( ; :; ) ( ) 888( <=; )

UnificandoSemicondutoresparaaceleraracomunicacao



Optoelectronic devices consist of different semiconductor alloys lying on substrates. During the growth of the M QW laser-active region, different layers of semiconductors are sequentially deposited on the substrate, alternating well and barrier regions. In well regions, electrons and holes recombine to provide the laser light, while barrier regions are important for the electrons and holes confinement in the wells. The parameters that are able to modulate the laser wavelength needed to match the minimum adsorption of the optical fibres are the chemical composition and the w idth of both well and barrier regions.

For low-speed communications, the sequence of “0” and “1” containing the information is produced by direc tly modulating the M QW laser emission by a variab le current. Such devices can be fully charac terised using laboratory X-ray dif frac tion (XRD) and photo luminescence (PL) techniques. For high-speed communications, device instab ilities prevent this simp le so lution and the M QW lasers are fed by a constant current that generates a constant emission, which is not carrying any information. To create the information, chips containing M QW lasers need to be modulated externally. This modulation is achieved w ith e lec troabsorption-modulator

(EA M) devices, which are normally connec ted externally to the M Q W laser. EA Ms are also M QW heterostruc tures w ith an energy gap that can be modulated at high frequency app lying an external potential (Stark effec t). In such a way the EA M can sw itch from opaque to transparent for the light emit ted by the M Q W laser.

Scientists are trying to integrate both M QW laser and EA M , occupying a small area (typically 30 × 700 µm2, so that in a single 2 inch InP substrate about 2 × 104 devices may be potentially processed). The optimisation of these EML devices has, until now, been carried out by empirical approaches because of the impossibility to carry out a micron-resolved XRD study w ith laboratory sources. A team from the University of Turin (Italy), Avago Technologies and the ESRF has, for the first time, managed to directly measure the structure of these semiconductors thanks to the micrometre X-ray beam of ID22.

The scientists investigated the EML devices by µ-XRD and µ-X-ray fluorescence at 35 different spatial points w ith a spatial resolution of 2 µm, moving from the M QW laser to the EA M region. W ith such data, it is possible to obtain the fundamental structural parameters (w idth along the growth direction and lattice parameter on

the growth plane) of both well and barrier parts of the heterostructure. The result is achieved by fitting the observed pattern using a model based on the dynamic theory of X-ray diffraction. Finally, the combination of synchrotron µ-XRD w ith laboratory µ-PL allowed the team to obtain the space-resolved chemical composition from the space-resolved lattice parameter.

This unprecedented characterisation gave the team the opportunity to determine the structure of the grown heterostructure w ith a monolayer resolution (3 Å) along the growth axis and w ith a micrometre resolution in the growth plane (i.e. to find out what has been empirically grown). This study, requiring a high flux of hard X-rays combined w ith a micrometre resolution can be achieved in very few beamlines worldw ide, such as ID22. “These results show us the way to improve the growth process, which was previously based only on a trial/error approach,” explains Carlo Lamberti, leader of the team and professor at the University of Turin.M Capellas

ReferencesL M ino et al. 2010 J. Anal. At. Spectrom. 25 831–836.L M ino et al. 2010 Adv. Mater. 22 2050–2054 .

In a technology-led world, optical-fibre communications allow, for example, people to be connected through the internet or cable-television signals. Multi-quantum well (MQW) electroabsorption-modulated lasers (EMLs) are semiconductors heterostructures used with this aim. An Italian team has managed to characterise it for the first time at the ESRF on

Unifying semiconductors to speed up communication

SAGinterfacefield

–2000 0 020

4060

–4000

105

106

107

2000 4000 ! (arcsec)

inte

nsity

(c.p

.s.)

d (µm)

Semiconductors play an extremely important role in communications technology.

Selection of some of the 35 full XRD patterns collected moving from the MQW laser (SAG region) to the EAM (FIELD region) that allowed to obtain the fundamental structural parameters of the system.

ISTO

CKP

HO

TO/V

LAD

IMIR

YU

DIN

! " # $%&’ ( ) $* + , " - " &. /’ 0123’ 4056- 7( 89/122:::( 8 ) 8;( <;<) ( ) :::( =><?





(EA M) devices, which are normally connec ted externally to the M Q W laser. EA Ms are also M QW heterostruc tures w ith an energy gap that can be modulated at high frequency app lying an external potential (Stark effec t). In such a way the EA M can sw itch from opaque to transparent for the light emit ted by the M Q W laser.








SAGinterfacefield

–2000 0 020

4060

–4000

105

106

107

2000 4000 ! (arcsec)

inte

nsity

(c.p

.s.)

d (µm)



ISTO

CKP

HO

TO/V

LAD

IMIR

YU

DIN

! " # $%&’ ( ) $* + , " - " &. /’ 0123’ 4056- 7( 89/122:::( 8 ) 8;( <;<) ( ) :::( =><?





(EA M) devices, which are normally connec ted externally to the M Q W laser. EA Ms are also M QW heterostruc tures w ith an energy gap that can be modulated at high frequency app lying an external potential (Stark effec t). In such a way the EA M can sw itch from opaque to transparent for the light emit ted by the M QW laser.








SAGinterfacefield

–2000 0 020

4060

–4000

105

106

107

2000 4000 ! (arcsec)

inte

nsity

(c.p

.s.)

d (µm)



ISTO

CKP

HO

TO/V

LAD

IMIR

YU

DIN

! " # $%&’ ( ) $* + , " - " &. /’ 0123’ 4056- 7( 89/122:::( 8 ) 8;( <;<) ( ) :::( =><?

Revelandocomoohumanoarmazenaenergia

9June 2010 ESRFnews

Focus on: nature and energy

G lycolysis is the metabolic pathway that breaks down glucose into two molecules of pyruvate w ith the concomitant production of a high-energy compound, called adenosine triphosphate (ATP). The process requires no oxygen and is probably one of the most ancient pathways because it evolved before the accumulation of oxygen in the Earth’s atmosphere. G lucose is an important fuel for all organisms and in mammals is the only source of energy used by the brain under normal conditions. It is also the only fuel that red blood cells can use.

The pathway consists of 10 separate reactions that comprise three main stages. The first stage traps glucose in a form that remains in cells and can be broken apart. The second stage is the cleavage of the six carbon ring into three carbon units. In the third stage, energy is harvested by the production of ATP, a molecule that is the universal “energy currency” in cells that can be used to do work such as muscle contraction. Phosphoglycerate kinase (PGK) catalyses the seventh step of the pathway and is arguably the most important because it is the first reaction that produces, rather than requires, energy. “ It is quite a long and complicated process,” explains Matthew

Bow ler, scientist at the ESRF who studies PGK. PGK harvests the energy produced in

glycolysis by transferring a phosphate “energy unit ” from one half of a glucose molecule and adds it to adenosine diphosphate (ADP – ATP w ith one missing phosphate) to form ATP. Bow ler teamed up w ith the University of Sheffield (UK), the Institute of Enzymology (Hungary) and the University of Manchester (UK) to unveil the structure of PGK .

PGK is formed from two lobes that bind the molecules separately. The protein then sw ings between fully open and a half-open conformation that binds the molecules. The protein closes completely around the molecules. One of the major problems is that phosphate groups are highly negatively charged and therefore repel each other when they get too close. PGK neutralises the negative charges of both ADP and phosphate allow ing them to get close enough to react. It then pulls the phosphate off the three carbon unit and creates ATP. When it opens again there is a new three carbon unit that goes into the next step of the pathway and ATP is released to be used by the body.

The team just published the structure of the protein in its fully closed conformation just at

the moment that ATP is formed. They looked at the chemistry of the phosphate “energy unit ” as it moves from one molecule to the other. Combining the techniques of fluorine nuclear magnetic resonance w ith X-ray crystallography has revealed in unprecedented detail the chemistry of the reaction (M J Cliff et al. 2010).

They also recently studied the large domain movements needed by PGK to bind and release molecules using the new ID14-3 beamline at the ESRF. By combining small angle scattering and macromolecular crystallography, a full picture of both the domain movements in physiological solutions and atomic details of the molecules needed to generate energy has been developed. The results are currently being submitted for publication.

“ It is important to know how proteins catalyse this reaction because it is so fundamental and universal, and nobody really knows what sort of transition states take place when it happens,” explains Bow ler. M Capellas

ReferenceM J Cliff et al. 2010 J. Am. Chem. Soc. 132 6507–6516.

Harvesting energy is one of the most primitive and fundamental requirements of life. Glycolysis is the pathway that breaks down sugar into energy in almost all forms of life. It consists of 10 different reactions and phosphoglycerate kinase (PGK) is the first enzyme that produces energy in this process. The ESRF has given scientists new insights into PGK.

Unravelling the way human metabolism harvests energy

The first energy-generating step in glycolysis. PGK (shown as a cartoon coloured as a rainbow) lies open ready to receive the breakdown product of glucose 1,3BPG and ADP (left). Once bound, the enzyme swings together (a 40º rotation) closing around the molecules and forcing them together (right). When together, the phosphate “energy unit ” is transferred to ADP to make ATP – the universal energy currency in all forms of life.

M B

OW

LER

! " # $%&’ ( ) $* + , " - ! ’ . / 0 12- 3) 456’ 778884 ) 9:) ; :<) ( ) 888( ( =>?

ArmazenamentoGlucose(1)+ClivagemC(2)+producaoATP(3)10reacoes

9June 2010 ESRFnews


G lycolysis is the metabolic pathway that breaks down glucose into two molecules of pyruvate w ith the concomitant production of a high-energy compound, called adenosine triphosphate (ATP). The process requires no oxygen and is probably one of the most ancient pathways because it evolved before the accumulation of oxygen in the Earth’s atmosphere. G lucose is an important fuel for all organisms and in mammals is the only source of energy used by the brain under normal conditions. It is also the only fuel that red blood cells can use.

The pathway consists of 10 separate reactions that comprise three main stages. The first stage traps glucose in a form that remains in cells and can be broken apart. The second stage is the cleavage of the six carbon ring into three carbon units. In the third stage, energy is harvested by the production of ATP, a molecule that is the universal “energy currency” in cells that can be used to do work such as muscle contraction. Phosphoglycerate kinase (PGK) catalyses the seventh step of the pathway and is arguably the most important because it is the first reaction that produces, rather than requires, energy. “ It is quite a long and complicated process,” explains Matthew

Bow ler, scientist at the ESRF who studies PGK. PGK harvests the energy produced in

glycolysis by transferring a phosphate “energy unit ” from one half of a glucose molecule and adds it to adenosine diphosphate (ADP – ATP w ith one missing phosphate) to form ATP. Bow ler teamed up w ith the University of Sheffield (UK), the Institute of Enzymology (Hungary) and the University of Manchester (UK) to unveil the structure of PGK .

PGK is formed from two lobes that bind the molecules separately. The protein then sw ings between fully open and a half-open conformation that binds the molecules. The protein closes completely around the molecules. One of the major problems is that phosphate groups are highly negatively charged and therefore repel each other when they get too close. PGK neutralises the negative charges of both ADP and phosphate allow ing them to get close enough to react. It then pulls the phosphate off the three carbon unit and creates ATP. When it opens again there is a new three carbon unit that goes into the next step of the pathway and ATP is released to be used by the body.

The team just published the structure of the protein in its fully closed conformation just at

the moment that ATP is formed. They looked at the chemistry of the phosphate “energy unit ” as it moves from one molecule to the other. Combining the techniques of fluorine nuclear magnetic resonance w ith X-ray crystallography has revealed in unprecedented detail the chemistry of the reaction (M J Cliff et al. 2010).

They also recently studied the large domain movements needed by PGK to bind and release molecules using the new ID14-3 beamline at the ESRF. By combining small angle scattering and macromolecular crystallography, a full picture of both the domain movements in physiological solutions and atomic details of the molecules needed to generate energy has been developed. The results are currently being submitted for publication.

“ It is important to know how proteins catalyse this reaction because it is so fundamental and universal, and nobody really knows what sort of transition states take place when it happens,” explains Bow ler. M Capellas

ReferenceM J Cliff et al. 2010 J. Am. Chem. Soc. 132 6507–6516.

Harvesting energy is one of the most primitive and fundamental requirements of life. Glycolysis is the pathway that breaks down sugar into energy in almost all forms of life. It consists of 10 different reactions and phosphoglycerate kinase (PGK) is the first enzyme that produces energy in this process. The ESRF has given scientists new insights into PGK.

Unravelling the way human metabolism harvests energy

The first energy-generating step in glycolysis. PGK (shown as a cartoon coloured as a rainbow) lies open ready to receive the breakdown product of glucose 1,3BPG and ADP (left). Once bound, the enzyme swings together (a 40º rotation) closing around the molecules and forcing them together (right). When together, the phosphate “energy unit ” is transferred to ADP to make ATP – the universal energy currency in all forms of life.

M B

OW

LER

! " # $%&’ ( ) $* + , " - ! ’ . / 0 12- 3) 456’ 778884 ) 9:) ; :<) ( ) 888( ( =>?

Ossegredosdafotosintese

10


June 2010 ESRFnews

At the end of April when the greyness of the w inter was fading away and longer and sunnier days gradually began, a greener landscape spread through France. At the same moment, a timely paper from a team of the University of Gothenburg (Sweden) and the ESRF shed new light on how photosynthetic bacteria are responsible for the transformation of light into chemical energy, a mechanism that is also shared by plants.

The focus of the study was a photosynthetic reaction centre where the primary energy conversion reactions of photosynthesis take place, and is therefore central to the conversion of light to chemical energy during photosynthesis. A lthough this membrane protein complex was isolated from a photosynthetic bacteria called Blastochloris viridis, it is closely related to Photosystems I and II, which perform the same task in plants. Scientists wanted to study the structural changes that happened w ithin the protein only milliseconds after inducing them w ith light. In order to follow the structural changes caused by light-induced electron movements, they used time-resolved Laue diffraction crystallography at ID9B. Their results showed that the membrane protein is able to stabilise the light-induced electron movements using subtle structural changes w ithin the protein involving atomic movements of only a fraction of a nanometre (A B Wöhri et al. 2010).

Richard Neutze, leader of the team, explains that “ this is the first time that the method of time-resolved Laue diffraction has been successfully used to observe structural changes w ithin a membrane protein complex.

Because our structural results provide new insight into how the charge separation reactions of photosynthesis are stabilised by protein structural changes, some key ideas could help guide the design of future synthetic systems for artificial photosynthesis.”

Photosystems I and IIIn plants, Photosystems I and II govern the first steps in the photosynthesis process (but, curiously, they were the last to be discovered). The way that photosynthesis works in plants is that Photosystem II harnesses light energy to split two water molecules (H2O) into O2, protons and electrons. It drives one of the most oxidising reactions known to occur in nature and is responsible for the production of atmospheric oxygen. Photosystem I also captures sunlight and takes the electrons released by Photosystem II through an antenna system, consisting of a pigment network, to the centre of the molecule, where it is used in the transmembrane electron transfer reaction.

A team from Te l Aviv University (Israe l) used the struc tural b io logy beamlines at the ESRF and Sw iss Light Source to uncover the most comp lete p lant Photosystem I struc ture obtained so far, revealing the locations of and interac tions among 17 prote in subunits and 193 non-covalently bound photochemical cofac tors. The new struc ture allowed the scientists to study the contac ts among prote in subunits, which can e lucidate

questions about its func tion and organisation (A Amunts et al. 2010).

Complementary techniquesDifferent X-ray techniques from X-ray crystallography can also be used to study photosynthesis.

Five years ago, M ichael Haumann and Ho lger Dau, from the Freie Universität Berlin, used X-ray fluorescence on ID26 to investigate the kinetics of the photosynthesis process in Photosystem II. They confirmed the existence of a fifth step in the catalysis process of water into oxygen (Haumann et al. 2005). This step is particularly important because it is direc tly invo lved in the formation of mo lecular oxygen. In 2008 , they used X-ray absorption near-edge spec troscopy to study the photosynthesis cycle w ith an additional intermediate and proposed a new reac tion mechanism on a mo lecular basis for the release of dioxygen. D ioxygen is formed as a produc t of the water oxidation chemistry in Photosystem II (M Haumann et al. 2008).M Capellas

ReferencesA Amunts et al. 2010 J Biol Chem. 285(5) 3478–86. M Haumann et al. 2005 Science 310 1019–1021.M Haumann et al. 2008 PNAS 105 17384 . A B Wöhri et al. 2010 Science 328(5978) 630–633.

Plants go through different steps in photosynthesis that are fuelled by water and light.

Scientists disclose some secrets of photosynthesisPlants, algae and photosynthetic bacteria produce more than 180 billion tonnes of organic matter each year from the fixation of carbon dioxide. Despite the apparent simplicity of this process, it consists of different steps and many proteins take part in the chemical reactions.

ISTO

CKP

HO

TO.C

OM

! " # $%&’ ( ) $* + , " - . / 01023’ 1/ 4252- 6( ) 75’ 88999( ) ) : ;) <;=) ( ) 999( ( >?=

10


June 2010 ESRFnews

At the end of April when the greyness of the w inter was fading away and longer and sunnier days gradually began, a greener landscape spread through France. At the same moment, a timely paper from a team of the University of Gothenburg (Sweden) and the ESRF shed new light on how photosynthetic bacteria are responsible for the transformation of light into chemical energy, a mechanism that is also shared by plants.

The focus of the study was a photosynthetic reaction centre where the primary energy conversion reactions of photosynthesis take place, and is therefore central to the conversion of light to chemical energy during photosynthesis. A lthough this membrane protein complex was isolated from a photosynthetic bacteria called Blastochloris viridis, it is closely related to Photosystems I and II, which perform the same task in plants. Scientists wanted to study the structural changes that happened w ithin the protein only milliseconds after inducing them w ith light. In order to follow the structural changes caused by light-induced electron movements, they used time-resolved Laue diffraction crystallography at ID9B. Their results showed that the membrane protein is able to stabilise the light-induced electron movements using subtle structural changes w ithin the protein involving atomic movements of only a fraction of a nanometre (A B Wöhri et al. 2010).

Richard Neutze, leader of the team, explains that “ this is the first time that the method of time-resolved Laue diffraction has been successfully used to observe structural changes w ithin a membrane protein complex.

Because our structural results provide new insight into how the charge separation reactions of photosynthesis are stabilised by protein structural changes, some key ideas could help guide the design of future synthetic systems for artificial photosynthesis.”

Photosystems I and IIIn plants, Photosystems I and II govern the first steps in the photosynthesis process (but, curiously, they were the last to be discovered). The way that photosynthesis works in plants is that Photosystem II harnesses light energy to split two water molecules (H2O) into O2, protons and electrons. It drives one of the most oxidising reactions known to occur in nature and is responsible for the production of atmospheric oxygen. Photosystem I also captures sunlight and takes the electrons released by Photosystem II through an antenna system, consisting of a pigment network, to the centre of the molecule, where it is used in the transmembrane electron transfer reaction.

A team from Te l Aviv University (Israe l) used the struc tural b io logy beamlines at the ESRF and Sw iss Light Source to uncover the most comp lete p lant Photosystem I struc ture obtained so far, revealing the locations of and interac tions among 17 prote in subunits and 193 non-covalently bound photochemical cofac tors. The new struc ture allowed the scientists to study the contac ts among prote in subunits, which can e lucidate

questions about its func tion and organisation (A Amunts et al. 2010).

Complementary techniquesDifferent X-ray techniques from X-ray crystallography can also be used to study photosynthesis.

Five years ago, M ichael Haumann and Ho lger Dau, from the Freie Universität Berlin, used X-ray fluorescence on ID26 to investigate the kinetics of the photosynthesis process in Photosystem II. They confirmed the existence of a fifth step in the catalysis process of water into oxygen (Haumann et al. 2005). This step is particularly important because it is direc tly invo lved in the formation of mo lecular oxygen. In 2008 , they used X-ray absorption near-edge spec troscopy to study the photosynthesis cycle w ith an additional intermediate and proposed a new reac tion mechanism on a mo lecular basis for the release of dioxygen. D ioxygen is formed as a produc t of the water oxidation chemistry in Photosystem II (M Haumann et al. 2008).M Capellas

ReferencesA Amunts et al. 2010 J Biol Chem. 285(5) 3478–86. M Haumann et al. 2005 Science 310 1019–1021.M Haumann et al. 2008 PNAS 105 17384 . A B Wöhri et al. 2010 Science 328(5978) 630–633.

Plants go through different steps in photosynthesis that are fuelled by water and light.

Scientists disclose some secrets of photosynthesisPlants, algae and photosynthetic bacteria produce more than 180 billion tonnes of organic matter each year from the fixation of carbon dioxide. Despite the apparent simplicity of this process, it consists of different steps and many proteins take part in the chemical reactions.

ISTO

CKP

HO

TO.C

OM

! " # $%&’ ( ) $* + , " - . / 01023’ 1/ 4252- 6( ) 75’ 88999( ) ) : ;) <;=) ( ) 999( ( >?=

BacteriatransformaluzemenergiaquimicaEletrons‐movimentosatomicos‐catalise‐H2O‐>O2+n+e

15

18871884

1450

1500 BC

1545

Diffraction reveals secrets of longevity of Maya blue pigment (2006 Journals of Materials Science 44 5524)

Studies of fibres and pigments in Dead Sea Scrolls helps date sacred texts (2010)

XANES studies of Egyptian glass reveal secrets of opacification (2009 Appl. Phys. A 98 1)

Egyptian make-up reveals wet chemistry has been practised for thousands of years (2001 Nucl. Instrum. Methods Phys. Res., Sect. B 181 744)

Shedding light on the past

TODAY

MILLION YEARS AGO

0

400 m

300 m

100 m

2000 BC

Infrared spectroscopy reveals use of oil in paintings found in Bamiyan caves in Afghanistan (2008 J. Anal. At. Spectrom. 23 820)

Micro X-ray beams reveal subtle chemical processes that cause yellow pigment to turn brown (2011 Anal. Chem. 83 1214)

Accumulation of sulphur compounds oxidising to sulphuric acid in wood from the Mary Rose (2005 Proc. Natl. Acad. Sci. 102 14165)

X-ray fluorescence reveals traces of mercury in the hair of Agnes Sorel, famous mistress of King Charles VII of France (2005)

Micro-diffraction shows degradation of Chinese silk fibres is due to loss of protein chains (2006 Biomacromolecules 7 777)

Sulphur and chlorine analysis from Pompeii frescos explains why red pigment turns to black (2006 Anal. Chem. 78 7484)

Microtomography shows Neanderthal teeth grew faster than human ones (2010 Proc. Natl. Acad. Sci. 107 20923)

3D imaging of rare hominid fossil Australopithecus sediba reveals new human ancestor (2011)

Complete imaging of our earliest pre-human ancestor – the Toumaï skull – the first synchrotron image of whole fossil hominid skull (2006)

First published picture of a fossil using synchrotron microtomography: lower molar of a close relative to orangutan (2003 Nature 422 61)

Microtomography resolves jaws of last ammonites, bringing clues about their extinction (2011 Science 331 7)

Laminography of snake with legs offers clues as to whether snakes evolved from land or sea creatures (2011 J. Vert. Paleontol. 31 1)

3D structure of 356 animal inclusions revealed in 2 kg of opaque amber (2008 Microsc. Microanal. 14 251)

Holotomography reveals oldest evidence of reproduction using sperm in microscopic bivalve crustaceans (2009 Science 324 1535)

Oldest and only fossil brain revealed in an ancient shark-like creature by holotomography (2009 Proc. Natl. Acad. Sci. 106 5224)

Internal structures of fossil algae revealed with 3D phase-contrast microtomography (2005 Am. J. Bot. 92 1152)

Sub-micron images of microfossils at early developmental stages show complex embryonic development (2006 Science 312 1644)

Pigment analysis of lost portrait beneath Van Gogh’s Patch of Grass (2008 Anal. Chem. 80 6436)

590 m

150 BC

800

500

750

65 m

95 m

12 m

7 m

0.1 m1.9 m

A selection of the ESRF’s fossil and cultural hits

!"#$%&’(($)*+",-./

!0.1!,2(34(56578’99:::(33;<=><3=((:::(=?@@

16

18871884

1450

1500 BC

1545

Diffraction reveals secrets of longevity of Maya blue pigment (2006 Journals of Materials Science 44 5524)

Studies of fibres and pigments in Dead Sea Scrolls helps date sacred texts (2010)

XANES studies of Egyptian glass reveal secrets of opacification (2009 Appl. Phys. A 98 1)

Egyptian make-up reveals wet chemistry has been practised for thousands of years (2001 Nucl. Instrum. Methods Phys. Res., Sect. B 181 744)

Shedding light on the past

TODAY

MILLION YEARS AGO

0

400 m

300 m

100 m

2000 BC

Infrared spectroscopy reveals use of oil in paintings found in Bamiyan caves in Afghanistan (2008 J. Anal. At. Spectrom. 23 820)

Micro X-ray beams reveal subtle chemical processes that cause yellow pigment to turn brown (2011 Anal. Chem. 83 1214)

Accumulation of sulphur compounds oxidising to sulphuric acid in wood from the Mary Rose (2005 Proc. Natl. Acad. Sci. 102 14165)

X-ray fluorescence reveals traces of mercury in the hair of Agnes Sorel, famous mistress of King Charles VII of France (2005)

Micro-diffraction shows degradation of Chinese silk fibres is due to loss of protein chains (2006 Biomacromolecules 7 777)

Sulphur and chlorine analysis from Pompeii frescos explains why red pigment turns to black (2006 Anal. Chem. 78 7484)

Microtomography shows Neanderthal teeth grew faster than human ones (2010 Proc. Natl. Acad. Sci. 107 20923)

3D imaging of rare hominid fossil Australopithecus sediba reveals new human ancestor (2011)

Complete imaging of our earliest pre-human ancestor – the Toumaï skull – the first synchrotron image of whole fossil hominid skull (2006)

First published picture of a fossil using synchrotron microtomography: lower molar of a close relative to orangutan (2003 Nature 422 61)

Microtomography resolves jaws of last ammonites, bringing clues about their extinction (2011 Science 331 7)

Laminography of snake with legs offers clues as to whether snakes evolved from land or sea creatures (2011 J. Vert. Paleontol. 31 1)

3D structure of 356 animal inclusions revealed in 2 kg of opaque amber (2008 Microsc. Microanal. 14 251)

Holotomography reveals oldest evidence of reproduction using sperm in microscopic bivalve crustaceans (2009 Science 324 1535)

Oldest and only fossil brain revealed in an ancient shark-like creature by holotomography (2009 Proc. Natl. Acad. Sci. 106 5224)

Internal structures of fossil algae revealed with 3D phase-contrast microtomography (2005 Am. J. Bot. 92 1152)

Sub-micron images of microfossils at early developmental stages show complex embryonic development (2006 Science 312 1644)

Pigment analysis of lost portrait beneath Van Gogh’s Patch of Grass (2008 Anal. Chem. 80 6436)

590 m

150 BC

800

500

750

65 m

95 m

12 m

7 m

0.1 m1.9 m

A selection of the ESRF’s fossil and cultural hits

Image cred i t s (top to bot tom): Van Gogh Museum, Ams t erdam; Mar y Rose Trus t ; Roya l Museum of F ine Ar t s , Ant werp; Amer ic an Chemic a l Soc ie t y; C Reyes -Va ler io; D Bagau l t C2RMF; P Ta f fore au, ESRF; P Ta f fore au, ESRF; A Houssaye; P Ta f fore au, ESRF; A Pr ade l /CNRS; P Ta f fore au, ESRF.

!"#$%&’(($)*+",-./

!0.1!,2(34(56578’99:::(53;<=><3=((:::(=?@>

VanGogh,1888

[aplicacoes] estrutura cristalina de solidos

Education

ppm si o

varying si o

nucleaoecristalizaodasio2

the2 d

d ravnsb

study the2 o

c ryot e

f e g se