Rather than comprehensively reviewing recent work, Wei You and co-workers from the University of North Carolina at Chapel Hill provide commentary on relevant advances in the field, and forecast where researchers should look to enhance the efficiency of organic solar cells.  Studies determining how the polymer interacts with fullerene derivatives are especially vital.  By structurally modifying the polymer to reduce its lowest unoccupied molecular orbital (LUMO) level, utilizing electron-withdrawing substituents advantageously, and employing appropriate side chains, researchers can elucidate further aspects of polymer-fullerene interactions while ultimately developing materials that will achieve higher efficiencies.

Image(s): FreeDigitalPhotos.net

The ripening process of many fruits is triggered when ethylene binds to a specific receptor. Bananas, for example, are usually unripe when they are harvested. They are transported under a nitrogen atmosphere to stop the ripening process and are then exposed to ethylene gas in a ripening facility before delivery. However, they must not be ripened too much because bananas become “overripe” very fast. It is thus important to precisely control the ethylene concentration in storage facilities. It is also interesting to know how much ethylene fruits release at any given point in their development because this could help determine the ideal time for harvest.

As a small, nonpolar molecule, ethylene (C₂H₄) is difficult to detect. Conventional methods are mainly based on expensive, complex instruments that are not well suited for use in the field or in an orchard. Timothy M. Swager and his team at the Massachusetts Institute of Technology (MIT) in Cambridge (USA) have now developed a portable sensor that can reliably measure tiny concentrations of ethylene, such as those released when fruit ripens. Their device is also easy and inexpensive to produce.

The sensory element consists of a small glass plate with two gold electrodes. A mixture of single-walled carbon nanotubes and a special copper complex is deposited between the electrodes. The copper complexes bind tightly to the carbon nanotubes. When the sensor comes into contact with ethylene, the ethylene binds to the copper complex, weakening the bond between the copper complex and the carbon nanotube. The electronic properties of carbon nanotubes are very sensitive to the strength of their interaction with the copper complexes. Their electrical resistance changes in relation to the ethylene concentration.

The researchers placed different fruit in an airtight chamber and allowed nitrogen to flow through the chamber and over the sensor. This made it possible for them to compare the ethylene emissions of different fruit and to follow the amount of ethylene reduced by a single fruit as it ripened. This revealed a clear ethylene peak during storage of fruits that ripen after harvest, such as bananas, pears, and avocados. The maximum is reached when the fruit is ripe. In contrast, fruit that do not ripen after harvest, such as oranges, release uniformly low amounts of ethylene. 

In addition to papers on graphene, recent articles on organic and oxide semiconductors, plasmonics, and nano structures round out the top ten.

Two articles from the Whitesides lab feature in the Top 40: “Paper-Based, Capacitive Touch Pads” moves up 12 spots from last week, while the evergreen guide to ”Writing a Paper” is number 24 again this week.

Do you find this useful? How else could we be visualizing this data? What’s your top paper? Let us know in the comments.

Updated 11:00 am 2012-05-16: Fixed broken links and removed duplicate listing.

A SEM image of one of the titanium dioxide microspheres synthesized in this experiment.

The challenge of studying such an important topic is to obtain photocatalysts with a tunable spatial distribution of heteroatoms while not changing other parameters. Now, an international collaboration between researchers at the Chinese Academy of Sciences and St. Andrews University in the UK has provided an innovative route, namely the acidic hydrolysis of TiB₂, to prepare anatase TiO₂ microspheres containing B^j- (j<2) in their core.

By simply heating the microspheres, the boron can diffuse from the core to the surface along [001] to form a ca. 50 nm shell with an interstitial B^s+ (s≤3) gradient. It is found that the preference for important photocatalytic hydrogen and oxygen producing reactions in water splitting can be sensitively switched by creating such a shell in the TiO₂ microspheres.

This switching stems from the downward-shift of the electronic band edges of the shell by a band bending effect, whose origin is the extra electrons coming from the interstitial B^s+. These results create new opportunities for designing and constructing efficient photocatalysts by spatial heteroatom engineering.

Because of this, much work has been done over the past few years to combat the decomposition of materials used on the sea. One important breakthrough came from the Leibniz Institute for New Materials in Saarbruecken/Germany, who developed a new composite material that prevents corrosion of metals even under extreme conditions in an environmentally friendly way.

Carsten Becker-Willinger, head of the Nanomere division of the program, explains: “What makes this coating so special is its structuring: the protective particles arrange themselves like roof-tiles. Similar to a wall, several layers of particles arrange themselves in a staggered pattern on top of each other, resulting in a self-organized, highly structured barrier”.

The protective coating is only a few millimeters thick and prevents the penetration of gases and electrolytes. It protects from corrosion caused by aggressive aqueous solutions, such as salty solutions or aqueous acids.

After thermal curing, the composite adheres on metallic substrate; it is abrasion and impact resistant. For this purpose, it also withstands a highly mechanical load. The new material can also, therefore, be used with sand or mineral dust without wear and tear. The composite can be deposited by spraying or with other wet-chemical processes and cured at temperatures from 150 to 200°C. It is suitable for steel, metal alloys, or copper. Panels, tubes, cogwheels, tools, or engine parts in any shape can be coated. The special mixture consists of a solvent, a binder, and nanoscale platelet-like particles, but no chrome VI or other heavy metals.

However, despite the great potential of this system, epoxy coatings remain the most commonly used corrosion protection, because of their good anti-corrosion performance and chemical resistance. They have excellent adhesion to many substrates and good flexibility. Furthermore, epoxy coatings can be solidified to paint film of different features and properties with multiple curing agents. However, their use is being restricted because of increasing environmental concerns.

To combat these concerns, Chinese scientists combined solvent-free and super high build (SHB) coating to introduce a heavy-duty epoxy coating with no organic solvent and an extremely low volatile organic compound content. The new coating system was mainly composed of liquid epoxy and amide curing agent. It shows excellent physical properties and anti-corrosion performance.

To evaluate anti-corrosion performance of such coatings in different marine environments, offshore samples have to be exposed. But offshore samples are disadvantageous because of heavy workload as well as difficult maintenance and observation. The reliability of field tests decreases due to loss of samples and data-recording abortion caused by unexpected typhoon and wave surging. To overcome the disadvantages, the Chinese scientists used a marine corrosion simulation apparatus. They showed that the simulation test apparatus can replace offshore field tests and better serve the need of coating evaluation. It worked reliably and simulated realistically the different corrosion environments existing in offshore field, such as splash, tidal, and immersed zones.

Image by Annika Kuhn

Dr. Mato Knez, winner of the 2012 Gaede prize.

The German Vacuum Society and the German Physical Society have honored Dr. Mato Knez for his exceptional achievements in the development of new concepts for materials synthesis on the nano and microscale via atomic layer deposition.

The Gaede Prize is awarded to young researchers working on the fields of vacuum physics and technology, thin films, surface science, solid state electronics and nanostructures.

Mato Knez is leader of the nanomaterials group at the nanoGUNE research center in San Sebastian, a position he has held since January 2012. He received his PhD in 2003 at the Max Planck Institute for Solid State Research in Stuttgart and went on to a post-doc position at the Max Planck Institute of Microstructure Physics in Halle. He worked on the development of the ALD technique in the department of Prof. Ulrich Gösele at first in the group of Kornelius Nielsch and then, since 2006, in his own group. For his outstanding research he received in 2006 the NanoFutur Award from the German Ministry of Education and Research.

His research is focused on the synthesis and functionalization of materials by atomic layer deposition. Currently he is working on thin film coatings, which can be used for corrosion protection, in flexible electronics or for energy applications, and on hybrid inorganic-organic materials for applications as textiles, among other applications. His third field of interest is in the area of bio-inorganic nanomaterials for applications in nanomedicine. Mato Knez authored more than 50 scientific papers and edited together with Nicola Pinna the book “Atomic Layer Deposition of Nanostructured Materials”. The book is giving insights into the key technique of ALD, which allows for materials synthesis and surface modification on the nanoscale.

Now, in new work, a German-Swedish research collaboration between the Chemnitz University of Technology, the Fraunhofer Institute of Electronic Nanosystems (Chemnitz), Linköping University, and Acreo AB (Norrköping, a research institute from the Swedish ICT sector), present a novel, hybrid manufacturing concept for organic electrochemical transistors (OECTs).

An optical microscopy image on of the channels in a printed OECT array.

Initiated by the EU ICT FP7 Network of Excellence “PolyNet” (2008-2010, grant agreement 214006), the researchers combined standard printing and laser microstructuring techniques. The nice thing with OECTs is that their electrical parameters do not strictly relate to the feature size: low-voltage operation is independent of the transistor channel length and the thickness of the dielectric layer, lowering the resolution demands compared to other transistor concepts like field-effect transistors.

Addressing the alignment precision, the key of the manufacturing concept is to have the laser light find its target automatically: only when and where the scanning laser hits the printed conductive layer, the material is delaminated and the layer is separated into the two electrodes, source and drain. At the same time, the deposited heat introduces a vertical void in the transparent dielectric layer above. The void is autonomously filled by capillary forces when applying a semiconductor material in a subsequent printing step. Finally, after printing a liquid electrolyte, a coated plastic foil is laminated on the stack from the top, forming the gate electrode and completing the transistor.

 The subtractive step allows for printing arrays of OECTs (17×50) on DIN A4 (297×210 mm²) flexible sheet substrates. As a perspective, the combined usage of digital techniques (scanning laser, inkjet printing) can pave the way for personalized devices, e.g. arrays of OECTs with varying electrolytes as the active elements in printed large-area sensor arrays.

Kim Harnow Klausen has been assigned as lead of the new global Competence Center in addition to his current responsibility as Managing Director of Bayer MaterialScience A/S, Denmark.

The plan for the center underlines the commitment of Bayer MaterialScience to develop innovative and sustainable materials and technologies for generating power from renewable sources. It will bundle the development capabilities from across the company’s entire portfolio of polyurethanes, polycarbonates as well as coatings, adhesives and specialties materials, pooling expertise from research and development teams around the world.

While full details of the global wind energy competence center have yet to be decided, Bayer MaterialScience CEO Patrick Thomas sees it as an opportunity to deploy the company’s expertise in chemistry and processing to help achieve a sustainable reduction in the cost of generating energy from wind turbines.

“This is an exciting step in the area of sustainable energy supply that will help open new horizons in the wind power industry. We have decades of experience in the field of advanced materials development and I am confident that with this specific focus we will be able to make a valuable contribution to this important industry sector“, says Patrick Thomas.

Bayer MaterialScience plans to extend its capabilities at the existing polyurethanes systems house site in Otterup, by additionally building on solutions for wind turbine applications that include raw materials for coatings and adhesives, carbon nanotubes, matrix materials and production processes for rotor blades, as well as fiber composite materials and production processes for nacelles. One example for latest technology developments in this field is Bayer’s hybrid system for the production of rotor blades based on vacuum infusion technology, which can significantly reduce the cost of generating energy.

Denmark was chosen for the location of the center because of the country’s expertise in the area of wind power and its leading position in energy efficiency. According to data by the Danish Wind Industry Association (DWIA) wind power to date already accounts for more than 20 percent of the total power consumption in Denmark which is intended to be increased to up to 50 percent by 2020. This reflects the pioneering role that the Danish wind energy industry has taken on throughout the past 40 years and its commitment to set high technological standards for the industry.

With meanwhile almost half of the wind turbines around the world being developed and produced by Danish manufacturers along with many component suppliers based in the country, Bayer MaterialScience is ready to contribute its material expertise and technical network worldwide at the forefront of technological development for this globally vital industry.

As soon as the steel sheet is cut, the zinc starts to corrode and dissolve. This is the starting shot for the intelligent, second protective system: the capsules are released from the zinc onto the steel and smeared along the surface by the cutting device. The inhibitor can be released and thus protects the steel surface.

“This is an intelligent protective system that automatically realises when and where corrosion happens, becomes active and stops again when the respective spot is healed”, explains Dr. Rohwerder, group leader in the Interface Chemistry and Surface Engineering department. “It works like a scratch in the skin: it is detected, healed and the initial status is restored.”

Three steps are required to prepare these smart coatings: loading of the silica microcapsules with the inhibitor, sealing them to avoid premature leaching, and finally incorporating the capsules into the zinc layer. The incorporation into the zinc layer is the most difficult part. Unmodified, the hydrophilic particles are repulsed by the zinc and only adsorb on the surface.

However, Tabrisur Rahman Khan, a PhD student from Bangladesh, has solved this problem. He has modified the particles with zinc affine functional groups, such as thiols, which make the solvation feasible.

Unfortunately, for efficient protection, a higher loading of the pores with the inhibitor must be realised. This is the focus of current research. Additionally, the concept of intelligent corrosion coatings has been expanded to systems with polymer coatings. Two Max-Planck and two Fraunhofer Institutes are sharing their competences with respect to nanocomposite coatings, agent containers, zinc coatings and the analysis of effective mechanisms in order to improve the protective coatings. “It is a huge challenge, but present results look very promising”, states Rohwerder.

The answer is yes!

A special issue in Macromolecular Rapid Communications highlighting the outstanding research of 21 young scientists from around the world is the best evidence. Three guest-editors from three different continents have compiled this great issue which reflects the diversity and excitement of today’s polymer science. Jean-Francois Lutz (Strasbourg, France), Shiyong Liu (Hefei, China) and Brent Sumerlin (Dallas, USA) – all of them well established scientists – are still young enough to know the latest generation of polymer scientists from their post-doc times.

A selection of what looks to be a bright future in polymer science can now be accessed for free.

• Anne McNeil from the University of Michigan presents a palladium catalyst that can mediate a living, chain-growth polymerization of π-conjugated monomers.

• Chun-Yan Hong from the University of Science and Technology of China, Hefei, reports on a novel nanocontainer fabricated by attaching zwitterionic sulfobetaine copolymer onto the mesoporous silica nanoparticles, which can regulate the release of payloads, has been successfully.

• Matthew Gibson from the University of Warwick, Coventry, discusses initial biophysical investigations on the interactions of thermoresponsive polymers with phospholipid bilayer membranes.

 Enjoy the reading!

The Macromolecular Journals also sponsor prizes for the best poster presentations at selected international conferences, preferably awarded to promising younger scientists. Find more information on the Macro-Awards here.

Photo: Courtesy of Carl Zeiss

The Carl Zeiss AG Supervisory Board has elected Dr. Dieter Kurz as the new Chairman of the Supervisory Board, effective immediately. “With Dr. Kurz, we are gaining a Chairman of the Supervisory Board who is very familiar with the company and the challenges of our portfolio through his many years of successful work as a Member of the Executive Board and President and CEO of Carl Zeiss AG,” said Dr. Michael Kaschke, President and CEO of Carl Zeiss AG. “We at Carl Zeiss are looking forward to working with him.” Kurz was already appointed as Chairman of the Shareholder Council of the Carl Zeiss Foundation in March. According to the Foundation’s constitution, this means that he is a Member of the Supervisory Boards of the two Foundation enterprises SCHOTT AG and Carl Zeiss AG and is to be elected as Chairman by the two Supervisory Boards.

Born in 1948, Dr. Dieter Kurz studied physics at the University of Tübingen, from which he also received his doctorate. He joined Carl Zeiss in 1979. After holding several positions in research and development, marketing, and sales, including a two-year stay in North America, he headed the Semiconductor Optics division and Semiconductor Manufacturing Technology business group. In 1999 he became a Member of the Executive Board and was appointed President and CEO in 2001. After the two Foundation enterprises had been transformed into stock corporations (AG) and the appropriate amendments to the Foundation’s constitution had come into effect, he was President and CEO of Carl Zeiss AG from 2004 to the end of 2010.

Kurz is also Chairman of the Shareholder Council of the Carl Zeiss Foundation, Heidenheim and Jena, which is the sole shareholder of Carl Zeiss AG. He succeeds Dr. Theo Spettmann, who held these offices from February 2010 and who stepped down for health reasons at the beginning of March 2012. “On behalf of the Executive Board I would like to thank Dr. Spettmann once again for his commitment and excellent work as Chairman of the Supervisory Board,” said Kaschke. 

Functional lipid-based microparticles can be used to mimic the pharmaceutical food effect and enhance drug absorption by controlling the enzymatic digestion of lipid colloids.

Some medicines have to be taken either before, after, or during a meal because food ingredients can affect their absorption or bioavailability. Australian researchers have now encapsulated drugs in a matrix of silicon dioxide and lipids to simulate the administration of pharmaceuticals with food. As the researchers report in the journal Angewandte Chemie, drug absorption is increased through control of the enzymatic digestion of the lipid droplets.

For example, the body only absorbs fat-soluble vitamins A and D in the presence of some fat. Also, the bioavailability of many poorly water-soluble drugs increases when they are taken with high-fat meals. There are many techniques for the lipid-based delivery of pharmaceuticals, including emulsions, micelles and “packaging” in liposomes. These methods prevent the active ingredients from precipitating out and improve transportation to the absorption sites in the gastrointestinal tract. However, in order for the drug to become active in the body, it must be released from its lipid shell. The enzymatic decomposition of the lipid coating plays an important role in this process, but it has proven to be difficult to control. In addition, it is difficult to calculate the extent to which such lipid “packaging” really increases the bioavailability of a drug.

Clive Prestidge and a team at the University of South Australia and Monash University have now developed a controllable packaging type. Their material consists of a nanostructured network of silicon dioxide nanoparticles that contains nanoscopic lipid droplets containing the drug. This system is produced by generating a fine emulsion of the drug-containing oil droplets in an aqueous phase. The silicon dioxide particles collect around the droplets at the phase boundary. Spray-drying results in solid microparticles of entrapped lipid droplets.

The team has demonstrated that the lipid in these microparticles is enzymatically digested much more rapidly than pure lipid drops. This is because the nanostructured silicon dioxide network holds the enzymes close to their substrate. The size of the silicon dioxide particles used and the porosity of the resulting matrix determine how fast the enzymatic decomposition of the lipids occurs.

Animal trials with Celecoxib, a drug used to treat arthritis, showed a higher drug content in plasma when the pharmaceutical was orally administered in this new form rather than in its pure state or as drug-containing lipid drops. In contrast to Celecoxib-containing lipid drops, the release rate did not vary from batch to batch or after a longer storage period.

The new nanomaterial imitates the food effect in a predictable fashion and allows for better control of drug release, it could minimise the food effect on drug absorption and enhance more predictable therapeutic responses.

Now, Ren et al. have shown that this is possible by first chemically grafting polyethylene glycol (PEG) onto the polyurethane, then in a second stage modifying the PU-PEG films by acryloyl chloride, and eventually grafting them with carboxymethyl chitosan. This sequence of passages improves the hydrophilicity of the films markedly, and in turn the biocompatibility of the materials, measured by bovine serum albumin (BSA) adsorption, dynamic blood clotting test, platelet adhesion test, and hemolytic test, all of which showed a statistically significant improvement of the biocompatibility of the materials compared both to the original polyurethane and to PEG-grafted polyurethane.  The synthesis method is quite simple, and therefore it has good chances of being actually applied in real-world biomedical devices.

Global Solar Council members will engage with policymakers worldwide to demonstrate the progress towards abundant, affordable and low emissions energy already made possible by the solar industry and to emphasize the importance of a supportive policy and trade environment, which will enable the ongoing development of competitively-priced solar energy, driving job creation and economic growth.

Through its members, the Global Solar Council brings industry knowledge and insights from all sides of the solar photovoltaic value chain; from the supply of materials to product manufacturing and financing, policy, research and innovation, cross-border cooperation, and grid development and management.

Roland-Jan Meijer, the newly-appointed Executive Director of the Global Solar Council said, “The Global Solar Council is an important and timely industry initiative.  It demonstrates a strong commitment by key players in the sector to work together to continue to make solar energy a global success.”

Bob Hansen, CEO of Dow Corning added, “Solar energy has already proven itself a viable contribution to energy sources in many markets, particularly in the EU and the US, and the industry continues to improve the cost-effectiveness of this technology.  The Global Solar Council will enable us to continue the expansion of cost-effective solar power in collaboration with governments and other stakeholders.”

Suntech CEO, Dr. Zhengrong Shi said, “A thriving solar industry is an important contributor to economic growth and employment in developing regions.  By joining forces in the Global Solar Council, we will be able to demonstrate these benefits to our key stakeholders with one voice and drive forward the growth of the green economy.”

The Global Solar Council’s role is complementary to regional trade associations and other stakeholders.  Members will work in concert with organizations such as EPIA, APVIA, and SEIA to support their efforts on a global level.

Global Solar Council founding members and their representatives are Applied Materials (Dr. Charles F. Gay, President, Applied Solar), Dow Corning (Robert D. Hansen, CEO), DuPont (David B. Miller, President, Dupont Electronics & Communication), First Solar (Michael J. Ahearn, Chairman and Interim CEO), Lanco Solar (Vutukuri Saibaba, CEO), Phoenix Solar (Dr. Andreas Hänel, CEO), and Suntech (Dr. Zhengrong Shi, CEO).

Biocatalysis in Polymer Chemistry

Enzymes are Nature’s catalysts, but they also mediate many reactions useful to the synthetic chemist. In the realm of polymer chemistry, biocatalytic pathways to polymeric materials have received much attention due to the environmental benefits associated with enzymes. Enzymes are non-toxic and derived from renewable resources, while most conventional polymerization catalysts are not. Moreover, the high stereo-, regio-, and substrate-selectivity of enzymes coupled with their ability to perform under mild conditions make them attractive as catalysts for the synthesis of monomers and polymers. Thus, biocatalysis is a vibrant field of research in polymer chemistry with many potential industrial applications.

In Biocatalysis in Polymer Chemistry a team of experts reviews fundamental studies, applications, and the successes and challenges of all relevant biocatalytic processes. The book is well-written, easy to understand and provides a complete overview of the state-of-the art in this area of research. As you would expect, the main focus of the book is on enzymatic polymerizations. The chapters are organized into the various classes of polymers that have been synthesized using biocatalysts. The synthesis of polyester by lipases, of polyamides and polypeptides by proteases and lipases, as well as the polymerization of vinyl-, and phenolic monomers by oxidoreductases are reviewed. Oxidoreductases have also been applied to the synthesis of conductive polymers such as polyaniline. Further chapters are dedicated to the synthesis of polysaccharides by glycosyltransferases and phosphorylases, as well as the bacterial synthesis of polyhydroxyalkanoates and related compounds.

A number of well-selected chapters cover adjacent topics and rounds out the book. These review monomers from renewable resources, enzyme immobilization, biocatalysis in non-aqueous solvents, the synthesis of chiral polymers and of block copolymers, molecular modeling to elucidate polymerase mechanisms, and enzymatic polymer modification and degradation. One aspect, however, could have been reviewed in more detail: Biotechnological routes to enhanced biocatalysts, such as directed evolution or rational design.

Each chapter concludes with a section discussing the current state of the art and highlighting future challenges. Reading these sections is eye-opening as, on the one hand, they show the great advancements that have been made in applying enzymes in synthetic polymer chemistry while, on the other, they point out many aspects of biocatalysis that have not yet been explored or elucidated. Thus, there is plenty of room for innovation and a tremendous scientific playground available for researchers who wish to engage this field. This will certainly inspire future research efforts.

In conclusion, the book covers all major enzymatic systems used to synthesize and modify polymers or monomers in an adequately detailed way. Therefore, the book is an excellent resource for researchers looking for an in-depth yet comprehensive overview of the field of biocatalysis in polymer chemistry, and it is an indispensable reference work for researches already active in this field.

A molecule is able to walk back and forth upon a five-foothold pentaethylenimine track without external intervention.

Within each of the cells in our bodies, and between individual cells, there are permanent transport processes occurring over distances ranging from a few nanometers to several millimeters. One of these cellular “cargo carriers” works by means of molecular motors that “walk” along the filaments of the cellular skeleton (cytoskeleton). British researchers have used these as inspiration to develop a molecular “track”, along which a small molecule can move back and forth like a courier. Their system is described in the journal Angewandte Chemie.

David A. Leigh and a team at the University of Edinburgh (UK) made their track from an oligoethylenimine. The filament contains amino groups that act as “stepping-stones” for the molecular “walker”. The walker is a small molecule (α-methylene-4-nitrostyrene). It resembles a stick figure that has an aromatic six-membered ring of carbon atoms for its torso, a nitro group for its head, and two short hydrocarbon legs. The molecule is initially bound to the first stepping-stone of the track by one leg. The molecular walker’s movement begins with a ring-closing rearrangement (an intramolecular Michael reaction). This causes the second leg to bind to the neighboring stepping-stone. A second, ring-opening rearrangement reaction (a retro-Michael reaction) then causes the first leg to detach from its stepping-stone. This allows the molecular walker to move along the track step by step.

There is, however, a catch: All of these rearrangement reactions are equilibrium reactions. If the stepping-stones are chemically equivalent, the tiny walker swings back and forth, lifts one leg and puts it down again, moves forward one step then back again; its movement has no directionality. However, it manages on average an amazingly high 530 “steps” before completely coming off the track. That is significantly more than natural systems like the kinesin motor proteins.

The miniature walker can even carry out a task: The researchers attached an anthracene group to the end of a track with five stepping-stones. As long as the walker stays at the beginning of the track, the anthracene fluoresces. However, if the walker reaches the anthracene end of the track, an electronic interaction between the walker and the anthracene “switches off” the fluorescence. The researchers found that the intensity of the fluorescence slowly sinks by about half. The final intensity is reached after about 6.5 hours, at which point there is an equilibrium between all possible positions of the walker.

The team’s next goal is to develop a walker that uses a “fuel” to march in a predetermined direction to transport cargoes over longer, branched tracks.

Bruker microCT presents its new product line of advanced, high-resolution micro computed tomography (CT) systems for three-dimensional (3D) X-ray imaging following the recent acquisition of SkyScan N.V..  Bruker microCT instruments can be configured for numerous applications in materials research and in the life sciences, including in vivo preclinical animal imaging, in vitro bone and soft tissue imaging, 3D imaging of electronic components, synthetic materials, new devices such as micro-sensors and cardio-stimulators, geological samples, fuel cell components, ceramics, and more.  The Bruker microCT products can be equipped with sample stages for in-situ scanning under compression and tension, cooling and heating.  The various product groups and products are described below in more detail.

1.    Compact and versatile Micro-CT imagers in which the sample is rotated between the X-ray source and the camera:

•    The SkyScan 1172TM represents a new generation of micro-CT systems.  A novel architecture, enabling both the sample stage and the X-ray camera to move automatically during magnification adjustment, allows an unprecedented combination of spatial resolution, image quality, sample size accommodation and scanning speed.
•    The SkyScan 1173 TM is a high-energy micro-CT scanner for large and dense objects.  It includes a newly developed 130kV X-ray source, a flat panel sensor with special protection by a lead-glass fiber optic window for long lifetime under high energy X-ray exposure, and a precision object manipulator for heavy objects with an embedded micro-positioning stage.
•    The SkyScan 1174 TM is a compact, cost-effective instrument. Fast scanning, straightforward control, small footprint and maintenance-free operation make this micro-CT scanner an ideal solution for scientific research, as well as for industrial applications, such as quality control.  The scanner can run from any desktop or portable computer requiring just one USB port and FireWire input.

2.    High-resolution 3D scanners with submicron spatial resolution:

•    The SkyScan 2011 TM system was introduced as the first revolutionary laboratory nano-CT scanner with spatial resolution in the range of a few hundreds of nanometers.  This spatial resolution in terms of volume is equal to or better than that of synchrotron tomography.  For the first time true sub-micron tomographic imaging is available in a laboratory instrument.
•    The SkyScan SEM-CT TM kit is a device that allows the generation of 3D images using any scanning electron microscope.  While a standard scanning electron microscope only images the sample surface, the simple addition of a SkyScan SEM-CT opens full access to the third dimension of the material’s internal micro-world without sample cutting, coating or other preparation.

3.    Hyphenated 3D scanner which adds true 3D chemical XRF analysis capability to high-resolution micro-tomography:

•    The SkyScan 2140 TM micro-CT/micro-XRF combines in one instrument a micro-CT scanner, which provides high-resolution morphological information and absorption correction maps for chemical analysis, with a full-field 3D micro-XRF scanner for reconstruction of the 3D chemical composition inside the sample.

4.    Advanced Micro-CT systems where the X-ray source and the camera are rotated around the object, as in a clinical CT scanner, forin-vivo scanning of small laboratory animals like mice and rats, as well as for ex-vivo scanning of other types of samples:

•    The SkyScan 1176 TM is a state-of-the-art high-resolution low-dose X-Ray scanner for in-vivo 3D-reconstruction with detail detectability (voxel size) down to 9 microns inside small laboratory animals (rats, mice, rabbit’s periphery, etc.). It allows non-invasive reconstruction of any cross section through the animal body and conversion of reconstructed datasets into realistic 3D-images, plus calculation of internal morphometric parameters, including bone architectural parameters.
•    The SkyScan 1178 TM is a high-throughput, fast, low-dose in-vivo micro-CT scanner. The animal bed holder is interchangeable for multimodality imaging with other imaging technologies like PET, SPECT and bioluminescence.

5.    All SkyScan micro-CT systems are equipped with the proprietary software package for 3D reconstruction, 2D/3D image analysis and realistic 3D visualization:

•    SkyScan NRecon TM high speed volumetric reconstruction software uses the set of acquired angular projections to create a set of virtual slices through the scanned object.  The GPU-accelerated reconstruction process can optionally be speeded up by a cluster of several computers connected by a gigabit network.
•    SkyScan Data Viewer TM software displays reconstructed results as a slice by slice movie or as three orthogonal sections centered at any selected point inside the reconstructed space with possibility to rotate and resample the dataset to any alternative orientation.
•    SkyScan CT-analyser TM (CT-An) software allows 2D and 3D quantitative analysis of reconstructed volumes. Powerful, flexible and programmable image processing tools allow a wide range of segmentation, enhancement and measurement functions for analysis with flexibility to create batch processing by custom build task-lists and to create user plug-ins.
•    SkyScan CT-volume TM (CT-Vol) software provides, by using triangulated models from CT-An, a virtual 3D viewing environment, flexible and rich in features with a wide range of options for 3D presentations of micro-CT results including surface rendering with the possibility to export into CAD programs.
•    SkyScan CT-Voxel TM (CT-Vox) software advances further 3D visualization capability, offering a volume rendering 3D environment with transfer function to export 3D images to mobile devices like iPhone and iPad, surface lighting adjustment plus maximum intensity projection (MIP) viewing combined with flexible cut and select tools, including movie making.

Bruker microCT
Kartuizersweg 3B
B-2550 Kontich
Belgium
T: +32 3 8775705
sales@bruker-microct.com
www.bruker.com/microct

“There are many things to consider when looking for the ideal material in a solar cell”, Scragg says. “It must be very effective in converting light into electricity, should not contain any rare, expensive or dangerous raw materials, and must be easy to manufacture with high quality”. However, most of the existing non-silicon inorganic thin-film solar cell technologies are based on either toxic substances, such as cadmium telluride (CdTe), or relatively rare substances, such as copper indium gallium selenide (CIGSe). Many researchers worldwide are therefore searching for alternative materials to overcome these limitations. “We are faced with a huge problem”, Scragg says. “Nature has provided such a large number of different materials that it is impossible to test every single one. We describe a method that can vastly simplify this problem”.

During the manufacturing process, solar cell materials must be heated to high temperatures—in a step called annealing—so that they can crystallize with the required quality. However, many materials cannot tolerate these high temperatures without breaking down, which makes them fundamentally unsuitable. Scragg and co-workers have now found a way to determine beforehand whether a substance will be able to resist the high temperatures encountered in the manufacturing process or not. They predicted the reactions taking place during the thermal treatment of layers of several multinary semiconductor compounds on different substrates and demonstrated that the annealing conditions can be controlled to maximize the stability and quality of the materials.

The scientists studied different substances, such as CIGSe, copper zinc tin selenide (CZTSe), and other less-known ternary and quaternary semiconductors. Scragg believes that the new approach will be of great help in the search for better absorber materials: “There are many alternative materials out there, some of which are very promising and some of which may never meet the demands of the solar cell. Few of these alternatives ever receive the time and resources required to develop them to a high enough level. Instead of focusing on one single material, we take a broader approach, providing a method to determine which materials are potentially useful, and which have fundamental limitations”, he says.

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Oh small molecule

Friend or foe

To love or hate

To understand you better

Before it’s too late!

Of the three small molecules that dominate the composition of our earth’s atmosphere, it is the minor component, CO₂, that we are beginning to fear because of the looming Armageddon global warming scenario arising from the accumulation of greenhouse gas in the troposphere. While O₂, N₂, and CO₂ brought about and maintain life on our planet, CO₂ - the combustion product of the human race – now threatens its demise.

It is the innate ability of humans to recognize and react defensively to danger and in doing so learn how to survive that has inspired a global effort to understand how to transform CO₂ into a clean-house gas!

While these days CO₂ might be considered the molecule to hate there are many reasons why our relationship with it could be transformed into an eternal love affair. In this article I will take a look at how CO₂ emerged into our scientific consciousness, how it became the molecule of choice for numerous products and processes, how its abuse and misuse are becoming a looming ecological, environmental, and sociological nightmare, and how this fear of the consequences of global warming is driving a scientific and technological revolution aimed at making CO₂ into a friend rather than a foe, by learning how to capture and recycle it back into a useful fuel rather than simply capture and store it, the latter considered an unsafe practice and banned in some countries. 

Jan Baptista van Helmont (1580–1644) a Flemish chemist, physiologist, and physician, whose research was contemporary with Paracelsus, remembered for his neologism of the word gas (Greek chaos), is given credit for the discovery in 1630 of carbon dioxide, as an off-gas in the combustion of wood, which he named gas sylvestre, wood gas.

The Scottish chemist Joseph Black (1728–1799) first proved in 1756 that carbon dioxide occurred in the atmosphere, and called it fixed air. He also showed it is a product of human and animal respiration and microbial fermentation and that it has a fascinating chemistry exemplified by the precipitation of limestone (calcium carbonate) by bubbling carbon dioxide into aqueous lime and reversed by heating the resulting limestone. He showed carbon dioxide to be denser than air and able to extinguish both flames and life.

Joseph Priestley (1733–1804) could be considered the father of the soft drink industry with his discovery in the mid-1700’s that carbon dioxide evolved from the action of oil of vitriol (sulfuric acid) on chalk (calcium carbonate) could be dissolved in water to produce a pleasantly flavored fresh sparkling soda water.

Imagine what these CO₂ pioneers would say today if they had known in addition to CO₂-driven photosynthesis in plants to produce carbohydrates, which feed humans and animals, and the beneficial effects of natural CO₂-based climate control of the planet to stabilize it at the right temperature for maintaining life, that if allowed to increasingly accumulate in the atmosphere, CO₂ could also cause long term harmful effects to the human race and life on earth.

Our love affair with CO₂ is seen in its many uses, including soft drinks, dry ice solid refrigerants, ingredients in frozen food, cooling bunches of grapes in wine making, atmosphere for reactive welding, capsules for air guns, extinguishers for electrical and oil fires that cannot be put out by water, supercritical solvent for the environmentally friendly and safe removal of caffeine from coffee to help the old to be put in the coca cola to help the young, the first infrared gas laser, and an enabler for enhanced oil recovery.

This affection is also found in chemically bound CO₂, pervasive as carbonate minerals with wide ranging uses that include construction, pharmaceuticals, food, glass, polymers, paper, coatings, pigments, paints, pottery, and jewelry manufacture.

In the natural world carbonate biominerals are omnipresent in calcareous forms such as calcite and aragonite coccolithophores, sponge spicules, echinoderms, corals and the molluscan shell, the shapes and patterns of which continue to visually impress and intellectually challenge our understanding of morphogenesis, the origin and control of natural form.

The manufacture of chemicals and pharmaceuticals, fuels, and polymers from CO₂ using well-established technologies is growing in importance but is currently having only a minor impact on the roughly 10 Gt of yearly anthropogenic CO₂ emissions. It has been estimated that the implementation of these chemical technologies in large-scale industrial processes could reduce CO₂ emission by as much as 350 Mt yearly; however, this only represents about 3-6% of annual anthropogenic CO₂ emissions even when added to the corresponding reduction in fossil fuel usage as a result of these kinds of CO₂ processes.

In this context, a promising area for research and development is the sunlight-driven conversion of CO₂ and H₂O to energy-rich and transportable fuels like CH₄, CH₃OH, and HCO₂H but to achieve a steady state in atmospheric CO₂ this will have to be implemented in a process that utilizes earth abundant, low cost, and non-toxic materials operating at globally significant rates and scales in order to stand a chance of making a real impact on the problem of anthropogenic CO₂.

While there are currently around half-a-dozen approaches competing for this CO₂+ H₂O + sunlight grand prize including solar thermal, homogeneous and heterogeneous catalysis, biomass, electrocatalysis and photoelectrochemistry, it is likely that the most practical and economically viable programs for large-scale CO₂ capture and recycling (CCR) to chemical fuels will involve gas-phase flow-based photocatalytic reactor units. They will likely work alongside CO₂ capture, purification and storage (CCS) technologies, possibly based on metal organic frameworks, frustrated Lewis pairs or amine resins, integrated into CO₂ emitting fossil fuel power plants and iron, steel, cement and aluminum production facilities, working at low pressures and temperatures and driven by sunlight (image credit, Dr Wendong Wang).

One can also imagine personalized versions of these CCS+CCR units installed in homes and buildings, generating from CO₂ + H₂O solar fuels like methanol or methane used for heating and lighting as well as for powering cars.

So what will it take for CO₂ + H₂O + sunlight photocatalysis to outperform photosynthesis? Simple, the right (nano)material!