MEETING DAYS 4 and 5, Thursday June 30 and Friday July 1
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At the end of a long, exciting conference, meeting chairman B.V.R. Chowdari spent a few minutes summing it up after the final plenary lectures on Friday. "Scientists presented 3,620 papers this week," he said. Four of these were by Nobel Laureates, some of whom also took the time to talk outside the meeting to the young, future scientists in Singapore's schools. Chowdari modestly reported that MRS Singapore encouraged the participation of 842 college students by offering them reduced registration fees, financial aid, or housing. He thanked all those who attended and encouraged them to come back for future meetings in 2012 and 2013.
Guest of Honor Bertil Andersson, President of Nanyang Technological University, Singapore, then took the stage to announce the 50 Best Poster Award winners. "The data reported in these poster sessions are going to be the hot discoveries of tomorrow," Andersson said, before handing an award certificate to each student or scientist whose name was called for the presentation. Afterwards, he and Chowdari joined all the winners on stage for a group photo that presented today's scientific mentors together with tomorrow's scientists: our hope for the future.
Drs. Chowdari and Andersson (in suits and ties at center) join the
50 Best Poster Award winners onstage
Meeting chairman Dr. B.V.R Chowdari summed up another successful meeting
in his status report to the attendees on Friday
Sixth Plenary Lecture: Ada Yonath
Ribosomes—RNA Machines that Survive Evolution Pressure
“I want to talk to you about a machine,” said Ada Yonath of the Weizmann Institute in Israel, at the start of her plenary lecture. The machine that Yonath, the 2009 Nobel Laureate in Chemistry, was eager to discuss was the ribosome. “Ribosomes, the largest molecular complexes in cells, are nano-machines,” she said. “They are the universal factories that produce proteins continuously by decoding the genetic information in all living cells.” The millions of ribosomes in each living human cell can make 15 to 40 peptide bonds in one second with only one mistake in a million attempts. In contrast, Yonath offered this story from her personal experience: “When I was a student, one of our exercises was to make a peptide bond. It took me 8 hours to make one peptide bond, and I was a good student.” The lab manual she used said that a 50% error rate was acceptable—far from the one-in-a-million error rate that ribosomes routinely achieve.
Yonath then described the basic workings of a ribosome. Messenger RNA (mRNA) carries the genetic code, and many ribosomes run along it working together as polysomes. Then transfer RNA (tRNA) connects to the mRNA and enters the first part of the ribosome, called the small ribosome sub-unit. Each ribosome is composed of two structures: the small ribosome subunit and the large ribosome subunit. The small subunit in a bacteria consists of one RNA chain about 1,600 nucleotides long; the large subunit in a bacteria consists of two RNA chains with approximately 3,000 nucleotides. The subunits come together to translate the information coming in on the tRNA into proteins. The newly formed proteins then exit through a tunnel in the large subunit of the ribosome, and eventually the small and large subunits separate. Yonath showed a brief movie clip detailing this fascinating process.
The most intriguing part of an already great lecture was still to come. Yonath described how she had identified a highly conserved, semi-symmetrical region in the ribosome that was a remnant of a pre-biotic bonding apparatus called the “proto-ribosome.” “The proto-ribosome exists and functions within the contemporary ribosome,” she said. “It started functioning billions of years ago, before there was life.” By studying 930 different species, she found that the proto-ribosome was conserved at a 98% level in all of them. Thus, the proto-ribosome was the first, primitive self-replicating part of cellular machinery – a dimeric enzyme, or catalyst. “Nature devised a way to take a lousy protein machine[the proto-ribosome] and turn it into an excellent protein machine [the current ribosome],” Yonath said. She calls this concept “Pre-Darwinian Darwinism.” “Usually, evolution is associated with species,” she said. “This is Darwinism of molecules.”
Seventh Plenary Lecture: Jean M.J. Frechet
The Design of Functional Macromolecules: from Energy Conversion to Therapeutics
“Can a system be designed for the direct conversion of light into work—motion?” This is the question that Jean M.J. Frechet of King Abdullah University of Science and Technology, Saudi Arabia, asked at the start of his plenary lecture. He soon told the audience that the answer is “yes,” and he had the video evidence to prove it. It showed a person moving a magnifying glass to focus sunlight on an “optothermal boat” made of PDMS polymer and carbon nanotubes, which were added to increase the light absorbance. The boat moved back and forth depending on which part of its structure the beam was focused.
This technology is based on the use of light to change surface tension. The optothermal boat is placed on water, and a surface tension develops between them. By shining light on the boat, it heats up, changing the surface tension, and causing the boat to move in the desired direction. Frechet said that this system has been used to make rotors that act as pumps for microfluidics applications.
His second example of designing functional macromolecules was the “site isolation concept” for producing white organic light emitting diodes (OLEDs). The challenge was in mixing chomophore colors to create a single layer of material that emits white light. Mixing red ,green, and blue chromophores results in the emission of only red light, because the higher energy emissions of the blue and green chromophores are absorbed by the red ones. The solution was to isolate the chromophores by encasing them in diblock copolymer shells. Using iridium as the substrate, lamellae of red polymers separated a sufficient distance from blue polymer layers minimized the energy transfer from blue to red. The result was a white OLED. “Domain spacing is the key to performance here,” Frechet said. “You must space the polymers appropriately using molecular design.”
Finally, Frechet described his team’s efforts to enhance the effectiveness of chemotherapeutic drugs to kill cancer cells using molecular size as the main parameter. Tumor tissue is hungry for food, so it has lots of “leaky” vasculature, while in healthy tissue the veins do not leak. They chose branched polymer-drug conjugate structures to control the passage of the structures though pores. When designed to the right size, these macromolecules will penetrate the leaky pores in tumor vasculature to deliver the cancer killing drug to its intended target, while simultaneously leaving healthy tissue untouched because they cannot penetrate the smaller pores in healthy vasculature. Branched polymers with two arms had a lifetime in the tumor of 1.5 hours, while those with 4 arms lasted 24 hours, leading to the conclusion that shape has a large effect on the efficiency of the macromolecules. The polymer-drug dendrimers were also engineered to release the chemotherapy drug doxorubicin in the optimal time range of 10 to 15 hours. The researchers found that the dendrimer-linked doxorubicin was much more effective at killing tumor cells than unmodified doxorubicin. Animal trials showed a much higher survival rate when a drug was linked to such a polymer system.
Eighth Plenary Lecture: Klaus von Klitzing
Nobel Prizes, Advanced Materials, and the New Kilogram
In what was surely the most humorous, though still highly informative, plenary lecture of the week, Klaus von Klitzing of the Max Planck Institut für Festkörperforschung in Germany regaled the audience with stories of what it’s like being a Nobel Laureate. The winner of the 1985 Nobel Prize in Physics for the discovery of the Quantum Hall Effect (QHE), von Klitzing pulled his Nobel Medal from his pocket to show the audience, making one wonder if he always carries it with him. “The real value of the Nobel Prize” he said, “is having some extra time to talk at conferences.” As evidence, he showed the cover of a published paper whose conclusion was that Nobel Laureates lived, on average, one to two years longer than scientists who never won the prize.
He then went on to discuss the Quantum Hall Effect and its importance as a fundamental constant. In 1980, he discovered that under QHE conditions, the Hall resistance, RH, always has the fundamental value of 25812.807, which is precisely equal to h/e2. This makes an integrated quantized circuit based on QHE a perfect device to calibrate electrical measurements all over the world with extremely high accuracy.
This brought his talk around naturally to the discussion of international standards measurements, with specific emphasis on the kilogram. Prof. von Klitzing said that he visited the Bureau International de Poids et Measures in Paris in recent years, and got to see for himself the “kilogram prototype” stored in a vault there, along with the complex process of accessing the vault, which involves multiple officials with keys and codes that rivals what one suspects is involved in a nuclear missile launch. In a video he showed, a group of scientists walk to the basement of the building where the prototype kilogram is stored, and clap when the vault finally opened. “Everyone wants to look,” von Klitzing quipped, “because if it disappears no one will know what the kilogram is.”
But, in fact, no one does know what the kilogram is. The mass of the prototype has changed with time, possibly due to emission of trapped gases. So scientists are now trying to define a “new kilogram” based on the Planck constant, h. Tests have been ongoing at standards laboratories around the world to fix the value of h by various methods, including the use of Watt balances based on highly reproducible Josephson junction voltages and QHE resistances. The different values reported for h from the various labs is an excellent lesson in the difficulty of making measurements and producing standards. An alternative method is based on the relationship between the value of Avogadro’s number (which has also been measured more precisely in recent years) and Planck’s constant. A meeting is scheduled in Paris on October 17, 2011, to develop a new SI system based on fundamental constants rather than samples stored in vaults. “The Quantum Hall Effect will play an important role in our new international system of units, “ von Klitzing concluded.
Ninth Plenary Lecture: Freddy, Yin Chiang Boey
Biodegradable Cardiovascular Implants
Following von Klitzing’s entertaining act was a tough assignment, but Freddy, Yin Chang Boey of the Nanyang Technological University, Singapore, succeeded nicely. Boey became interested in the biomedical field when his sister was dying of lung cancer, and he asked the doctors why they couldn’t implant a device near the tumor to meter out the chemotherapeutic agents at an optimal rate. When the doctors told him that such technology didn’t exist, Boey resolved to dedicate his research to finding materials solutions to biomedical challenges. Following this resolution has led him to the study of biodegradable cardiovascular implants (stents), and to the founding of Amaranth Medical, Inc., in Mountain View, California.
Most stents in use today are metallic. “The problem is that a few months after it is inserted, a stent becomes a liability, but you can’t remove it,” Boey said. He explained that scars sometimes form around the stent, blocking the artery it was supposed to open. The drugs that are added to the surface of the stent can prevent scarring, but they sometimes also prevent the beneficial formation of a protective layer of endothelial cells over the stent. The endothelial cells remove the foreign agent factor from consideration, because once the stent is covered with a smooth layer of cells, the blood comes into contact with cells instead of metal. Studies have shown that after 3 to 6 months the blood vessel has recovered enough to no longer need the stent, but removal is impossible due to the damage it would cause. For Boey, this clearly indicated that a biodegradable polymer stent needed to be developed. “We were materials scientists who had no knowledge of the heart,” he said of his team of researchers, “but we did know how to make layered structures.”
The goal was a stent that self-expanded at body temperature, maintained its structural integrity for 3 to 6 months, fully degraded after 9 months, and released multiple drugs at controlled rates over the life of the stent. So they experimented with double-layered hollow tubes, with the interior layer made of the polymer PLA and the outer layer of PLGA, both biodegradable polymers. By varying the thickness of the layers, the rate of degradation in the body can be controlled. Also, the polymers have the benefit of incorporating drugs into their structures, which is an improvement over metal stents that can only support drugs on their surfaces. This allows the doctor to infuse a higher concentration of drugs into a layer, and to vary the drug type from layer to layer if desired.
Boey reported great success with this approach so far in test done on animals. The polymer stents self-expand in 3 to 10 minutes to open the clogged vessel; they degrade layer-by-layer at rates controlled by the thickness and composition of the layers; they deliver high concentrations of drugs for a long period of time; they encourage overgrowth of a protective epithelial layer; and they biodegrade inside this epithelial pocket so the degradation byproducts don’t enter the blood stream, where they might cause a stroke. Cross sections of removed blood vessels show an open artery and good blood flow in the region of the degraded stent after 60 days in animal studies. Much more testing must be done before these bidegradable polymer stents might be ready for use in humans.
Symposium A: Nanostructured Oxides, Interfaces, Heterostructures, and Devices
Electric Field Induced Metallization of Vanadium Dioxide and Vanadium Sesquioxide on Ultrashort Timescales
Metal-insulator transitions can be induced by a number of means in a number of materials, but Stuart Parkin of IBM Research, USA, thinks they've found a new one. Speaking at a characteristic rapid-fire pace, Parkin showed new results on VO2 and V2O3, in which they believe a mechanism based on Zener tunelling is responsible for the observed metal-insulator transition. For films grown by PLD and MBE, they measure the resistivity as a function of applied electric field and observe a shift in the transition temperature relative to the bulk materials. The critical field-strength for transition can be varied by oxygen pressure during growth, which adjusts the film stoichiometry.
These films of VO2 and V2O3 are noteworthy on their own, but the surprise, Parkin showed, is in the details. They find that as the electric field is turned on, the resulting current through the films initially decreases. Once critical potential is reached, the current shoots up like a regular Mott insulator. This unusual “incubation period” before the transition is not consistent with the usual models for metal-insulator transitions. They describe it with a new model: Highly localized d electrons undergo Zener tunneling as the field is applied, becoming localized in a now-filled d-band of a neighboring atom rather than contributing to a current. Thus a higher field is required before critical carrier densities are reached for metallic behavior. The model is consistent with their computational investigations, and they are now expanding to related metal-insulator systems for further confirmation.
Panel members of the Education Forum, designed to discuss the best practices for teaching materials science by comparing methods used around the world. (Left to right: session moderator John Baglin, United States; Tadashi Itoh, Japan; Andrew Wee, Singapore; G.U. Kulkarni, India; John Shapter, Australia; Steven Fonash, United States; and Meifang Zhu, China)
Symposium B: Synthesis and Architecture of Nanomaterials
Control Over Surface Plasmon Resonance Wavelengths of Conductive Nanoparticles
Conductive metal nanoparticles are incredibly interesting due to their tunable surface properties. In a nanoparticle, absorbed light can collectively oscillate the electrons on the surface of a metal, called localized surface plasmon resonance (LSPR). This is important because in the local area of the excitation on the metal surface, and the surrounding area, the electric fields become enormous, enhanced by several orders of magnitude, which can lead to enhanced electric, optical, and chemical properties.
According to Toshiharu Teranishi of Tsukuba University in Japan, it is possible to selectively tune the LSPR across a broad light spectrum by many different methods. The first and the most obvious ways are to change nanoparticle size or shape, since LSPR is an inherent surface effect. Also, changing the surrounding solvent or bringing two nanoparticles in close proximity will achieve enhanced LSPR. Another interesting method that Teranishi promotes is changing the charge carrier density. Gold and silver nanoparticles have carrier densities on the order of 1023, which naturally make their LSPR occur in the visible range, and they have been well researched. Teranishi uses these metals and others to tune the UV-visible wavelengths. However, the carrier density in conductive metal oxides/sulfides is two orders of magnitude less (~1021) and thus he uses them to tune LSPR in the near infrared region, something that has never been accomplished before. Indium tin oxide (ITO) spheres and copper sulfide (Cu7S4) disks were used for this purpose. Introducing defects as charge carriers led to the fine tunability of the LSPR in this newly accessible region. From a fundamental standpoint this is interesting because, as any IR spectroscopist knows, a wealth of molecules have natural resonant vibrational modes in the IR and NIR wavelength region. The variety of nanoparticles and the visual beauty of their reproducibility in size was truly remarkable.
The Ferris wheel on the marina, Singapore
Synthesis and Plasmonic Properties of Aluminum Nanoparticles
Working at the other end of the visible wavelength spectrum, Ravi Soni of the Indian Institute of Technology in Delhi, used a much different technique to tune the plasmon resonance of aluminum nanoparticles. Below 400 nm wavelengths (approaching UV), aluminum nanoparticles can outperform silver by 100 times in terms of local electric field enhancement, making them extremely attractive for Raman scattering applications. It is also noteworthy that aluminum is an extremely commercially cheap metal.
Soni and colleagues used laser ablation of an aluminum metal target to systematically control the size and shape of aluminum particles. Solid spheres as well as hollow spheres were investigated. The plasmon tuning was performed by controlling the amount of oxide content in the aluminum particles, which was easily performed by adjusting the ethanol content of the water solution. The laser ablation technique is very different from wet chemical methods, and it is completely green since there are no surfactants or chemical byproducts, and the particles are well-stabilized by adsorbed surface charge.
Strolling to the next symposium
Record Properties of Layer-by-layer Assembled Nanocomposites: From Bio to Energy
A simple and straightforward method to manufacture something large from individual small components is to simply stack them on top of one another. Instead of one solid piece of material, this method results in a more deformable material with far more interfacial regions than a solid, rigid single unit. This is the simple structure of a brick building: many small pieces glued together at their surface to form a strong structure.
The bricklaying technique on the nano and microscale is called layer-by-layer (LBL) assembly, and it surprisingly bestows the final material with some remarkable properties, owing to the ability to tune the interfacial as well as constituent particle properties. Nicholas Kotov of the University of Michigan could not have driven this point home clearer. Layering carbon nanotubes or grapheme sheets can create composite materials that have tensile strength and stiffness that are close to steel. He demonstrated almost-shatter-proof glass by showing side-by-side images of a bullet passing through plate glass and (amazingly) transparent LBL glass. The constant emphasis on the increased interface of LBL assemblies and how it is a universal phenomenon was very intriguing. By increasing the interface activity in a material one can tune the mechanical properties and achieve increased strength, flexibility, lower weight, and greater biocompatibility. Although still in their infancy, neural implants have shown marked increase in biocompatibility, corrosion resistance, and charge capacity, all due to LBL assembly methods.
On a lab tour of the Center for Ion Beam Applications at the National University
Singapore, Jeroen van Kan explains his 4-line proton beam instrumentation
Symposium F: Toxicology of Engineered Nanomaterials
Effects of Size and Exposure Routes of Gold Nanoparticles on Biodistribution and Gene Expression
As nanoparticles have been slowly introduced to the public, concern over their toxicity to humans (and the environment) has been on the rise. Naturally, many particles are more toxic the smaller they get, since the chemically active surface increases exponentially. Also, the surfactants or surface ligands can incur some inherent toxic effects. Most synthetic methods for aqueous gold or silver use citrate or PVP, which are very safe for humans; they are vitamin C and food packaging material, respectively. However, a systematic study is still necessary. Gold itself isn’t toxic, but that is because it is rarely absorbed into cells, but what about small gold particles?
Particles with diameters of 20 nm and 7 nm were aggregated and introduced into rats through inhalation and injection. Naturally, Suresh Balasubramanian and researchers of the National University of Singapore found that inhaled particles tend to accumulate primarily in the lungs and olfactory bulb (nasal pathway), although some were transported through the bloodstream to the aorta, spleen, kidneys, etc. Injected particles tended to follow the blood stream and deposit in organs across the body, although some made it back to the lungs. Surprisingly, very few nanoparticles were found in the urine of the animals, which means that they are not passing through the animal at all. An interesting question, which might lead to interesting possibilities for treatment of brain conditions with gold nanoparticle drug delivery is: what is the critical diameter for an injected nanoparticle to pass through the blood brain barrier?
Symposium I: Semiconductor Nanowires and Heterostructures: Synthesis, Properties and Multifunctions
Semiconductor Nanowire Fabric
Nanowires are a delicately synthesized structure. Careful and tedious control must be given to ensure uniform size and aspect ratio, and it seems to be almost more art than science at times. As was pointed out in an earlier eScene Newsletter this week, Brian Korgel’s group at the University of Texas at Austin made the point that even chemical suppliers cannot consistently provide starting materials that create nanorods (shorter nanowires) reproducibly. Producing them on the gram scale, which commercial processing will soon demand, seems unfeasible.
However, Korgel’s group has developed a method to create silicon and germanium nanowires that are around 50 nm in diameter and 100 micrometers in length. They also produce a gram of the material, which comes out looking like a wet, matted hairball. It can be dissolved onto a substrate and cut out to resemble a swatch of cloth, and on the nanoscale it resembles a woolen-like textile. They are highly charged, can conduct electricity, and in terms of elastic modulus they are nearly on par with carbon nanotubes. Several fascinating movies were shown of the fabric bending, folding, tearing, and breaking when modified chemically. Individual nanowire mechanical properties such as bending, resonant vibrating, and others were also presented. The material is truly novel, and the ability to synthesize single crystal nanowires on a gram scale is very promising for industry.
Waiting for the banquet doors to open
Symposium K: Nanotechnology with Soft Matter
Direct Characterization of Enhanced Electromagnetic Fields on Single Ag Nanostructure
It seems that no matter what symposia one goes to, people are talking about nanoparticles and their electric field enhancement. Most scientists are only measuring the absorbance and emission spectra of these particles though. Direct quantification and measurement of field enhancement of individual nanoparticles is tough indeed. However, the effects of enhanced electric fields due to nanoparticles are staggering. In surface-enhanced Raman scattering (SERS), if you have 1,000,000 molecules, less than 100 of those molecules, which are specifically trapped in so called electric field “hot spots,” can contribute the majority of the scattering intensity. So creating a single hot spot, or controllable hot spot, is a high priority and pressing research issue.
This is exactly what W. David Wei of the University of Florida has done. A silver film, with a single silver nanoparticle shaped like the top half of an eggshell, was measured with laser scattering and a homebuilt two-photon photoemission electron microscopy apparatus. The measurement of local field enhancement was 4 times that of the surrounding silver film, and was also found to be highly polarization dependent. This is one of the first few quantitative measurements of a single nanostrucure’s effect on field enhancement. Hopefully, this technique can be applied to arrays of particles as well, to determine field enhancement from coupled particle structures, which might have serious implications for future hard disk memory applications.
Enjoying the indoor architecture
Symposium M: Nanonets and Nanomaterials for Energy Harnessing and Storage
Nanomaterials for Battery Electrodes: The Characterization Challenge
Beyond pulling in grant money, what use is “nano” when it comes to batteries? That provocative question was at the heart of a talk by Petr Novak of the Paul Scherrer Institute, Switzerland. At the outset of his talk, Novak made a careful analysis of the benefits and drawbacks of nanoparticles for batteries. If diffusion in the solid state of a material is important, then nano-sizing may be useful, but the energy density of a system of nanoparticles will always be lower than the bulk. Novak cited the Li/O reaction as the theoretical maximum for a Li system, with roughly 7200 Wh/kg energy density, or 2000 Wh/kg specific energy density. No amount of nano-sizing will improve that scenario. Given their greater surface areas, aging will also be a bigger problem for nanoparticles of any material.
Nano-structuring, however, can be effective, Novak said. He recommended “going nano” with the primary structures, but “going micro” for the final device. As an example, he showed improved capacity of Li1.1V3O8 when fabricated as nanoparticles which then agglomerate into larger structures, resulting in short diffusion paths and very high surface conductivity. The key to advancing battery research, Novak stated, is understanding what's inside these systems. He showed a broad sampling of his own work to that end, developing in-situ methods for characterization of materials and structures at scales of nano and up.
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High-performance Nanostructured Anodes, Cathodes and Thermal Protectants for Li-ion Batteries: Fabrication by Novel Bio-inspired, Kinetically Controlled, Low-temperature Catalysis
Marine sponges might seem far removed from the world of high-tech materials, but for Daniel Morse of the University of California, Santa Barbara (USA), they provide a critical inspiration. Close examination of these sponges reveal a skeleton of nanostructured silicon that looks like woven glass and is very strong and light-weight, grown without caustic chemicals or extreme conditions. The keys to growth, Morse found, are a slow rate and vectorial control to regulate orientation and connectivity. Morse applied these lessons to synthetic growth, growing nanostructures in aqueous environments driven by a concentration gradient of the catalyst.
The results can be stunning. As an example, Morse showed Co(OH)2 nanostructures thus grown, formed as a cluster of highly crystalline plates, with potential application in photocatalysis and photovoltaics. The slower the growth rate, the higher the ratio of tetrahedral to octahedral coordinated Co. For battery applications, he showed they can grow uniformly disperse Sn nanoparticles in-situ on graphite, preserving the crystallinity and porosity of the graphite. The material exhibits very good properties for battery applications, including full recovery of capacity after very high discharge rates.
Synthesis and Visible Light Photocatalytic Activities of Bismuth Doped NaTaO3 Powders
In the numerous sustainable-energy talks this week, photoelectrolysis made only a modest appearance. Pushkar Kanhere made a compelling case for its relevance, however, pointing out that direct solar-to-hydrogen energy conversion using water would be both clean and sustainable. With refreshing clarity, he presented his work on Bi-doping NaTaO3 to reduce the bandgap for solar water-splitting. He showed two doping approaches, a high-temperature solid-state route and a low-temperature hydrothermal route. For both, he identified optimal parameters of a Bi concentration around 7.5% and an intermediate Na content, such that Bi occupies both Na and Ta sites. The reactivities were evaluated based on hydrogen evolution from methanol, not water, and under “near visible” illumination, which Kanhere admits is only a first step, but the preliminary results look promising.
Playing along with the percussion band at the banquet
Symposium N: Advanced Materials for Energy Storage Systems
Potentiality of Organic Electrode Materials for a "Greener" Electrochemical Storage System
Philippe Poizot of the University of Picardie, France, wants to “decarbonize” electricity generation and transport. Large-scale use of renewable energy will require improved electrical energy storage, and Poizot wants that part of the problem to have a "green" solution, too. He's therefore investigating organic electrode materials that come from plants. The benefits to the approach, he stated, are the great number of chemical combinations and redox potentials available, abundant resources, and the ease of recycling. The drawbacks are lower energy density, potential for instability and side reactions, and the solubility of the electrode materials in common electrolytes. Poizot's work has focused on 1,4-quinone-type units, using simple synthesis reactions and testing the resulting electrochemistry. Some results are promising and Poizot is optimistic, though the solubility problem remains an issue.
Symposium O: Photovoltaic Materials and Devices
Starting a PV Module Manufacturing Company in Singapore - Challenges and Opportunities
Taking a break from scientific research, an attentive audience learned from Lean Chooi Loh about the practical considerations involved in starting a company in photovoltaics. Loh founded the company PV World three years ago. During those years, the solar industry boomed and contracted, and boomed again, Loh said. He described the wild atmosphere in 2008, when “euphoria in solar industries began to reach irrational levels,” and the ensuing fall-out when the market couldn't absorb the rapid growth.
Loh went on to lay out the important things to consider when starting a company in solar, from the level of automation used in production to targeting mass versus niche markets. When it comes to business ventures in Singapore, specifically, Loh pointed out the good and the bad. Compared to most of Asia, the land and labor are very expensive, but Singapore boasts strong research and development in solar, and a “made in Singpore” vintage carries a good deal of market clout. The strongest take-home message was that you need deep pockets for this kind of endeavor. Minimize borrowing from the bank, Loh said, and plan to have enough capital to ride out the inevitable waves.
Symposium II: Computational Science of Transport Phenomena in Materials
Investigation of Binary and Ternary Shape Memory Alloys Using TBLMTO and VASP
Rita John of the University of Madras, India, is using the power of first-principles calculations to tackle shape-memory alloys, materials which recover their original shape on heating. A staple of materials outreach programs, these exotic materials also find a number of technical applications. John works on systems of Ti alloyed with a wide sampling of the transition metals. Within first-principles methodologies, she calculates heats of formation of the alloys in cubic, orthorhombic and monoclinic crystal structures, and identifies trends as a function of the d-electron count. She presented preliminary investigations, including a dizzying array of band-structure and density-of-states calculations, searching for trends on which to build a physical understanding.
Slide from K. von Klitzing's Plenary Lecture
Research on III-V-Based Concentrator Solar Cells
Andreas Bett of the Fraunhofer Institute for Solar Energy Systems, Germany, is also pursuing ambitious goals for photovoltaics. He first showed off the impressive facilities at Fraunhofer for fabrication and testing of solar cells, then made the case for III-V multijunction cells. The high efficiency and low weight (important for space applications) of III-V solar cells make them some of the best around, but their use in large-scale power production is prevented by the high cost of the Ge substrate. However, Bett showed a way around this by shrinking the cells and implementing on-board solar concentrators that provide a 500- to 1000-times concentration. The resulting cells are fabricated at high densities -- 1200 on a single 4-inch Ge wafer -- and have been deployed in centralized power stations in the US. He cited 25% AC efficiencies and an energy payback time of less than 10 months as overwhelming motivators for the technology.
Bett's work on solar cells has two goals: improving efficiency and reducing cost. The industry standard today is 38 to 40% efficiency, in GaInP/GaInAs/Ge multijunction cells. Bett outlined three thrusts of their work at Fraunhofer, aiming to exceed the industry standard. The first is lattice mismatch, in which buffer layers are used to marry layers with differing lattice constants. The second is using more layers to capture more of the solar spectrum, and the third is development of III-V solar cells on Si by direct wafer bonding.
Suntec Singapore Convention Center
Scanning the Meeting
We all had a great time at the 2011 ICMAT in Singapore. See you in 2013!
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The Meeting Scene e-newsletter of the Materials Research Society (MRS) presents news from MRS and other conferences directly from the conference venue.
This work was partially supported by the IMI Program of the National Science Foundation under Award No. DMR 08-43934. Specifically, the work of Apprentice Science Reporters Alison Hatt and Matthew Martin was funded under this NSF award, which is managed by the International Center for Materials Research, University of California, Santa Barbara, USA.
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