Posts Tagged ‘Lawrence Berkeley National Laboratory’

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Integrated artificial photosynthesis nanosystem, a first for Lawrence Berkeley National Laboratory

Friday, May 17th, 2013

There’s such a thing as too much information and not enough knowledge, a condition I’m currently suffering from with regard to artificial photosynthesis. Before expanding on that theme, here’s the latest about artificial photosynthesis from a May 16, 2013 Lawrence Berkeley National Laboratory news release (also available on EurekAlert),

In the wake of the sobering news that atmospheric carbon dioxide is now at its highest level in at least three million years, an important advance in the race to develop carbon-neutral renewable energy sources has been achieved. Scientists with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have reported the first fully integrated nanosystem for artificial photosynthesis. While “artificial leaf” is the popular term for such a system, the key to this success was an “artificial forest.”

Here’s a more detailed description of the system, from the news release,

“Similar to the chloroplasts in green plants that carry out photosynthesis, our artificial photosynthetic system is composed of two semiconductor light absorbers, an interfacial layer for charge transport, and spatially separated co-catalysts,” says Peidong Yang, a chemist with Berkeley Lab’s Materials Sciences Division, who led this research. “To facilitate solar water- splitting in our system, we synthesized tree-like nanowire  heterostructures, consisting of silicon trunks and titanium oxide branches. Visually, arrays of these nanostructures very much resemble an artificial forest.”

…

… Artificial photosynthesis, in which solar energy is directly converted into chemical fuels, is regarded as one of the most promising of solar technologies. A major challenge for artificial photosynthesis is to produce hydrogen cheaply enough to compete with fossil fuels. Meeting this challenge requires an integrated system that can efficiently absorb sunlight and produce charge-carriers to drive separate water reduction and oxidation half-reactions.

More specifically,

“In natural photosynthesis the energy of absorbed sunlight produces energized charge-carriers that execute chemical reactions in separate regions of the chloroplast,” Yang says. “We’ve integrated our nanowire nanoscale heterostructure into a functional system that mimics the integration in chloroplasts and provides a conceptual blueprint for better solar-to-fuel conversion efficiencies in the future.”

When sunlight is absorbed by pigment molecules in a chloroplast, an energized electron is generated that moves from molecule to molecule through a transport chain until ultimately it drives the conversion of carbon dioxide into carbohydrate sugars. This electron transport chain is called a “Z-scheme” because the pattern of movement resembles the letter Z on its side. Yang and his colleagues also use a Z-scheme in their system only they deploy two Earth abundant and stable semiconductors – silicon and titanium oxide – loaded with co-catalysts and with an ohmic contact inserted between them. Silicon was used for the hydrogen-generating photocathode and titanium oxide for the oxygen-generating photoanode. The tree-like architecture was used to maximize the system’s performance. Like trees in a real forest, the dense arrays of artificial nanowire trees suppress sunlight reflection and provide more surface area for fuel producing reactions.

“Upon illumination photo-excited electron−hole pairs are generated in silicon and titanium oxide, which absorb different regions of the solar spectrum,” Yang says. “The photo-generated electrons in the silicon nanowires migrate to the surface and reduce protons to generate hydrogen while the photo-generated holes in the titanium oxide nanowires oxidize water to evolve  oxygen molecules. The majority charge carriers from both semiconductors recombine at the ohmic contact, completing the relay of the Z-scheme, similar to that of natural photosynthesis.”

Under simulated sunlight, this integrated nanowire-based artificial photosynthesis system achieved a 0.12-percent solar-to-fuel conversion efficiency. Although comparable to some natural photosynthetic conversion efficiencies, this rate will have to be substantially improved for commercial use. [emphasis mine] However, the modular design of this system allows for newly discovered individual components to be readily incorporated to improve its performance. For example, Yang notes that the photocurrent output from the system’s silicon cathodes and titanium oxide anodes do not match, and that the lower photocurrent output from the anodes is limiting the system’s overall performance.

“We have some good ideas to develop stable photoanodes with better performance than titanium oxide,” Yang says. “We’re confident that we will be able to replace titanium oxide anodes in the near future and push the energy conversion efficiency up into single digit percentages.”

Now I can discuss my confusion, which stems from my May 24, 2013 posting about work done at the Argonne National Laboratory,

… Researchers still have a long way to go before they will be able to create devices that match the light harvesting efficiency of a plant.

One reason for this shortcoming, Tiede [Argonne biochemist David Tiede] explained, is that artificial photosynthesis experiments have not been able to replicate the molecular matrix that contains the chromophores. “The level that we are at with artificial photosynthesis is that we can make the pigments and stick them together, but we cannot duplicate any of the external environment,” he said.  “The next step is to build in this framework, and then these kinds of quantum effects may become more apparent.”

Because the moment when the quantum effect occurs is so short-lived – less than a trillionth of a second – scientists will have a hard time ascertaining biological and physical rationales for their existence in the first place. [emphasis mine]

It’s not clear to me whether or not the folks at the Berkeley Lab bypassed the ‘problem’ described by Tiede or solved it to achieve solar-to-fuel conversion rates comparable to natural photosynthesis conversions. As I noted, too much information/not enough knowledge.

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Bubblicious

Friday, May 10th, 2013

Mathematicians love their bubbles according to the May 9, 2013 news release on EurekAlert,

Two University of California, Berkeley, researchers have now described mathematically the successive stages in the complex evolution and disappearance of foamy bubbles, a feat that could help in modeling industrial processes in which liquids mix or in the formation of solid foams such as those used to cushion bicycle helmets.

Applying these equations, they created mesmerizing computer-generated movies showing the slow and sedate disappearance of wobbly foams one burst bubble at a time.

The applied mathematicians, James A. Sethian and Robert I. Saye, will report their results in the May 10 issue of Science. Sethian, a UC Berkeley professor of mathematics, leads the mathematics group at Lawrence Berkeley National Laboratory (LBNL). Saye will graduate from UC Berkeley this May with a PhD in applied mathematics.

The May 9, 2013 University of California Berkeley news release by Robert Sanders, which originated the news release on EurekAlert, describes a serious side to the work,

“This work has application in the mixing of foams, in industrial processes for making metal and plastic foams, and in modeling growing cell clusters,” said Sethian. “These techniques, which rely on solving a set of linked partial differential equations, can be used to track the motion of a large number of interfaces connected together, where the physics and chemistry determine the surface dynamics.”

The problem with describing foams mathematically has been that the evolution of a bubble cluster a few inches across depends on what’s happening in the extremely thin walls of each bubble, which are thinner than a human hair.

“Modeling the vastly different scales in a foam is a challenge, since it is computationally impractical to consider only the smallest space and time scales,” Saye said. “Instead, we developed a scale-separated approach that identifies the important physics taking place in each of the distinct scales, which are then coupled together in a consistent manner.”

Saye and Sethian discovered a way to treat different aspects of the foam with different sets of equations that worked for clusters of hundreds of bubbles. One set of equations described the gravitational draining of liquid from the bubble walls, which thin out until they rupture. Another set of equations dealt with the flow of liquid inside the junctions between the bubble membranes. A third set handled the wobbly rearrangement of bubbles after one pops.

Using a fourth set of equations, the mathematicians solved the physics of a sunset reflected in the bubbles, taking account of thin film interference within the bubble membranes, which can create rainbow hues like an oil slick on wet pavement. Solving the full set of equations of motion took five days using supercomputers at the LBNL’s National Energy Research Scientific Computing Center (NERSC).

The mathematicians next plan to look at manufacturing processes for small-scale new materials.

Here’s a still image from the video the researchers created to demonstrate their work on soap bubble clusters,

A soap bubble cluster shown with physically accurate thin-film interference, which produces rainbow hues like an oil slick on pavement. A beach at sunset is reflected in the bubbles. Courtesy: UC Berkeley

A soap bubble cluster shown with physically accurate thin-film interference, which produces rainbow hues like an oil slick on pavement. A beach at sunset is reflected in the bubbles. Courtesy: UC Berkeley

You can find the full animation here.

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Disorder engineering turns ‘white’ nanoparticles to ‘black’ nanoparticles for clean energy

Wednesday, April 10th, 2013

Titanium dioxide crystals are white, except when they’re black. According to an Apr. 10, 2013 news item on Nanowerk, researchers at the Lawrence Berkeley National Laboratory (US) have found a way to change white titanium dioxide crystals to black thereby changing some of their properties,

A unique atomic-scale engineering technique for turning low-efficiency photocatalytic “white” nanoparticles of titanium dioxide into high-efficiency “black” nanoparticles could be the key to clean energy technologies based on hydrogen.

Samuel Mao, a scientist who holds joint appointments with Berkeley Lab’s Environmental Energy Technologies Division and the University of California at Berkeley, leads the development of a technique for engineering disorder into the nanocrystalline structure of the semiconductor titanium dioxide. This turns the naturally white crystals black in color, a sign that the crystals are now able to absorb infrared as well as visible and ultraviolet light. The expanded absorption spectrum substantially improves the efficiency with which black titanium dioxide can use sunlight to split water molecules for the production of hydrogen.

The Apr. 10, 2013 Berkeley Lab news release, which originated the news item, provides more detail about how this discovery might have an impact on clean energy efforts,

The promise of hydrogen in batteries or fuels is a clean and renewable source of energy that does not exacerbate global climate change. The challenge is cost-effectively mass-producing it. Despite being the most abundant element in the universe, pure hydrogen is scarce on Earth because hydrogen combines with just about any other type of atom. Using solar energy to split the water molecule into hydrogen and oxygen is the ideal way to produce pure hydrogen. This, however, requires an efficient photocatalyst that water won’t corrode. Titanium dioxide can stand up to water but until the work of Mao and his group was only able to absorb ultraviolet light, which accounts for barely ten percent of the energy in sunlight.In his ACS [American Chemical Society]  talk [at the 245th meeting, Apr. 7 - 11, 2013], titled “Disorder Engineering: Turning Titanium Dioxide Nanoparticles Black,” Mao described how he developed the concept of “disorder engineering,” and how the introduction of hydrogenated disorders creates mid-band gap energy states above the valence band maximum to enhance hydrogen mobility. His studies have not only yielded a promising new photocatalyst for generating hydrogen, but have also helped dispel some widely held scientific beliefs.

“Our tests have shown that a good semiconductor photocatalyst does not have to be a single crystal with minimal defects and energy levels just beneath the bottom of conduction band,” Mao said.

Characterization studies at Berkeley Lab’s Advanced Light Source also helped answer the question of how much of the hydrogen  detected in their experiments comes from the photocatalytic reaction, and how much comes from hydrogen absorbed in the titanium oxide during the hydrogenation synthesis process.

“Our measurements indicate that only a very small amount of hydrogen is absorbed in black titanium dioxide, about 0.05 milligrams, as compared to the 40 milligrams of hydrogen detected during a 100 hour solar-driven hydrogen production experiment,” Mao said.

I must say, this ‘disorder engineering’ sounds much more appealing than some of the other disorders one hears about (e.g. personality disorders).

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Computer simulation errors and corrections

Thursday, January 3rd, 2013

In addition to being a news release, this is a really good piece of science writing by Paul Preuss for the Lawrence Berkeley National Laboratory (Berkeley Lab), from the Jan. 3, 2013 Berkeley Lab news release,

Because modern computers have to depict the real world with digital representations of numbers instead of physical analogues, to simulate the continuous passage of time they have to digitize time into small slices. This kind of simulation is essential in disciplines from medical and biological research, to new materials, to fundamental considerations of quantum mechanics, and the fact that it inevitably introduces errors is an ongoing problem for scientists.

Scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have now identified and characterized the source of tenacious errors and come up with a way to separate the realistic aspects of a simulation from the artifacts of the computer method. …

Here’s more detail about the problem and solution,

How biological molecules move is hardly the only field where computer simulations of molecular-scale motion are essential. The need to use computers to test theories and model experiments that can’t be done on a lab bench is ubiquitous, and the problems that Sivak and his colleagues encountered weren’t new.

“A simulation of a physical process on a computer cannot use the exact, continuous equations of motion; the calculations must use approximations over discrete intervals of time,” says Sivak. “It’s well known that standard algorithms that use discrete time steps don’t conserve energy exactly in these calculations.”

One workhorse method for modeling molecular systems is Langevin dynamics, based on equations first developed by the French physicist Paul Langevin over a century ago to model Brownian motion. Brownian motion is the random movement of particles in a fluid (originally pollen grains on water) as they collide with the fluid’s molecules – particle paths resembling a “drunkard’s walk,” which Albert Einstein had used just a few years earlier to establish the reality of atoms and molecules. Instead of impractical-to-calculate velocity, momentum, and acceleration for every molecule in the fluid, Langevin’s method substituted an effective friction to damp the motion of the particle, plus a series of random jolts.

When Sivak and his colleagues used Langevin dynamics to model the behavior of molecular machines, they saw significant differences between what their exact theories predicted and what their simulations produced. They tried to come up with a physical picture of what it would take to produce these wrong answers.

“It was as if extra work were being done to push our molecules around,” Sivak says. “In the real world, this would be a driven physical process, but it existed only in the simulation, so we called it ‘shadow work.’ It took exactly the form of a nonequilibrium driving force.”

They first tested this insight with “toy” models having only a single degree of freedom, and found that when they ignored the shadow work, the calculations were systematically biased. But when they accounted for the shadow work, accurate calculations could be recovered.

“Next we looked at systems with hundreds or thousands of simple molecules,” says Sivak. Using models of water molecules in a box, they simulated the state of the system over time, starting from a given thermal energy but with no “pushing” from outside. “We wanted to know how far the water simulation would be pushed by the shadow work alone.”

The result confirmed that even in the absence of an explicit driving force, the finite-time-step Langevin dynamics simulation acted by itself as a driving nonequilibrium process. Systematic errors resulted from failing to separate this shadow work from the actual “protocol work” that they explicitly modeled in their simulations. For the first time, Sivak and his colleagues were able to quantify the magnitude of the deviations in various test systems.

Such simulation errors can be reduced in several ways, for example by dividing the evolution of the system into ever-finer time steps, because the shadow work is larger when the discrete time steps are larger. But doing so increases the computational expense.

The better approach is to use a correction factor that isolates the shadow work from the physically meaningful work, says Sivak. “We can apply results from our calculation in a meaningful way to characterize the error and correct for it, separating the physically realistic aspects of the simulation from the artifacts of the computer method.”

You can find out more in the Berkeley Lab news release, or (H/T)  in the Jan. 3, 2013 news item on Nanowerk, or you can read the paper,

“Using nonequilibrium fluctuation theorems to understand and correct errors in equilibrium and nonequilibrium discrete Langevin dynamics simulations,” by David A. Sivak, John D. Chodera, and Gavin E. Crooks, will appear in Physical Review X (http://prx.aps.org/) and is now available as an arXiv preprint at http://arxiv.org/abs/1107.2967.

This casts a new light on the SPAUN (Semantic Pointer Architecture Unified Network) project, from Chris Eliasmith’s team at the University of Waterloo, which announced the most  successful attempt (my Nov. 29, 2012 posting) yet to simulate a brain using virtual neurons. Given the probability that Eliasmith’s team was not aware of this work from the Berkeley Lab, one imagines that once it has been integrated that SPAUN will be capable of even more extraordinary feats.

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Space-time crystals and everlasting clocks

Tuesday, September 25th, 2012

Apparently, a space-time crystal could be useful for such things as studying the many-body problem in physics.  Since I hadn’t realized the many-body problem existed and have no idea how this might affect me or anyone else, I will have to take the utility of a space-time crystal on trust.As for the possibility of an everlasting clock, how will I ever know the truth since I’m not everlasting?

The Sept. 24, 2012 news item on Nanowerk about a new development makes the space-time crystal sound quite fascinating,

Imagine a clock that will keep perfect time forever, even after the heat-death of the universe. This is the “wow” factor behind a device known as a “space-time crystal,” a four-dimensional crystal that has periodic structure in time as well as space. However, there are also practical and important scientific reasons for constructing a space-time crystal. With such a 4D crystal, scientists would have a new and more effective means by which to study how complex physical properties and behaviors emerge from the collective interactions of large numbers of individual particles, the so-called many-body problem of physics. A space-time crystal could also be used to study phenomena in the quantum world, such as entanglement, in which an action on one particle impacts another particle even if the two particles are separated by vast distances. [emphasis mine]

While I’m most interested in the possibility of studying entanglement, it seems to me the scientists are guessing since the verb ‘could’ is being used where they used ‘would’ previously for studying the many body problem.

The Sept. 24, 2012 news release by Lynn Yarris for the Lawrence Berkeley National Laboratory  (Berkeley Lab), which originated the news item, provides detail on the latest space-time crystal development,

A space-time crystal, however, has only existed as a concept in the minds of theoretical scientists with no serious idea as to how to actually build one – until now. An international team of scientists led by researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has proposed the experimental design of a space-time crystal based on an electric-field ion trap and the Coulomb repulsion of particles that carry the same electrical charge.

“The electric field of the ion trap holds charged particles in place and Coulomb repulsion causes them to spontaneously form a spatial ring crystal,” says Xiang Zhang, a faculty scientist  with Berkeley Lab’s Materials Sciences Division who led this research. “Under the application of a weak static magnetic field, this ring-shaped ion crystal will begin a rotation that will never stop. The persistent rotation of trapped ions produces temporal order, leading to the formation of a space-time crystal at the lowest quantum energy state.”

Because the space-time crystal is already at its lowest quantum energy state, its temporal order – or timekeeping – will theoretically persist even after the rest of our universe reaches entropy, thermodynamic equilibrium or “heat-death.”

This new development builds on some work done earlier this year at the Massachusetts Institute of Technology (MIT), from the Yarris news release,

The concept of a crystal that has discrete order in time was proposed earlier this year by Frank Wilczek, the Nobel-prize winning physicist at the Massachusetts Institute of Technology. While Wilczek mathematically proved that a time crystal can exist, how to physically realize such a time crystal was unclear. Zhang and his group, who have been working on issues with temporal order in a different system since September 2011, have come up with an experimental design to build a crystal that is discrete both in space and time – a space-time crystal.

Traditional crystals are 3D solid structures made up of atoms or molecules bonded together in an orderly and repeating pattern. Common examples are ice, salt and snowflakes. Crystallization takes place when heat is removed from a molecular system until it reaches its lower energy state. At a certain point of lower energy, continuous spatial symmetry breaks down and the crystal assumes discrete symmetry, meaning that instead of the structure being the same in all directions, it is the same in only a few directions.

“Great progress has been made over the last few decades in exploring the exciting physics of low-dimensional crystalline materials such as two-dimensional graphene, one-dimensional nanotubes, and zero-dimensional buckyballs,” says Tongcang Li, lead author of the PRL paper and a post-doc in Zhang’s research group. “The idea of creating a crystal with dimensions higher than that of conventional 3D crystals is an important conceptual breakthrough in physics and it is very exciting for us to be the first to devise a way to realize a space-time crystal.”

Just as a 3D crystal is configured at the lowest quantum energy state when continuous spatial symmetry is broken into discrete symmetry, so too is symmetry breaking expected to configure the temporal component of the space-time crystal. Under the scheme devised by Zhang and Li and their colleagues, a spatial ring of trapped ions in persistent rotation will periodically reproduce itself in time, forming a temporal analog of an ordinary spatial crystal. With a periodic structure in both space and time, the result is a space-time crystal.

Here’s an image created by team at the Berkeley Lab to represent their work on the space-time crystal,

Imagine a clock that will keep perfect time forever or a device that opens new dimensions into quantum phenomena such as emergence and entanglement. (courtesy of Xiang Zhang group[?] at Berkeley Lab)

For anyone who’s interested in this work, I suggest reading either the news item on Nanowerk or the Berkeley Lab news release in full. I will leave you with Natalie Cole and Everlasting Love,

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Insomniac iron oxide (rust) electrons and environmentally friendly semiconductors

Friday, September 7th, 2012

The Sept. 7, 2012 news item by Lynn Yarris for physorg.com highlights some research on rust being conducted (pun intended) at Lawrence Berkeley National Laboratory (Berkeley Labs).

Rust – iron oxide – is a poor conductor of electricity, which is why an electronic device with a rusted battery usually won’t work. Despite this poor conductivity, an electron transferred to a particle of rust will use thermal energy to continually move or “hop” from one atom of iron to the next. Electron mobility in iron oxide can hold huge significance for a broad range of environment- and energy-related reactions, including reactions pertaining to uranium in groundwater and reactions pertaining to low-cost solar energy devices.  …

“We believe this work is the starting point for a new area of time-resolved geochemistry that seeks to understand chemical reaction mechanisms by making various kinds of movies that depict in real time how atoms and electrons move during reactions,” says Benjamin Gilbert, a geochemist with Berkeley Lab’s Earth Sciences Division and a co-founder of the Berkeley Nanogeoscience Center who led this research. “Using ultrafast pump-probe X-ray spectroscopy, we were able to measure the rates at which electrons are transported through spontaneous iron-to-iron hops in redox-active iron oxides. Our results showed that the rates depend on the structure of the iron oxide and confirmed that certain aspects of the current model of electron hopping in iron oxides are correct.”

The news item provides a wealth of detail about electron hopping and iron oxide but I was most intrigued by future applications,

Katz [Jordan Katz, the lead author, now with Denison University]  is excited about the application of these results to finding ways to use iron oxide for solar energy collection and conversion.

“Iron oxide is a semiconductor that is abundant, stable and environmentally friendly, and its properties are optimal for absorption of sunlight,” he says. “To use iron oxide for solar energy collection and conversion, however, it is critical to understand how electrons are transferred within the material, which when used in a conventional design is not highly conductive. Experiments such as this will help us to design new systems with novel nanostructured architectures that promote desired redox reactions, and suppress deleterious reactions in order to increase the efficiency of our device.”

I find rust quite attractive although, admittedly, very irritating at times. I have never before considered the possibility it might prove useful nor had I realized that it never rests (sleeps).

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Flipping chirality at the Lawrence Berkeley National Laboratory

Thursday, July 12th, 2012

First, it might be a good idea to define chirality. From the Lawrence Berkeley National Laboratory (Berkeley Lab) July 10, 2012 news release by LynnYarris,

Chirality is the distinct left/right orientation or “handedness” of some types of molecules, meaning the molecule can take one of two mirror image forms. The right-handed and left-handed forms of such molecules, called “enantiomers,” can exhibit strikingly different properties. For example, one enantiomer of the chiral molecule limonene smells of lemon, the other smells of orange. The ability to observe or even switch the chirality of molecules using terahertz (trillion-cycles-per-second) electromagnetic radiation is a much coveted asset in the world of high technology.

As for why anyone would want  to flip molecules back and forth between left- and right-handedness (from the news release),

A multi-institutional team of researchers that included scientists with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has created the first artificial molecules whose chirality can be rapidly switched from a right-handed to a left-handed orientation with a  beam of light. This holds potentially important possibilities for the application of terahertz technologies across a wide range of fields, including reduced energy use for data-processing, homeland security and ultrahigh-speed communications.

Here’s how the technique works, from the July 10, 2012 news item on physorg.com,

Working with terahertz (THz) metamaterials engineered from nanometer-sized gold strips with air as the dielectric – Zhang [Xiang Zhang, one of the leaders of this research and a principal investigator with Berkeley Lab's Materials Sciences Division] and his colleagues fashioned a delicate artificial chiral molecule which they then incorporated with a photoactive silicon medium. Through photoexcitation of their metamolecules with an external beam of light, the researchers observed handedness flipping in the form of circularly polarized emitted THz light. Furthermore, the photoexcitation enabled this chirality flipping and the circular polarization of THz light to be dynamically controlled.

“In contrast to previous demonstrations where chirality was merely switched on or off in metamaterials using photoelectric stimulation, we used an optical switch to actually reverse the chirality of our THz metamolecules,” Zhang says.

The researchers describe in more detail the potential for this new technique,

“The observed giant switchable chirality we can engineer into our metamaterials provides a viable approach towards creating high performance polarimetric devices that are largely not available at terahertz frequencies,” says corresponding author Antoinette Taylor. “This frequency range is particularly interesting because it uniquely reveals information about physical phenomena such as the interactions between or within biologically relevant molecules, and may enable control of electronic states in novel material systems, such as cyclotron resonances in graphene and topological insulators.”

Taylor and her co-authors say that the general design principle of their optically switchable chiral THz metamolecules is not limited to handedness switching but could also be applied to the dynamic reversing of other electromagnetic properties.

From what I understand metamaterials are very expensive and difficult to produce which means this exciting advance is likely to remain in the laboratory of at least 10 years.

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Carbon sequestration (capturing carbon dioxide) and Zeo++

Thursday, March 1st, 2012

Carbon capture has been proposed as a way to mitigate global climate change and Zeo++ is a software which promises to help the search for porous materials that will filter out carbon (capture carbon) before it reaches the atmosphere. From the Mar. 1, 2012 news item on Nanowerk,

Approximately 75 percent of electricity used in the United States is produced by coal-burning power plants that spew carbon dioxide (CO2) into the atmosphere and contribute to global warming. To reduce this effect, many researchers are searching for porous materials to filter out the CO2 generated by these plants before it reaches the atmosphere, a process commonly known as carbon capture. But identifying these materials is easier said than done.

“There are a number of porous substances—including crystalline porous materials, such as zeolites, and metal-organic frameworks—that could be used to capture carbon dioxide from power plant emissions,” says Maciej Haranczyk, a scientist in the Lawrence Berkeley National Laboratory’s (Berkeley Lab) Computational Research Division.

In the category of zeolites alone, Haranczyk notes that there are around 200 known materials and 2.5 million structures predicted by computational methods. That’s why Haranczyk and colleagues have developed a computational tool that can help researchers sort through vast databases of porous materials to identify promising carbon capture candidates—and at record speeds. They call it Zeo++.

Here’s a description of the software from the Zeo++ home page,

Zeo++ is a software package for analysis of crystalline porous materials. Zeo++ can be used to perform geometry-based analysis of structure and topology of the void space inside a material, to alternate structures as well as to generate structure representations to-be-used in structure similarity calculations. Zeo++ can be used to either analyze a single structure or perform high-throughput analysis of a large database.

Here’s what the scientists are trying to determine when they use the software to analyze the proposed carbon capture materials (from the news item),

Porous materials like zeolites or metal organic frameworks come in a variety of shapes and have a range of pore sizes. It is actually the shape and pore sizes that determine which molecules get absorbed into the material and which ones pass through.

Like molecular sponges, porous materials can also be reused in a cycle of capture and release. For instance, in the case of carbon capture, once the material is saturated and cannot absorb any more CO2, the gas can be extracted, and the cycle repeated.

“Understanding how all of these factors combine to effectively capture carbon is a challenge,” says Richard Luis Martin, a member of the Zeo++ development team and a postdoctoral researcher in Berkeley Lab’s Computational Research Division. “Until Zeo++, there were no easy methods for analyzing such large numbers of material structures and identifying what makes a material an outstanding carbon catcher.”

He notes that silicious zeolites, to take one example, are composed of the same tetrahedral blocks of silicon and oxygen atoms, but the geometric arrangement of these blocks differs from one zeolite to the next, and this configuration is what determines how CO2 or any other molecule will interact with the porous material.

Before Zeo++, scientists would typically characterize a porous structure based on a single feature, like the size of its largest pore or its total volume of empty space, then compare and categorize it based on this single observation.

“The problem with this one-dimensional description is that it does not tell you anything about how a molecule like CO2 will move through the material,” says Martin. “To identify the most effective materials for absorbing CO2, we need to understand the porous structure from the perspective of the penetrating molecule.”

This is precisely why Zeo++ characterizes these structures by mapping the empty spaces between their atoms. Drawing from a database of the coordinates of all the atoms in each porous structure, Zeo++ generates a 3D map of the voids in each material. This 3D network allows researchers to see where the channels between atoms intersect to create cavities. The size and shape of these cavities determine whether a molecule will pass through the system or be absorbed.

…

“Zeo++ allows us to do things that would otherwise be physically impossible,” says Smit [Berend Smit leads the Energy Frontier Research Center for Gas Separations Relevant to Clean Energy Technologies at the University of California at Berkeley], whose group is developing laboratory and computational methods for identifying carbon dioxide-absorbing nanomaterials.

For anyone who’s curious about zeolites, I’ve excerpted this from an essay on Wikipedia (all notes and links have been removed),

Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents.The term zeolite was originally coined in 1756 by Swedish mineralogist Axel Fredric Cronstedt, who observed that upon rapidly heating the material stilbite, it produced large amounts of steam from water that had been adsorbed by the material. Based on this, he called the material zeolite, from the Greek ζέω (zéo̱), meaning “to boil” and λίθος (líthos), meaning “stone”.

I first mentioned zeolite on this blog in a July 1, 2010 posting about ‘green’ nanotechnology in Alberta’s oil sands.

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Abracadabra! A new material!

Wednesday, December 21st, 2011

A Nov. 3, 2011 news release from the US Dept. of Energy (DOE) announced the Materials Project,

Researchers from the Department of Energy’s (DOE’s) Lawrence Berkeley National Laboratory (Berkeley Lab) and the Massachusetts Institute of Technology (MIT) jointly launched today a groundbreaking new online tool called the Materials Project, which operates like a “Google” of material properties, enabling scientists and engineers from universities, national laboratories and private industry to accelerate the development of new materials, including critical materials.

…

Discovering new materials and strengthening the properties of existing materials are key to improving just about everything humans use – from buildings and highways to modern necessities. For example, advances in a group of materials called “critical materials” are more important to America’s competitiveness than ever before – particularly in the clean energy field.  Cell phones, wind turbines, solar panels and a variety of military technologies depend on these roughly fourteen elements (including nine “rare earth” elements).  With about 90 percent coming from China, there are growing concerns about potential supply shortages and disruptions.

The Dec. 20, 2011 news item on Nanowerk provides more detail,

The project is a direct outgrowth of MIT’s Materials Genome Project, initiated in 2006 by Gerbrand Ceder, the Richard P. Simmons (1953) Professor of Materials Science and Engineering. The idea, he says, is that the site “would become the Google of material properties,” making available data previously scattered in many different places, most of them not even searchable.

For example, it used to require months of work — consulting tables of data, performing calculations and carrying out precise lab tests — to create a single phase diagram showing when compounds incorporating several different elements would be solid, liquid or gas. Now, such a diagram can be generated in a matter of minutes, Ceder says.

The new tool could revolutionize product development in fields from energy to electronics to biochemistry, its developers say, much as search engines have transformed the ability to search for arcane bits of knowledge.

…

Already, more than 500 researchers from universities, research labs and companies have used the new system to seek new materials for lithium-ion batteries, photovoltaic cells and new lightweight alloys for use in cars, trucks and airplanes. The Materials Project is available for use by anyone, although users must register (free of charge) in order to spend more than a few minutes, or to use the most advanced features.

Interestingly, the Materials Project could have an impact on education too,

The tools could also make a big difference in education, Ceder says: When professors set up experiments to help students learn specific principles, “it used to be that we had to pick easy examples” with known outcomes, he says. Now, it’s possible to set much more challenging exercises.

I wasn’t expecting to find a quote from a Canadian academic but here goes,

Mark Obrovac, an associate professor of chemistry and physics at Dalhousie University in Nova Scotia, says, “The Materials Project has made complex computational techniques available to materials researchers at a click of a mouse. This is a major innovation in materials science, enabling researchers to rapidly predict the structure and properties of materials before they make them, and even of materials that cannot be made. This can significantly accelerate materials development in many important areas, including advanced batteries, microelectronics and telecommunications.”

You can find the Materials Project here.

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The latest in smart windows

Wednesday, September 7th, 2011

At last there’s a new development in smart windows giving me fresh hope that I will see these in my lifetime. From the Sept. 6, 2011 news item on Nanowerk,

Researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have unveiled a semiconductor nanocrystal coating material capable of controlling heat from the sun while remaining transparent (“Dynamically Modulating the Surface Plasmon Resonance of Doped Semiconductor Nanocrystals”). Based on electrochromic materials, which use a jolt of electric charge to tint a clear window, this breakthrough technology is the first to selectively control the amount of near infrared radiation. This radiation, which leads to heating, passes through the film without affecting its visible transmittance. Such a dynamic system could add a critical energy-saving dimension to “smart window” coatings.

“To have a transparent electrochromic material that can change its transmittance in the infrared portion of sunlight is completely unprecedented,” says Delia Milliron, director of the Inorganic Nanostructures Facility with Berkeley Lab’s Molecular Foundry, who led this research.

These kinds of coatings offer substantive energy savings. A lot of people don’t realize that buildings account for approximately 40% of the carbon emissions in the US. A smart window could theoretically lower the use of air conditioning and lighting by as much as 49% and 51% respectively according to the authors of the news item. I have seen similarly high numbers elsewhere so I am inclined to believe them.

Here’s what I think is the nifty part,

“Traditional electrochromic windows cannot selectively control the amount of visible and near infrared light that transmits through the film. When operated, these windows can either block both regions of light or let them in simultaneously,” says Guillermo Garcia, a graduate student researcher at the Foundry. “This work represents a stepping stone to the ideal smart window, which would be able to selectively choose which region of sunlight is needed to optimize the temperature inside a building.”

And then there’s the robot,

“Our ability to leverage plasmons in doped semiconductors with a very sensitive switching response in the near-infrared region also brings to mind applications in telecommunications,” Milliron adds. “We’ve also brought this synthesis into WANDA, our nanocrystal robot, which means we will be able to provide materials for a wide variety of user projects. “

I don’t see anything which indicates when this might be commercially available.

This latest development reminded me of Switch Materials, the Canadian smart window company that’s located in the Vancouver region. I last wrote about them in my May 14, 2010 posting and thought I’d check them out again. They have a new look on their website and a number of headings for different categories of purchasers such as architects, manufacturers, owners, etc. There’s also a list of the various media outlets that have featured the company. Strangely, there’s no mention of any customers and other than a very general description heavily weighted towards the advantages of the technology I was not able to find much detail about the technology. That’s also true of the news item but I expect more from a company website, especially a company offering an emerging technology. Finally, I was not able to discover how to purchase the product other than contacting a general phone number or sending a general inquiry to info@switchmaterials.com.

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