Lessons to be learned from nature in photosynthesis

Photosynthesis is one of nature's finest miracles. Through the photosynthetic process, green plants absorb sunlight in their leaves and convert the photonic energy into chemical energy that is stored as sugars in the plants' biomass. If we can learn from nature and develop an artificial version of photosynthesis we would have an energy source that is absolutely clean and virtually inexhaustible.

"Solar energy is forecasted to provide a significant fraction of the world's energy needs over the next century, as sunlight is the most abundant source of energy we have at our disposal," says Graham Fleming, Vice Chancellor for Research at the University of California (UC) Berkeley who holds a joint appointment with Lawrence Berkeley National Laboratory (Berkeley Lab). "However, to utilize solar energy harvested from sun¬light efficiently we must understand and improve both the effective cap¬ture of photons and the transfer of electronic excitation energy."

Fleming, a physical chemist and authority on the quantum phenomena that underlie photosynthesis, is one of four international co-authors of a paper in Nature Chemistry, entitled "Lessons from nature about solar light harvesting." The other co-authors are Gregory Scholes, of the University of Toronto, Alexandra Olaya-Castro, of London's University College, and Rienk van Grondelle, of the University of Amsterdam. The paper describes the principles behind various natural antenna complexes and explains what research needs to be done for the design of effective artificial versions.

Solar-based energy production starts with the harvesting of the photons in sunlight by the molecules in antenna complexes. Energy from the photons excites or energizes electrons in these light-absorbing molecules and this excitation energy is subsequently transferred to suitable acceptor molecular complexes. In natural photosynthesis, these antenna complexes consist of light-absorbing molecules called "chromophores," and the captured solar energy is directed to chemical reaction centers -- a process that is completed within 10-to-100 picoseconds (a picosecond is one trillionth of second).

"In solar cells made from organic film, this brief timescale constrains the size of the chromophore arrays and how far excitation energy can travel," Fleming says. "Therefore energy-transfer needs and antenna design can make a significant difference to the efficiency of an artificial photosynthetic system."

Scientists have been studying how nature has mastered the efficient capture and near instantaneous transfer of the sun's energy for more than a century, and while important lessons have been learned that can aid the design of optimal synthetic sys¬tems, Fleming and his co-authors say that some of nature's design principles are not easily applied using current chemical synthesis procedures. For example, the way in which light harvesting is optimized through the organization of chromophores and the tuning of their excitation energy is not easily replicated. Also, the discovery by Fleming and his research group that the phenomenon of quantum coherence is involved in the transport of electronic excitation energy presents what the authors say is a "challenge to our understanding of chemical dynamics."

In their paper, Fleming and his international colleagues say that a clear frame¬work exists for the design and synthesis of an effective antenna unit for future artificial photosynthesis systems providing several key areas of research are addressed. First, chromophores with large absorption strengths that can be conveniently incorporated into a synthetic protocol must be developed. Second, theoretical studies are needed to determine the optimal arrangement patterns of chromophores. Third, experiments are needed to elucidate the role of the environment on quantum coherence and the transport of electronic excitation energy. Experiments are also needed to determine how light-harvesting regulation and photo protection can be introduced and made reasonably sophisticated in response to incident light levels.

"There remains a number of outstanding questions about the mechanistic details of energy transfer, especially concerning how the electronic system interacts with the environment and what are the precise consequences of quantum coherence," Fleming says. "However, if the right research effort is made, perhaps based on synthetic biology, artificial photosynthetic systems should be able to produce energy on a commercial scale within the next 20 years."

Support for this work was provided by the U.S. Department of Energy (DOE) Office of Science, the Natural Sciences and Engineering Research Council of Canada, the Engineering and Physical Sciences Research Council of the United Kingdom, and the Netherlands Organization for Scientific Research, and the European Research Council.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by DOE/Lawrence Berkeley National Laboratory.

Journal Reference:

Gregory D. Scholes, Graham R. Fleming, Alexandra Olaya-Castro, Rienk van Grondelle. Lessons from nature about solar light harvesting. Nature Chemistry, 2011; 3 (10): 763 DOI: 10.1038/nchem.1145

New method cleans up textile industry’s most dangerous chemicals

 Textile dying is one of the most environmentally hazardous aspects of the textile industry. During dying, harmful chemicals that are difficult to break down are released, all too often into rivers and agricultural land. However, Maria Jonstrup, a doctoral student in Biotechnology at Lund University, has developed a new, environmentally friendly purification process which leaves only clean water.

The findings are presented in Maria Jonstrup's thesis. The research is so far only research, and has therefore only been tested in the laboratory, but Maria Jonstrup is optimistic about its future potential.

"In the long term it should be possible for textile factories in India, China and Bangladesh to use the technique. If it works on a laboratory scale it is quite likely that it will also work in a real-life situation," she says.

While working on her thesis, she has conducted experiments with both fungal enzymes and bacteria from the drains at textile industry and municipal wastewater treatment plants. However, it was only when she combined two different types of purification process, one biological and one chemical, that the breakthrough came.

"First, microorganisms break down the dyes in a reactor. This biological step is the most important. However, to be certain that the water is completely purified, I also use some chemicals. Small amounts of iron and hydrogen peroxide in combination with UV light break down even the most difficult structures," she explains.

A combination of both biological and chemical purification is already used in some places, but these methods are rarely effective, which means that large quantities of hazardous chemicals are released.

Soon, two Master's students will be taking over the baton. They will spend a year testing the technique in larger volumes of water, which more closely reflect the conditions in real textile factories. Their challenge will be to study how the UV light in the chemical stage could be replaced with normal sunlight. Maria Jonstrup will be their supervisor. After that it is hoped that the technique will be tested 'live', in a real factory.

"Through contacts with the Swedish clothing company Indiska Magasinet and their suppliers, we have already taken samples and performed tests at a factory in India. Because clothing manufacture has received quite a bad reputation over recent years, it can otherwise be quite difficult to gain access to the factories," she explains.

One obstacle on the path to implementation is legislation. The law only stipulates that the water is to be clean. This has made it legally permissible to filter out large amounts of environmentally hazardous mud and dump it on agricultural land and elsewhere -- since the water itself is clean!

"But sometimes factories don't bother to clean the water at all and only do it when the inspectors come round," she says.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Lund University.

Nature offers key lessons on harvesting solar power, say chemists

Clean solutions to human energy demands are essential to our future. While sunlight is the most abundant source of energy at our disposal, we have yet to learn how to capture, transfer and store solar energy efficiently. According to University of Toronto chemistry professor Greg Scholes, the answers can be found in the complex systems at work in nature.

"Solar fuel production often starts with the energy from light being absorbed by an assembly of molecules," said Scholes, the D.J. LeRoy Distinguished Professor at U of T. "The energy is stored fleetingly as vibrating electrons and then transferred to a suitable reactor. It is the same in biological systems. In photosynthesis, for example, antenna complexes composed of chlorophyll capture sunlight and direct the energy to special proteins called reaction centres that help make oxygen and sugars. It is like plugging those proteins into a solar power socket."

In an article in Nature Chemistry to be published Sept. 23, Scholes and colleagues from several other universities examine the latest research in various natural antenna complexes. Using lessons learned from these natural phenomena, they provide a framework for how to design light harvesting systems that will route the flow of energy in sophisticated ways and over long distances, providing a microscopic "energy grid" to regulate solar energy conversion.

A key challenge is that the energy from sunlight is captured by coloured molecules called dyes or pigments, but is stored for only a billionth of a second. This leaves little time to route the energy from pigments to molecular machinery that produces fuel or electricity. How can we harvest sunlight and utilize its energy before it is lost?

"This is why natural photosynthesis is so inspiring," said Scholes. "More than 10 million billion photons of light strike a leaf each second. Of these, almost every red-coloured photon is captured by chlorophyll pigments which feed plant growth." Learning the workings of these natural light-harvesting systems fostered a vision, proposed by Scholes and his co-authors, to design and demonstrate molecular "circuitry" that is 10 times smaller than the thinnest electrical wire in computer processors. These energy circuits could control, regulate, direct and amplify raw solar energy which has been captured by human-made pigments, thus preventing the loss of precious energy before it is utilized.

Last year, Scholes led a team that showed that marine algae, a normally functioning biological system, uses quantum mechanics in order to optimize photosynthesis, a process essential to its survival. These and other insights from the natural world promise to revolutionize our ability to harness the power of the sun.

"Lessons from nature about solar light harvesting" was written by Scholes, Graham Fleming of the University of California, Berkeley, Alexandra Olaya-Castro of University College, London UK and Rienk van Grondelle of VU University in Amsterdam, The Netherlands.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Toronto.

Journal Reference:

Gregory D. Scholes, Graham R. Fleming, Alexandra Olaya-Castro, Rienk van Grondelle. Lessons from nature about solar light harvesting. Nature Chemistry, 2011; 3 (10): 763 DOI: 10.1038/nchem.1145

Carnivorous plant inspires coating that resists just about any liquids

After a rain, the cupped leaf of a pitcher plant becomes a virtually frictionless surface. Sweet-smelling and elegant, the carnivore attracts ants, spiders, and even little frogs. One by one, they slide to their doom.

Adopting the plant's slick strategy, a group of applied scientists at Harvard have created a material that repels just about any type of liquid, including blood and oil, and does so even under harsh conditions like high pressure and freezing temperatures.

The bio-inspired liquid repellence technology, described in the September 22 issue of Nature, should find applications in biomedical fluid handling, fuel transport, and anti-fouling and anti-icing technologies. It could even lead to self-cleaning windows and improved optical devices.

"Inspired by the pitcher plant, we developed a new coating that outperforms its natural and synthetic counterparts and provides a simple and versatile solution for liquid and solid repellency," says lead author Joanna Aizenberg, Amy Smith Berylson Professor of Materials Science at the Harvard School of Engineering and Applied Sciences (SEAS), Director of the Kavli Institute for Bionano Science and Technology at Harvard, and a Core Faculty member at the Wyss Institute for Biologically Inspired Engineering at Harvard.

By contrast, current state-of-the-art liquid repellent surfaces have taken cues from a different member of the plant world. The leaves of the lotus resist water due to the tiny microtextures on the surface; droplets balance on the cushion of air on the tips of the surface and bead up.

The so-called lotus effect, however, does not work well for organic or complex liquids. Moreover, if the surface is damaged (e.g., scratched) or subject to extreme conditions, liquid drops tend to stick to or sink into the textures rather than roll away. Finally, it has proven costly and difficult to manufacture surfaces based on the lotus strategy.

The pitcher plant takes a fundamentally different approach. Instead of using burr-like, air-filled nanostructures to repel water, the plant locks in a water layer, creating a slick coating on the top. In short, the fluid itself becomes the repellent surface.

"The effect is similar to when a car hydroplanes, the tires literally gliding on the water rather than the road," says lead author Tak-Sing Wong, a postdoctoral fellow in the Aizenberg lab. "In the case of the unlucky ants, the oil on the bottom of their feet will not stick to the slippery coating on the plant. It's like oil floating on the surface of a puddle."

Inspired by the pitcher plant's elegant solution, the scientists designed a strategy for creating slippery surfaces by infusing a nano/microstructured porous material with a lubricating fluid. They are calling the resulting bio-inspired surfaces "SLIPS" (Slippery Liquid-Infused Porous Surfaces).

"Like the pitcher plant, SLIPS are slippery for insects, but they are now designed to do much more: they repel a wide variety of liquids and solids," says Aizenberg. SLIPS show virtually no retention, as very little tilt is needed to coax the liquid or solid into sliding down and off the surface.

"The repellent fluid surface offers additional benefits, as it is intrinsically smooth and free of defects," says Wong. "Even after we damage a sample by scraping it with a knife or blade, the surface repairs itself almost instantaneously and the repellent qualities remain, making SLIPS self-healing." Unlike the lotus, the SLIPS can be made optically transparent, and therefore ideal for optical applications and self-cleaning, clear surfaces.

In addition, the near frictionless effect persists under extreme conditions: high pressures (as much as 675 atmospheres, equivalent to seven kilometers under the sea) and humidity, and in colder temperatures. The team conducted studies outside after a snowstorm; SLIPS withstood the freezing temperatures and even repelled ice.

"Not only is our bio-inspired surface able to work in a variety of conditions, but it is also simple and cheap to manufacture," says co-author Sung Hoon Kang, a Ph.D. candidate in the Aizenberg lab. "It is easily scalable because you can choose just about any porous material and a variety of liquids."

To see if the surface was truly up to nature's high standards, they even did a few experiments with ants. In tests, the insects slid off the artificial surface or retreated to safer ground after only a few timorous steps.

The researchers anticipate that the pitcher plant-inspired technology, for which they are seeking a patent, could one day be used for fuel- and water-transport pipes, and medical tubing (such as catheters and blood transfusion systems), which are sensitive to drag and pressure and are compromised by unwanted liquid-surface interactions. Other potential applications include self-cleaning windows and surfaces that resist bacteria and other types of fouling (such as the buildup that forms on ship hulls). The advance may also find applications in ice-resistant materials and may lead to anti-sticking surfaces that repel fingerprints or graffiti.

"The versatility of SLIPS, their robustness and unique ability to self-heal makes it possible to design these surfaces for use almost anywhere, even under extreme temperature and pressure conditions," says Aizenberg. "It potentially opens up applications in harsh environments, such as polar or deep sea exploration, where no satisfactory solutions exist at present. Everything SLIPS!"

Aizenberg is also Professor of Chemistry and Chemical Biology in the Department of Chemistry and Chemical Biology, and Susan S. and Kenneth L. Wallach Professor at the Radcliffe Institute for Advanced Study. Her co-authors included Tak-Sing Wong, Sung Hoon Kang, Sindy K.Y. Tang, Benjamin D. Hatton, and Alison Grinthal, all at SEAS, and Elizabeth J. Smythe, at the Schlumberger-Doll Research Center.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Harvard University, via EurekAlert!, a service of AAAS.

Journal Reference:

Tak-Sing Wong, Sung Hoon Kang, Sindy K. Y. Tang, Elizabeth J. Smythe, Benjamin D. Hatton, Alison Grinthal, Joanna Aizenberg. Bioinspired self-repairing slippery surfaces with pressure-stable omniphobicity. Nature, 2011; 477 (7365): 443 DOI: 10.1038/nature10447

Catalyst discovery potential has to revolutionize chemical industry

 University of Alberta Chemistry Professor Steve Bergens and his graduate student Jeremy Johns have discovered a catalyst that has the potential to revolutionise the chemical industry by reducing its environmental footprint, improving efficiency and minimizing risks.

Their findings were published in a top international chemistry journal Angewandte Chemie this month and provide the chemical industry with a potential solution to issues surrounding economics, efficiency and environmental factors.

"Our findings are a game changer that people having been seeking an answer to for decades," said Bergens.

Bergen said researchers have been working for more than 50 years to find a "clean" and stable catalyst that produces little to no waste and also has a capacity to provide multiple turnovers. In February of this year his student Jeremy Johns created such a catalyst in his laboratory.

"After years of producing disappointing results I was thrilled to see the results that came out of this particular experiment," said Dr Bergens.

"The chemical industry is making huge efforts to reduce its environmental footprint and their economists and accountants are also looking to reduce the cost of not just transporting catalyst but improving its efficiency," said Dr Bergens.

He said the February 2011 discovery opens numerous doors to make these things happen for industries ranging from pharmaceuticals to agrochemicals.

"Catalysts are notoriously unstable and challenging to transport, and the waste products the reactions to produce chemicals produce are equally challenging," Bergens added.

John's catalyst only produces hydrogen as a waste, something that is easy to burn off or react to produce water.

Bergens says early indications are the catalyst is not just safe but also efficient. The researchers have pushed the experiment to produce 7000 turnovers for one unit of catalyst.

"We are hugely excited , and the challenge now is to identify exactly how this catalyst is made up and how we can produce it in amounts to further advance this discovery," said Bergens.

The above story is reprinted (with editorial adaptations) from materials provided by University of Alberta, via EurekAlert!, a service of AAAS.

Journal Reference:

Jeremy M. John, Steven H. Bergens. Catalyst for the Hydrogenation of Amides to Alcohols and Amines. Angewandte Chemie International Edition, 2011; DOI: 10.1002/anie.201105348