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Rescooped by Cristóbal Kurth from Amazing Science
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Solar energy harvesting with a multitude of man-made leaves

Solar energy harvesting with a multitude of man-made leaves | School. | Scoop.it
Two-step artificial photosynthesis mimics nature’s efficient way of gathering energy

 

Scientists from Japan have harvested solar energy using an exceptionally large number of light absorbers to relay photons via antennas into one final energy acceptor. This two-step sequence closely mimics natural photosynthesis, resulting in greater and more efficient energy transfer.

 

Previously, researchers had only used one-step light harvesting systems, greatly limiting the number of absorbers able to feed light into a single reaction centre. Now, by imitating photosynthetic systems, Osamu Ishitani at the Tokyo Institute of Technology, Shinji Inagaki at the Japan Science and Technology Agency and their co-workers have efficiently harvested light using the highest number of artificial leaves to date.

 

The team combined 440 periodic mesoporous organosilica (PMO) tubes bridged by light-absorbing biphenyl (Bp) groups with five stick-shaped rhenium(I) pentamer units connected to one ruthenium(II) trisdiimine complex (Ru–Re5). This Ru–Re5–Bp–PMO hybrid system concentrates photons absorbed by the large framework of Bp–PMO in two steps: first to the rhenium oligomers, and then to the ruthenium reaction centre.

 

‘Photon collection has always been a problem in developing efficient solar energy conversion systems because the molecules are so small and solar light is so dilute,’ says Ishitani. ‘This new system is fantastic because now we can accumulate light from a large area and into, say, a photocatalyst.’

 

Other researchers are enthusiastic about the work. ‘The bio-inspired design of their synthetic assembly is certainly intriguing, because it mimics some important features of photosynthetic light harvesting systems,’ comments Erwin Reisner, an expert in solar fuel generation at the University of Cambridge in the UK.

 

Steve Dunn, who investigates energy harvesting materials at Queen Mary, University of London, UK, regards the system as ‘genuinely transformational’. ‘While it might prove difficult to manufacture real world devices or applications with this latest breakthrough, there is no doubt that this development is significant and exciting.’

 

Ishitani and his team plan to merge their light harvesting technique with their work on photocatalysts for CO2 reduction, and hope to eventually apply this future system to water oxidation photocatalysis. He emphasises the long road ahead and says many more breakthroughs are needed before we can use such artificial photosynthesis in daily life, but that developing these systems is crucial for humanity.

 


Via Dr. Stefan Gruenwald
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Barry Mapp's curator insight, October 31, 2013 3:10 PM

This is definitely the direction that sustainable energy systems should be going. It's not wind that we should be trying to harness but the sun and millions of years of evolution have shown that photosynthesis is the most effective way utilise the sun's energy

Rescooped by Cristóbal Kurth from Amazing Science
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The secret math of plants: UCLA biologists uncover rules that govern leaf design

The secret math of plants: UCLA biologists uncover rules that govern leaf design | School. | Scoop.it

Life scientists from UCLA's College of Letters and Science have discovered fundamental rules of leaf design that underlie plants' ability to produce leaves that vary enormously in size. In their mathematical design, leaves are the "perfect machines," said Lawren Sack, a professor of ecology and evolutionary biology and senior author of the research.

 

 The UCLA team discovered the mathematical relationships using "allometric analysis," which looks at how the proportions of parts of an organism change with differences in total size. This approach has been used by scientists since Galileo but had never before been applied to the interior of leaves. Reporting in the October issue of the American Journal of Botany, the biologists focused on how leaf anatomy varies across leaves of different sizes. They examined plant species from around the world, all grown on the UCLA campus.

 

While it is easy to observe major differences in leaf surface area among species, they said, differences in leaf thickness are less obvious but equally important. "Once you start rubbing leaves between your fingers, you can feel that some leaves are floppy and thin, while others are rigid and thick," said Grace John, a UCLA doctoral student in ecology and evolutionary biology and lead author of the research. "We started with the simplest questions — but ones that had never been answered clearly — such as whether leaves that are thicker or larger in area are constructed of different sizes or types of cells."

 

The researchers embedded pieces of leaf in plastic and cut cross-sections thinner than a single cell to observe each leaf's microscopic layout. This allowed them to test the underlying relationship between cell and tissue dimensions and leaf size across species. Leaves are made up of three basic tissues, each containing cells with particular functions: the outer layer, or epidermis; the mesophyll, which contains cells that conduct photosynthesis; and the vascular tissue, whose cells are involved in water and sugar transport.

 

The team found that the thicker the leaf, the larger the size of the cells in all of its tissues — except in the vascular tissue. These relationships also applied to the components of the individual cells. Plant cells, unlike animal cells, are surrounded by carbohydrate-based cell walls, and the scientists discovered that the larger cells of thicker leaves are surrounded by thicker cell walls, in a strict proportionality.

 

The team was surprised by the "extraordinary" strength of the relationships linking cell size, cell-wall thickness and leaf thickness across diverse and distantly related plant species. These relationships can be described by new, simple mathematical equations, effectively allowing scientists to predict the dimension of cells and cell walls based on the thickness of a leaf. In most cases, the relationships the team found were what is known as "isometric."


Via Dr. Stefan Gruenwald
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