[ASC-media] Re-inventing nature for cheaper solar power

Sarah Brooker sarah at scienceinpublic.com
Wed Aug 30 07:20:17 CEST 2006

A research team in Sydney has created molecules that mimic those in plants
which harvest light and power life on Earth.  

"A leaf is an amazingly cheap and efficient solar cell," says Dr Deanna
D'Alessandro, a postdoctoral researcher in the Molecular Electronics Group
at the University of Sydney. "The best leaves can harvest 30 to 40 percent
of the light falling on them. The best solar cells we can build are between
15 and 20 percent efficient, and expensive to make."

"We've recreated some one of the key systems that plants use in
photosynthesis," says Deanna. 

Bacteria and green plants use photosynthesis to convert light energy into
usable chemical energy. Wheel-shaped arrays of molecules called porphyrins
collect light and transfer it to the hub where chemical reactions use the
light energy to convert carbon dioxide into energy-rich sugar and oxygen.  

"This process, which occurs in about 40 trillionths of a second is
fundamental to photosynthesis and is at the base of the food chain for
almost all life on Earth," says Deanna.

"We have been able to construct synthetic porphyrins.  More than 100 of them
can be assembled around a tree-like core called a dendrimer to mimic the
wheel-shaped arrangement in natural photosynthetic systems."

These molecules designed by the team are about 1 trillionth the size of a
soccer ball. But the large number of porphyrins in a single molecule means
that a significant amount of light can be captured and converted to
electrical energy - just like in nature.  

"Since they are so efficient at storing energy, we think they could also be
used as batteries - replacing the metal-based batteries that our high
technology devices depend on today," Deanna says. 

"Our preliminary results are very promising. We are still in the early
stages of building practical solar energy devices using our molecules," said
Deanna.  "The challenge is immense, but is crucial to providing alternative
energy solutions for Australia and the world."

Now they've made the molecules, the team along with their Japanese
collaborators at Osaka University are working to combine them in the
equivalent of a plant cell. Then, over the next five years they will attempt
to scale up the technology to commercial scale solar panels.

Deanna D'Alessandro is one of 16 Fresh Scientists who are presenting their
research to school students and the general public for the first time thanks
to Fresh Science, a national program hosted by the Melbourne Museum and
sponsored by the Federal and Victorian governments, British Council and New
Scientist.  One of the Fresh Scientists will win a trip to the UK courtesy
of the British Council to present his or her work to the Royal Institution.

For further information or an interview, contact Dr Deanna D'Alessandro (02)
9351 3951, 0411 416 449 email deanna at chem.usyd.edu.au or Jasmine Chambers
(02) 9351 5397, jasminec at science.usyd.edu.au.

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Media contact for Fresh Science: Sarah Brooker on 0413 332 489 or
sarah at freshscience.org 

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