Researchers determine improved pattern for artificial light-harvestin...( nergy best. What surprised us is that ...)

Many scientists have envisioned building bigger and bigger molecules, since a dendrimer needs as many light-catching limbs as possible to capture light, much as a big tree snares more light than a smaller one. But the researchers found a problem: the larger the molecule, the harder time it had funneling that light energy toward its center. Like a squirrel running along a tree branch, when the light encountered a fork in the limb it could either run out toward a twig, or in toward the trunk. If the tree were too big, the squirrel might not know which way was twigward or trunkward, and the hapless creature would run around lost until it died. In the same way, the researchers watched as their simulations showed that dendrimers lost the light they captured if they were too big. The light would simply dissipate long before it reached the center, where a drug or other chemical was waiting to be activated.

In research funded by the National Science Foundation, the team of chemists and theoretical physicists ran the simulations over and over until they found the magic number for one particular family of dendrimers: nine. The dendrimers could branch out up to nine times before their ability to funnel light became compromised. The team expects the findings to set the guidelines for the synthesis of large fractal-like dendrimers that could be used in many chemical reactions, from making magnetic resonance imaging (MRI) scans more accurate, to converting sunlight to energy for weakened plants.

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Contact: Jonathan Sherwood
jsherwood@admin.rochester.edu
716-273-4726
University of Rochester
18-Jul-2000