Tuesday, November 17, 2009

Organic LED's in nature

Just how efficient are biomolecular systems? For a long time it was claimed that fireflies had a quantum efficiency close to 100 per cent. However, it was recently found this is not the case, the efficiency being about 40%. A nice summary of the work is in this News and Views article in Nature Photonics last year.

Besides measuring the quantum efficiency Ando et al. find that there are three components to the light emission and all are pH dependent. One component is of unknown origin. Clearly there is a correlation between the colour of the emission and the protonation state of the chromophore.

Only in a 2006 Nature paper was a structural basis for two different emission states proposed. I am curious as to how much quantum chemistry has been done on these issues. This may help address questions such as:

What determines the quantum efficiency of emission?
How are non-radiative decay channels suppressed?
What role does the protein environment play?

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