POLYMER SCIENCE

Collecting the Light

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Science  16 Nov 2001:
Vol. 294, Issue 5546, pp. 1419
DOI: 10.1126/science.294.5546.1419d

Much in the way that the chlorophyll in plants collects sunlight, synthetic molecules have been designed to harvest incoming light. Light harvesting has been demonstrated with conjugated polymers, in which multilayered systems can exhibit an increase in surface fluorescence. These systems have been limited to thin films of up to 16 layers, because beyond this, internal energy losses reduce the light-collecting abilities.

Now Kim et al. have overcome this problem by maximizing the one-dimensional energy transfer by using a series of photoluminescent polymers. The systems are designed to have a large spectral overlap, so that the emission spectra maxima of the lower layers are similar to the absorbance spectra maxima of the higher layers. Energy is transferred through the thickness of the sample, because any photons traveling back toward the substrate are not absorbed by the lower layers. The interfaces between the different materials create energy traps and thus a decrease in the photoluminesence. Nevertheless, the preferential transfer of the energy toward the surface is increased. These materials can be used as very sensitive sensors for light-trapping materials, such as the explosive TNT.—MSL

J. Am. Chem. Soc., 10.1021/ja016693g.

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