Coloring with Intensity

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Science  05 Nov 2010:
Vol. 330, Issue 6005, pp. 733
DOI: 10.1126/science.330.6005.733-a

Photoswitching of molecules between two isomeric states has been directed toward a range of applications, including data storage, drug delivery, and actuation. One shortcoming of most systems is that they require two distinct wavelengths to toggle between the two states, and thus two light sources. Further, the light sources may not be compatible for use with biological tissues. Boyer et al. devised a clever way to bypass this problem by using lanthanide-doped up-converting nanoparticles. On exposure of the particles to high-intensity near-infrared (NIR) light, emission due to Tm3+ dopant ions dominates, and the output spectrum has strong ultraviolet and blue peaks. At low NIR intensity, emission from Er3+ dopant ions in the green and red region dominates. When the nanoparticles are mixed with dithienylethene photoswitches, a single monochromatic light source can then be used to drive both ring-closing and -opening reactions, with the switching controlled by the source's intensity.

J. Am. Chem. Soc. 132, 10.1021/ja107184z (2010).

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