All Glow Together

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Science  09 Feb 2007:
Vol. 315, Issue 5813, pp. 741
DOI: 10.1126/science.315.5813.741a

The appeal of quantum dots stems from their highly tunable optical and electronic properties. Their size-dependent luminescence, for example, is finding use in biological sensing and imaging. However, with the exception of this application, most technologies that could take advantage of quantum dots do not operate in solution. It can be difficult to pack a large concentration of quantum dots into a solid structure, and even if assembly is successful, the luminescent properties can be lost because of the formation of trap states or to quenching interactions between neighboring dots. Arachchige and Brock used a sol-gel process to prepare aerogel and xerogel monoliths with CdSe/ZnS core-shell nanoparticles as the primary building blocks. Throughout the transformation process from sols to wet gels and on to monoliths, little change was observed in the photoluminesence spectra for the three sizes of particles tested. This behavior contrasts strongly with that of nanostructured networks assembled from bare CdSe particles, which lost the favorable absorption and emission properties observed in solution. In both the aerogels and xerogels, transmission electron microscopy images suggested that the ZnS shells may have partially fused together to form a matrix containing CdSe particles, particularly in the 20-fold denser xerogels. — MSL

J. Am. Chem. Soc. 129, 10.1021/ja066749c (2007).

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