How do molecules grow into crystals? Growth of a crystal from a single molecule attached to solid surface probed
A huge number of nanosized clusters form on single-molecule templates bonded to nanocarbon surface, and a very small portion of the clusters grow into large crystals. © Eiichi Nakamura
Although solution crystallization of organic compounds on a solid surface is an essential process in industry and our daily life, fundamental understanding of how crystals of organic molecules nucleate on a surface remains limited because of the difficulty of probing rare events at the molecular scale. Prof. Nakamura of the University of Tokyo and his research group showed for the first time that single-molecule templates on the surface of carbon nanohorns, sea-urchin-shaped carbon nanotube aggregates, can nucleate the crystallization of organic compounds from a supersaturated solution by mediating the formation of disordered and mobile molecular nanoclusters on the templates. Single-molecule real-time transmission electron microscopy (SMRT-TEM) indicates that each nanocluster consists of a maximum of approximately 15 molecules, that there are fewer nanoclusters than crystals in solution, and that in the absence of templates physisorption, but not crystal formation, occurs. In addition, they successfully estimated that only one out of a billion templates becomes incorporated into a large crystal, indicating an extremely small probability of nucleation. This finding allows us to control shapes and properties of crystals by on-demand molecular design of single molecular templates and contributes to development of new organic electric devices and pharmaceuticals.
Paper
Koji Harano, Tatsuya Homma, Yoshiko Niimi, Masanori Koshino, Kazu Suenaga, Ludwik Leibler, iichi Nakamura,
“Heterogeneous nucleation of organic crystals mediated by single-molecule templates”,
Nature Materials: 2012/8 (Japan time), doi: 10.1038/NMAT3408.
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