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Light-Induced Ostwald Ripening of Organic Nanodots to Rods

Mahesh S, Gopal A, Thirumalai R, Ajayaghosh A. Light-induced Ostwald ripening of organic nanodots to rods. J Am Chem Soc 2012, 134(17):7227–7230.


Ostwald ripening allows the synthesis of 1D nanorods of metal and semiconductor nanoparticles. However, this phenomenon is unsuccessful with organic π-systems due to their spontaneous self-assembly to elongated fibers or tapes. Here we demonstrate the uses of light as a versatile tool to control the ripening of amorphous organic nanodots (ca. 15 nm) of an azobenzene-derived molecular assembly to micrometer-sized supramolecular rods. A surface-confined dipole variation associated with a low-yield (13–14%) trans–cis isomerization of the azobenzene moiety and the consequent dipole–dipole interaction in a nonpolar solvent is believed to be the driving force for the ripening of the nanodots to rods.