Structural Diversity in Binary Nanoparticle Superlattices: Beyond Hard Spheres to Charge-Controlled Packing

A team of Columbia University and IBM scientists has created conditions necessary for the successful self-assembly of new nanotechnological structures ? crystal arrangements that could form the basis of tomorrow's leading edge technology. The breakthrough provides a simpler, less costly method of generating new structures, helping scientists "grow" ordered superlattice crystals, as opposed to manipulating or "machining" them. Nanotechnology, a scientific field in which the placement of specific atoms or molecules is controlled on the scale of nanometers (one billionth of a meter), allows for the assembly of unique structures that have a wide range of manufacturing and technological implications -- from magnetic storage in computer hard drives to surgical robotics to a number of defense-related technologies.
The Columbia/IBM team of Drs. Stephen O?Brien, Chris Murray, Elena Shevchenko, Dmitri Talpin and others, has borrowed ideas from the natural world, in which the right conditions can stimulate the slow growth of highly uniform structures out of miniature building blocks. Opals are an example of this phenomenon: opals consist of tiny spherical building blocks of silica packed into an ordered structure. In this new research, the materials used as building blocks are a variety of man-made nanocrystals with known useful magnetic or electronic properties. The properties of these nanocrystals can be tailored during synthesis, and they can be deposited to form the desired ordered array by controlling particle charge and other properties.


Transmission electron micrographs of a variety of the binary superlattices self-assembled from colloidal solutions of different nanoparticle mixtures (including PbSe, Pd, gamma-Fe2O3 and Au particles).

Posted on: May 12, 2006
(This work has been published in Letters to Nature, 439, 55-59 (2006) and J. Am. Chem. Soc. 127(24), 8741-8747 (2005).)