11-10 :: October 2011

nanotimes News in Brief

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DNA-functionalized particles, which then present a large number of DNA “sticky ends” at a controlled distance from the particle surface; these sticky ends then bind to the sticky ends of adjacent particles, forming a macroscopic arrangement of nanoparticles.

Different crystal structures are achieved by using different combinations of nanoparticles (with varying sizes) and DNA linker strands (with controllable lengths). After a process of mixing and heating, the assembled particles transition from an initially disor- dered state to one where every particle is precisely located according to a crystal lattice structure. The process is analogous to how ordered atomic crystals are formed. The researchers report six design rules that can be used to predict the relative stability of different structures for a given set of nanoparticle sizes and DNA lengths. In the paper, they use the- se rules to prepare 41 different crystal structures with nine distinct crystal symmetries. However, the design rules outline a strategy to independently adjust each of the relevant crystallographic parame- ters, including particle size (varied from 5 to 60nm), crystal symmetry and lattice parameters (which can range from 20 to 150nm). This means that these 41

crystals are just a small example of the near infinite number of lattices that could be created using diffe- rent nanoparticles and DNA strands.

Robert J. Macfarlane, Byeongdu Lee, Matthew R. Jones, Nadine Harris, George C. Schatz, and Chad A. Mirkin: Nanoparticle Superlattice Engineering with DNA, In: Science, Vol. 334, No. 6053, October 14, 2011, Pages 204-208, DOI: 10.1126/science.1210493: http://dx.doi.org/10.1126/science.1210493

ht tp:/ /www.northwestern.edu/newscenter/sto- ries/2011/10/chad-mirkin-nanomaterials.html

Image: Gold nanoparticles have been assembled with DNA linkers into crystalline lattices, where particle sizes, crystal symmetries and lattice parameters can be inde- pendently controlled. This has been achieved through the development of 6 design rules that allow one to predict the relative stability of a particular structure for a given set of design parameters, such as nanoparticle size or DNA length. These rules enable the construction of both nanoscale analogues of atomic lattices, and lattices that have no naturally occuring mineral equivalent. The lattices shown here are isostructural with (from left) Cr3Si, AlB2, CsCl, NaCl and Cs6C60. © Northwestern University