Cube-shaped nanoparticles with thick shells of DNA assemble into a never-before-seen 3-D “zigzag” pattern that breaks orientational symmetry; understanding such nanoscale behavior is key to engineering new materials with desired organizations and properties.
From the ancient pyramids to modern buildings, various three-dimensional (3-D) structures have been formed by packing shaped objects together. At the macroscale, the shape of objects is fixed and thus dictates how they can be arranged. For example, bricks attached by mortar retain their elongated rectangular shape. But at the nanoscale, the shape of objects can be modified to some extent when they are coated with organic molecules, such as polymers, surfactants (surface-active agents), and DNA. These molecules essentially create a “soft” shell around otherwise “hard,” or rigid, nano-objects. When the nano-objects pack together, their original shape may not be entirely preserved because the shell is flexible—a kind of nanoscale sculpturing.
Now, a team of scientists from the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory and Columbia Engineering has shown that cube-shaped nanoparticles, or nanocubes, coated with single-stranded DNA chains assemble into an unusual “zigzag” arrangement that has never been observed before at the nanoscale or macroscale. Their discovery is reported in the May 17 online issue of Science Advances.
Image: Brookhaven Lab scientists Fang Lu (sitting), (left to right, standing) Oleg Gang, Kevin Yager, and Yugang Zhang in an electron microscopy lab at the Center for Functional Nanomaterials. The scientists used electron microscopes to visualize the structure of nanocubes coated with DNA.