Argonne scientists reveal secret of nanoparticle crystallisation in real time

A collaboration between the Advanced Photon Source and Centre for Nanoscale Materials at U.S. Department of Energy's (DOE) Argonne National Laboratory has "seen" the crystallization of nanoparticles in unprecedented detail.

''Nanoscience is a hot issue right now, and people are trying to create self-assembled nanoparticle arrays for data and memory storage,'' Argonne assistant physicist Zhang Jiang said. ''In these devices, the degree of ordering is an important factor.''

In order to call up a specific bit of data, it is ideal to store information on a two-dimensional crystal lattice with well-defined graphical coordinates. For example, every bit of information of a song saved on a hard drive must be stored at specific locations, so it can be retrieved later. However, in most cases, defects are inherent in nanoparticle crystal lattices.

''Defects in a lattice are like potholes on a road,'' Argonne physicist Jin Wang said. ''When you're driving on the highway, you would like to know whether it is going to be a smooth ride or if you will have to zigzag in order to avoid a flat tire. Also, you want to know how the potholes form in the first place, so we can eliminate them.''

Controlling the degree of ordering in nanoparticle arrays has been elusive. The number of nanoparticles a chemist can make in a small volume is astonishingly large.

''We can routinely produce 1014 particles in a few droplets of solution. That is more than the number of stars in the Milky Way Galaxy,'' Argonne nanoscientist Xiao-Min Lin. ''To find conditions under which nanoparticles can self-assemble into a crystal lattice with a low number of defects is quite challenging.''