Chemists grow nano menagerie

Researchers from Sandia National Laboratories have found a simple way to make tiny, complicated shapes from zinc oxide, including arrays of vertically-aligned rods, flat disks, and columns that resemble stacks of coins.

The researchers grew the structures, which are similar to those found in biomaterials, by seeding a solution with zinc oxide nanoparticles. They were able to produce different shapes by changing the amount of citrate in the solution at different points during particle growth.

Zinc oxide is a widely-used, inexpensive ceramic material that has useful optical and semiconductor properties and can also be used as a catalyst. The material is already used in solar cells, microsensors and decontamination systems.

The nanostructures could be used in many ways, including microelectronics, chemical and biological sensing, energy conversion and storage, light-emitting displays and drug delivery, according to the researchers.

The researchers grew arrays of nanorods that measured 250 nanometers in diameter and three microns long. Their nanoplates measured five to ten microns thick. A nanometer is one thousandth of a micron, which is one thousandth of a millimeter; a red blood cell is five microns wide.

Zinc oxide nanostructures could be used as catalysts within the next two years, for chemical and biological sensing into five years, and for more efficient photovoltaics in something more than five years, according to the researchers. The work appeared in the November 23, 2003 issue of Nature Materials.