Scientists from Columbia University, IBM and the University of New Orleans have assembled a new, three-dimensional designer material from two different types of particles only billionths of a meter across. As reported in the June 26 2003 issue of Nature, the team used precision chemistry methods to tune the particles' sizes in increments of less than one nanometer and to tailor the experimental conditions causing the particles to self-assemble into repeating 3-D patterns.
Two-dimensional patterns had previously been created from gold nanoparticles of different sizes and mixtures of gold and silver. The extension of this to three dimensions with more diverse types of materials demonstrates the ability to bring more materials together than previously realized. Sometimes referred to as "metamaterials”, the development of new materials with otherwise unattainable properties is one of the promises of nanotechnology.
The materials used were chosen for their dissimilar, yet complementary properties. Lead selenide is a semiconductor with applications in infrared detectors and thermal imaging and can be tuned to be more sensitive to specific infrared wavelengths. The other material, magnetic iron oxide, is best known for coating magnetic recording media. It is hoped that the combination of these nanoparticles will have novel magneto-optical properties and properties key to the realization of quantum computing. For example, it might be possible to change the material's optical properties by applying an external magnetic field.