A collection of iron oxide nanoparticles (blue) and smaller lead selenide nanoparticles (red) -- a.k.a. quantum dots -- beginning to interact and organize in solution on their way to crystallizing into a binary superlattice. The resulting assembly captures the magnetic properties of the iron oxide while retaining the distinct optical signature of the quantum dots.
A schematic of a binary superlattice where thirteen small lead selenide quantum dots (red) are grouped together, filling the spaces between the 11 nm diameter iron oxide (blue). The distance between the iron oxide particle is exaggerated to allow a clear view of how the lead selenide particles pack together.
Scientists from Columbia University, IBM and the University of New Orleans today announced a new, three-dimensional designer material assembled from two different types of particles only billionths of a meter across.
In the June 26 issue of the journal Nature, the team describes the precision chemistry methods developed to tune the particles’ sizes in increments of less than one nanometer and to tailor the experimental conditions so the particles would assemble themselves into repeating 3-D patterns. The work was supported in part by the National Science Foundation, the independent agency that supports basic research in all fields of science and engineering, through the Center for Nanostructured Materials at Columbia University and by the Defense Advanced Research Agency (DARPA) through programs on metamaterials and advanced thermoelectric materials.
Designing new materials with otherwise unattainable properties, sometimes referred to as "metamaterials," is one of the promises of nanotechnology. Two-dimensional patterns had previously been created from gold nanoparticles of different sizes and mixtures of gold and silver. Extending this concept to three dimensions with more diverse types of materials demonstrates the ability to bring more materials together than previously realized.
David Hart | National Science Foundation
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