Size matters, but so does shape, at least in the world of semiconducting nanocrystals, report chemists at Washington University in St. Louis.
Washington University chemists have shown that the shape of nanowires such as this one can affect its electronic and optical properties.
Heng Yu and William Buhro
Their findings, published in the August 2003 issue of Nature Materials, demonstrate experimentally that the shape of a semiconductor nanocrystal can affect its electronic and optical properties. The study, led by graduate student Heng Yu and William E. Buhro, Ph. D., professor of chemistry in Arts & Science, is the first comprehensive comparison relating shape to the phenomenon known as "quantum confinement."
Quantum confinement describes how the electronic properties - the organization of energy levels into which electrons can climb or fall - and optical properties change when the material sampled is in sufficiently small amounts - typically 10 nanometers or less. Specifically, the phenomenon results from electrons and holes being squeezed into a dimension that approaches a critical quantum measurement, called the exciton Bohr radius. Holes are the positively-charge species left over when an electron vacates its position in a crystal.
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