Nanosized versions of one of the oldest navigational instruments known, a magnetite compass needle, have been built by Frank Osterloh, associate professor of chemistry at UC Davis and graduate student Jin Young Kim. Particles of magnetite (iron oxide) were strung on nanowires of lithium molybdenum selenide to create magnetic needles about 400 nanometers long and 30 across. The structures are so small that they are effectively one-dimensional. Because they are magnetic, they could be used in devices for measuring magnetic fields or for making patterns on surfaces, Osterloh said. They are similar (although smaller) to structures created by some bacteria that use magnetic fields to orient themselves.
Osterloh and Kim have used similar approaches to build two-dimensional arrays of cadmium selenide nanoparticles, or "quantum dots," on surfaces. Arranging and stacking these quantum dots in different ways changes their optical and light-emitting properties, Osterloh said. These arrays could be used as waveguides or lasers.