The problem was that all nonmetal nanocrystals were essentially one-dimensional dots, says Paul Alivisatos, head of a research team at the lab's materials sciences division. And those limited shapes limited the uses of the nanocrystals. All that changed when Alivisatos and his team invented a method to make semiconductor nanocrystals shaped like rods. By controlling the kinetics of semiconductor nanocrystal growth the researchers are able to change the shapes of the resulting particles, Alivisatos says. To grow crystals shaped like elongated rods that maximize the crystals' surface area, the researchers maintain a relatively fast growth rate using the right mix of surfactant.
Tests show that the rod-shaped nanocrystals emit light that is polarized along their long axis.
In contrast, cadmium-selenide nanocrystal dots emit nonpolarized light. Packed and aligned just so, the rods can also be used in both LEDs and photovoltaic cells. All rights reserved.