Berkeley researchers have found an easy way to make crystal-studded nanorods: self-assembly.

These rods would be useful in devices that convert light or heat into electricity, such as high-efficiency solar cells.

Synthesizing these nanorods in the past required special conditions such as a vacuum and micromanagement from chemists. Now the nanorods can be synthesized by putting the ingredients in a test tube, stirring, and letting them emerge independently.

The rods are made by combining methanol and silver salt into a solution that already contains cadmium-sulfide nanorods. The cadmium ions are drawn out by the methanol, leaving holes which get filled by silver ions, producing silver sulfide. Differences in the crystal structure between the cadmium-sulfide rods and silver-sulfide crystals regulate the dots’ size and spacing.