Light-Controlled Nanowires

Researchers in China have prepared hybrid organic-inorganic semiconducting nanowires where electrical conductivity can be switched on and off with light (J. Am. Chem. Soc. 2008, 130, 9198). The study broadens understanding of photoelectrical phenomena on the nanometer scale and may lead to new types of miniature circuits. Yanbing Guo, Yuliang Li, and coworkers at the Chinese Academy of Sciences' Institute of Chemistry, in Beijing, used porous templates to grow nanowires composed of polypyrrole (PPY) and cadmium sulfide. On the basis of single-nanowire microscopy images (top) and elemental maps (bottom), the team reports that the nanowires, which measure 200–400 nm in diameter, grow with an abrupt interface between the CdS and PPY segments. Furthermore, they find that unlike pure CdS or pure PPY nanowires, the hybrid structures' electrical conductivity can be controlled with light. In the dark, the hybrid nanowires are insulators. Under illumination, however, their capacity for carrying electrical current varies strongly with the intensity of the radiation.