Nanodevice amplifies signals from single electrons

Nature : A single-electron transistor has been developed that can monitor a living cell’s vital signs. Thousands of gold nanoparticles are strung into long necklaces, which form a tangled network that connects two electrodes some 30 μm apart. The device detects the flow of single electrons as they pass through the gold semiconductor. Although roughly 5% of the nanoparticles have defects, a single electron can settle on the defective particle, creating a bridge. Unlike earlier versions, the new transistor design works at room temperatures as well as in water. To test the device, Ravi Saraf at the University of NebraskaâLincoln and his colleagues placed about five green algae cells between the electrodes. Shining a light on the cells started a series of biochemical reactions, which switched the transistor on. By using different wavelengths of light or adding more carbon dioxide, the researchers altered the cells’ rate of photosynthesis, which affected the current flow. Such a device could be used to determine the ideal biochemistry of green algae for making biofuels or to study the effects of candidate drugs on the metabolism of human cells, writes Mark Peplow for Nature.