A SINGLE molecule that acts as a binary switch has brought nanoscale computers a step closer. 快猫短视频s in Japan have created molecules that alternate between two different shapes when exposed to pulses of light. In a computer, one shape would correspond to a 1 and the other to a 0, allowing binary information to be stored in grids of molecules.
Naotoshi Nakashima and his colleagues developed the molecules at Nagasaki University. Each looks like a piece of string (an azobenzene molecule) threaded through a bead (a cylindrical cyclodextrin molecule). The bead moves between two positions on the string depending on whether the molecule is exposed to ultraviolet or visible light.
The beads are held on the string by molecular stoppers-bulky chemical groups at each end. The whole assembly is known as a rotaxane. The researchers say that the energy of ultraviolet light converts the straight azobenzene molecule into another stable form which has a kink in the centre (Journal of the American Chemical Society, vol 119, p 7605). This forces the bead to slide to a new position. Visible light returns the azobenzene to its straight state, allowing the bead to return to its original place.
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Nakashima and his colleagues say the two forms of the rotaxane absorb light in a different way, which would allow information encoded in the molecules to be 鈥渞ead鈥�.
Rotaxanes that perform a similar trick have already been made, but temperature dictates the position of the 鈥渂ead鈥�. Nakashima鈥檚 group is the first to make a rotaxane switch operated by light, a feature that could make it more convenient for computing applications.
Jon McCleverty of Bristol University says the work is a breakthrough. But he adds that practical applications may be far away. Currently, the switching process takes 11 to 15 minutes. 鈥淚n terms of a real device, they are too slow,鈥� he says.
