Nano Lett. 12, 2117–2122 (2012)

Elton Graugnard and co-workers from Boise State University in the USA have developed molecular optical logical gates that operate by using DNA, dyes and fluorescence resonant energy transfer to switch visible fluorescence on and off. The switches are made from serpentine DNA scaffold that is hybridized with three strands containing the dyes FAM (input), TAMRA (intermediate) and Cy5 (output). The three dyes form a linear series of exciton transmission lines along a single DNA double helix, which allows excitation energy to flow from the input dye (peak emission wavelength of 520 nm) through to the intermediate dye (580 nm) and the output dye (670 nm). Strand invasion can be used to modify a DNA control strand and turn fluorescence off by removing a fluorophore, or turn it on by removing a quencher. Strands can also be used to restore the chromophores, thus allowing the switches to be reset and cycled through many operations. The authors say it is possible to create AND and OR logic functionality by cascading switches that are complementary in their operation. Such molecular photonic circuits could be useful for logical information processing in nanoscale devices and networks.