Chemical smile

Michel Rickhaus and Andrew Frawley at the University of Oxford drew a smiley face in a solution of a special dye using an everyday laser pointer. The dye consisted of a fluorescent molecule attached to spironaphthoxazine, which changes its structure from a closed one to an open conformation when exposed to blue light—405 nm, to be exact. “By coupling this spironaphthoxazine to a fluorescent dye, we can reversibly switch the dye off and on,” Rickhaus explains, with the dye going from yellow in the closed form to purple in the open. After about 30 seconds, the molecule reverts to yellow, and the smiley gradually disappears. The two chemists’ lab is examining such photoswitchable dyes for use in superresolution microscopy. “The video came about as a bit of fun during my synthesis—hence the smiley. But we do use the laser pointer in the purification process,” he says. The laser allows them to quickly check that what they’ve purified contains the correct product.

Credit: Michel Rickhaus and Andrew Frawley

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