PARIS, Sept. 27 (UPI) -- French researchers have found a hair dye developed 2,000 years ago relied on nanotechnology to change graying hair into a youthful black color.
Philippe Walter and colleagues at the French Museums Restoration Research Center in Paris studied a hair-dyeing recipe first described in Greco-Roman times. The recipe, Walter said, is also the basis of modern hair dyes that gradually darken gray or white hair.
The researchers found the ancient dye worked by causing formation of nanocrystals of lead sulfide. That chemical compound forms inside hair shafts and colors hair black without damaging it.
The lead sulfide crystals look much like the lead sulfide quantum dots synthesized recently using techniques from materials science, the scientists said.
"In contrast to modern nanotechnology, the dyeing process is characterized by basic chemistry methods and has been developed more than 2,000 years ago with low-cost natural products," the scientists report.
The research appears in the current issue of the journal Nano Letters.
