An ancient hair-dyeing formula based on lime and lead oxide has revealed the presence of chemical nanoreactors in our hair.1 Researchers from LC2RMF2 have focused on the history of cosmetic products for the last ten years. This includes analyzing and recreating make-up and ointments discovered in Egyptian tombs. Now, together with other teams,3 they have reproduced and applied the lime/lead oxide dye to hair samples. First, they noticed that the tiny black crystals of dye measured on average just five nanometers4 in size, explaining why this ancient formula was so efficient. But the study has also revealed a promising new mechanism for growing nano-objects. “The examination of the cross-section of dyed hair shows that, after reacting with the sulfur in the keratin, the lead binds to the core of the hair in the form of crystals of lead sulfide,” explains Philippe Walter from LC2RMF. “Highly-localized areas in the hair provide the sulfur needed for growing these crystals. These areas behave exactly like nanoreactors, a very popular concept in nanotechnology today.” In addition, the crystals obtained are similar to certain quantum dots synthesized using extremely expensive methods, which “are used as markers in biological imaging, as infrared sensors, as well as possibly playing a role in the production of the photovoltaic cells of the future, due to their semi-conducting properties,” Walter concludes.
1. P. Walter et al., “Early use of PbS nanotechnology for an ancient hair dyeing formula,” Nano Lett. 6(10): 2215-9. 2007.
2. Laboratoire du Centre de recherche et de restauration des musées de France (CNRS / Ministère de la Culture et de la Communication joint lab).
3. L'Oréal-Recherche, laboratoire d'étude des microstructures (CNRS / Onera joint lab) and the Electron Microscopy Center at Argonne National Laboratory (University of Chicago, US).
4. 1 nanometer = 10-9 meter.