Dr. Philippe Walter and his team used an ancient Egyptian hair-dyeing recipe, dating to the Graeco-Roman period, to dye black hair. The hair was later shown to contain lead-sulphide nanocrystals of 5 nanometre diameter (left).
“Metal sulfide nanoparticles easily crystallize and get organized inside…the hair shaft. It seems that sulfur-rich peptides in the matrix surrounding supramolecular-organized keratin proteins serve as nanoscale reactors,” says Walter, who is head of the analytical chemistry group which carried out the research.
The nanoparticles alter the optical, but not the mechanical, properties of hair. According to Walter, who is lead author of the Nano Letters paper describing the work, this is a remarkable example of synthetic nanoscale biomineralization.
The findings may help researchers to better control the growth and organization of nanoparticles in organic matrices, which should help in the development of nanocomposites.