Now, gold nanoparticles for permanent hair dye

The process involves soaking white hair in a solution of a gold compound, turning them pale yellow and then darkening them to a deep brown.

Using an electron microscope, French scientists confirmed that the particles were forming inside the central core cortex of the hair. The colour remained even after repeated washings.

Scientists reported the discovery had applications ranging from hair dyeing to electronic sensors to development of materials with improved properties.

Philippe Walter, director of a lab at the Centre National de la Recherche Scientifique (CNRS) and colleagues explain that gold nanoparticles