Hair dyeing is a complicated chemical process. Hair is covered by a kind of protective dandruff layer of overlapping cells called the cuticle. It needs chemicals like ammonia to break these and to allow the dyeing molecules to go inside the hair structure. This damages the structure of the hair, making it brittle, and the chemical cocktail often also contains toxic substances.

Jiaxing Huang, Northwestern University, Evanston, IL, USA, and colleagues have used graphene oxide (GO) and its reduced form r-GO to create water-based formulations to form smooth and continuous coatings on hair. The solution of graphene and a polymeric binder dyes platinum-blonde strands black. The color remained for at least 30 washes – the prerequisite to reaching the performance requirement of permanent hair dyes. It is also possible to produce brown tones or color variations by simple chemical changes. Graphene hair dyes can be applied by spraying, brushing, and then drying.

Instead of penetrating the hair, the thin, flexible graphene layers wrap around a single hair, thus causing less damage. Tinting works on the same principle but they wash out very quickly. Once this graphene color coat has formed, the graphene is very good at repelling water. So it is not quickly decomposed during washing. Also, the colorant contains no toxic substances and cannot easily enter the body. Graphene is conductive, therefore, the coating on hair surfaces greatly improves antistatic performance.

According to the researchers, the graphene hair dye renders new properties, for example, by making the hair surface conductive and then combining it with portable electronics.

• Multifunctional Graphene Hair Dye,
  Chong Luo, Lingye Zhou, Kevin Chiou, Jiaxing Huang,
  Chem 2018.
  https://doi.org/10.1016/j.chempr.2018.02.021