Graphene oxide hair dye is not only non-toxic, it also imbues hair with antistatic and thermal conductive properties

It is non-toxic, non-damaging, quick to apply, durable and even makes hair antistatic and more thermally conductive: graphene makes an excellent hair dye, claim researcher from the US and China.

Most hair dyes contain an array of organic compounds such as anilines and phenols, some of which are toxic or can cause allergic reactions. To avoid the colour disappearing after a few washes, ammonia is used to open up the hair’s cuticle scales, allowing the dye to diffuse into the fibres – a process that can permanently damage the hair’s structure.

Photo showing bundles of blonde hair before and after coating with r-GO/chitosan dye with increasing graphene concentrations, in comparison with another sample treated with a commercial permanent black hair dye.

Source: © Elsevier Ltd

The reduced graphene oxide and chitosan dye can produce progressively darker colouring by applying more of the nanomaterial. A commercial dye is shown far right

Jiaxing Huang from Northwestern University and his colleagues believe reduced graphene oxide can solve these problems. The 2μm-thick, non-toxic sheets wrap themselves around the hair shafts to produce a permanent colour that last for more than 30 washes. Moreover, the graphene dye gives hair some special features: graphene oxide is electrically conductive and dissipates the charge responsible for flyaway hair. And the material increases hair heating and cooling rates, helping the wearer keep a cool head.

While graphene oxide is transparent, partially reducing it with vitamin C makes it take on a deep black colour. Huang’s hair dye mixture also contains chitosan, which helps the carbon sheets form a lasting bond with the hair protein keratin.

SEM images showing the surfaces of uncoated and coated hair (0.25 wt %).

Source: © Elsevier Ltd

Scanning electron microscopy images of a hair treated with reduced graphene oxide (right) and without. The graphene oxide can wrap around hairs dyeing them black

By altering the amount of graphene in the dye, the team could dye blonde hair any shade of medium brown to black. While applying organic dyes is a lengthy process, taking up to an hour, dying hair with graphene can be as quick as 10 minutes. The dying mixture is sprayed on or applied with a comb, and the colour takes effect after the hair is blow-dried.

Huang’s team suggests that graphene-coated hair strands could even be repurposed for wearable electronics, energy storage or sensing devices.