Hair of gold – now a possibility as nanoparticle use could lead to permanent hair dyes

A study conducted French scientist, Dr Philippe Walter and his team, published in ACS Nano Letters, ​found that hair could synthesize gold nanoparticles into the hair cuticle.

It is understood that 40,000-60,000 gold nanoparticles could fit across the width of a human hair.

The original aim of the study was to look at the structure of keratin within hair, and how keratin breaks down, with gold nanoparticles used as a tracking substance within the subject.

Startling discovery​

The team soaked white hairs in a solution of a gold compound, and the hairs turned pale yellow and then darkened to a deep brown.

Using an electron microscope, the scientists confirmed that the particles were forming inside the hairs’ central core cortex, and that colour remained even after repeated washings.

Walter noted that after the hair was exposed to the gold, it was synthesized into the hair, which is a normal process for a hair dye. However, in this instance the gold nanoparticles remained, suggesting there could be implications for permanent hair colouring products.

The stumbling blocks at this stage would be that the dye changed colour once in the hair, and a lot of testing would have to be done to ensure product safety.

However, this first synthesis of nanoparticles into human hair could open the door to further development in hair care and other applications.

Let’s get into detail…​

The synthesis and detailed characterization of gold nanoparticles (AuNPs) inside human hair was achieved by treatment of hair with HAuCl4 in alkaline medium.

The AuNPs, which show a strong red fluorescence under blue light, are generated inside the fibre and are arranged in the cortex in a remarkably regular pattern of whorls based on concentric circles, like a fingerprint.

It opens an area of genuine nanocomposites with novel properties due to AuNPs inside the hair shaft.