A novel method for dyeing human hair fibres using coloured silica nanoparticles of 206 nm has been
developed. Diffusion of coloured silica nanoparticles into hair fibres has been investigated; silica
nanoparticles do not penetrate at all, or do so only sparingly, into the structure of Caucasian virgin hair.
However, coloured silica nanoparticles diffused readily into bleached hair fibres. Scanning electron
microscopy showed that coloured silica nanoparticles were present mainly in the outer regions of the
hair structure (the inner layers of the cuticle and the outer region of the cortex). It was found that the
silica nanoparticles were physically entrapped in the hair fibres and results showed a good shampoo
fastness to washing
