How old is nanotechnology in human history? 10 years? 100 years? No, it’s over 4000 years old. Back in ancient Egyptian times, people used nanotechnology for cosmetics and hair dyes. In the Greco-Roman period, organic hair dyes from plants, such as henna, were commonly used for human hair, and have been used up to modern times. However, some unusual formulas using lead compounds were also used to dye hair and wool black.
Recently, studies on the use of lead salts for hair darkening have shown that lead sulfide nanocrystals form inside a hair during the dyeing procedure. The picture on the left shows some blonde hair being treated with the ancient hairdye recipe and the progression of darkening. These lead sulfide crystals that form are 5 nanometers in diameter and appaear to be very similar to the lead sulfide quantum dots that are being synthesized by modern scientists. However, unlike modern technology, the dyeing process uses basic chemistry methods and low-cost natural materials. By studying this process of synthetic nanoscale biomineralization in hair, scientists can better understand how to grow and organize nanoparticles for other uses.