Graphene is a two-dimensional sheetlike material made of a single atomic layer of carbon. It is strong, thin and a great conductor of electricity and heat. When it was discovered in 2004, it was viewed as revolutionary for the electronics industry. But its thin, flexible sheets can adapt to uneven surfaces, which also makes it a good coating material, the study said. An added advantage is the elimination of static and flyaway hair on dry winter days. Another plus, Dr. Huang said, is that the graphene flakes are too large to be absorbed through the skin, unlike other ingredients generally used today in current dark hair dyes that can penetrate the skin barrier.
“Because we now have a coating-based dye, we don’t have to get into the hair or change the chemical structure,” he said. “It’s a nanomaterial solution to solve a chemistry problem.”
Exactly how big a problem is not known. The Food and Drug Administration reports that two ingredients that were found to cause cancer in animals are no longer used in hair dyes. But there are thousands of different chemicals in use, and of these, many have not been studied either alone or in combination with others.
The F.D.A.’s website is vague on the matter. “We do not have reliable evidence showing a link between cancer and coal-tar hair dyes on the market today,” the agency stated.
The National Cancer Institute notes that some studies have suggested possible links to blood cancers and bladder cancers, while other studies have not found any connection. In a combined analysis of 4,461 women who had non-Hodgkin’s lymphoma, and 5,799 women who did not, researchers found that women who began using hair dye before 1980 had a 30 percent increase risk of non-Hodgkin’s lymphoma, compared to those who began using hair dye after 1980. The researchers were not sure if the reduced risk was due to safer dyes, or the fact that those who began using them after 1980 reflected lower cumulative exposure.
Dr. Huang said he was traveling in Europe when it occurred to him that graphene might work as a hair coloring.
“I got curious, why do people have so many different hair colors, and how do people change their hair color?” he said. “After I looked into this problem I realized there is a significant demand for people to dye their hair black or close to black.”
Dr. Huang said he hopes his finding leads to a useful product.
The total retail sales of at-home hair coloring products in the United States in 2016 was $1.9 billion, according to Kline & Company, a market research firm.