New black hair dye uses no harsh chemicals | Science News for Students

New black hair dye uses no harsh chemicals

It lasts as long as store-bought products, but is nontoxic and environmentally friendly
May 16, 2018 — 6:45 am EST
applying dye

Traditional hair dyes contain lots of nasty, smelly chemicals. Some scientists are working to change all that. Their new graphene-based black dye is nontoxic and as long-lasting as today’s store-bought hair colorings.

Khosrork/istockphoto

“Green” is the new black, at least in hair dyes.

Scientists in Illinois have developed a new environmentally friendly hair dye that delivers stunning black locks. The raven color comes from a form of black carbon — the same basic ingredient as in soot and pencil lead.

Traditional hair dyes are made up of a lot of harsh chemicals. Each performs a certain function. For example, the job of bleach and ammonia is to pry open cellular “scales” on the outside of the hair (the cuticle). This allows the dye’s color to enter the hair strands. A chemical reaction then occurs which produces more color.

graphene dye
The graphene-based hair dye has worked its magic on a lock of blonde hair (top). The dyed hair (bottom) now has an even, rich, black color.
Chong Luo/Northwestern Univ.

But the pungent smell of hair dyes leaves you wondering what type of damage it might do to the scalp and hair. In fact, those chemicals can make hair so fragile that the strands can easily break. Dye ingredients also can dry out the skin. Some scientists worry that hair dyes might even pose more serious risks. Animal studies, for instance, have suggested some ingredients might cause cancer. And some of those chemicals can enter the body as inhaled fumes or by passing through the skin. (To date, however, no studies have confirmed that using these dyes poses health risks to people.)

The new dye uses none of those harsh chemicals, notes Jiaxing Huang. He works at Northwestern University in Evanston, Ill. As a materials scientist, he looks at how to develop new materials based on their physical and chemical properties. He was intrigued by graphene [GRAA-feen]. It’s made from nothing but carbon atoms (and won its initial investigators the 2010 Nobel Prize in physics). This material’s carbon atoms are all locked together into flat sheets, each a single atom thick. And it was the sheet’s thinness that inspired Huang to ponder: What if these black, graphene sheets could wrap around individual strands of hair? Would it change their color?

To find out, he says, “We did a few Friday afternoon experiments in the lab.” And they confirmed “that graphene did, indeed, work quite well at dying hair.” Huang’s team described its test results April 12 in the journal Chem.

Staying power

These black sheets offer an ideal alternative to harsh chemicals for dying hair, Huang suspects. “Graphene sheets are flexible,” he explains. That makes them a good coating to impart an even, black color. Using another version of graphene, known as graphene oxide, the team was able to improve the color palette to include various shades of brown and black.

Graphene also binds well to hair. So this dye will last a long time without fading — through more than 30 washes. That 30-wash durability is a minimum for today’s store-bought hair dyes.

Huang explains why graphene-based hair dyes will last as long, if not longer, than store-bought hair dyes. He likens the color particles in traditional hair dyes to tennis balls. They don’t easily stick. That means that with each shampooing, some can easily roll off of strands of hair, bit by bit. Graphene’s flakes are instead like itsy bitsy wet paper towels. Each can wrap around a hair shaft and really stick.  

The new dye should also be safer for hair, skin and overall health, Huang says. Why? It only coats the hair. No cuticles are pried open to insert chemicals. The nontoxic dye doesn’t hurt the skin, and each graphene flake is too big to move through the skin and enter the body.

“Current hair dyes tend to be among the nastier chemical mixtures that people voluntarily put on their bodies,” notes Chris Fellows. He’s a chemist at the University of New England in Armidale, Australia. He, too, thinks the Northwestern formula “seems to be much less toxic” than conventional dyes. Stacks of graphene form graphite, which is the material known as the “lead” in pencils. And, he quips, “We have probably all drawn on ourselves with those at one time or another without any negative consequences.”

Huang would like to see his formula developed into a commercial product. And while dark brown and black are popular hues in hair dyes, he has plans to develop other colors, too.

Graphene also conducts heat and electricity very well. So hair dyed with the graphene-based formula might be used to form part of an electrical circuit. Huang imagines using hair strands as a series of electrodes (electrical conductors). Hair could then be used to measure things. They might work with electronic devices attached to the skin, for instance, to measure such things as heart rate, breathing rate, body temperature or oxygen levels. “This is actually a very fun and potentially useful thing to imagine,” he says. “But I encourage kids to use their free minds and dig deep into their imagination to think of [other] possible uses.” 

Fellows let his imagination run wild, too. “Maybe there is a way to use it [graphene] to make an electrochromic [Ee-LEK-troh-KRO-mik] hair dye,” he says. This would allow it to change colors in response to some electrical signal. “Then you could change the color of your hair on the fly. Or make it continuously change in swirling paisley patterns. Or … okay now,” he admits, “I’m just being silly.”

This video shows some new, emerging uses for graphene and highlights some of its properties — especially its flexibility and conductivity.
CNET/YouTube

Power Words

(for more about Power Words, click here)

ammonia     A colorless gas with a nasty smell. Ammonia is a compound made from the elements nitrogen and hydrogen. It is used to make food and applied to farm fields as a fertilizer. Secreted by the kidneys, ammonia gives urine its characteristic odor. The chemical also occurs in the atmosphere and throughout the universe.

atom     The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.

bleach     A dilute form of the liquid, sodium hypochlorite, that is used around the home to lighten and brighten fabrics, to remove stains or to kill germs. Or it can mean to lighten something permanently, such as: Being in constant sunlight bleached most of the rich coloring out of the window drapes.

carbon     The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

chemical reaction     A process that involves the rearrangement of the molecules or structure of a substance, as opposed to a change in physical form (as from a solid to a gas).

circuit     A network that transmits electrical signals. In the body, nerve cells create circuits that relay electrical signals to the brain. In electronics, wires typically route those signals to activate some mechanical, computational or other function.

commercial     (in research and economics) An adjective for something that is ready for sale or already being sold. Commercial goods are those caught or produced for others, and not solely for personal consumption.

current     A fluid — such as of water or air — that moves in a recognizable direction. (in electricity) The flow of electricity or the amount of charge moving through some material over a particular period of time.

cuticle     Term for a tough but bendable protective outer shell or cover of some organism, or of parts of an organism.

electrical circuit     A path in which electrons flow. The point where those electrons enter an electrical circuit is called the “source.”

electricity     A flow of charge, usually from the movement of negatively charged particles, called electrons.

electrochromic     An adjective that describes the ability of certain dyes to change color when they encounter an electric field. It’s the principle behind the color-changing attribute of certain liquid-crystal displays.

graphene     A superthin, superstrong material made from a single-atom-thick layer of carbon atoms that are linked together.

graphite     Like diamond, graphite (the substance found in pencil lead) is a form of pure carbon. Unlike diamond, graphite is very soft. The main difference between these two forms of carbon is the number and type of chemical bonds between carbon atoms in each substance.

green     (in chemistry and environmental science) An adjective to describe products and processes that will pose little or no harm to living things or the environment.

particle     A minute amount of something.

risk     The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

toxic     Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.

NGSS: 

  • MS-PS1-3
  • MS-LS1-1
  • HS-ETS1-3

Citation

Journal: C. Luo et al. Multifunctional graphene hair dye. Chem. Vol. 4, April 12, 2018, p. 784. doi: 10.1016/j.chempr.2018.02.021.