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The chemistry that delighted us in 2018

These scientific findings might not be the most significant of the year, but C&EN’s editors were amused and amazed by them

by Megha Satyanarayana
December 12, 2018 | A version of this story appeared in Volume 96, Issue 49


This isn’t the bunny you’re looking for

A photo shows a bunny wearing a white, stringy cape on its back; the infrared image shows just its head. Below that is a bunny wearing a solid, blue cape on its back; its infrared image shows its whole body.
Credit: Adv. Mater.
A lab rabbit wearing a cloak with fibers that mimic polar bear hair (top left) is invisible to a thermal imaging camera (top right). Under a mere polyester cape (bottom left), the bunny’s cover is blown (bottom right).

A team of researchers in China fashioned a silk-based cloak that appears to fool night-vision technology. The cloak was woven from fibers that were at once porous and strong, thanks to a protocol of freezing, and then freeze-drying, a mixture of fibroin (a silk protein) and chitosan (a sugar). The inspiration was polar bear hairs, which are hollow, allowing them to reflect infrared emissions from a bear’s body back toward the animal to keep it warm. To test the fibers, the team made a little cape that it placed on a rabbit. Behind the lens of a thermal-imaging camera, the ninja bunny all but disappeared (Adv. Mater. 2018, DOI: 10.1002/adma.201706807). The process to make this fiber is still slow, but the researchers hope it can be used in some commercial product. Let your lettuce be warned.

Resin from the dead

A photo shows a mummy in the fetal position on top of sand with other artifacts surrounding it.
Credit: Stephen Buckley
Plant extracts in the wrapping of this mummy at the Egyptian Museum in Turin, Italy, show that it is the oldest-known embalmed body.

By using gas chromatography and mass spectrometry, researchers figured out in 2018 what went into the fluid used by Egyptians in the second and third millennia BCE. The mixture, gathered from the wrist of the oldest-known mummy in the world, included plant oils, phenolic acids, and plant sugars, plus dehydroabietic acid and diterpenoids from conifer resin (J. Archaeol. Sci. 2018, DOI: 10.1016/j.jas.2018.07.011). The recipe was a surprise to some experts, who thought that during that era, people turned to the dry sands of the desert to mummify corpses. The study’s authors noted that these chemicals were common at later times in the mummification rites of ancient Egypt. The findings suggest that mummification was part of Egyptian cultural identity well before the time of the pharaohs, with whom it is most identified. Mummy mia!

If it’s yellow, let it mellow

A photo compares samples of unrefined Indian yellow, which is cut into small, smooth chunks, and raw Indian yellow, which is a rough, orangey-brown, basketball-sized ball that is formed from cow pee.
Credit: Jennifer Aubin/President and Fellows of Harvard College
Researchers found hippuric acid in a ball of unrefined Indian yellow pigment (right).

Feed a cow only mango leaves and water, and the cow will give you urine that you can turn into paint. And that paint has made artists swoon. In 2018, researchers confirmed that Indian yellow, a brilliant golden pigment prized by artists in the 1800s, was likely manufactured from dried cakes of cow pee (Dyes Pigm. 2018, DOI: 10.1016/j.dyepig.2018.08.014). For years, people pooh-poohed this idea, documented by only one person in 1883, but by using gas and liquid chromatography and mass spectrometry on unrefined samples of the pigment, researchers teased out a chemical called hippuric acid, which is found, you guessed it, in cow urine.

A fizzy splash of color

A photo shows two samples of white paint. A gloved finger is clean after touching the left one, whereas a gloved finger has white residue on it after touching the paint on the right.
Credit: Jaddie Ho
A commercial latex paint (right) has poor resistance to mechanical abrasion, but a new coating made with carbonated water is relatively clean to the touch.

In the quest for more ecofriendly coatings that can withstand heavy-duty use came this bubbly idea from a research team in Canada during 2018: a paint made with carbonated water. The paint consists of a polymer with charged side chains that dissolves in carbonation. But after it’s applied to a surface, the water and carbon dioxide evaporate, leaving behind a neutral polymer film. The coating withstood submersion and appeared to be durable in testing (Green Chem.2018, DOI: 10.1039/c8gc00130h). But there’s one downside to this low-pressure, Perrier-like paint: it doesn’t pop and hiss when you open the can.

I frizz you not

The left and center panels of the photo show hair frizzing out at all angles, whereas the hair sample on the right stays straight.
Credit: Chem
Unlike natural hair (left) and a sample colored with a commercial dye (center), graphene-dyed hair (right) resists frizz caused by electrostatic charging (bottom panels).

Could bad hair days be a thing of the past? Researchers in Chicago think so, thanks to a graphene-based hair dye that lends locks a variety of dark hues, tamps down flyaways, and lasts for up to 30 washes (Chem 2018, DOI: 10.1016/j.chempr.2018.02.021). Most hair dyes disrupt the hair shaft, allowing chemicals to meddle with melanin pigments, but lead researcher Jiaxing Huang explained that his team’s hair dye, formulated with the biopolymer chitosan and vitamin C, binds to the surface of hair. It does so through hydrogen bonds and interactions between chitosan and the hair’s keratin. And it seems to stop the electrostatic interactions that lead to the enemy of all good hairdos: frizz.

It’s all in the bag

A black-and-white video clip shows a droplet falling into water and being enclosed.
Credit: Science
In just 36 µs, a polystyrene sheet wraps around a plummeting droplet of oil, creating a capsule about 1 mm wide.

They may not hold a laptop, wallet, and keys, but tiny cargo bags made in 2018 may work for targeted delivery of reagents or as mini flasks for reactions. The US-based research team that made them dropped a hydrophobic liquid onto an ultrathin polymer disk floating on top of a water-based solution. As the hydrophobic droplet hit the surface and plunged into the solution, the polymer disk wrapped around the water-hating liquid, forming a capsule (Science2018, DOI: 10.1126/science.aao1290). This action, which creates tiny polymer-coated vesicles, takes just a fraction of a second.



This story was updated on Jan. 15, 2019, to correct when Egyptians used the embalming fluid studied. The fluids were used during the second and third millennia BCE.


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