Enlarge / Brewing kombucha tea. Note the trademark gel-like layer of SCOBY (symbiotic culture of bacteria and yeast). (credit: Olga Pankova/Getty Images)

Kombucha tea is all the rage these days as a handy substitute for alcoholic beverages and for its supposed health benefits. The chemistry behind this popular fermented beverage is also inspiring scientists at MIT and Imperial College London to create new kinds of tough "living materials" that could one day be used as biosensors, helping purify water or detect damage to "smart" packing materials, according to a recent paper published in Nature Materials.

You only need three basic ingredients to make kombucha . Just combine tea and sugar with a kombucha culture known as a SCOBY (symbiotic culture of bacteria and yeast), aka the "mother," also known as a tea mushroom, tea fungus, or a Manchurian mushroom. (It's believed that kombucha tea originated in Manchuria, China, or possibly Russia.) It's basically akin to a sourdough starter. A SCOBY is a firm, gel-like collection of cellulose fiber (biofilm), courtesy of the active bacteria in the culture, creating the perfect breeding ground for the yeast and bacteria to flourish. Dissolve the sugar in non-chlorinated boiling water, then steep some tea leaves of your choice in the hot sugar water before discarding them.

Once the tea cools, add the SCOBY and pour the whole thing into a sterilized beaker or jar. Then cover the beaker or jar with a paper towel or cheesecloth to keep out insects, let it sit for two to three weeks, and voila! You've got your own home-brewed kombucha. A new "daughter" SCOBY will be floating right at the top of the liquid (technically known in this form as a pellicle). But be forewarned: it's important to avoid contamination during preparation because drinking tainted kombucha can have serious, even fatal, adverse effects . And despite claims that drinking kombucha tea can treat aging, arthritis, cancer, constipation, diabetes, or even AIDS, to date there is no solid scientific evidence to back those claims.

Enlarge / Pluto's atmosphere is fairly hazy. (credit: NASA )

Saturn’s moon Titan is distinctive, in part for its orange-ish and hazy atmosphere. It’s virtually impossible to see surface features because the haze is so opaque in the visible portion of the spectrum; what we know of it comes from things like radar imagery, instead. The haze is the product of chemical reactions in the upper atmosphere, driven by ultraviolet radiation. These then cascade into larger and more complex organic (reminder: that doesn’t mean biological) molecules.

The New Horizons mission to Pluto showed that the dwarf planet, too, has a haze. It’s less prominent in Pluto’s meager atmosphere, but it is there (it's actually similar to the one on Neptune’s moon Triton ). Because Pluto’s atmosphere isn’t that different from the upper reaches of Titan’s atmosphere, it has been thought that the same chemistry is responsible.

But a new study led by Panayotis Lavvas at the University of Reims Champagne-Ardenne shows that Pluto’s haze may require a different explanation. On both bodies, the atmosphere contains methane, carbon monoxide, and nitrogen. But if Titan’s process worked at the same rate on Pluto, it wouldn’t make enough haze particles to match what we’ve measured there. As Pluto’s atmosphere is even colder than the upper atmosphere on Titan, that haze particle chemistry should be running slower on Pluto.

Enlarge / The concoction featured in Road Dahl's 1981 children's book, George's Marvelous Medicine , could be harmful—even fatal—to grandmas, new BMJ study finds. (credit: YouTube/Storyvision Studios UK )

Famed children's author Roald Dahl greatly admired doctors who pioneered new medicines, and even dedicated his 1981 book, George's Marvelous Medicine —in which a young boy cooks up a potion using various ingredients around his family farm—to "doctors everywhere." Copies of the book contain a disclaimer to readers, warning them not to try to make George's concoction at home, as it could be dangerous. And now a recent paper published in the annual Christmas issue of the British Medical Journal (BMJ) has determined just how toxic the concoction could be if ingested.

The BMJ's Christmas issue is typically more light-hearted in nature, although the journal maintains that the papers published therein still "adhere to the same high standards of novelty, methodological rigour, reporting transparency, and readability as apply in the regular issue." Past years have included papers on such topics as why 27 is not a dangerous age for musicians, and the side effects of sword swallowing, among others. The most widely read was 1999’s infamous “ Magnetic resonance imaging of male and female genitals during coitus and female sexual arousal .” (We wrote about the paper last year to mark the 20th anniversary of its publication.)

(Spoilers for the 1981 children's book below.)

Enlarge / There could soon be an easier way to tell how hot that chili pepper is. (credit: Azman Mohamad / EyeEm via Getty Images )

Capsaicin is the compound responsible for determining just how hot a variety of chili pepper will be; the higher the capsaicin levels, the hotter the pepper. There are several methods for quantifying just how much capsaicin is present in a pepper—its "pungency"—but they are either too time-consuming, too costly, or require special instruments, making them less than ideal for widespread use.

Now a team of scientists from Prince of Songkla University in Thailand has developed a simple, portable sensor device that can connect to a smartphone to show how much capsaicin is contained in a given chili pepper sample, according to a new paper in the journal ACS Applied Nano Materials. Bonus: the device is whimsically shaped just like a red-hot chili pepper.

An American pharmacist named Wilbur Scoville invented his eponymous Scoville scale for assessing the relative hotness of chili peppers back in 1912. That testing process involves dissolving a precise amount of dried pepper in alcohol so as to extract the capsaicinoids. The capsaicinoids are then diluted in sugar water. A panel of five trained tasters then tastes multiple samples with decreasing concentrations of capsaicinoids until at least three of them can no longer detect the heat in a given sample. The hotness of the pepper is then rated according to its Scoville heat units (SHU).

Enlarge / Workers sort plastic waste as a forklift transports plastic waste at Yongin Recycling Center in Yongin, South Korea. (credit: Bloomberg/Getty Images )

A few years back, it looked like plastic recycling was set to become a key part of a sustainable future. Then, the price of fossil fuels plunged, making it cheaper to manufacture new plastics. Then China essentially stopped importing recycled plastics for use in manufacturing. With that, the bottom dropped out of plastic recycling, and the best thing you could say for most plastics is that they sequestered the carbon they were made of.

The absence of a market for recycled plastics, however, has also inspired researchers to look at other ways of using them. Two papers this week have looked into processes that enable "upcycling," or converting the plastics into materials that can be more valuable than the freshly made plastics themselves.

Make me some nanotubes

The first paper, done by an international collaboration, actually obtained the plastics it tested from a supermarket chain, so we know it works on relevant materials. The upcycling it describes also has the advantage of working with very cheap, iron-based catalysts. Normally, to break down plastics, catalysts and the plastics are heated together. But in this case, the researchers simply mixed the catalyst and ground up plastics and heated the iron using microwaves.

Enlarge / Popeye reaches for a can of spinach in a still from an unidentified Popeye film, c. 1945. Scientists at American University believe the leafy green has the potential to help power future fuel cells. (credit: Paramount Pictures/Courtesy of Getty Image)

When it comes to making efficient fuel cells , it's all about the catalyst. A good catalyst will result in faster, more efficient chemical reactions and, thus, increased energy output. Today's fuel cells typically rely on platinum-based catalysts. But scientists at American University believe that spinach —considered a "superfood" because it is so packed with nutrients—would make an excellent renewable carbon-rich catalyst, based on their proof-of-principle experiments described in a recent paper published in the journal ACS Omega. Popeye would definitely approve.

The notion of exploiting the photosynthetic properties of spinach has been around for about 40 years now. Spinach is plentiful, cheap, easy to grow, and rich in iron and nitrogen. Many (many!) years ago, as a budding young science writer, I attended a conference talk by physicist Elias Greenbaum (then with Oak Ridge National Labs) about his spinach-related research . Specifically, he was interested in the protein-based "reaction centers" in spinach leaves that are the basic mechanism for photosynthesis—the chemical process by which plants convert carbon dioxide into oxygen and carbohydrates.

There are two types of reaction centers. One type, known as photosystem 1 (PS1), converts carbon dioxide into sugar; the other, photosystem 2 (PS2), splits water to produce oxygen. Most of the scientific interest is in PS1, which acts like a tiny photosensitive battery, absorbing energy from sunlight and emitting electrons with nearly 100 percent efficiency. In essence, energy from sunlight converts water into an oxygen molecule, a positively charged hydrogen ion, and a free electron. These three molecules then combine to form a sugar molecule. PS1s are capable of generating a light-induced flow of electricity in fractions of a second.

Enlarge / Equipment including a diamond anvil cell (blue box) and laser arrays in the lab of Ranga Dias at the University of Rochester. Undoubtedly, they cleaned up the typical mess of cables and optical hardware before taking the photo.

In the period after the discovery of high-temperature superconductors, there wasn't a good conceptual understanding of why those compounds worked. While there was a burst of progress towards higher temperatures, it quickly ground to a halt, largely because it was fueled by trial and error. Recent years brought a better understanding of the mechanisms that enable superconductivity, and we're seeing a second burst of rapidly rising temperatures.

Equipment including a diamond anvil cell (blue box) and laser arrays are pictured in the lab of assistant professor of Mechanical Engineering and Physics and Astronomy Ranga Dias in Hopeman Hall August 26, 2020. Dias is studying the potential and applications of room temperature superconductivity in dense hydrogen-rich materials and carbon based materials. (Photo by J. Adam Fenster / University of Rochester) (credit: Adam Fenster)

The key to the progress has been a new focus on hydrogen-rich compounds, built on the knowledge that hydrogen's vibrations within a solid help encourage the formation of superconducting electron pairs. By using ultra-high pressures, researchers have been able to force hydrogen into solids that turned out to superconduct at temperatures that could be reached without resorting to liquid nitrogen.

Now, researchers have cleared a major psychological barrier by demonstrating the first chemical that superconducts at room temperature. There are just two catches: we're not entirely sure what the chemical is, and it only works at 2.5 million atmospheres of pressure.

Enlarge / Layers of phosphorene sheets form black carbon. (credit: Wikimedia Commons )

Right now, electric vehicles are limited by the range that their batteries allow. That's because recharging the vehicles, even under ideal situations, can't be done as quickly as refueling an internal combustion vehicle. So far, most of the effort on extending the range has been focused on increasing a battery's capacity. But it could be just as effective to create a battery that can charge much more quickly, making a recharge as fast and simple as filling your tank.

There are no shortage of ideas about how this might be arranged, but a paper published earlier this week in Science suggests an unusual way that it might be accomplished: using a material called black phosphorus, which forms atom-thick sheets with lithium-sized channels in it. On its own, black phosphorus isn't a great material for batteries, but a Chinese-US team has figured out how to manipulate it so it works much better. Even if black phosphorus doesn't end up working out as a battery material, the paper provides some insight into the logic and process of developing batteries.

Paint it black

So, what is black phosphorus? The easiest way to understand it is by comparisons to graphite, a material that's already in use as an electrode for lithium-ion batteries. Graphite is a form of carbon that's just a large collection of graphene sheets layered on top of each other. Graphene, in turn, is a sheet formed by an enormous molecule formed by carbon atoms bonded to each other, with the carbons arranged in a hexagonal pattern. In the same way, black phosphorus is composed of many layered sheets of an atom-thick material called phosphorene.