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.

Enlarge / Emmanuelle Charpentier reminds everybody about pandemic safety at the start of a press conference following the announcement of her Nobel Prize. (credit: Pictures Alliance/Getty Images)

On Wednesday, the Nobel Prize Committee awarded the Chemistry Nobel to Emmanuelle Charpentier and Jennifer Doudna, who made key contributions to the development of the CRISPR gene-editing system, which has been used to produce the first gene-edited humans. This award may spur a bit of controversy, as there were a lot of other contributors to the development of CRISPR (enough to ensure a bitter patent fight), and Charpentier and Doudna's work was well into the biology side of chemistry. But nobody's going to argue that the gene editing wasn't destined for a Nobel Prize.

Basic science

The history of CRISPR gene editing is a classic story of science: a bunch of people working in a not-especially-cutting-edge area of science found something strange. The "something" in this case was an oddity found in the genome sequences of a number of bacteria. Despite being very distantly related, the species all had a section of the genome where a set of DNA sequences were repeated, with a short spacer in between them. The sequences picked up the name CRISPR for "clustered regularly interspaced short palindromic repeats," but nobody knew what they were doing there.

The fact that they might be important became apparent when researchers recognized that bacteria that had CRISPR sequences invariably also had a small set of genes associated with them. Since bacteria tended to rapidly lose genes and repeat sequences that weren't performing useful functions, this obviously implied some sort of utility. But it took 18 years for someone to notice that the repeated sequences matched those found in the genomes of viruses that infected the bacteria.

Enlarge / Seven La Chamba unglazed ceramic pots were used in a yearlong cooking experiment analyzing the chemical residues of the meals prepared. (credit: Melanie Miller )

Archaeologists are fascinated by many different aspects of cultures in the distant past, but determining what ancient people cooked and ate can be particularly challenging. A team of researchers spent an entire year analyzing the chemical residues of some 50 meals cooked in ceramic pots and found such cookware retained not just the remnants of the last meal cooked, but also clues as to earlier meals, spanning a pot's lifetime of usage. This could give archaeologists a new tool in determining ancient diets. The researchers described their results in a recent paper published in the journal Scientific Reports.

According to co-author Christine Hastorf , an archaeologist at the University of California, Berkeley (UCB), the project has been several years in the making. Hastorf has long been interested in the relationships between people and plants throughout history, particularly as they pertain to what people ate in the past. Back in 1985, she co-authored a paper examining the isotopes of charred plant remains collected from the inside of pots. She has also long taught a food archaeology class at UCB. A few years ago, she expanded the course to two full semesters (nine months), covering both the ethnographic aspects as well as the archaeological methods one might use to glean insight into the dietary habits of the past.

The class was especially intrigued by recent molecular analysis of pottery, yet frustrated by the brevity of the studies done to date on the topic. Hastorf proposed conducting a longer study, and her students responded enthusiastically. So they devised a methodology, assigned research topics to each student, and located places to purchase grain (maize and wheat from the same region of the Midwest), as well as receiving venison in the form of donated deer roadkill. She even bought her own mill so they could grind the grains themselves, setting it up in her home garage.

Enlarge / Ordered rock crystals, courtesy of a salt mine. (credit: Lech Darski )

Better batteries are a critical enabling technology for everything from your gadgets all the way up to the stability of an increasingly renewable grid. But most of the obvious ways of squeezing more capacity into a battery have been tried, and they all run straight into problems. While there may be ways to solve those problems, they're going to need a lot of work to overcome those hurdles.

Earlier this week, a paper covers a new electrode material that seems to avoid the problems that have plagued other approaches to expanding battery capacity. And it's a remarkably simple material: a variation on the same structure that's formed by crystals of table salt. While it's far from being ready to throw in a battery, the early data definitely indicate it's worth looking into further.

Lithium density

Lithium-ion batteries, as their name implies, involve shuffling lithium between the cathode and the anode of the battery. The consequence of this is that both of the electrodes will end up needing to store lithium atoms . So most ideas for next-generation batteries involve finding electrode materials that do so more effectively.

Sour beer has been around for centuries, and has become a favorite with craft brewers in recent years. But the brewing process can be unpredictable. To help brewers better understand how sour beers develop their distinctive complex flavors, chemists at the University of Redlands in California have been tracking various chemical compounds that contribute to those flavor profiles, monitoring how their concentrations change over time during the aging process. They presented their initial findings during the American Chemical Society's Fall 2020 Virtual Meeting & Expo last week.

Goses, lambics, and wild ales, oh my!

Brewers of standard beer carefully control the strains of yeast they use, taking care to ensure other microbes don't sneak into the mix, lest they alter the flavor during fermentation. Sour beer brewers use wild yeasts , letting them grow freely in the wort, sometimes adding fruit for a little extra acidity. Then the wort is transferred to wooden barrels and allowed to mature for months or sometimes years, as the microbes produce various metabolic products that contribute to sour beer's unique flavor. But the brewers don't always know exactly which compounds end up in the final product or how it will impact the overall flavor profile. "That is the quandary of the sour beer brewer," said co-author David Soulsby during a virtual press conference .

"Sour beer tastes very different from regular beer, but it's a very complex and rich flavor experience. These different flavors come from the complex processes that are occurring during aging," said co-author Teresa Longin, who also happens to be married to Soulsby. "These processes are hard to control and can be hard to reproduce. Our research focuses on understanding what these processes are, what's happening over time, so that the brewer can ultimately understand them and make better beer."