Tag Archives: #chemical

Why Do Onions Make Us Cry (Science / Food)

Sometimes a strange but simple fact—that onions make you cry, for example—is so accepted that you forget to ever stop and wonder…why? That is, until you’re chopping with a 3-year-old who gets mad at you because you made her weep for no reason. For example.

How does it work? So what’s going on with onions that make you cry, or make you shell out $20 for a pair of onion goggles? As Eric Block, author of the book Garlic and Other Alliums (onions are part of the plant genus allium) explained to NPR, “the onion is a perennial bulb that lives in the ground with lots of critters who are looking for a snack.” And so they have a chemical defense system, which, like a skunk fending off predators with a stench, releases the tear-jerker chemical to protect itself from being eaten. Within each cell of an onion is a sealed vacuole filled with enzymes that rupture when cut into. The enzymes then mix with other chemicals in the onion cell and, in Blocks words, “a whole cascade of chemical processes happen within an instant.”

The result of all those chemical processes are syn-propanethial-S-oxide molecules, the irritating culprit making you (or your 3-year-old) cry. “[It] really is quite beautiful from a scientific viewpoint,” Block said.

So what can I do? You’ve probably heard plenty of tips: Hold a silver spoon in your mouth, hold a piece of bread in your mouth, cut the onion underwater, use a super sharp knife… But Block’s tip is simple, and makes plenty of sense once you understand the onion science. “If you just cut the onion in a stream of air blowing away from your face,” he says, “then you’ll pull the molecules away and they won’t get to your eyes.”

Scientists Find Efficient Way to Convert Carbon Dioxide into Ethylene (Chemistry)

Electrochemical CO2 reduction to value-added chemical feedstocks is of considerable interest for renewable energy storage and renewable source generation while mitigating CO2 emissions from human activity. Copper represents an effective catalyst in reducing CO2 to hydrocarbons or oxygenates, but it is often plagued by a low product selectivity and limited long-term stability. Now Choi and colleagues reported that copper nanowires with rich surface steps to catalyze a chemical reaction that reduces carbon dioxide (CO2) emissions while generating ethylene (C2H4), an important chemical used to produce plastics, solvents, cosmetics and other important products globally.

Copper represents an effective catalyst in reducing carbon dioxide to hydrocarbons or oxygenates, but it is often plagued by a low product selectivity and limited long-term stability. Choi et al report that copper nanowires with rich surface steps exhibit a remarkably high Faradaic efficiency for ethylene that can be maintained for over 200 hours. Image credit: Choi et al, doi: 10.1038/s41929-020-00504-x.

Using copper to kick start the carbon dioxide reduction into ethylene reaction has suffered two strikes against it.

First, the initial chemical reaction also produced hydrogen and methane — both undesirable in industrial production.

Second, previous attempts that resulted in ethylene production did not last long, with conversion efficiency tailing off as the system continued to run.

To overcome these two hurdles, Professor Goddard III and colleagues focused on the design of the copper nanowires with highly active steps — similar to a set of stairs arranged at atomic scale.

One intriguing finding of this collaborative study is that this step pattern across the nanowires’ surfaces remained stable under the reaction conditions, contrary to general belief that these high energy features would smooth out.

This is the key to both the system’s durability and selectivity in producing ethylene, instead of other end products.

The scientists demonstrated a carbon dioxide-to-ethylene conversion rate of greater than 70%, much more efficient than previous designs, which yielded at least 10% less under the same conditions.

The new system ran for 200 hours, with little change in conversion efficiency, a major advance for copper-based catalysts.

In addition, the comprehensive understanding of the structure-function relation illustrated a new perspective to design highly active and durable carbon dioxide reduction catalyst in action.

References: Choi, C., Kwon, S., Cheng, T. et al. Highly active and stable stepped Cu surface for enhanced electrochemical CO2 reduction to C2H4. Nat Catal (2020). https://doi.org/10.1038/s41929-020-00504-x link: https://www.nature.com/articles/s41929-020-00504-x

Wearables Could Detect Chemical Threats (Chemistry)

In a time when chemical attacks have occurred in different parts of the world, the race is on to find better ways to identify harmful substances in a hurry. A major game-changer could be a new type of glove, outfitted with the latest biosensor technology that could analyze chemicals with a simple swipe of the finger.

Wearable devices are one of the fastest-growing areas of technology, and estimated to be worth over $34 billion by 2020. Until recently, they have mostly centered around health, fitness, and geolocation. You can monitor your heart rate and number of calories burned, and track the number of steps you’ve taken during your morning run, and always find your way back home thanks to the GPS on your wrist or in your pocket.

Scientists are now exploring new applications for wearable technology. One of the important frontiers is security. Consider the “lab on a glove,” a concept developed by a team led by Joseph Wang at the University of California, San Diego that allows first responders to detect chemicals from explosives, gunpowder residue, drugs, or other substances (even on a suspect’s clothing) without worry of injury from skin exposure or inadvertently compromising the crime scene.

Fig: The ‘lab-on-a-glove’ developed by us and the University of California, San Diego can detect OP compounds, a group of toxic chemicals found in some pesticides. Image: Joseph Wang/University of Californla, San Diego

Wang and colleague Joseph Hubble recently published an op-ed article in Chemistry World regarding the potential for their glove technology to help solve crimes and aid victims. It could not only detect chemicals in terror attacks, it could also help in accidents (such as environmental spills), and factory mishaps. Similar devices including a hazard-detecting badge developed by Timothy Swager and his team at the Massachusetts Institute of Technology (MIT) could also play a role. Eventually, they envision wearable technology that could simultaneously detect threats and alert first responders, saving precious time (and lives) in the event of an emergency.

Fig: The lab-on-a-glove uses a printed carbon pad on the thump to swipe for nerve agents. A special stretchable ink is printed onto the index finger in a serpentine design, ideal for stretching. The glove uses enzyme-based biosensors to detect OP nerve agents and integrated electronics to analyse the sample. Image: Joseph Wang/University of California, San Diego

Beyond the potential for external wearable devices such as glasses or clothing, Wang and Hubble are also intrigued by the future of non-invasive wearable technology integrated with the human body, citing the Derma Abyss project developed at MIT’s Media Lab to serve as real-time health monitors for those with chronic health conditions such as diabetes. As they write, “The possibilities around what the future holds for wearable sensors are boundless, freeing ourselves from the laboratory bench and taking chemical analysis directly to people.”


References: (1) https://www.forbes.com/sites/paullamkin/2016/02/17/wearable-tech-market-to-be-worth-34-billion-by-2020/ (2) https://www.chemistryworld.com/news/forensic-fingers/6406.article (3) http://news.mit.edu/2016/wireless-wearable-toxic-gas-detector-0630 (4) https://www.iflscience.com/health-and-medicine/biosensing-tattoo-changes-color-blood-sugar-levels-change/

This Is A Metal That Melts In Your Hands (Chemistry)

When you think of metal, you most likely think of strength and toughness. Well, element gallium is here to change that perception.

The element gallium is an unexpected metal—it’s a soft, silvery-white metal that is solid at room temperature (similar to aluminum) but it can literally melt in the palm of your hand. It’s bizarre and a little unsettling to see, but it makes sense. The melting point for gallium (which is represented on the Periodic Table as Ga) is relatively low, at 85.6°F (29.8°C). However, the boiling point for this element is quite high, at 4044°F (2229°C). This quality makes gallium ideal for recording temperatures that would destroy a thermometer. According to the Los Alamos National Laboratory, gallium is “one of four metals — mercury, cesium, and rubidium — which can be liquid near room temperature and, thus, can be used in high-temperature thermometers. It has one of the longest liquid ranges of any metal and has a low vapor pressure even at high temperatures.”

WHAT ELSE IS IT GOOD FOR?

Gallium is more than just a weirdo substance to poke at in the palm of your hand. As the Los Alamos National Laboratory explains, “Gallium wets glass or porcelain and forms a brilliant mirror when it is painted on glass. It is widely used in doping semiconductors and producing solid-state devices such as transistors. Magnesium gallate containing divalent impurities, such as Mn+2, is finding use in commercial ultraviolet-activated powder phosphors. Gallium arsenide is capable of converting electricity directly into coherent light. Gallium readily alloys with most metals, and has been used as a component in low-melting alloys.”


References: (1) http://www.rsc.org/periodic-table/element/31/gallium (2) https://periodic.lanl.gov/31.shtml (3) https://periodic.lanl.gov/80.shtml (4) https://periodic.lanl.gov/55.shtml (5) https://periodic.lanl.gov/37.shtml

Azidoazide Azide Is The World’s Most Explosive Chemical (Chemistry)

What’s the most explosive chemical you can think of? Nitroglycerin? Napalm? Let us introduce you to most volatile chemical known to man: azidoazide azide.

THE CHEMICAL MOST CHEMISTS WON’T TOUCH

Azidoazide azide is the most explosive chemical compound ever created. It is part of a class of chemicals known as high-nitrogen energetic materials, and it gets its “bang” from the 14 nitrogen atoms that compose it in a loosely bound state. This material is both highly reactive and highly explosive. It’s so sensitive, that it will explode in virtually any scenario—even when left completely alone.

In his aptly named article, Things I Won’t Work With: Azidoazide Azides, More Or Less, chemist Derek Lowe explains a research group’s attempt to study the stuff, illustrating just how explosive we’re talking: “The compound exploded in solution, it exploded on any attempts to touch or move the solid, and (most interestingly) it exploded when they were trying to get an infrared spectrum of it.” Suffice it to say, this chemical will explode if you so much as look at it funny.

WHY DOES IT EXIST?

Obviously, you won’t see azidoazide azide for sale in your local hardware store any time soon. While other azides have their uses in creating explosives and aiding medicine—sodium azide, for example, plays a role in the world of medical devices—azidoazide azide is entirely the realm of experimental chemistry. It’s a good thing, too. We’d rather leave this chemical to the professionals.


References: (1) https://blogs.sciencemag.org/pipeline/archives/2013/01/09/things_i_wont_work_with_azidoazide_azides_more_or_less (2) https://www.fda.gov/MedicalDevices/Safety/AlertsandNotices/TipsandArticlesonDeviceSafety/ucm186147.htm