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Category: chemistry

A personal, handheld device emitting high-intensity ultraviolet light to disinfect areas by killing the novel coronavirus is now feasible, according to researchers at Penn State, the University of Minnesota and two Japanese universities.

There are two commonly employed methods to sanitize and disinfect areas from bacteria and viruses—chemicals or ultraviolet radiation exposure. The UV radiation is in the 200 to 300 nanometer range and known to destroy the virus, making the virus incapable of reproducing and infecting. Widespread adoption of this efficient UV approach is much in demand during the current pandemic, but it requires UV radiation sources that emit sufficiently high doses of UV light. While devices with these high doses currently exist, the UV radiation source is typically an expensive mercury-containing gas discharge lamp, which requires high power, has a relatively short lifetime, and is bulky.

The solution is to develop high-performance, UV light emitting diodes, which would be far more portable, long-lasting, energy efficient and environmentally benign. While these LEDs exist, applying a current to them for light emission is complicated by the fact that the also has to be transparent to UV light.

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Batteries that use a sodium-ion chemistry rather than the commonplace lithium-ion could offer a number of advantages, owing to the cheap and abundant nature of the element. Scientists at Washington State University have come up with a design billed as a potential game changer in this area – a sodium-ion battery offering a comparable energy capacity and cycling ability to some lithium-ion batteries already on the market.

In a way, sodium-ion batteries function just like lithium-ion batteries, generating power by bouncing ions between a pair of electrodes in a liquid electrolyte. One of the problems with them in their current form, however, is that while this is going on inactive sodium crystals tend to build up on the surface of the negatively-charged electrode, the cathode, which winds up killing the battery. Additionally, sodium-ion batteries don’t hold as much energy as their lithium-ion counterparts.

“The key challenge is for the battery to have both high energy density and a good cycle life,” says Washington State University’s Junhua Song, lead author on the paper.

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One of the biggest challenges for renewable energy research is energy storage. The goal is to find a material with high energy storage capacity and energy storage material with high storage capacity that can also quickly and efficiently discharge a large amount of energy. In an attempt to overcome this hurdle, researchers at the Queensland University of Technology (QUT) have proposed a brand-new carbon nanostructure designed to store energy in mechanical form.

Most portable energy storage devices currently rely on storing energy in chemical form such as batteries, however this proposed new structure, made from a bundle of diamond nanothread (DNT) does not suffer from the same limiting properties as batteries, such as temperature sensitivity, or the potential to leak or explode. I have previously written about carbon nanotubes, and their applications in everything from Batman-like artificial muscle, to an analogy of the fictional element Vibranium, but a lot of research around carbon nanotubes is already focused on energy harvesting and energy storage applications.

What makes this energy storage method different is the method by which energy is stored, and also the related increased robustness of the resultant material. Dr Haifei Zhan and his team at the QUT Centre for material science used computer modelling to propose the structure of these ultra-thin one-dimensional carbon threads. The theory is that these threads should be able to store energy when they are twisted or stretched, similar to the way we store energy in wind-up toys. By turning the key, we force the spring inside into a tight coil. Once the key is released, the coil wishes to release the extra tension held within it and begins to unfurl. In doing so it transfers that mechanical energy into the movement of the toy’s wheels.

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In the periodic table of elements there is one golden rule for carbon, oxygen and other light elements: Under high pressures, they have similar structures to heavier elements in the same group of elements. But nitrogen always seemed unwilling to toe the line. However, high-pressure chemistry researchers of the University of Bayreuth have disproved this special status. Out of nitrogen, they created a crystalline structure which, under normal conditions, occurs in black phosphorus and arsenic. The structure contains two-dimensional atomic layers, and is therefore of great interest for high-tech electronics. The scientists have presented this “black nitrogen” in Physical Review Letters.

Nitrogen—an exception in the periodic system?

When you arrange the chemical elements in ascending order according to their number of protons and look at their properties, it soon becomes obvious that certain properties recur at large intervals (periods). The brings these repetitions into focus. Elements with similar properties are placed one below the other in the same column, and thus form a group of elements. At the top of a column is the element that has the fewest protons and the lowest weight compared to the other group members. Nitrogen heads element group 15, but was previously considered the “black sheep” of the group. The reason: In earlier experiments, showed no structures similar to those exhibited under normal conditions by the of this group—specifically, phosphorus, arsenic and antimony. Instead, such similarities are observed at high pressures in the neighboring groups headed by carbon and oxygen.

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Study co-led by Berkeley Lab reveals how wavelike plasmons could power up a new class of sensing and photochemical technologies at the nanoscale.

Wavelike, collective oscillations of electrons known as “plasmons” are very important for determining the optical and electronic properties of metals.

In atomically thin 2D materials, plasmons have an energy that is more useful for applications, including sensors and communication devices, than plasmons found in bulk metals. But determining how long plasmons live and whether their energy and other properties can be controlled at the nanoscale (billionths of a meter) has eluded many.

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Circa 2007

This chapter describes detection of explosives by terahertz Imaging ™. There has been an amplified interest in terahertz (THz) detection for imaging of covered weapons, explosives, chemical and biological agents. THz radiation is readily transmitted through most nonmetallic and nonpolar mediums. This process enables the THz systems to see through concealing barriers, which includes packaging, corrugated cardboard, clothing, shoes, book bags, and such others to find potentially dangerous materials concealed within. Apart from many materials of interest for security applications, which include explosives, chemical agents, and other such biological agents that have characteristic THz spectra which can be used for fingerprint testing and identify concealed materials. The Terahertz radiation poses either no or minimal health risk to either a suspect being scanned by a THz system or the system’s operator. As plastic explosives, fertilizer bombs, and chemical and biological agents increasingly become weapons of war and terrorism, and the trafficking of illegal drugs increasingly develops as a systemic threat, effective means for rapid detection, and an identification of these threats are required. One proposed solution for locating, detecting, and characterizing concealed threats is to use THz electromagnetic waves to spectroscopically detect and identify concealed materials through their characteristic transmission or reflectivity spectra in the range of 0.5–10 THz.

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VICE.

What do a frying pan, an LED light, and the most cutting edge camouflage in the world have in common? Well, that largely depends on who you ask. Most people would struggle to find the link, but for University of Michigan chemical engineers Sharon Glotzer and Michael Engel, there is a substantial connection, indeed one that has flipped the world of materials science on its head since its discovery over 30 years ago.

The magic ingredient common to all three items is the quasiperiodic crystal, the “impossible” atomic arrangement discovered by Dan Shechtman in 1982. Basically, a quasicrystal is a crystalline structure that breaks the periodicity (meaning it has translational symmetry, or the ability to shift the crystal one unit cell without changing the pattern) of a normal crystal for an ordered, yet aperiodic arrangement. This means that quasicrystalline patterns will fill all available space, but in such a way that the pattern of its atomic arrangement never repeats. Glotzer and Engel recently managed to simulate the most complex quasicrystal ever, a discovery which may revolutionize the field of crystallography by blowing open the door for a whole host of applications that were previously inconceivable outside of science-fiction, like making yourself invisible or shape-shifting robots.

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The strongest permanent magnets today contain a mix of the elements neodymium and iron. However, neodymium on its own does not behave like any known magnet, confounding researchers for more than half a century. Physicists at Radboud University and Uppsala University have shown that neodymium behaves like a so-called ‘self-induced spin glass,’ meaning that it is composed of a rippled sea of many tiny whirling magnets circulating at different speeds and constantly evolving over time. Understanding this new type of magnetic behavior refines our understanding of elements on the periodic table and eventually could pave the way for new materials for artificial intelligence. The results will be published in Science on May 29, 2020.

“In a jar of honey, you may think that the once clear areas that turned milky yellow have gone bad. But rather, the jar of honey starts to crystallize. That’s how you could perceive the ‘aging’ process in neodymium.” Alexander Khajetoorians, professor in Scanning probe microscopy, together with professor Mikhail Katsnelson and assistant professor Daniel Wegner, found that the material neodymium behaves in a complex magnetic way that no one ever saw before in an element on the periodic table.

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There has been plenty of empirical evidence which shows that the single-particle picture holds to a good approximation in atomic nuclei. In this picture, protons and neutrons move independently inside a mean-field potential generated by an interaction among the nucleons. This leads to the concept of nuclear shells, similar to the electronic shells in atoms. In particular, the magic numbers due to closures of the nucleonic shells, corresponding to noble gases in elements, have been known to play an important role in nuclear physics. Here we propose a periodic table for atomic nuclei, in which the elements are arranged according to the known nucleonic shells. The nuclear periodic table clearly indicates that nuclei in the vicinity of the magic numbers can be understood in terms of a shell closure with one or two additional nucleons or nucleon holes, while nuclei far from the magic numbers are characterized by nuclear deformation.

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A machine-learning algorithm has been developed by scientists in Japan to breathe new life into old molecules. Called BoundLess Objective-free eXploration, or Blox, it allows researchers to search chemical databases for molecules with the right properties to see them repurposed. The team demonstrated the power of their technique by finding molecules that could work in solar cells from a database designed for drug discovery.

Chemical repurposing involves taking a molecule or material and finding an entirely new use for it. Suitable molecules for chemical repurposing tend to stand apart from the larger group when considering one property against another. These materials are said to be out-of-trend and can display previously undiscovered yet exceptional characteristics.

‘In public databases there are a lot of molecules, but each molecule’s properties are mostly unknown. These molecules have been synthesised for a particular purpose, for example drug development, so unrelated properties were not measured,’ explains Koji Tsuda of the Riken Centre for Advanced Intelligence and who led the development of Blox. ‘There are a lot of hidden treasures in databases.’

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