Author: chemistadmin

A team of physical chemists at Wageningen University and Research, Maastricht University and EnzyTag BV, all in the Netherlands, has uncovered the physical chemistry behind the ticks’ ability to adhere to the skin of its host. In their study, published in the journal Nature Chemistry, the group observed the evaporation of a drop of artificially synthesized amino acid similar to the kind produced in tick saliva to see if it would show phase separation.

Prior research has shown that when a tick catches a ride on a passing host, it adheres, then pierces the skin and feeds. In this new study, the research team noted that the sticking mechanism has not previously been well studied. They began by collecting samples of the saliva protein produced by the ticks, which they noted formed into solid cones when extruded onto the skin of its host. That meant that it was a bio-adhesive, the only one known to stick to a living substrate.

They found that the tick saliva had glycine-rich proteins, which was due to the tick upping its production just prior to latching onto a host. Prior research has shown that such proteins can prevent protein folding, which accounts for the degree of hardness of the cone that forms.

In studying the tick saliva and its proteins, the team found evidence of a possible liquid-to-liquid phase separation. To confirm it, they created a synthetic version of one of the main amino acids found in the saliva and placed a drop on a flat surface and watched it evaporate.

Prior research has shown that other liquid-to-liquid phase separations, such as those that occur in coffee, result in the creation of rings as they dry. After a few minutes, the research team found the rings they were expecting—they also noted fluorescence at the ring boundary and the creation of a rim. Finally, they observed tiny droplets of the synthesized protein floating in the rim.

Taken together, the behavior of the drop showed that liquid-to-liquid phase separation. The addition of salt helped to strengthen the bonds in the fluid, resulting in harder cones. To confirm that the natural tick saliva exhibited phase separation, they captured enough ticks to extract a quantity of saliva sufficient to repeat the earlier work using real saliva and found the same results.

© 2024 Science X Network

Screens for TVs, smartphones or other displays could be made with a new kind of organic LED material developed by an international team, co-led by University of Michigan engineers. The material maintains sharp color and contrast while replacing the heavy metal with a new hybrid material.

Curiously, the material also seemed to break a quantum rule.

OLED devices currently on the market include heavy metal components like iridium and platinum, which improve the efficiency, brightness and color range of the screen. But they come with drawbacks—significantly higher cost, a shorter device lifetime and increased health and environmental hazards.

In OLEDs, light emission through the more energy-efficient phosphorescence is preferred over fluorescence, but phosphorescence happens more slowly, taking milliseconds or longer without the heavy metal component. Speeding up phosphorescence to happen in microseconds is necessary to keep up with modern displays, which operate at 120 frames per second, without producing a lingering “ghost” image. This is a key role of the heavy metals.

“We found a way to make a phosphorescent organic molecule that can emit light on the microsecond scale, without including heavy metals in the molecular framework,” said Jinsang Kim, U-M professor of materials science and engineering and co-corresponding author of the study published in Nature Communications.

Dong Hyuk Park, professor of chemical and biomedical science and engineering at Inha University, and Sunkook Kim, professor of advanced materials science and engineering at Sungkyunkwan University, both in the Republic of Korea, are also co-corresponding authors.

The speed difference between fluorescence and phosphorescence is driven by what happens after electrons from the electrical current running through the OLED material slide into the high energy level within the molecule’s available electron orbitals, known as an excited state—sort of like jumping onto a rung of a ladder. In fluorescence, they can immediately release the energy as light, jumping back down to the ground state. But in phosphorescence, they have to make a conversion first.

The conversion has to do with the electron’s spin. Each electron has a partner in its ground state, and a quantum mechanical rule—Pauli Exclusion Principle—demands that they spin in opposite directions. But when an electron slides into that higher rung, it can end up spinning in either direction because each electron is now alone in its orbital. It only remains opposite its partner a quarter of the time, and this is the case that results in fluorescence.

Phosphorescence is three times more efficient because it harnesses the other 75% of excited electrons too, but it requires the electron to flip its spin before it can come back down. In conventional phosphorescent materials, the large atomic nucleus of the heavy metal generates a magnetic field that forces the same spin direction excited electron to turn quickly, resulting in faster light emission as it returns to its ground state.

The new material positions a 2D layer of molybdenum and sulfur near a similarly thin layer of the organic light emitting material, achieving the same effect by physical proximity without any chemical bonding. This hybrid construction sped up light emission by 1,000 times, achieving speeds fast enough for modern displays.

Light emission happens entirely within the organic material without having the weak metal-organic ligand bonding, helping the material last longer. Phosphorescent OLEDs that rely on heavy metals also use the metals to help produce the color, and the weaker chemical bonds between the metal and organic material can break apart when two excited electrons come into contact, dimming out the pixel.

Pixel burnout is a particular problem for high energy blue light that has yet to be solved, but the research team hopes their new design approach can help work towards stable, blue phosphorescent pixels. Current OLEDs use phosphorescent red and green pixels and fluorescent blue pixels, avoiding blue pixel burnout at the expense of lower energy efficiency.

Beyond the potential applications, analysis of this molecular hybrid system measured something once thought to be impossible—paired electrons sharing an orbital seemed to have a combined spin under dark conditions, suggesting a forbidden ‘triplet’ state when instead their spins should cancel one another out.

“We don’t yet fully understand what causes this triplet character in the ground state because this violates the Pauli Exclusion Principle. That is very impossible, but looking at the measurement data, yes, that seems to be the case,” Kim said. “That’s why we have a lot of questions about what really makes that happen.”

The research team will explore how the material achieves triplet character ground states while also pursuing potential spintronics device applications.

Collaborators from the University of California, Berkeley and Dongguk University contributed to the study. Jinsang Kim is also a director of academic programs for macromolecular science and engineering and a professor of chemistry.

Water electrolysis is a cornerstone of global sustainable and renewable energy systems, facilitating the production of hydrogen fuel. This clean and versatile energy carrier can be utilized in various applications, such as chemical CO₂ conversion, and electricity generation. Utilizing renewable energy sources such as solar and wind to power the electrolysis process may help reduce carbon emissions and promote the transition to a low-carbon economy.

The development of efficient and stable anode materials for the Oxygen Evolution Reaction (OER) is essential for advancing Proton Exchange Membrane (PEM) water electrolysis technology. OER is a key electrochemical reaction that generates oxygen gas (O₂) from water (H₂O) or hydroxide ions (OH⁻) during water splitting.

This seemingly simple reaction is crucial in energy conversion technologies like water electrolysis as it is hard to efficiently realize and a concurrent process to the wanted hydrogen production. Iridium (Ir)-based materials, particularly amorphous hydrous iridium oxide (am-hydr-IrO_x), are at the forefront of this research due to their high activity. However, their application is limited by high dissolution rates of the precious iridium.

A collaborative effort led by scientists from the Department of Interface Design at the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH and the Theory Department at the Fritz-Haber-Institut der Max-Planck-Gesellschaft provided now fundamental insights into the intertwined mechanisms of OER and Ir dissolution in amorphous, hydrous iridium oxides (am-hydr-IrO_x). Traditionally, the understanding of these processes has been limited by reliance on crystalline iridium oxide models. The paper is published in the journal Energy & Environmental Science.

In this joint effort, Hydrous Iridium Oxide Thin Films (HIROFs) was explored as a model system, which revealed a unique iridium suboxide species associated with high OER activity. In situ X-ray photoelectron and X-ray absorption spectroscopy at BESSY II and ALBA synchrotrons and Density Functional Theory (DFT) was employed to investigate the local electronic and geometric structures of these materials under operating conditions, leading to the introduction of a novel surface H-terminated nanosheet model.

This model better represents the short-range structure of am-hydr-IrO_x, revealing elongated Ir-O bond lengths compared to traditional crystalline models.

Moreover, Ir dissolution was identified as a spontaneous, thermodynamically driven process, already occurring at potentials lower than OER activation, while the prevalent mechanistic picture assumes degradation to be driven by rare events during OER. This discovery required the development of a new mechanistic framework to describe Ir dissolution through the formation of Ir defects.

The study also offered insights into the relationship between activity and stability of am-hydr-IrO_x by systematically analyzing the DFT-calculated OER activity across different Ir and O chemical environments.

Overall, the current research results challenge conventional perceptions of iridium dissolution and OER mechanisms, offering an alternative dual-mechanistic framework. By examining a highly active and porous catalyst with a singular hydroxylated Ir suboxide species, the study develops a nanosheet atomistic model that surpasses conventional crystal-based models.

This research not only challenges traditional understanding but also offers a new atomistic perspective on the delicate relationship between OER activity and durability of precious metal oxide catalysts. The findings are expected to be broadly applicable, potentially guiding the development of more efficient and stable anode materials for advancing PEM.

The chemicals known as PFAS are considered a severe threat to human health. Among other things, they can cause liver damage, cancer, and hormonal disorders. Researchers at the Technical University of Munich (TUM) have now developed a new, efficient method of filtering these substances out of drinking water. They rely on so-called metal-organic framework compounds, which work much better than the materials commonly used to date. Even extremely low concentrations of per- and polyfluoroalkyl substances (PFAS) in the water can still be captured.

Per- and polyfluoroalkyl substances (PFAS) are considered “forever chemicals”; they generally do not decompose on their own even after centuries and, therefore, pose a long-term threat to humans and animals. PFAS have been used in numerous products such as textiles, fire-fighting foams, and food packaging, and have thus been released into the environment. The substances can accumulate in the body via food and drinking water, and thus cause serious health issues.

The team led by Nebojša Ilić from the TUM Chair of Urban Water Systems Engineering and Prof. Soumya Mukherjee, a former Alexander von Humboldt postdoctoral researcher at the TUM Chair of Inorganic and Organometallic Chemistry during the study period and now Assistant Professor of Materials Chemistry at the University of Limerick, identified water-stable metal-organic framework compounds made of zirconium carboxylate as particularly effective PFAS filters.

The bespoke class of materials is characterized by adaptable pore sizes and surface chemistry. The materials are water-resistant and highly electrostatically charged. By specifically designing the structures and combining them with polymers, the filter capacity has been significantly improved compared to materials already in use, such as activated carbon and special resins.

Prof. Jörg Drewes, Chair of Urban Water Systems Engineering, emphasizes the great social significance of the research results, “PFAS pose a constant threat to public health. For too long, the negative effects of the chemicals, which, among other things, ensure that rain jackets are waterproof and breathable, have been underestimated. The industry has now started to rethink this, but the legacy of PFAS will continue to affect us for several generations to come.”

Researchers from the TUM School of Natural Sciences worked together with colleagues from the TUM School of Engineering and Design and simulation experts from the TUM School of Computation, Information, and Technology to develop and research the new filters.

Prof. Roland Fischer, Chair of Inorganic and Organometallic Chemistry, emphasizes, “When solving such major challenges, experts from a wide range of disciplines have to work together. You simply can’t get anywhere on your own. I am delighted that this approach has again proved its worth here.”

However, it will be some time before this new filter material is adopted at large scale in waterworks. The newly discovered principle would have to be implemented with sustainably available, inexpensive materials that are safe in every respect. This will require considerable further research and engineering solutions.

A team of scientists led by Professor Annette Beck-Sickinger from the Institute of Biochemistry at Leipzig University has made an important advance in pain relief research. They discovered that hederagenin, a naturally occurring substance found in the medicinal plant ivy, binds to the pain regulation receptor. Extracts of ivy (Hedera helix) have antispasmodic and analgesic effects in phytomedicine.

In the search for selective inhibitors of the protein neuropeptide FF receptor 1, which is relevant for human pain regulation, the researchers discovered that hederagenin is well suited for this purpose. They have now published their findings in the journal Angewandte Chemie International Edition.

Neuropeptide FF receptor 1 (NPFFR1) is a G protein-coupled receptor (GPCR) involved in the signaling of various physiological processes in the human body. In recent years, it has been discovered that this protein is mainly found in the spinal cord and in areas of the brain involved in pain perception. Blocking this receptor could help treat chronic pain. This has not been possible until now because NPFFR1 has many similar relatives.

Two scientists from Beck-Sickinger’s research group tested thousands of substances. Michael Schaefer, Professor of Pharmacology at the Faculty of Medicine, provided a screening platform for this purpose. The researchers came across the naturally occurring substance hederagenin.

They characterized the binding mode of the inhibitor in detailed in vitro studies. Computer modeling of the three-dimensional receptor-inhibitor complex by Professor Jens Meiler’s group at the Institute for Drug Discovery confirmed this insight.

“These findings make a significant contribution to understanding the activation mechanism of NPFFR1 and may facilitate the rational design of future therapeutics for chronic pain. They demonstrate the importance of basic research in translating findings into applications,” says Professor Beck-Sickinger.