Chemistry news and discussions

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Chemists create quantum dots at room temperature using lab-designed protein
https://phys.org/news/2022-12-chemists- ... ature.html
by Wendy Plump, Princeton University
Nature uses 20 canonical amino acids as building blocks to make proteins, combining their sequences to create complex molecules that perform biological functions.

But what happens with the sequences not selected by nature? And what possibilities lie in constructing entirely new sequences to make novel (de novo) proteins bearing little resemblance to anything in nature?

That's the terrain where Michael Hecht, professor of chemistry, works with his research group. Recently, their curiosity for designing their own sequences paid off.

They discovered the first known de novo (newly created) protein that catalyzes (drives) the synthesis of quantum dots. Quantum dots are fluorescent nanocrystals used in electronic applications from LED screens to solar panels.
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3D printing of single atom catalysts pioneered
https://phys.org/news/2023-01-3d-atom-catalysts.html
by Susan Bogle, Australian Nuclear Science and Technology Organisation (ANSTO)

A large international collaboration led by Prof Shizhang Qiao, an Australian Laureate Fellow at the University of Adelaide has developed a straightforward and cost-effective synthesizing approach using a 3D printing technique to produce single-atom catalysts (SACs)—potentially paving the way for large-scale commercial production with broad industrial applications.

The research has been published in Nature Synthesis.

The team mailed in samples to the Australian Synchrotron during the COVID lockdown for materials characterization using the X-ray absorption spectroscopy (XAS) beamline.

A catalyst is a substance that is designed to drive a specific chemical reaction to convert chemicals to other, less harmful, valuable industrial products. The efficiency at which a given catalyst aids the reaction is often found to be determined by its surface area.

For example, a bulk metallic cobalt foil may aid in chemical reductions, but the same number of cobalt atoms in the form of nanoparticles would be significantly more efficient given the greater surface area available for the reaction to take place.

Taken to its extreme, single-atom catalysts (SACs) refer to individual metal atoms, not bonding to metal but often dispersed uniformly on a fixed substrate (such as carbon), offering the highest possible value of atom economy.

The ideal atom economy, known as 100% atom economy, for a chemical reaction is a process in which all reactant atoms are found in the desired product.
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Scientists created a weird new type of ice that is almost exactly as dense as water
By Stephanie Pappas
https://www.livescience.com/new-medium- ... rphous-ice
Part of the experimental setup for making medium-density amorphous ice.

Using ultracold temperatures and some steel ball bearings, scientists have created a brand-new, bizarre form of ice that has the same density of liquid water.

The ice, known as medium-density amorphous ice, fits into a gap in the annals of frozen water that scientists weren't sure would ever be filled. Unlike the crystalline ice that forms naturally on Earth, the newly created ice doesn't have an organized molecular structure. Instead, its molecules are in a chaotic mismatch, more like glass — a state known as amorphous. Other types of amorphous ice have been made before, but they've been either much less dense or far denser than liquid water. This new Goldilocks version of amorphous ice is right in the middle, almost exactly matching liquid water's density, researchers explained in a new study published in the journal Science today (Feb. 2).

"It's something completely new," said study senior author Christoph Salzmann (opens in new tab), a professor of physical and materials chemistry at University College London.
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How a record-breaking copper catalyst converts carbon dioxide into liquid fuels

by Theresa Duque, Lawrence Berkeley National Laboratory
https://phys.org/news/2023-02-record-br ... oxide.html
Since the 1970s, scientists have known that copper has a special ability to transform carbon dioxide into valuable chemicals and fuels. But for many years, scientists have struggled to understand how this common metal works as an electrocatalyst, a mechanism that uses energy from electrons to chemically transform molecules into different products.

Now, a research team led by Lawrence Berkeley National Laboratory (Berkeley Lab) has gained new insight by capturing real-time movies of copper nanoparticles (copper particles engineered at the scale of a billionth of a meter) as they convert CO2 and water into renewable fuels and chemicals: ethylene, ethanol, and propanol, among others. The work was reported in the journal Nature last week.

"This is very exciting. After decades of work, we're finally able to show—with undeniable proof—how copper electrocatalysts excel in CO2 reduction," said Peidong Yang, a senior faculty scientist in Berkeley Lab's Materials Sciences and Chemical Sciences Divisions who led the study. Yang is also a professor of chemistry and materials science and engineering at UC Berkeley.

"Knowing how copper is such an excellent electrocatalyst brings us steps closer to turning CO2 into new, renewable solar fuels through artificial photosynthesis."

The work was made possible by combining a new imaging technique called operando 4D electrochemical liquid-cell STEM (scanning transmission electron microscopy) with a soft X-ray probe to investigate the same sample environment: copper nanoparticles in liquid. First author Yao Yang, a UC Berkeley Miller postdoctoral fellow, conceived the groundbreaking approach under the guidance of Peidong Yang while working toward his Ph.D. in chemistry at Cornell University.

Scientists who study artificial photosynthesis materials and reactions have wanted to combine the power of an electron probe with X-rays, but the two techniques typically can't be performed by the same instrument.

Electron microscopes (such as STEM or TEM) use beams of electrons and excel at characterizing the atomic structure in parts of a material. In recent years, 4D STEM (or "2D raster of 2D diffraction patterns using scanning transmission electron microscopy") instruments, such as those at Berkeley Lab's Molecular Foundry, have pushed the boundaries of electron microscopy even further, enabling scientists to map out atomic or molecular regions in a variety of materials, from hard metallic glass to soft, flexible films.

On the other hand, soft (or lower-energy) X-rays are useful for identifying and tracking chemical reactions in real time in an operando, or real-world, environment.
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Newly discovered form of salty ice could exist on surface of extraterrestrial moons
https://phys.org/news/2023-02-newly-sal ... trial.html
by University of Washington
The red streaks crisscrossing the surface of Europa, one of Jupiter's moons, are striking. Scientists suspect it is a frozen mixture of water and salts, but its chemical signature is mysterious because it matches no known substance on Earth.

A team led by the University of Washington may have solved the puzzle with the discovery of a new type of solid crystal that forms when water and table salt combine in cold and high-pressure conditions. Researchers believe the new substance created in a lab on Earth could form at the surface and bottom of these worlds' deep oceans.

The study, published Feb. 20 in the Proceedings of the National Academy of Sciences, announces a new combination for two of Earth's most common substances: water and sodium chloride, or table salt.
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Researchers describe promising method to optimize and scale up the production of fuel cell input
https://phys.org/news/2023-03-method-op ... -fuel.html
by Ricardo Muniz, FAPESP
A novel process described in an article published in the journal Electrochemistry Communications converts nitrogen and hydrogen to ammonia (NH3) at ambient temperature and pressure with high energy efficiency. Ammonia, a gas composed of nitrogen and hydrogen, is the world's most synthesized molecule and is used in agriculture as well as many production processes.

It does not emit CO2 when burned and is expected to become a next-generation fuel as it contains properties ideally suited for the hydrogen economy. Annual output of ammonia amounts to about 1.2 million metric tons.

In response to growing interest in decarbonization routes, researchers have recently turned their attention to the use of ammonia in fuel cells—electrochemical or galvanic cells that generate electricity from specific chemical reactions, such as the nitrogen reduction reaction (NRR).

NRR electrochemistry is studied with two main goals: production of a key industrial input and potential future fuel; and storing hydrogen in a molecule—ammonia—that can easily be diluted in water and transported more safely and cheaply than hydrogen alone. If ammonia fuel cell research initiatives are successful, global demand for ammonia will grow even more strongly.

The group used an electrochemical reactor to outperform the Haber-Bosch process, which releases large amounts of heat into the environment. Haber-Bosch is the primary industrial method of producing ammonia from nitrogen and hydrogen.
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Observing what happens in the first picosecond when a proton detaches from a dye after exposure to light
https://phys.org/news/2023-04-picosecon ... osure.html
by Ruhr-Universitaet-Bochum
In certain molecules, the so-called photoacids, a proton can be released locally by excitation with light. There is a sudden change in the pH value in the solution—a kind of fast switch that is important for many chemical and biological processes. Until now, however, it was still unclear what happens at the moment of proton release. This is exactly what researchers in the Cluster of Excellence Ruhr Explores Solvation RESOLV at Ruhr University Bochum, Germany, have now been able to observe in an experiment using new technology.

They observed a beating between solute and solvent initiating a tiny quake, lasting only three to five picoseconds, before the proton starts to detach. They report on this in the journal Chemical Sciences.
So far, the focus has been on dye or base

One of the most studied so-called photoacids is pyranine, the fluorescent dye used, for instance, in yellow highlighters. "Despite a wealth of experimental studies, the process that is at the very beginning of proton detachment still remained the subject of controversial debate," reports Professor Martina Havenith, spokesperson for RESOLV. However, the entire detachment process also happens on a time scale of only 90 picoseconds. A picosecond corresponds to a millionth of a millionth of a second.

While previous studies focused mainly on the change of the dye after light excitation, the team was able to observe the change of the solvent, in this case water, during this process for the first time. This was achieved with the help of a newly developed technique, "Optical Pump THz Probe Spectroscopy."
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Birch reduction simplified to a one-minute mechanochemical process
https://phys.org/news/2023-04-birch-red ... mical.html
by Hokkaido University
The traditionally cumbersome yet widely-used Birch reduction can now be carried out in a mere minute in air using an optimized mechanochemical approach.

The Birch reduction is a reaction commonly used to make medicines and bioactive compounds, but the laborious process typically requires that chemists handle liquid ammonia, use cryogenic temperatures, and carry out time-consuming steps.

Researchers at the Institute for Chemical Reaction Design and Discovery (WPI-ICReDD) in Hokkaido University have developed a simplified method for performing the Birch reduction that avoids the use of ammonia, can be done at room temperature and in ambient air, and is 20–150 times faster than conventional methods. Their findings are published in the journal Angewandte Chemie International Edition.

A number of lithium-based methods for performing the Birch reduction in solution have been previously developed, but since lithium reacts with both air and water, these processes still required complicated reaction setups with an inert atmosphere or dehydrated conditions. Researchers in this study saw an opportunity to avoid these issues by switching from a solution-based method to a solvent-less method using a ball mill, in which reactants are shaken rapidly in a small metal jar along with a metal ball that smashes the solid reactants together.
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Catalyst cleans up CO2 better with different preparation
https://phys.org/news/2023-05-catalyst-co2.html
by Utrecht University

An international research team led by Bert Weckhuysen (Utrecht University) and Sara Bals (University of Antwerp) has shown that a promising catalyst for clearing CO2 becomes significantly more active and selective if its pretreatment is modified. The scientists have visualized the mechanism underlying this concept with unparalleled precision. The results of the study are published in Science on May 11. Matteo Monai, Kellie Jenkinson and Angela Melcherts are the first authors.

Cleaning up carbon dioxide or converting it into something useful is becoming increasingly common, for example in the energy and transportation sectors, where huge amounts of the greenhouse gas are emitted. Catalysts are necessary for such a cleanup process to proceed properly and quickly. In the case of CO2 hydrogenation, which is a widely used chemical reaction to clean up CO2, a nickel-supported titanium dioxide catalyst is used.

In this study, the scientists show that the catalyst's performance is highly dependent on the temperature at which it is prepared. The selectivity and activity of the catalyst were much better during CO2 hydrogenation at a pretreatment temperature of 600°C than at 400°C. Better selectivity is desirable because the catalyst provides fewer unwanted by-products. Improved activity results in a faster progression of the catalytic reaction. The researchers expect the same principle to apply to catalysts with metal oxides other than titanium oxide.
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When crystals flow: Semicrystalline polymer shown to flow at temperatures below its melting point
https://phys.org/news/2023-05-crystals- ... tures.html
by Thamarasee Jeewandara , Phys.org
Semicrystalline polymers are solids that are assumed to flow only above their melting temperature. In a new study published in Science Advances, Chien-Hua Tu and a research team at the Max Planck Institute for Polymer Research in Germany and the University of Ioannina Greece confined crystals within nanoscopic cylindrical pores to show the flowing nature of semicrystalline polymers below their melting point, alongside an intermediate state of viscosity to the melt and crystal states.

The capillary process was strong during the phenomenon and dragged the polymer chains into the pores without melting the crystal. The unexpected improvement in flow facilitated polymer processing conditions applicable to low temperatures, suited for use in organic electronics.
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