Category: Chemistry

by McMaster University

Think of it as recycling on the nanoscale: a tantalizing electrochemical process that can harvest carbon before it becomes air pollution and restructure it into the components of everyday products.The drive to capture airborne carbon dioxide from industrial waste and make it into fuel and plastics is gaining momentum after a team of researchers based at McMaster University, working with computational chemistry experts at Copenhagen’s Danish Technical University, have uncovered precisely how the process works and where it bogs down.Their work is published in the journal Nature Communications.The researchers set out to resolve why synthetic materials that have been shown to catalyze and convert carbon dioxide break down too quickly for the process to be practical at an industrial level.Using extremely powerful magnification equipment at the Canadian Centre for Electron Microscopy (CCEM), which is based on McMaster’s campus, the researchers were able to capture the chemical reaction at nanoscale—billionths of a meter—allowing them to study both the conversion process and understand how the catalyst breaks down under operating conditions.Lead author Ahmed Abdellah spent years developing the techniques that made it possible to observe the process, using an electrochemical reactor small enough to work under the electron microscopes at the center.

“It’s exciting for us that this is the first time anyone has been able to look at both the shapes of these structures and their crystal structures, to see how they evolve at the nanoscale,” says Abdellah, a former Ph.D. student in the chemical engineering lab of Drew Higgins and now a postdoctoral fellow at the CCEM.Higgins, a corresponding author of the paper, hopes the new information will facilitate the global effort to reduce carbon pollution by drawing carbon dioxide away from waste streams and instead recycling it to create useful products that would otherwise be produced from fossil fuels.”What we have found is that catalysts that can convert carbon dioxide into fuels and chemicals restructure quite rapidly under operating conditions. Their structures change and their properties change, right before our very eyes” Higgins says. “That dictates how efficient they are at converting carbon dioxide and how long they last. The catalysts eventually degrade and stop working and we want to know why they do that and how they do that so that we can develop strategies to improve their operational lifetimes.”Abdellah, Higgins and their colleagues are hopeful they and other researchers around the world can use the research results described in the new paper to make the reactive materials last longer and catalyze the process more efficiently, to allow the lab-based process to be scaled up for commercial use.Industries such as cement manufacturing, brewing and distilling, as well as chemical refineries, produce high volumes of readily retrievable carbon dioxide, Higgins explains, making them likely first targets for rolling out the technology once it is improved to the point where it is commercially viable.Other less concentrated forms of CO2 in industrial waste would come next.Though it’s a longshot today, Higgins says it’s possible the same technology could become efficient and stable enough to pull carbon dioxide from ambient air as “feedstock” for fuel and useful chemicals.”We’re still a little ways off, but progress has been very rapid in this field of research and development in the last five years or so,” Higgins says. “Ten years ago, people weren’t thinking about this kind of conversion, but now we’re starting to see promise. Efficiency and durability, though, just aren’t high enough yet. Once these bottlenecks are removed, this idea can really take off.”

by National Institute for Materials Science

An international research team has succeeded for the first time in controlling the chirality of individual molecules through structural isomerization. The team, led by NIMS, the Osaka University Graduate School of Science and the Kanazawa University Nano Life Science Institute (WPI-NanoLSI), also succeeded in synthesizing highly reactive diradicals with two unpaired electrons. They accomplished these tasks using a scanning tunneling microscope probe at low temperatures.

The research is published in the journal Nature Communications.

It is usually quite challenging to control the chirality of individual molecular units and synthesize extremely reactive diradicals in organic chemistry; this has prevented detailed investigation of the electronic and magnetic properties of diradicals. These issues inspired the development of chemical reaction techniques to control structures of individual molecules on the surface.

The research team recently developed a technique that allows them to modify the chirality of specific individual molecular units in a three-dimensional nanostructure in a controlled manner. They achieved this by exciting a target molecular unit with tunneling current from a scanning tunneling microscope probe at low temperature under ultrahigh vacuum conditions.

By precisely controlling current injection parameters (e.g., the molecular site, at which the tunneling current is injected at a given applied voltage), the team was able to rearrange molecular units into three different configurations: two different stereoisomers and a diradical. Finally, the team demonstrated the controllability and reproducibility of the structural isomerization by encoding ASCII characters (reading “NanoProbe Grp. NIMS”) using binary and ternary values in a series of one-dimensional molecular arrays with each array representing a single character.

In future research, the team plans to fabricate novel carbon nanostructures composed of designer molecular units, whose configurations are controlled via the structural isomerization technique developed in this project. In addition, the team will explore the possibility of creating quantum materials in which radical molecular units lead magnetic exchange couplings between the units as designed—a quantum mechanical effect.

This project was carried out by a research team consisting of Shigeki Kawai (Leader, Nanoprobe Group (NG), Center for Basic Research on Materials (CBRM), NIMS), Zhangyu Yuan (Junior Researcher, NG, CBRM, NIMS), Kewei Sun (ICYS Research Fellow, NG, CBRM, NIMS), Oscar Custance (Managing Researcher, NG, CBRM, NIMS), Takashi Kubo (Professor, Department of Chemistry, Graduate School of Science, Osaka University) and Adam S. Foster (Professor, Nano Life Science Institute, Kanazawa University; also Professor, Aalto University).

by Zhang Nannan, Chinese Academy of Sciences

Biological hydrogen-methane conversion refers to the production of methane through the action of microorganisms using hydrogen generated by electrolysis of water with residual power and carbon dioxide present in biogas. This approach promises to overcome the limitations of hydrogen storage, lowering the financial burden of biogas upgrading, and enabling carbon-negative utilization of CO₂ in biogas.

Previously, researchers from the Qingdao Institute of Bioenergy and Bioprocess Technology of the Chinese Academy of Sciences have domesticated and obtained microorganisms with high hydrogen-methane conversion efficiencies. They have also developed two production processes for in-situ and ex-situ biological hydrogen-methane conversion. However, the main factor limiting the efficiency of hydrogen-methane conversion remains the low gas-liquid mass transfer rate of hydrogen.

To address the limitations of low hydrogen mass transfer rates in the hydrogen-methane conversion process, the researchers developed a biotrickling filter (BTF), which facilitates microorganisms growth by using packing material with a rough internal surface. It ensures full contact between the gas and liquid phases, thereby increasing the efficiency of hydrogen utilization.

The study ia published in Chemical Engineering Journal.

In this study, the researchers started by exploring the effects of temperatures (25°C, 37°C, and 55°C) on the hydrogen-methane conversion pathway to determine the optimal temperature for the biotrickling filters. During the operation of the biotrickling filter, the effects of the packing materials (ceramite, volcanic stone, activated carbon) and the optimal ratio of the input gas (H₂/CO₂, v/v) on the conversion process were evaluated.

According to the researchers, the selected packing materials were environmentally friendly, and their large specific surface area and porosity facilitated the growth and attachment of microorganisms. This ensures sufficient contact between the microorganisms and the gas phase, which greatly enhances gas-liquid mass transfer.

The results showed that higher temperature is conducive to hydrogen-methane conversion. At 25°C, the hydrogen-methane conversion efficiency was low (2.5 L/Lw·d), and most of the hydrogen and carbon dioxide were used to produce acetate.

At 55°C, although the reaction process was initially unstable, it eventually reached stability and obtained a hydrogen-methane conversion efficiency of 8.3 L/Lw·d. In contrast, the conversion efficiency was still substantial at 37°C, achieving 7.1 L/Lw·d. Notably, there was no significant difference in the overall methanogenesis process between 37°C and 55°C.

In addition, the optimal input gas (H₂/CO₂) ratio was determined in the BTF experiment, achieving the most satisfactory ratio at 2.5:1 (H₂/CO₂, v/v), which was lower than previously reported values, but higher carbon dioxide removal efficiency was achieved.

The biofilms adhering to the three packing materials all achieved effective hydrogen-methane conversion efficiency at the ratio of 2.5:1, with the BTF using activated carbon as the packing material achieved the highest and the most stable conversion efficiency (91.9%).

The relative fluorescence intensity measurement confirmed that activated carbon had superior microbial immobilization. This study provides a promising approach for the application of BTFs in biogas hydrogen-methane conversion.

by Liu Jia, Chinese Academy of Sciences

Ammonia is essential for food and future energy supply. In the industry, it is mainly produced by the Haber-Bosch process, which operates at high temperatures and pressures. Due to the high energy consumption and carbon emissions of ammonia industry, it is important to develop alternative materials and approaches for efficient N₂ reduction to ammonia driven by renewable energy.

A research group led by Prof. Chen Ping from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) has realized photo-driven nitrogen fixation and ammonia synthesis mediated by lithium hydride (LiH). The study is published in Nature Chemistry.

LiH is the simplest saline hydride with a band gap of 3.7 eV. It has been investigated for hydrogen storage due to its high hydrogen content (12.5 wt%). However, the dehydrogenation of LiH is thermodynamically unfavorable.

In this study, the researchers found that ultraviolet (UV) illumination of LiH could induce a notable color change from white to light blue, accompanied by the release of a small amount of H₂ under ambient conditions. Such a phenomenon implied that under UV illumination, LiH underwent photolysis resulting in photon-generated electrons trapped in its hydrogen vacancy as long-lived and electron-rich F centers, which showed a fundamentally different mechanism for charge carrier separation.

The researchers indicated that illuminated LiH had an electron-rich surface with hydrogen vacancies, which facilitated the activation of N₂ to form N-H bond. They co-fed a N₂/H₂ mixture with a low H₂ partial pressure into the LiH powders, leading to photo-catalytic ammonia production under ambient conditions.

“This photochemical route is flexible in operation, which may be amenable to the small-scale and distributed ammonia synthesis powered by intermittent solar energy,” said Prof. Chen.

by Bob Yirka , Phys.org

A team of molecular engineers have developed a type of plastic that can be shape-shifted using tempering. In their paper published in the journal Science the team, from the University of Chicago, with a colleagues from the US DEVCOM Army Research Laboratory, Aberdeen Proving Ground, the National Institutes of Standards and Technology and the NASA Glenn Research Center, describe how they made their plastic and how well it was able to shape shift when they applied various types of tempering.

Haley McAllister and Julia Kalow, with Northwestern University, have published a Perspective piece in the same issue of Science outlining the work.

Over the past several years, it has become evident that the use of plastics in products is harmful to not only the environment but also human health—bits of plastic have been found in the soil, the atmosphere, the oceans, and the human body.

Consequently, scientists have begun looking for ways to reduce the amount of plastic that is created, used and dumped into the trash. In this new effort, the research team has created a type of plastic that can be converted to something new once its initial purpose has been exhausted—using tempering. A plastic bag holding food, for example, could be converted to a fork or spoon.

To allow for such shape-shifting, the researchers developed a type of plastic using a dynamic cross-linked approach that was based on the reversible addition of thiols to benzalcyanoacetates—a process known as a “Michael addition.” The resulting plastic was of a type that could be modified by tempering, which is where a material is heated to a certain point, then chilled quickly. Tempering is most often associated with metalwork.

The researchers found by that heating the plastic to temperatures ranging between 60°C and 110°C, then transferring it to a standard food freezer, they could create different objects from the same material based on a whim.

They created a spoon first, which they used to scoop peanut butter from a jar. They then used tempering to change the spoon to a fork, and then to an adhesive material capable of holding two panes of glass together. However, tests showed that there was a limit to the number of times the plastic could be changed, which was seven times. After that, it began to degrade.

by Gisela Olias, Leibniz-Institut für Lebensmittel-Systembiologie

A research team led by the Leibniz Institute for Food Systems Biology at the Technical University of Munich has solved the mystery of a novel clove-like off-flavor in orange juice, the cause of which was previously unknown.

The study, published in Food Chemistry, proves for the first time that the undesirable flavor note is due to the odorant 5-vinylguaiacol. As the results of the study show, the substance is mainly produced during the pasteurization process when residues of a cleaning agent react with a natural orange juice component under the influence of heat.

This is not the first time that the orange juice industry has had to contend with clove odor. So far, 4-vinylguaiacol has been considered the main cause of this undesirable flavor note, which is particularly abundant in orange juices that have been stored for a long time. The quantitative determination of this odorant has therefore long been an established part of routine quality controls.

Eva Bauersachs, Ph.D. student at the Leibniz Institute in Freising and first author of the study, explains, “Recently, however, we have received reports of orange juice samples that had a pronounced clove odor despite a low concentration of 4-vinylguaiacol. We therefore asked ourselves which other odorants contribute to this undesirable off-flavor.”

On the trail of off-flavors

To investigate this question, the research group led by Martin Steinhaus, head of the Food Metabolome Chemistry research group at the Leibniz Institute, carried out extensive investigations in cooperation with the Professorship of Functional Phytometabolomics and the Chair of Food Chemistry and Molecular Sensory Science at the Technical University of Munich. The aim was to identify the odorants that cause the previously unexplained off-flavor and to elucidate their origins.

Using techniques such as gas chromatography-olfactometry and aroma extract dilution analysis, the team identified the odorant 5-vinylguaiacol as the source of the off-flavor in an orange juice with a pronounced clove odor. The presence of this substance in orange juice was previously unknown. Compared to 4-vinylguaiacol, it even proved to be more odor-active in five out of six commercially available orange juices with a clove-like off-flavor.

Further studies suggested that 5-vinylguaiacol is formed during pasteurization when the characteristic orange juice component hesperidin reacts with peracetic acid. Peracetic acid is used as a cleaning agent for cleaning-in-place (CIP) in the fruit juice industry, among others.

“Inadequate rinsing of the machines after the CIP process could therefore have led to contamination of the orange juice with peracetic acid and caused the formation of 5-vinylguaiacol during further processing,” says principal investigator Martin Steinhaus. Based on the new scientific findings, the team recommends that orange juice processing companies should no longer use peracetic acid as a cleaning agent.

by RIKEN

Chemists at RIKEN have developed a method for making synthetic derivatives of the natural dye indigo that doesn’t require harsh conditions. This discovery could inspire advances in electronic devices, including light-responsive gadgets and stretchy biomedical sensors.

Semiconductors based on organic molecules are attracting much interest because—unlike conventional rigid semiconductors based on silicon—they could be flexible, ductile and lightweight, opening up new possibilities for designing semiconductor devices.

Organic molecules also have the advantage of realizing a broad range of structures. “Organic semiconductors have flexibility in molecular design, enabling them to adopt new functionalities,” says Keisuke Tajima of the RIKEN Center for Emergent Matter Science, who led the research published in Chemical Science.

To explore this potential for enhanced electronic function through molecular design, Tajima and his team investigated a molecule related to indigo, called 3,3-dihydroxy-2,2-biindan-1,1-dione (BIT). “This project started with a simple question: Can protons and electrons move in concert in the solid state?” says Tajima.

Proton-coupled electron transfer—in which the motion of electrons is linked to that of protons—is often considered critical for realizing efficient electron transfer in biological systems. If it can be incorporated in organic solid-state materials, it could lead to semiconductors with unique dynamic properties. Until now, however, no solid-state material displaying proton-coupled electron transfer has been demonstrated.

Tajima and his team have now found that BIT and its derivatives undergo unusual rearrangements in their structures involving double-proton transfer, which may lend them unique capabilities as electronic functional materials.

Tajima identified BIT and its derivatives as promising materials for solid-state proton-coupled electron transfer, because the molecule incorporates two protons that appear ideally positioned to hop from one position to another during electron transfer.

Until now, making BIT required harsh conditions that severely restricted the range of derivatives that could be made. Members of the team developed a room-temperature approach that enabled the synthesis of several BIT derivatives under much milder conditions.

With BIT derivatives in hand, the team explored the molecules’ properties. “The most difficult part was to prove that the protons in BIT undergo proton transfer between molecules in the solid state,” says Tajima. In collaboration with RIKEN experts in X-ray crystallography and solid-state nuclear magnetic resonance (NMR), the team demonstrated that the two protons do rapidly exchange their positions.

Calculations suggest that proton transfer is indeed coupled with charge transport; the team’s next target is to confirm this coupling experimentally. “We don’t know if the presence of a proton will enhance charge transport, but as fundamental physics it could open interesting avenues,” says Tajima.

by The Korea Advanced Institute of Science and Technology (KAIST)

Bone regeneration is a complex process, and existing methods to aid regeneration including transplants and growth factor transmissions face limitations such as the high cost. But recently, a piezoelectric material that can promote the growth of bone tissue has been developed.

A KAIST research team led by Professor Seungbum Hong from the Department of Materials Science and Engineering (DMSE) has developed a biomimetic scaffold that generates electrical signals upon the application of pressure by utilizing the unique osteogenic ability of hydroxyapatite (HAp). HAp is a basic calcium phosphate material found in bones and teeth. This biocompatible mineral substance is also known to prevent tooth decay and is often used in toothpaste.

This research was conducted in collaboration with a team led by Professor Jangho Kim from the Department of Convergence Biosystems Engineering at Chonnam National University. The results are published in the journal ACS Applied Materials & Interfaces.

Previous studies on piezoelectric scaffolds confirmed the effects of piezoelectricity on promoting bone regeneration and improving bone fusion in various polymer-based materials, but were limited in simulating the complex cellular environment required for optimal bone tissue regeneration. However, this research suggests a new method for utilizing the unique osteogenic abilities of HAp to develop a material that mimics the environment for bone tissue in a living body.

The research team developed a manufacturing process that fuses HAp with a polymer film. The flexible and free-standing scaffold developed through this process demonstrated its remarkable potential for promoting bone regeneration through in-vitro and in-vivo experiments in rats.

The team also identified the principles of bone regeneration that their scaffold is based on. Using atomic force microscopy (AFM), they analyzed the electrical properties of the scaffold and evaluated the detailed surface properties related to cell shape and cell skeletal protein formation. They also investigated the effects of piezoelectricity and surface properties on the expression of growth factors.

Professor Hong from KAIST’s DMSE said, “We have developed a HAp-based piezoelectric composite material that can act like a ‘bone bandage’ through its ability to accelerate bone regeneration.” He added, “This research not only suggests a new direction for designing biomaterials, but is also significant in having explored the effects of piezoelectricity and surface properties on bone regeneration.”

by Pacific Northwest National Laboratory

Lipids are a class of biomolecules that play an important role in many cellular processes. Analyses that seek to characterize all lipids in a sample—called lipidomics—are crucial to studying complex biological systems.

An important challenge in lipidomics is connecting the variety of structures of lipids with their biological functions. The positions of the double bonds within fatty acid chains is particularly important. This is because they can affect the physical properties of cellular membranes and modulate cell signaling pathways.

This information is not routinely measured in lipidomics studies because it requires a complicated experimental setup that produces complex data. Thus, scientists at Pacific Northwest National Laboratory (PNNL) developed a streamlined workflow to determine the positions of double bonds. This workflow uses both automation and machine learning approaches.

Their new method, LipidOz, streamlines the data analysis to determine the positions of double bonds. By addressing this key part of the analysis of lipids, LipidOz offers researchers a more efficient and accurate method for lipid characterization. The study is published in the journal Communications Chemistry.

The unambiguous identification of lipids is complicated by the presence of molecular parts that have the same chemical formula but different physical configurations. Specifically, the differences in these molecular parts include the fatty acyl chain length, stereospecifically numbered (sn) position, and position/stereochemistry of double bonds.

Conventional analyses can determine the fatty acyl chain lengths, the number of double bonds, and—in some cases—the sn position but not the positions of carbon–carbon double bonds. The positions of these double bonds can be determined with greater confidence using a gas-phase oxidation reaction called ozone-induced dissociation (OzID), which produces characteristic fragments.

However, the analysis of the data obtained from this reaction is complex and repetitive, and there is lack of software tool support. The open-source Python tool, LipidOz, automatically determines and assigns the double bond positions of lipids using a combination of traditional automation and deep learning approaches. New research demonstrates this ability for standard lipid mixtures and complex lipid extracts, enabling practical application of OzID for future lipidomics studies.

by University of Cambridge

The “ten electron rule” provides guidance for the design of single-atom alloy catalysts for targeted chemical reactions.

A collaborative team across four universities has discovered a very simple rule to design single-atom alloy catalysts for chemical reactions. The “ten electron rule” helps scientists identify promising catalysts for their experiments very rapidly. Instead of extensive trial and error experiments of computationally demanding computer simulations, catalysts’ composition can be proposed simply by looking at the periodic table.

Single-atom alloys are a class of catalysts made of two metals: a few atoms of reactive metal, called the dopant, are diluted in an inert metal (copper, silver or gold). This recent technology is extremely efficient at speeding up chemical reactions but traditional models don’t explain how they work.

The team, which worked across the University of Cambridge, University College London, the University of Oxford and the Humboldt-University of Berlin, has published their research in Nature Chemistry. The scientists made computer simulations to unravel the underlying laws that control how single-atom alloy catalysts work.

The rule showed a simple connection: chemicals bind the most strongly to single-atom alloy catalysts when the dopant is surrounded by ten electrons. This means that scientists designing experiments can now simply use the columns on the periodic table to find which catalysts will have the desired properties for their reactions.

Dr. Romain Réocreux, a postdoctoral researcher in the group of Prof. Angelos Michaelides, who led this research, says, “When you have a difficult chemical reaction, you need a catalyst with optimal properties. On the one hand, a strong-binding catalyst may poison and stop accelerating your reaction; on the other hand, a weakly-binding catalyst may just do nothing.”

“Now we can identify the optimal catalyst just by looking at a column on the periodic table. This is very powerful since the rule is simple and can speed up the discovery of new catalysts for particularly difficult chemical reactions.”

Prof. Stamatakis, Professor of Computational Inorganic Chemistry at the University of Oxford, who contributed to the research, says, “After a decade of intense research on single-atom alloys, we now have an elegant, simple but powerful theoretical framework that explains binding energy trends and enables us to make predictions about catalytic activity.”

Using this rule, the team proposed a promising catalyst for an electrochemical version of the Haber-Bosch process, a key reaction for the synthesis of fertilizers that has been using the same catalyst since it was first discovered in 1909.

Dr. Julia Schumann, who started the project at the University of Cambridge and is now at Humboldt-Universität of Berlin, explains, “Many catalysts used in the chemical industry today were discovered in the laboratory using trial and error methods. With a better understanding of the materials’ properties, we can propose new catalysts with improved energy efficiency and reduced CO₂ emissions for industrial processes.”