Category: Chemistry

by Li Yuan, Chinese Academy of Sciences

The stress-induced reorientation of low-symmetry defects due to substitution atom pairs can give rise to an internal friction peak called Zener relaxation. It is one of the most representative point defect relaxations in metal.

Recently, researchers from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences have revealed that Zener relaxation in the body-centered cubic (BCC) Fe-Ga single crystals originates primarily from the stress-induced reorientation of the second-nearest-neighbor Ga-Ga atom pairs, not the previously thought first-nearest-neighbor substitutional atom pairs. The study was published in Acta Materialia.

Fe-Ga alloys have great potential in the field of actuators, sensors, and micro-vibration suppression. However, their magnetostriction and damping capacity are closely related to the occupation of Ga atoms. The internal friction technique is sensitive to internal defect relaxation, so it is expected to solve the problem of evaluating Ga atom occupation and provide guidance for improving Fe-Ga alloy properties.

In this study, the team prepared large FeGa single crystals and FeGa binary single-crystal alloys with different orientation factors. A comparative study of the internal friction behavior of FeGa polycrystals and single crystals confirmed that the relaxation peak near 450°C originated from Zener relaxation behavior within the grains. It was observed that the net peak height of Zener relaxation increased with the orientation factor of single crystals.

Further analysis revealed that the relaxation strengths of BCC cells with different atom-pair configurations varied. Trigonal and orthorhombic configurations exhibited decreased relaxation strengths with increased orientation factors, while tetragonal configuration showed the opposite trend. The relaxation activation energy for Fe-17at.% Ga single crystals was found to be around 1.8 eV, lower than that measured in polycrystalline materials.

Additionally, the researchers revealed a positive correlation between Zener relaxation strength and the magnetostriction coefficient through electronic structure and strain analysis.

More information: Meng Sun et al, Tetragonal dipole dominated Zener relaxation in BCC-structured Fe-17at.%Ga single crystals, Acta Materialia (2023). DOI: 10.1016/j.actamat.2023.119245

Journal information: Acta Materialia 

Provided by Chinese Academy of Sciences 

by Newcastle University in Singapore

A team of researchers from Thailand, Malaysia and Singapore has successfully harnessed pineapple waste materials from agriculture to create biodegradable rigid composite foams. The foam’s base was formulated using starch extracted from pineapple stems, known for their high amylose content, while the filling material was derived from non-fibrous cellulosic components found in pineapple leaves.

Diverging from conventional techniques which involve preparing a batter, this study introduced a unique methodology. It began by creating a starch gel mixed with glycerol, achieved through the use of a common household microwave oven. The resulting mixture was then blended with the filling material using a two-roll mill. Subsequently, the amalgam was transformed into foam through compression molding at a temperature of 160°C.

The produced foams exhibited densities ranging from 0.43 to 0.51 g/cm³ and displayed a notably amorphous structure. Impressively, the foams showcased equilibrium moisture levels of approximately 8%–10%, demonstrating their capacity to absorb 150%–200% of their weight without deteriorating. The foams’ flexural strengths varied between 1.5 and 4.5 MPa, with fluctuations based on the filler and glycerol contents.

Furthermore, biodegradability assessments utilizing a soil burial method demonstrated that the foam disintegrated completely into particles measuring 1 mm or smaller within a mere 15 days. Additionally, the researchers fabricated an environmentally friendly, single-use foam tray to illustrate potential practical applications.

This innovative approach, encompassing gel formation followed by filler integration, distinguishes itself from prior methodologies. The study’s outcomes underscore the substantial potential of pineapple waste materials in crafting sustainable biodegradable foams with desirable attributes. Ultimately, these findings contribute significantly to the advancement of sustainable materials.

The paper is published in the journal Polymers.

More information: Atitiya Namphonsane et al, Development of Biodegradable Rigid Foams from Pineapple Field Waste, Polymers (2023). DOI: 10.3390/polym15132895

Provided by Newcastle University in Singapore 

by JooHyeon Heo, Ulsan National Institute of Science and Technology

A research team, led by Professor Jong-Beom Baek and his team in the School of Energy and Chemical Engineering at UNIST have achieved a significant breakthrough in battery technology. They have developed an innovative method that enables the safe synthesis of fluorinated carbon materials (FCMs) using polytetrafluoroethylene (PTFE) and graphite.

Fluorinated carbon materials have garnered considerable attention due to their exceptional stability, attributed to the strong C-F bonding—the strongest among carbon single bonds. However, traditional methods of fluorination involve highly toxic reagents such as hydrofluoric acid (HF), making them unsuitable for practical applications.

In this study, the research team introduced a straightforward and relatively safe approach for scalable synthesis of FCMs through mechanochemical depolymerization of PTFE—a commonly used compound found in everyday items—and fragmentation of graphite. By utilizing ball-milling techniques that induce both mechanical and chemical reactions, they successfully produced FCMs with significantly improved performance compared to graphite.

The use of hazardous compounds like fluorine gas or HF in conventional carbon fluoride production raises safety concerns, increasing manufacturing costs associated with stringent safety measures. To address these challenges, Professor Baek’s team devised a solid-phase fluorination method using PTFE—an inert polymer known for its stability under atmospheric conditions and harmlessness when consumed orally.

Through experiments, it was observed that subjecting PTFE to higher energy than it can withstand leads to molecular chain breakage and radical formation—initiating a reaction resulting in the production of carbon fluoride complexes. These complexes then adhere to the surface and edges of graphite particles during subsequent processes.

The resulting FCMs demonstrated superior storage capacity and electrochemical stability compared to traditional graphite anodes. At a low charging rate of 50 mA/g, the FCMs exhibited storage capacities 2.5 times higher (951.6 mAh/g) than graphite, while at a high charging rate of 10,000 mA/g, their storage capacity was tenfold higher (329 mAh/g). Remarkably, even after more than 1,000 charge/discharge cycles at a rate of 2,000 mA/g, the FCMs retained 76.6% of their initial capacity compared to only 43.8% for graphite.

“This study highlights not just safe fluorination methods but also the broader potential of solid-phase reactions,” stated Boo-Jae Jang, a researcher in the School of Energy and Chemical Engineering at UNIST.

“This research prompts us to reconsider materials that are commonly found in our surroundings,” added Professor Baek. He further emphasized the significance of understanding solid-phase reactions as it opens doors to developing novel materials that were previously unexplored.

The study findings have been published in Advanced Functional Materials.

More information: Boo‐Jae Jang et al, Direct Synthesis of Fluorinated Carbon Materials via a Solid‐State Mechanochemical Reaction Between Graphite and PTFE, Advanced Functional Materials (2023). DOI: 10.1002/adfm.202306426

Journal information: Advanced Functional Materials 

Provided by Ulsan National Institute of Science and Technology

by Chinese Academy of Sciences

NH₃ is the second largest chemical produced in the world and nearly 80% of produced NH₃ is employed in fertilizer synthesis. Meanwhile, NH₃ is an indispensable raw material for manufacturing nitric acid, which can be further employed in chemical production.

Moreover, NH₃ possesses high hydrogen capacity, making it a potential carbon-free fuel. As one of the greatest inventions, the Haber-Bosch process enables the large-scale production of value-added NH₃; however, it is against the principle of sustainable development theory due to the high operational costs and negative environmental impacts of the Haber-Bosch process.

Hence, it is imperative to explore green and sustainable approaches to produce NH₃ and simultaneously realize global environmental sustainability.

Artificial electrocatalytic NH₃ synthesis (which can couple with clean renewable electricity) is recently becoming a research hotspot, where the majority of researchers use N₂ gas as the N source. Although electrocatalytic N₂ reduction reaction (NRR) provides an eco-friendly and sustainable route for ambient NH₃ production, the conversion efficiency of N₂ reduction to NH₃ is unsatisfactory because of the high thermodynamic stability of the N₂ molecule.

Fortunately, the more active N sources (i.e., NO, NO₂⁻, NO₃⁻) have been deemed as attractive precursors to achieve effective NH₃ production, and meanwhile, the development of electrocatalytic NO reduction reaction (NORR) and NO₃⁻/NO₂⁻ (NO_x⁻) reduction reaction (NtrRR) is also expected to control and mitigate the related environmental pollution.

Although many promising studies have been done in the field of artificial electrosynthesis of NH₃, the design and development of active electrocatalysts with high selectivity and stability to achieve efficient NH₃ production remain certain challenges.

Recently, a research team led by Prof. Xuping Sun from University of Electronic Science and Technology of China introduced three electrochemical NH₃ synthesis routes (NRR, NORR, and NtrRR) then summarized recent advances in electrocatalyst development for ambient NH₃ synthesis, mainly involving catalytic mechanisms, theoretical advances, and electrochemical performance.

The challenges and future perspectives are also proposed in the concluding remarks, aiming to provide experience and inspire more critical insights for the electrocatalytic NH₃ synthesis reactions. The results were published in the Chinese Journal of Catalysis.

More information: Ling Ouyang et al, Recent advances in electrocatalytic ammonia synthesis, Chinese Journal of Catalysis (2023). DOI: 10.1016/S1872-2067(23)64464-X

Provided by Chinese Academy of Sciences 

by Tampere University

Joint research groups at Tampere University, University of Helsinki, Lund University and Pi-Numerics, Salzburg, have established key early steps in the conversion of aromatic molecules, a major constituent of traffic and other urban volatile emissions, into aerosol. Published in Nature Communications, their findings increase understanding of the chemical processes that degrade urban air quality and influence climate change.

Many aromatic molecules are carcinogenic and have negative impacts on health. Their primary source is exhaust fumes from motor vehicles. Aromatics can form aerosol particles when they collide in the atmosphere with the hydroxyl radical, a molecule colloquially dubbed “atmospheric detergent” due to its acute propensity to react chemically.

When breathed in, aerosol particles can lead to a myriad of chronic health issues and even death. These particles also affect Earth’s climate by reflecting sun light and increasing the formation of clouds.

Despite their importance to the urban environment, details of the reaction processes that form aerosol from aromatics have until now remained unresolved.

The group of researchers used a combination of quantum mechanics, targeted experiments, and modeling to establish the early steps in the reaction process of toluene, one of the most abundant aromatic molecules.

“We found out that a reaction product that was previously thought to be stable is in fact transient and converts to new hot molecules. These molecules have residual energy that makes subsequent chemistry fast and promptly lead to aerosol precursor products,” says Siddharth Iyer, Postdoctoral Research Fellow of Aerosol Physics at Tampere University.

“This result bridges the gap between theory and observation and provides better understanding of the chemistry of aerosol formation in urban environments.”

More information: Siddharth Iyer et al, Molecular rearrangement of bicyclic peroxy radicals is a key route to aerosol from aromatics, Nature Communications (2023). DOI: 10.1038/s41467-023-40675-2

Journal information: Nature Communications 

Provided by Tampere University

by Universität Paderborn

Scientists from Paderborn University, working under Professor Matthias Bauer, have achieved a breakthrough in the field of sustainable chemistry: together with a team of researchers from the universities of Rostock, Mainz, Göttingen, Innsbruck and Kassel, they have developed a chemical complex that converts light into energy for reactions and optical applications—in a sustainable way, since the material can be used to save huge amounts of CO₂.

The new compound has potential applications in areas such as diodes, or in converting solar energy into chemical energy. The results have now been published in Nature Chemistry.

Saving carbon dioxide

“What makes this complex special is that unlike the systems currently in use, it contains iron as the central element,” Bauer explains. Previously, precious-metal-based compounds were generally used for photochemical reactions and photophysical applications.

“However, manufacturing these produces carbon dioxide emissions of around 30 tons per kilogram. If precious metals are replaced with iron, the potential reduction in climate-damaging CO₂ is huge,” Bauer adds. By comparison, manufacturing a kilogram of iron only produces around two kilograms of the climate-damaging gas.

‘Sustainability to the power of two’

“For the first time, the design of the compound being examined has enabled us to implement a property that is extremely rare in chemical compounds and unprecedented in iron compounds,” explains Dr. Jakob Steube, one of the key members of Bauer’s team. The complex glows in two different colors when exposed to light of a certain energy.

These photophysical properties will for example enable white light-emitting diodes to be made using iron compounds. In addition, the complex can be used to transform solar energy into chemical energy.

“We were able to demonstrate that following absorption with light, chemical reactions are possible with our new compound,” Bauer explains. “This gives us sustainability to the power of two, namely energy conversion using a virtually CO₂-neutral compound plus the combination of areas of application in photochemistry and photophysics. This can absolutely be described as a mini breakthrough.”

These findings were gained as part of the priority program “Light-controlled reactivity of metal complexes.” Headed by co-author Professor Katja Heinze of the University of Mainz, the program examines the question of how to ensure sustainable chemical reactions in the future despite increasingly scarce resources, as well as ways of using new energy sources such as sunlight.

More information: Jakob Steube et al, Janus-type emission from a cyclometalated iron(iii) complex, Nature Chemistry (2023). DOI: 10.1038/s41557-023-01137-w

Journal information: Nature Chemistry 

Provided by Universität Paderborn

by Chiba University

Lanthanide-containing complexes are important compounds for sophisticated nuclear-fuel processing and medical imaging. Moreover, they often have interesting symmetric crystal structures and associated dynamics that render unique properties for practical applications. The seven-coordinate lanthanide complex Ho(III) aqua-tris(dibenzoylmethane) or Ho-(DBM)₃·H₂O was first reported in the late 1960s.

It has a three-fold symmetric structure with holmium (Ho) at the center of three propeller-shaped dibenzoylmethane (DBM) ligands and a water (H₂O) molecule hydrogen-bonded to the ligands. Unfortunately, the understanding of the molecular dynamics (MD) of such lanthanide complexes has been limited due to challenges in describing their interactions using the classical MD framework.

This motivated a team of researchers from the Graduate School of Engineering at Chiba University, led by Associate Professor Takahiro Ohkubo, to elucidate the structure and dynamics of the Ho-(DBM)₃·H₂O complex. This study was published in Inorganic Chemistry and is co-authored by Associate Professor Hyuma Masu, Professor Keiki Kishikawa, and Associate Professor Michinari Kohri.

“Hydrogen bonds between the water molecule and the ligands surrounding Ho are considered to play an important role in the formation of the symmetrical structure of the novel lanthanide complex. After synthesizing its single crystal and bulk samples, the next logical step was to model this complex to test this hypothesis and understand its structure and dynamics,” explains Dr. Ohkubo.

Considering the shortcomings of existing general force-fields (a functional form used to estimate forces between atoms) in satisfactorily describing the interactions of lanthanide metals such as Ho, the researchers developed new force-field parameters for conducting classical MD simulations of the Ho-(DBM)₃·H₂O complex. They performed structural optimization and MD steps using ab initio calculations based on the plane-wave pseudopotential method to make training data for force-fields’ development.

Further, the team tuned the force-field parameters for the simulations to reproduce the data obtained from the ab initio calculations. They validated the thus-obtained novel force-field using both the experimental crystalline structure information as well as the theoretical ab initio data. The lattice constant and atomic distances around Ho calculated using the new force-field parameters were found to be in good agreement with the observations of single-crystal X-ray diffraction.

On examining the vibrational properties of water in the Ho-(DBM)₃·H₂O complex and comparing them to those in bulk liquid water, they observed that the vibrational motion of water in the complex had a characteristic mode.

It originated from stationary rotational motion along the c-axis of Ho-(DBM)₃·H₂O. Remarkably, the hydrogen bond dynamics of water, including lifetime, in seven-coordinate lanthanide complexes are quite like those in bulk water, except for librational or reciprocating motion. This novel finding is contrary to basic expectations.

In summary, this innovative strategy of developing force-field parameters for classical MD examination unveils the role of water dynamics in complexes such as Ho-(DBM)₃·H₂O. As Dr. Ohkubo explains, “This approach helped us understand the nature of metal complexes of lanthanides with water and actinide metals with high coordination numbers. In the future, this strategy could possibly pave the way for accurate molecular simulations of any metal complex and prediction of its structure and dynamics.”

More information: Takahiro Ohkubo et al, Molecular Dynamics Studies of the Ho(III) Aqua-tris(dibenzoylmethane) Complex: Role of Water Dynamics, Inorganic Chemistry (2023). DOI: 10.1021/acs.inorgchem.3c01277

Provided by Chiba University

by Washington University in St. Louis

Chenfeng Ke, an incoming associate professor of chemistry in Arts & Sciences at Washington University in St. Louis, developed a unique design for tough but stretchable hydrogels, reported Aug. 23 in the journal Chem. The new material is both flexible and durable thanks to a ring-shaped sugar molecule that encases its polymer network and allows it to stretch without sacrificing strength.

Ke can 3D-print the so-called crystalline-domain reinforced slide-ring hydrogels, or CrysDoS-gels. He and his co-authors also created a materials library and offer methods for how the material can be added to existing materials to enhance their durability, such as in plastic additives to enhance the durability for parts in automobiles in the future.

“There are a series of tradeoffs with these traditional plastic materials—they’re usually one or the other,” stretchable or rigid, Ke said. “But if you connect two things with a slidable joint, you have very interesting properties of both.”

The new material is simple and adaptable, Ke said, and can be combined with a variety of hydrogels to improve the properties of different plastics. For example, it could be added to stretchable materials to make them stronger, or to rigid materials to make them more flexible. In this study, the chemists demonstrated a potential application of their newly discovered CrysDoS-gels by 3D-printing them as stress sensors.

“Think of it increasing the lifespan of plastic parts to reduce the waste we produce,” Ke said.

More information: Chenfeng Ke, Reinforced double-threaded slide-ring networks for accelerated hydrogel discovery and 3D printing, Chem (2023). DOI: 10.1016/j.chempr.2023.07.020. www.cell.com/chem/fulltext/S2451-9294(23)00371-6

Journal information: Chem 

Provided by Washington University in St. Louis 

by University of California, Irvine

A research team led by University of California, Irvine scientists has developed an innovative method for quickly and efficiently creating vast collections of chemical compounds used in drug discovery by harnessing the power of ribosomes, the molecules found in all cells that synthesize proteins and peptides.

Findings recently published in ACS Central Science describe this transformative technique, which could replace the current manually intensive process, accelerating the discovery of new drugs that could affect treatment of a wide array of diseases and conditions.

Chemical libraries are collections of molecules that are screened to identify those with promising activity or therapeutic potential. Screening involves asking the same biological question of each chemical in the library in the form of a rapid experiment or assay.

“Library synthesis and screening are the first steps in the discovery of new medicines,” said Brian M. Paegel, UCI professor of pharmaceutical sciences and the study’s co-corresponding author. “This new technology allows us to synthesize libraries of ultra-miniaturized gel beads that each contain hundreds of thousands of copies of a single compound from the library. The arrangement of so many copies of molecules on beads allows scientists to evaluate the biological activity of each library member directly, an invaluable capability in the search for new medicines.”

The team invented a novel approach to generate gel beads that are roughly the size of a human cell, each containing vast quantities of ribosomes, an enzyme called RNA polymerase and a magnetic core adorned with DNA, not unlike a human cell’s nucleus. The DNA cores encode—or provide assembly instructions for—specific peptide molecules. Insulin is an example of a naturally occurring peptide that has become a drug.

By mimicking a cell’s flow of genetic information from DNA to RNA to peptide synthesis, the researchers successfully localized genetically encoded peptide synthesis within each individual gel bead. Importantly, this technique can be executed in parallel on millions of beads, each with a unique DNA tag, forming an expansive library.

“The beads themselves are also an important achievement. Chemical synthesis that currently depends on labor-intensive manual procedures is now facilitated by the ribosome, allowing us to prepare very large libraries using nature as our inspiration. Scientists can now explore a vast number of molecules simultaneously, advancing pharmaceutical discoveries, while the DNA-encoded magnetic cores enable efficient tracking and analysis of individual compounds,” said Paegel, who also has appointments in chemistry and biomedical engineering.

This method also has applications in other areas, such as enzyme engineering, the development of environmentally friendly pesticides or the creation of materials with specific physical properties.

Other team members included co-corresponding author Christian Cunningham and Alix Chan, both scientists at Genentech in South San Francisco, and Valerie Cavett, UCI project specialist in pharmaceutical sciences.

More information: Valerie Cavett et al, Hydrogel-Encapsulated Beads Enable Proximity-Driven Encoded Library Synthesis and Screening, ACS Central Science (2023). DOI: 10.1021/acscentsci.3c00316

Journal information: ACS Central Science 

Provided by University of California, Irvine 

SRCs) are inexpensive, lightweight, and have advantages in terms of disposal and recycling as the reinforcement and the base material are composed of the same material. For this reason, it is attracting attention as a next-generation composite material to replace carbon fiber-reinforced composites used in aircraft.

The Korea Institute of Science and Technology (KIST) has announced that Dr. Jaewoo Kim of the Solutions to Electromagnetic Interference in Future-mobility (SEIF), together with Prof. Seonghoon Kim of Hanyang University and Prof. O-bong Yang of Jeonbuk National University have successfully developed a 100% SRC using only one type of polypropylene (PP) polymer. Their work is published in the Chemical Engineering Journal.

Until now, in the manufacturing process of SRCs, chemically different components have been mixed in the reinforcement or matrix to improve fluidity and impregnation, resulting in poor physical properties and recyclability. The research team succeeded in controlling the melting point, fluidity, and impregnation by adjusting the chain structure of the polypropylene matrix through a four-axis extrusion process.

The developed SRCs achieved the highest level of mechanical properties, with adhesion strength, tensile strength, and impact resistance improved by 333%, 228%, and 2,700%, respectively, compared to previous studies. When applied as a frame material for a small drone, the material was 52% lighter than conventional carbon fiber reinforced composites and the flight time increased by 27%, confirming its potential for next-generation mobility applications.

Dr. Kim of KIST said, “The engineering process for 100% SRCs developed in this study can be immediately applied to industry, and we will continue to work with the joint research team and industries to secure the global competitiveness of magnetically reinforced composites.”

More information: Hyeseong Lee et al, True self-reinforced composites enabled by tuning of molecular structure for lightweight structural materials in future mobility, Chemical Engineering Journal (2023). DOI: 10.1016/j.cej.2023.142996

Provided by National Research Council of Science & Technology