Proposed chemical recycling of waste polyolefins and this work on transformation of post-consumer waste polyethylene into chemically recyclable materials. Credit: Journal of the American Chemical Society (2022). DOI: 10.1021/jacs.2c11949
Researchers at the U.S. Department of Energy’s (DOE) Institute for Cooperative Upcycling of Plastics (iCOUP) have developed a new method for recycling high-density polyethylene (HDPE).
Using a novel catalytic approach, scientists at DOE’s Argonne National Laboratory and Cornell University converted post-consumer HDPE plastic into a fully recyclable and potentially biodegradable material with the same mechanical and thermal properties of the starting single-use plastic. Their paper describing the results was published December 16 in the Journal of the American Chemical Society.
HDPE is ubiquitous in single-use applications because it is strong, flexible, long-lasting and inexpensive. But the ways we produce and dispose of HDPE pose serious threats to our own health and that of our planet.
Many HDPE products are produced from fossil fuels, and most post-consumer HDPE is either incinerated, dumped in landfills or lost in the environment. When it is recycled with current methods, the quality of the material degrades.
This new approach could reduce carbon emission and pollution associated with HDPE by using waste plastic as untapped feedstock and transforming it into a new material that can be recycled repeatedly without loss of quality.
Current HDPE recycling approaches yield materials with inferior properties. The team’s alternative approach uses a series of catalysts to cleave the polymer chains into shorter pieces that contain reactive groups at the ends. The smaller pieces can then be put back together to form new products of equal value. The end groups have the added benefit of making the new plastic easier to decompose, both in the lab and in nature.
More information: Alejandra Arroyave et al, Catalytic Chemical Recycling of Post-Consumer Polyethylene, Journal of the American Chemical Society (2022). DOI: 10.1021/jacs.2c11949
A new tool from the Imperiali Lab uses directed evolution to generate glycan-binding proteins (GBPs) from small, hyper-thermostable DNA-binding protein. Credit: Massachusetts Institute of Technology
One of the major obstacles that those conducting research on carbohydrates are constantly working to overcome is the limited array of tools available to decipher the role of sugars. As a workaround, most researchers utilize lectins (sugar-binding proteins) isolated from plants or fungi, but they are large, with weak binding, and they are limited in their specificity and in the scope of sugars that they detect.
In a new study published in ACS Chemical Biology, researchers in Professor Barbara Imperiali’s group have developed a platform to address this shortcoming.
“The challenge with polymers of carbohydrates is that their biosynthesis is not template-driven,” says Imperiali, the senior author of the study and a professor in the departments of Chemistry and Biology. “Biology, medicine, and biotechnology have been fueled by technological advancements for proteins and nucleic acids. The carbohydrate field lags terribly behind and is desperately seeking tools.”
Identifying carbohydrate-binding proteins
Biosynthesizing carbohydrates requires every link between individual sugar molecules to be made by a particular enzyme, and there’s no ready way to decipher the structures and sequences of complex carbohydrates. Antibodies to carbohydrates can be generated, but doing so is challenging, expensive, and results in a molecule that is far larger than what is really needed for the research.
An ideal resource for this field plagued with limited mechanisms would be discovery of binding proteins, of limited size, that recognize small chunks of carbohydrates to piece together a structure by using those binders, or methods to detect and identify particular carbohydrates within complicated structures.
The authors of this study used directed evolution and clever screen design to identify carbohydrate-binding proteins from proteins that have absolutely no ability to bind carbohydrates at all. Their findings lay the groundwork for identifying carbohydrate-binding proteins with diverse and programmable specificity.
Streamlining for collaboration
This advance will allow researchers to go after a user-defined sugar target without being limited by what a lectin does, or challenged by the abilities of generating antibodies. These results could serve to inspire future collaborations with engineering communities to maximize the efficiency of glycobiology’s yeast surface display pipeline. As it is, this pipeline works well for proteins, but sugars are far more difficult targets and require the pipeline to be modified.
In terms of future applications, the potential for this innovation ranges from diagnostic to, in the longer term, therapeutic, and paves the way for collaborations with researchers at MIT and beyond. For example, chemistry Professor Laura Kiessling’s research group works with Mycobacterium tuberculosis (Mtb), which has an unusual cell wall composition with unique, distinct, and exclusive sugars. Using this method, a binder could potentially be evolved to that particular feature on Mtb.
Chemical engineering Professor Hadley Sikes develops paper-based diagnostic tools where the binding partner for a particular epitope or marker is laid down, and with the use of this discovery, in the longer term, a lateral flow assay device could be developed.
Laying the groundwork for future solutions
In cancer, certain sugars are overrepresented on cell surfaces, so theoretically, researchers can utilize this finding, which is also amenable to labeling, to develop a tool out of the evolved glycan binder for detection.
This discovery also stands to contribute significantly to improving cell imaging. Researchers can modify binders with a fluorophore using a simple ligation strategy, and can then choose the best fluorophore for tissue or cell imaging. The Kiessling group, for example, could apply small protein binders labeled with fluorophore to detect bacterial sugars to initiate fluorescence-activated cell sorting to probe a complex mixture of microbes.
This could in turn be used to determine how a patient’s microbiome has been disturbed. It also has the potential to screen the microbiome of a patient’s mouth or their upper or lower gastrointestinal tract to read out the imbalance within the community using these types of reagents. In the more distant future, the binders could potentially have therapeutic purposes like clearing the gastrointestinal tract or mouth of a particular bacterium based on the sugars that the bacterium displays.
More information: Elizabeth M. Ward et al, Engineered Glycan-Binding Proteins for Recognition of the Thomsen–Friedenreich Antigen and Structurally Related Disaccharides, ACS Chemical Biology (2022). DOI: 10.1021/acschembio.2c00683
The separation of carbazole/anthracene with N, N-dimethylformamide: NMR study substantiated carbazole separation. Credit: Yan Qiao, Institute of Coal Chemistry, Chinese Academy of Sciences
Coal tar, once considered waste, has become a huge treasure trove because hundreds of compounds can be isolated from it. Most of these compounds tend to be aromatic hydrocarbons, polycyclic aromatic hydrocarbons, and heterocyclic compounds.
Carbazole and anthracene, two aromatic hydrocarbon components contained in coal tar, are used as essential organic intermediates to synthesize various carbazole derivatives and anthraquinones. The effective separation of carbazole and anthracene takes advantage of their different solubility in solvents. In this process, solvent screening and performance optimization are essential, and their optimization mainly follows the principle of trial and error. Thus, it is necessary to use a versatile detection technique for understanding this separation process on the molecular level.
N,N-Dimethylformamide (DMF) has been developed as an efficient solvent for carbazole and anthracene separation due to the high solubility of carbazole in DMF; moreover, researchers have found that the separation of carbazole and anthracene may benefit from an intermolecular hydrogen bond between carbazole and DMF. However, there was no detailed study concerning the interaction mechanism between carbazole/anthracene and a solvent capable of hydrogen bonding. It is important to use a versatile detection technique for analyzing hydrogen bond interaction, and hence to explain the interaction mechanism between carbazole/anthracene and DMF via hydrogen bonding on the molecular level.
Recently, the group of Yan Qiao, a professor of the State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, CAS, studied the intermolecular interaction mechanism between DMF and carbazole/anthracene by various advanced liquid state NMR techniques. They observed that the N-H chemical shift of carbazole changed significantly in 1H NMR titration and VT-NMR experiments, indicating strong intermolecular hydrogen bonds between carbazole and DMF, which was further supported by the decrease in molecular self-diffusion coefficients (D) of both carbazole and DMF according to diffusion-ordered spectroscopy (DOSY) measurements.
Moreover, the Nuclear Overhauser Effect Spectroscopy (NOESY) experiment revealed that the distance between the aldehydic hydrogen of DMF and the N-H of carbazole was smaller than 5 Å. Accordingly, an intermolecular hydrogen bond between carbazole and DMF in the form of C=O···H-N was proposed.
“Solvent screening is still lacking theoretical guidance, with most work on the basis of ‘like dissolves like’ and lacks direct spectroscopic evidence,” Qiao said, “Our research helps researchers to understand the interaction mechanism between carbazole/anthracene and DMF in this process from the molecular and even atomic levels. It will also guide the further expansion of alternative solvent media and optimization of separation processes, and play an important role in promoting the development of coal tar separation industry.”
This research is published in the journal Industrial Chemistry & Materials.
More information: Hui Cao et al, Understanding the interaction mechanism of carbazole/anthracene with N,N-dimethylformamide: NMR study substantiated carbazole separation, Industrial Chemistry & Materials (2022). DOI: 10.1039/D2IM00020B
Provided by Institute of Process Engineering, Chinese Academy of Sciences
Overview of tRNA-MaP. Credit: Ehime University, Ryota Yamagami, Hiroyuki Hori
Genetic information encoded in genomic DNA is transcribed to mRNAs and then the codons on mRNA are decoded by transfer RNAs (tRNAs) during protein synthesis. tRNAs deliver amino acids to ribosomes and proteins are synthesized from the amino acids on the ribosomes according to the decoded genetic information. Therefore, tRNA plays a key role during the translation of genetic information.
tRNAs contain numerous modified nucleosides, which regulate the accuracy and efficiency of protein synthesis. Modified nucleosides in tRNA are synthesized by tRNA modification enzymes. Therefore, unveiling the mechanisms by which tRNA modification enzymes selectively recognize substrate tRNAs from non-substrate RNAs; the when, where, and how many tRNAs are being modified by the modification enzymes, is of crucial importance to understand the protein synthesis machinery.
Addressing these key questions is, however, challenging due to the lack of a high-throughput technique that identifies the characteristic properties of tRNA modification enzymes.
To overcome this issue, Drs. Yamagami and Hori at Ehime University applied next-generation DNA sequencing technology to functional analyses of tRNA modification enzymes and developed a new high-throughput assay method, “tRNA-MaP.”
The tRNA-MaP technique can rapidly screen an RNA pool consisting of more than 5,000 RNA species and identify the substrate tRNAs of the target tRNA modification enzyme(s) with comparative sensitivity to already-established methods. By tRNA-MaP, in combination with protein orthology analyses, the researchers predicted numerous natural modifications in Geobacillus stearothermophilus tRNAs.
Furthermore, they analyzed the substrate recognition mechanism of G. stearothermophilus tRNA m1A22 methyltransferase (TrmK), which methylates adenosine at position 22 to 1-methyladenosine (m1A22) in tRNA, using tRNA-Map. Mutation profiling has revealed that TrmK selects a subset of tRNAs for the substrate.
Using 240 variants of G. stearothermophilus tRNALeu transcripts, the researchers found that U8, A14, G15, G18, G19, U55, Purine57 and A58 are important for the methylation by TrmK. In addition, based on the recognition sites in tRNA and the crystal structure of TrmK, a docking model between TrmK and tRNA has been constructed.
This study, now published in the Journal of Biological Chemistry, revealed that tRNA-Map is applicable for the analysis of the tRNA modification enzyme. Notably, because tRNA-Map can analyze any RNA molecular species from any organism, even DNA molecules, tRNA-Map can be used for analysis of all nucleic acid-related proteins except for tRNA modification enzymes. Thus, tRNA-Map can accelerate the integrative understanding of the flow of genetic information.
More information: Ryota Yamagami et al, Application of mutational profiling: New functional analyses reveal the tRNA recognition mechanism of tRNA m1A22 methyltransferase, Journal of Biological Chemistry (2022). DOI: 10.1016/j.jbc.2022.102759
UMAP plot visualizing the distribution of the polymer backbones. The UMAP plots show the distribution of (a) 15,335 homopolymers in PoLyInfo and (b) 1070 homopolymers calculated in this study. The 21 classes of the polymer backbones are color-coded according to the definition of PoLyInfo. Credit: npj Computational Materials (2022). DOI: 10.1038/s41524-022-00906-4
A research team has published their method to create a comprehensive database of polymer properties, as well as experimental validation, in npj Computational Materials.
“Materials informatics (MI), a new branch of materials research that combines materials data with data science, is gaining traction,” said co-corresponding author Yoshihiro Hayashi, assistant professor, Institute of Statistical Mathematics in the Research Organization of Information and Science (ROIS). Hayashi is also affiliated with the University of Tokyo’s Department of Mechanical Engineering. “MI applies machine learning to predict new materials with innovative properties and their fabrication methods from a vast design space. As such, data is the most important resource in MI.”
Despite the need, Hayashi said, efforts to create a comprehensive database of polymer properties to enable data-driven research have fallen short.
“To construct a database of polymer properties by molecular simulations, we developed RadonPy,” Hayashi said. “It’s the first open-source software that successfully automates polymer physical property calculations using simulations of classical molecular dynamics based on atomistic models—which account for the behaviors and characteristics of individual constituents.”
The program takes an assigned polymer and runs calculations to equilibrate it in prescribed system parameters. Once it does, it can then calculate the polymer’s density, radius of gyration, refractive index, thermal conductivity, specific heat capacities at constant pressure and at constant volume, among other information. RadonPy produces and stores the data, which can then be accessed later. The researchers also implemented a machine learning technique called transfer learning to correct biases and variations between the simulated property values and experimental data.
“In this study, more than 1,000 unique amorphous polymers were computed in about two months, mainly using the supercomputer Fugaku,” said co-corresponding author Ryo Yoshida, professor, Institute of Statistical Mathematics in ROIS, the National Institute for Materials Science’s Research and Services Division of Materials Data and Integrated System and The Graduate University of Advance Studies’ Department of Statistical Science.
“The program implements a set of automatic computation functions for 15 different properties, which were systematically compared with experimental data to validate the calculation conditions. We also comprehensively verified the agreement between six properties obtained from high-throughput molecular dynamics calculations and experimental values.”
The research team also identified eight amorphous polymers with high conductivity, according to Yoshida. Now, the group is using RadonPy to create the world’s largest open database of polymer physics, with more than 100,000 different polymer species. In addition to ROIS, three universities and 19 companies are partnering to jointly develop other databases with RadonPy for a variety of applications in academia and industry.
“This project will create a world map of polymer material properties,” Hayashi said. “Such exhaustive observations cannot be achieved solely via experimental approaches requiring considerable costs, such as in material synthesis. This research is the first step toward a new horizon of polymer science.”
More information: Yoshihiro Hayashi et al, RadonPy: automated physical property calculation using all-atom classical molecular dynamics simulations for polymer informatics, npj Computational Materials (2022). DOI: 10.1038/s41524-022-00906-4
Provided by Research Organization of Information and Systems
A team from the Universitat Politècnica de València (UPV), the Universitat de València (UV), and the Centro de Investigación Biomédica en Red sobre Enfermedades Raras (CIBERER) has developed a lateral flow test that identifies and quantifies the level of allergens reliably in food with the help of a smartphone. The work has been published in the journal Biosensors.
“Food allergy or hypersensitivity is estimated to affect about 520 million people worldwide. These reactions occur mainly through the consumption of foods containing trace allergens. Therefore, identifying and quantifying them before the food is consumed is essential, and this is what the test we have developed allows,” says Sergi Morais, professor in the Department of Chemistry at the Universitat Politècnica de València and researcher at the Inter-University Institute of Molecular Recognition and Technological Development (IDM).
The prototype has been developed as a proof of concept for simultaneously detecting almond and peanut allergens and has been validated with everyday commercial foods such as biscuits and energy bars.
Among its advantages, the researchers highlight the reliability of the test, which contains multiple internal controls and calibrators integrated into a miniaturized 36-point array.
“With microarray technology, we perform 36 assays in a single step. The derived information allows us to identify whether the result is a true positive or negative. In addition, with the internal calibrators and the smartphone, we can quantify with high precision traces of allergen in the food,” says Ángel Maquieira, full professor in the Department of Chemistry at the Universitat Politècnica de València.
Regarding the extraction method, the UPV, UV, and CIBERER team stresses its simplicity, which means anyone can carry it out at any time.
“Current extraction methods consist of multiple steps and require sophisticated equipment for grinding, degreasing, extraction, and purification of allergens. Therefore, the analysis is carried out in qualified laboratories. The aim is to decentralize the analysis, as has been done with the COVID-19 test. We want anyone to be able to analyze a food just before consuming it,” adds Sergi Morais.
The extraction method developed is based on the use of a portable grinder, which is used to grind and filter the sample in a single step; 5 mL of a solution is then added to extract the allergen, and, once the sample is prepared, the test strip is immersed in the solution. And in just 5 minutes, the result is obtained, which can be read with a mobile phone.
“At an estimated cost of €1 per strip, the developed test has great commercial potential, for example, in the food sector for rapid identification of allergens in situ and in the pharmaceutical sector to quantify the potency of allergenic extracts used in allergy testing,” says Amadeo Sena, a postdoctoral researcher at the Inter-University Institute for Molecular Recognition and Technological Development (IDM).
Future development
Looking to the future, the UPV, UV, and CIBERER team points out that, given the characteristics of the test strip, it could easily be adapted for other allergens, as the group has specific antibodies for a wide range of allergens and biomarkers.
“Our challenge is to develop a test for the simultaneous quantification of the 14 allergens that must be declared according to Royal Decree 126/2015,” concludes Patricia Casino, a researcher at Instituto Universitario de Biotecnología i Biomedicina (BIOTECMED)—Universitat de València and the CIBERER.
More information: Amadeo Sena-Torralba et al, Lateral Flow Microimmunoassay (LFµIA) for the Reliable Quantification of Allergen Traces in Food Consumables, Biosensors (2022). DOI: 10.3390/bios12110980
The synthesis route for the controlled synthesis of Co-NiOx@GDY through a three-step strategy including the first growth of a film of cobalt-nickel bimetal mixed nanosheets on the surface of nickel foam (Co-NiOxHy), followed by a calcination treatment to obtain Co-NiOx, and finally the in-situ growth of ultrathin GDY films on the surface of Co-NiOx through a cross-coupling reaction with hexaethynylbenzene (HEB) as the precursor. Credit: Science China Press
A major impediment to industrial urea synthesis is the lack of catalysts with high selectivity and activity. Prof. Yuliang Li (Institute of Chemistry, Chinese Academy of Sciences) and coworkers reported a new catalyst system suitable for the highly selective synthesis of industrial urea by in-situ growth of graphdiyne on the surface of cobalt-nickel mixed oxides.
The researchers found that such a catalyst is a multi-heterojunction interfacial structure resulting in the obvious incomplete charge transfer phenomenon between graphdiyne and metal oxide interface and multiple intermolecular interactions. These intrinsic characteristics are the origin of the high performance of the catalyst.
The team also demonstrated that the catalyst could effectively optimize the adsorption/desorption capacities of the intermediate and promote the direct C-N coupling by significantly suppressing by-product reactions toward the formation of H2, CO, N2, NH3.
The catalyst can selectively synthesize urea directly from nitrite and carbon dioxide in water at room temperature and pressure and exhibits record-high Faradaic Efficiency (FE) of 64.3%, nitrogen selectivity (Nurea-selectivity) of 86.0%, carbon selectivity (Curea-selectivity) of ~100%, as well as the urea yield rates of 913.2 μg h–1 mgcat–1 and remarkable long-term stability.
The work is published in the journal National Science Review.
More information: Danyan Zhang et al, Multi-heterointerfaces for selective and efficient urea production, National Science Review (2022). DOI: 10.1093/nsr/nwac209
(a) 3D neutron tomography of the spine bones saturated with water (green). (b) 3D neutron tomography after saturation with deuterated water (orange). (c) 3D dataset of the difference, corresponding to the expelled water volume (red). (d) Matching neutron tomography with X-ray μCT scans helped to identify water in the bone extracellular matrix. Credit: HZB/Charité
Around 500 million years ago, early vertebrates in the seas became fish, adopting an inner skeleton and a flexible spine based on a nanocomposite of fibers and mineral, known as bone material. This “invention” of evolution was so successful that the basic structure was also adopted for later vertebrates that lived on land.
However, while the bones of all terrestrial vertebrates are basically equipped with bone cells (osteocytes), certain fish species continued to evolve and finally managed to create a more energy efficient material: bone lacking bone cells, found today for example in fish such as salmon, medaka or tilapia.
Samples with and without bone cells
“We asked ourselves how bone samples with and without bone cells actually differ in their microstructures and properties,” says Prof. Paul Zaslansky, who heads a research group at Charité Berlin and specializes in mineralized biomaterials including teeth and bones.
Together with Ph.D. student Andreia Silvera and international partners, they have now compared bone samples from zebrafish and medaka. Both fish species are of similar size and live in similar conditions, so their skeletons must withstand similar stresses. However, while zebrafish have bone cells, the skeleton of medaka do not.
“The background to the question is that the function of bone cells in bone and how they change with age is of great interest to the aging population,” Silvera explains. Bone cells can respond to physical stress by sending biochemical signals that lead to the formation or resorption of bone tissue, adapting to load. But with age or in diseases such as osteoporosis, this mechanism no longer seems to work.
“With our basic research, we want to find out how bones with and without bone cells differ and cope with the challenges of external stress,” Zaslansky says.
Strength and elasticity
Bones have a complex structure: they comprise nanofibers of collagen and nanoparticles of mineral but also other minor ingredients. Certain protein compounds, so called Proteoglycans (PGs), are embedded in a tissue of collagen fibers and nanocrystals and play important roles in tissue formation and maintenance.
“PGs may be compared to salt in the soup. Too little or too much of it is not good,” Zaslansky says. The PGs can retain water, and there are plenty of PGs in healthy cartilage, making it as elastic as a sponge. Together, these components form an extracellular matrix (ECM), a 3D structure that provides strength and elasticity, ensuring function for many years.
In bones, an open network (Lacunar Channel Network or LCN) of channels and pores with diameters ranging from a few hundred nanometers to micrometers is created in this 3D structure. This LCN hosts the bone osteocytes, cells that sense load and orchestrate bone remodeling. In the LCN and within the nanocomposite, bone contains up to 20% of its volume in water, with many functions including toughening and adaptation to mechanical stress.
Neutron tomography at BER II
To determine the amount of incorporated water, the researchers first immersed bone samples in water and transilluminated them with neutrons, provided by the Berlin experimental reactor BER II at HZB—followed by saturation in deuterated heavy water (D2O). 3D data was collected again and the difference between the two bone states allowed the team to determine for each spine vertebrae the precise amount of water displaced by diffusion of the D2O.
“In addition, we examined sections of the bone samples, analyzed them by electron microscopy and micro CT and we also determined the PG concentration with Raman spectroscopy,” Silvera explains.
Surprising results: PGs make the difference
Until now, it was assumed that both bone types contain similar amounts of water and had very similar composition and properties. In fact however, the neutron examination showed that the bone material of zebrafish releases half as much water as that of medaka. This is all the more surprising because these bones have a very similar microstructure of mineralized collagen fibers, but zebrafish also contain large cell spaces within the LCN.
“My first reaction was, ‘This must be wrong!’ So we checked everything thoroughly and realized it’s really revolutionary,” recalls Zaslansky. The only explanation for the difference is that the bone matrices of the two species differ in a fundamental compositional component that affects water permeability. And here, both histological studies and Raman spectroscopy show: it’s the small but important contribution of PGs. The medaka samples contain far less PG than the zebrafish samples.
“This is a new finding: although both fish cope with similar stresses, their bone materials do not have the same water permeability properties,” says Silveira.
The study is published in the journal Materials & Design.
“We hope these results will help us better understand bone diseases as well,” Zaslansky says. Why are some bones better at responding to stress than others? What happens when bones age? Could it be that they lose PGs, and become less watertight? Perhaps aging or pathology such as osteoporosis changes the bone that surrounds bone cells, which makes it difficult to remodel and form bone tissue that works correctly?
More information: Andreia Silveira et al, Water flow through bone: Neutron tomography reveals differences in water permeability between osteocytic and anosteocytic bone material, Materials & Design (2022). DOI: 10.1016/j.matdes.2022.111275
Chemical reactions occur on the scale of atomic vibrations—one million times smaller than the thickness of a human hair. These tiny movements are difficult to control.
Established methods include the control of temperature or providing surfaces and complexes in solution made from rare materials. They tackle the problem on a larger scale and cannot target specific parts of the molecule. Ideally, researchers would like to provide only a small amount of energy to some atoms at the right time, just like a billiard player wants to nudge just one ball on the table.
In recent years, it became clear that molecules undergo fundamental changes when they are placed in optical cavities with opposing mirrors. Inside those confines, the system is forced to interact with virtual light, or photons. Crucially, this interaction changes the rate of chemical reactions—an effect that was observed in experiments but whose underlying mechanism remained a mystery.
Now a team of theoretical physicists from Germany, Sweden, Italy and the U.S.A. has come up with a possible explanation, which qualitatively agrees with the experimental results.
The team involved researchers from the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) in Hamburg, Germany, Chalmers University of Technology in Sweden, the Center for Computational Quantum Physics at the Flatiron Institute, Harvard University (both in the U.S.A.), and the Istituto per i Processi Chimico Fisici at the CNR (National Research Council) in Italy.
Using an advanced theoretical method, called Quantum-Electrodynamical Density-Functional Theory (QEDFT), the authors have unveiled the microscopic mechanism which reduces the chemical reaction rate, for the specific case of the deprotection reaction of 1-phenyl-2-trimethylsilylacetylene. Their findings are in agreement with the observations by the group of Thomas Ebbesen in Strasbourg.
The team discovered that the conditions inside the optical cavity affect the energy which makes the atoms vibrate around the molecule’s single bonds, which are critical for the chemical reaction.
Outside the cavity, that energy is usually deposited in a single bond during the reaction, which can ultimately break the bond—a key step in a chemical reaction. “However, we find that the cavity introduces a new pathway, so that the energy is less likely to be funneled only into a single bond,” says lead author Christian Schäfer. “This is the key process which inhibits the chemical reaction, because the probability to break a specific bond is diminished.”
Manipulating materials through the use of cavities (“polaritonic chemistry”) is a powerful tool with many potential applications, according to the paper’s author Enrico Ronca, who works at CNR: “For instance, it was observed that coupling to specific vibrational excitations can inhibit, steer, and even catalyze a chemical process at room temperature. Our theoretical work enhances the understanding of the underlying microscopic mechanisms for the specific case of a reaction inhibited by the field.”
While the authors point out that important aspects remain to be understood and further experimental validation is required, they also highlight the special role of this new direction.
“This works puts the controversial field of polaritonic chemistry onto a different level,” adds Angel Rubio, the Director of the MPSD’s Theory Department. “It provides fundamental insights into the microscopic mechanisms that enable the control of chemical reactions. We expect the present findings to be applicable to a larger set of relevant reactions (including click chemical reactions linked to this year’s Nobel Prize in chemistry) under strong light-matter coupling conditions.”
The paper is published in the journal Nature Communications.
More information: Christian Schäfer et al, Shining light on the microscopic resonant mechanism responsible for cavity-mediated chemical reactivity, Nature Communications (2022). DOI: 10.1038/s41467-022-35363-6
When it comes to kitchen spills, paper towels and rags do the job. But using a hydrogel—a gelatin-like material in the form of a dry sheet—researchers have crafted a better picker-upper that absorbs and holds about three times more water-based liquid. The method, presented on December 21 in the journal Matter, produces an absorbent, foldable, and cuttable “gel sheet” that may one day find use in our kitchens or operating rooms to soak up liquids.
There are generally two types of materials that absorb liquids—porous materials and hydrogels. Porous materials like cloth and paper are flexible, foldable, and easy to use, but not very absorbent. On the other hand, superabsorbent hydrogels that are made of polymer, a web of large molecules, can soak up more than 100 times their weight in water. However, when dried, these hydrogels become brittle solids that crumble.
“We reimagined what a hydrogel can look like,” says corresponding author Srinivasa Raghavan of the University of Maryland. “What we’ve done is combine the desired properties of a paper towel and a hydrogel.”
To craft the gel sheets, the research team first mixed in acid, base, and other ingredients for the hydrogel in a zip-top bag. Like vinegar meeting baking soda, the mixture released carbon dioxide bubbles within the gel, creating a porous and foam-like material. Next, the zip-top bag was sandwiched between glass slabs to form a sheet and then exposed to UV light, which sets the liquid around the bubbles, leaving pores behind. Lastly, the team dipped the set sheet in alcohol and glycerol and air-dried it. This enabled the dried gel sheet to remain soft and flexible, similar to a fabric’s texture.
Compared to gauze dressing, a “gel sheet” made from a gelatin-like material can quickly soak up more blood without dripping, as shown in the video. The sheets may one day help clean up blood during surgeries or stop bleeding from wounds. Credit: Matter/Choudhary et al
“To our knowledge, this is the first hydrogel that has been reported to have such tactile and mechanical properties,” says Raghavan. The gel sheets also stayed soft and flexible in ambient conditions for a year, indicating stability. “We are trying to achieve some unique properties with simple starting materials.”
Compared to a commercial cloth pad and a paper towel, a gel sheet the same size can absorb more than three times the amount of liquid than others. When researchers placed the gel sheet over 25 mL (0.8 oz) of spilled water, the sheet swelled and soaked it up within 20 seconds, holding the water without dripping. However, the cloth pad only absorbed about 60% of the water, leaving drips behind.
The gel sheet also performed well with thick liquids, such as syrup, blood, and even fluids that are a million times thicker than water. The researchers found that the gel sheet could absorb nearly 40 mL (1.4 oz) of blood within 60 seconds, while gauze dressing soaked up only 55% of the blood. The gel sheet also holds its liquid well, whereas the blood-soaked gauze trickles. Compared to sanitary pads, sponges, and gauze, the gel sheet absorbed over two times more blood than the others.
Compared to gauze dressing, a “gel sheet” made from a gelatin-like material can quickly soak up more blood without dripping, as shown in the video. The sheets may one day help clean up blood during surgeries or stop bleeding from wounds. Credit: Matter/Choudhary et al
“To our knowledge, this is the first hydrogel that has been reported to have such tactile and mechanical properties,” says Raghavan. The gel sheets also stayed soft and flexible in ambient conditions for a year, indicating stability. “We are trying to achieve some unique properties with simple starting materials.”
Compared to a commercial cloth pad and a paper towel, a gel sheet the same size can absorb more than three times the amount of liquid than others. When researchers placed the gel sheet over 25 mL (0.8 oz) of spilled water, the sheet swelled and soaked it up within 20 seconds, holding the water without dripping. However, the cloth pad only absorbed about 60% of the water, leaving drips behind.
The gel sheet also performed well with thick liquids, such as syrup, blood, and even fluids that are a million times thicker than water. The researchers found that the gel sheet could absorb nearly 40 mL (1.4 oz) of blood within 60 seconds, while gauze dressing soaked up only 55% of the blood. The gel sheet also holds its liquid well, whereas the blood-soaked gauze trickles. Compared to sanitary pads, sponges, and gauze, the gel sheet absorbed over two times more blood than the others.
“Gel sheet” developed by researchers at the University of Maryland can quickly absorb more water than a commercial cloth pad. As shown in the video, the sheet swells and holds water without dripping. Credit: Matter/Choudhary et al.
Next, the team plans to optimize their gel sheets by increasing absorbency, strengthening the material, lowering the cost, and making the sheets reusable. The researchers are also looking to develop gel sheets for absorbing oil.
“In principle, the gel sheets could be a superior form of paper towels,” says Raghavan. He envisions the gel sheets picking up spills in kitchens and laboratories, as well as cleaning up blood from surgeries and menstrual bleeding. Because of their flexible and absorbent nature, gel sheets also have the potential to stop bleeding from severe wounds as dressing. “I’m always interested in taking our inventions further than just publishing a paper. It would be wonderful to take it to actual practical use.”
