What Are The Effects Of Magnetic Field On The Inflation’s Potential? (Quantum / Cosmology)

By considering a warm inflaton model, Piccinelli and Sanchez carried out study on the effects of a magnetic field on the inflation’s potential. They found that the effect of the magnetic field on the effective potential is to make it less steep, preserving the slow-roll conditions. Their study recently appeared in Arxiv.

Magnetic fields are present at all scales in the universe. It seems probable that these fields should be present at all times, during the universe evolution. Thus, it is important to consider effects of magnetic field if you are addressing some early universe events. In particular, if magnetic field has to play any role in inflationary process, one must have to consider dissipative processes. This could happen in models where inflaton is coupled to gauge fields, to supersymmetric light fields, as in models of trapped inflation or to heavy ones, as in warm inflation.

Piccinelli and Sanchez considered warm inflation model, where the inflaton is assumed to interact with other fields, both during the inflationary expansion as well as at reheating, in a continuous and more natural way. It is a model where (near) thermal equilibrium conditions are maintained during the inflationary expansion, with no need for very flat potentials, nor for a tiny coupling constant. The model is based on global supersymmetry and a coupling between the inflaton and heavy intermediate superfields which are in turn coupled to light particles.

“Previously, we explored the effect of a weak magnetic field on the warm inflation effective potential, up to one loop, for neutral heavy bosons interacting with the charged light sector and showed that the magnetic field makes the potential flatter, retarding the transition, and works as an additional SUSY breaking scale. In this paper, we broaden the scenario, allowing for magnetic fields of arbitrary strength and charged heavy fields.”

FIG. 1: Effective potential normalized by V(0, 0), for different magnetic field strengths for Ms/φ0 = 0.05, m1/φ0 = 10¯3, m2/φ0 = 5 × 10¯3, g = 0.1 and h = 0.1. © Piccinelli and Sanchez

They found that the effect of magnetic field on the effective potential is to make it less steep as compared with the vacuum case, showing that magnetic fields do not spoil the inflationary process.

“This result could be relevant in order to continue exploring the role played by magnetic fields on cosmological events, since there are good chances that they were present during the early stages of the universe, where phase transitions provided suitable conditions for their generation.”, concluded authors of the study.


References: (1) Gabriella Piccinelli, Angel Sanchez, “Magnetic warm inflation”, Arxiv, pp. 1-13, 2021.
arXiv:2106.14791 (2) Gabriella Piccinelli, Ángel Sánchez, Alejandro Ayala, and Ana Julia Mizher, “Warm inflation in the presence of magnetic fields”, Phys. Rev. D 90, 083504 – Published 3 October 2014.


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LIH Identifies ‘Key’ Protein That Allows Cancer-destroying Viruses To Enter Tumour Cells (Medicine)

Researchers from the Laboratory of Oncolytic-Virus-Immuno-Therapeutics (LOVIT) at the LIH Department of Oncology (DONC) are working on the development of novel anticancer strategies based on oncolytic viruses, “good” viruses that can specifically infect, replicate in and kill cancer cells. In particular, the LOVIT team elucidated the mechanism through which the H-1PV cancer-destroying virus can attach to and enter cancer cells, thereby causing their lysis and death. At the heart of this process lie laminins, and specifically laminin γ1, a family of proteins on the surface of a cancer cell to which this virus binds, and which therefore act as the ‘door’ through which the virus enters the cells. The findings, which were published in the prestigious international journal Nature Communications, carry significant implications for the advancement of virus-based anticancer strategies and for the prediction of a patient’s response to this innovative therapeutic approach. 

Oncolytic viruses, such as the rat virus H-1PV, have the ability to selectively infect and kill tumour cells, inducing their lysis and stimulating an anticancer immune response, without however harming normal healthy tissues. Despite their notable clinical potential, their use as a standalone treatment does not currently result in complete tumour regression, mainly due to the varying degree of patient sensitivity and responsiveness. It is therefore important to be able to identify patients whose tumours display genetic characteristics that make them vulnerable to the virus and who are thus most likely to benefit from this novel anticancer therapy.

In this context, we sought to elucidate the features of host cancer cells that enable oncolytic viruses to effectively infect and destroy them, focusing specifically on the factors required for cell attachment and entry”, says Dr Antonio Marchini, leader of LOVIT and corresponding author of the publication.

Using a technique known as RNA interference, the research team progressively ‘switched off’ close to 7,000 genes of cervical carcinoma cells to detect those that negatively or positively modulate the infectious capacity of H-1PV. They thus identified 151 genes and their resulting proteins as activators and 89 as repressors of the ability of H-1PV to infect and destroy cancer cells. The team specifically looked at those genes that coded for proteins localised on the cell surface, in order to characterise their role in determining virus docking and entry. They found that a family of proteins called laminins, and particularly laminin γ1, play a crucial role in mediating cell attachment and penetration. Indeed, deactivating the corresponding LAMC1 gene in glioma, cervical, pancreatic, colorectal and lung carcinoma cells resulted in a significant reduction in virus cell binding and uptake, and in increased cancer cell resistance to virus-induced death. A similar effect was observed when switching off the LAMB1 gene encoding the laminin β1 protein. 

“Essentially, laminins at the surface of the cancer cell are the ‘door’ that allows the virus to recognise its target, attach itself and penetrate into it, subsequently leading to its destruction. In particular, the virus interacts with a specific portion of the laminin, a sugar called sialic acid, which is essential for this binding and entry process and for infection”, explains Dr Amit Kulkarni, first author of the publication. 

The team went a step further and sought to assess the clinical implications of their findings for cancer patients. They found that laminins γ1 and β1 are differentially expressed across different tumours, being for instance overexpressed in pancreatic carcinoma and glioblastoma (GBM) cells compared to healthy tissues. Moreover, in brain tumours, their expression increases with tumour grade, with late-stage GBM displaying higher laminin levels than lower grade gliomas. Similarly, based on the analysis of 110 biopsies from both primary and recurrent GBM, the researchers reported significantly higher levels of laminins in recurrent GBM compared to primary tumours.

These observations indicate that elevated laminin expression is associated with poor patient prognosis and survival in a variety of tumours, including gliomas and glioblastoma. The encouraging fact, however, is that cancers displaying high laminin levels are more susceptible to being infected and destroyed by the H-1PV virus and that patients with these tumours are therefore more likely to be responsive to this therapy”, adds Dr Marchini.  

These findings could lead to the classification of cancer patients according to their individual laminin expression levels, thereby acting as a biomarker that predicts their sensitivity and responsiveness to H-1PV-based anticancer therapies. This will in turn allow the design of more efficient clinical trials with reduced costs and approval times and, ultimately, the development of enhanced combinatorial treatments to tangibly improve patient outcomes.

The study was published in June 2021 in the renowned journal Nature Communications, with the full title “Oncolytic H-1 parvovirus binds to sialic acid on laminins for cell attachment and entry”.


FUNDING AND COLLABORATIONS

This study was initially supported by a seeding grant from the Institut National du Cancer (INCA) to Dr Marchini and at later stages by a grant from ORYX GmbH to Dr Marchini. It also benefited from a generous private donation from Mr André Welter. 

The study was performed in close collaboration with national and international partners, and involved the Laboratory of Oncolytic-Virus-Immuno-Therapeutics (LOVIT) and the NORLUX Neuro-Oncology Laboratory of the LIH Department of Oncology, the LIH Quantitative Biology Unit, the German Cancer Research Center (Germany), the University of Bergen (Norway), Haukeland University Hospital (Norway), the University of Heidelberg (Germany) and the Institut de Génétique et de Biologie Moléculaire et Cellulaire (France).

The LOVIT team would also like to express its deep gratitude to the Luxembourg Cancer Foundation and to Télévie for supporting projects on oncolytic virus immunotherapy.

Featured image: Drs Amit Kulkarni (left) and Antonio Marchini (right) from LOVIT © LIH


Provided by Luxembourg Institute of Health

Researchers Identify Muscle Proteins Whose Quantity is Reduced in Type 2 Diabetes (Medicine)

The new finding confirms the significance of muscle mitochondria in the development of type 2 diabetes

Globally, more than 400 million people have diabetes, most of them suffering from type 2 diabetes.

Before the onset of actual type 2 diabetes, people are often diagnosed with abnormalities in glucose metabolism that are milder than those associated with diabetes. The term used to indicate such cases is prediabetes. Roughly 5-10% of people with prediabetes develop type 2 diabetes within a year-long follow-up.

Insulin resistance in muscle tissue is one of the earliest metabolic abnormalities detected in individuals who are developing type 2 diabetes, and the phenomenon is already seen in prediabetes.

In a collaborative study, researchers from the University of Helsinki, the Helsinki University Hospital and the Minerva Foundation Institute for Medical Research investigated the link between skeletal muscle proteome and type 2 diabetes.

In the study, the protein composition of the thigh muscle was surveyed in men whose glucose tolerance varied from normal to that associated with prediabetes and type 2 diabetes. A total of 148 muscle samples were analysed.

The results were published in the iScience journal.

“Our study is the broadest report on human muscle proteomes so far. The findings confirm earlier observations that have exposed abnormalities in muscle mitochondria in connection with type 2 diabetes,” says Docent Heikki Koistinen from the University of Helsinki, Helsinki University Hospital and Minerva Foundation Institute for Medical Research, who headed the study.

Protein concentration already decreases in prediabetes

The researchers utilised mass spectrometry, enabling them to identify over 2,000 muscle proteins.

According to the findings, the quantity of dozens of proteins had already changed in prediabetic study subjects.

The greatest changes were observed in connection with type 2 diabetes, where the quantity of more than 400 proteins had primarily dropped. Most of these proteins were associated with mitochondrial energy metabolism.

In fact, the results highlight the significance of mitochondria when prediabetes is progressing toward type 2 diabetes.

“We found that the levels of mitochondrial muscle proteins are clearly reduced already in prediabetes,” Koistinen notes.

The researchers also observed abnormalities, both in conjunction with prediabetes and type 2 diabetes, in the concentration of a range of phosphoproteins, which affect metabolism and muscle function.

Regular physical activity as targeted therapy

The researchers believe their new observations have multiple uses, including in the search for new drug targets.

“Still, there already exists an excellent and economical targeted therapy, since regular physical activity increases the number of muscle mitochondria and improves metabolism diversely,” Koistinen points out.

Physical activity is also key when reducing the risk of developing diabetes.

“You can halve the risk of developing diabetes by losing weight, increasing physical activity and observing a healthy diet,” Koistinen says.


Reference: Tiina Öhman, Jaakko Teppo, Neeta Datta, Selina Mäkinen, Markku Varjosalo, Heikki A. Koistinen, Skeletal muscle proteomes reveal downregulation of mitochondrial proteins in transition from prediabetes into type 2 diabetes, iScience, Volume 24, Issue 7, 2021, 102712, ISSN 2589-0042, https://doi.org/10.1016/j.isci.2021.102712. (https://www.sciencedirect.com/science/article/pii/S2589004221006805)


Provided by University of Helsinki

“Scintillating Starburst” Stimulus: A New Kind of Visual Illusion Uncovers How Our Brains Connect the Dots (Neuroscience)

‘Scintillating starburst’ offers insights into visual processing

A new class of illusion, developed by a visual artist and a psychology researcher, underscores the highly constructive nature of visual perception.

The illusion, which the creators label “Scintillating Starburst,” evokes illusory rays that seem to shimmer or scintillate–like a starburst. Composed of several concentric star polygons, the images prompt viewers to see bright fleeting rays emanating from the center that are not actually there.

“The research illustrates how the brain ‘connects the dots’ to create a subjective reality in what we see, highlighting the constructive nature of perception,” explains Pascal Wallisch, a clinical associate professor in New York University’s Department of Psychology and Center for Data Science and senior author of the paper, which appears in the journal i-Perception.

“Studying illusions can be helpful in understanding visual processing because they allow us to distinguish the mere sensation of physical object properties from the perceptual experience,” adds first author Michael Karlovich, founder and CEO of Recursia Studios, a multidisciplinary art and fashion production company.

This stimulus is made up of several concentric pairs of scaled star polygons. Most observers perceive fleeting rays, beams, or lines emanating from the center that appear to be brighter than the background. Courtesy of Michael Karlovich, Recursia LLC

The authors acknowledge that the visual effects of this illusion are superficially similar to a number of previously described effects of other, grid-based illusions. However, their Scintillating Starburst, unlike known visual illusions, evokes a number of newly discovered effects, among them that fleeting illusory lines diagonally connect the intersection points of the star polygons.

To better understand how we process this class of illusion, the researchers ran a series of experiments with more than 100 participants, who viewed 162 different versions of the Scintillating Starburst, which varied in shape, complexity, and brightness.

The research participants were then asked a series of questions about what they saw–for instance, “I do not see any bright lines, rays, or beams,” “I maybe see bright lines, rays, or beams, but they are barely noticeable,” and “I see bright lines, rays, or beams, but they are subtle and weak.”

The authors found that the confluence of several factors, including contrast, line width, and number of vertices, matters.

“In particular, a large number of prominent intersection points leads to stronger and more vivid rays, as there are more cues to indicate the implied lines,” observes Wallisch.

Thus, this research illustrates how the brain “connects the dots” to create one’s subjective reality, even on the perceptual level, highlighting the constructive nature of perception.


Reference: Michael W. Karlovich and Pascal Wallisch, “Scintillating Starbursts: Concentric Star Polygons Induce Illusory Ray Patterns”, i-Perception, 2021. https://doi.org/10.1177%2F20416695211018720


Provided by New York University

Polymers in Meteorites Provide Clues to Early Solar System (Planetary Science)

A group of polymers across several members of the oldest meteorite class, the CV3 type, shed light on space chemistry as early as 12.5 billion years ago

Many meteorites, which are small pieces from asteroids, do not experience high temperatures at any point in their existence. Because of this, these meteorites provide a good record of complex chemistry present when or before our solar system was formed 4.57 billion years ago.

For this reason, researchers have examined individual amino acids in meteorites, which come in a rich variety and many of which are not in present-day organisms.

In Physics of Fluids, by AIP Publishing, researchers from Harvard University show the existence of a systematic group of amino acid polymers across several members of the oldest meteorite class, the CV3 type. The polymers form organized structures, including crystalline nanotubes and a space-filling lattice of regular diamond symmetry with density estimated to be 30 times less than water.

“Because the elements required to form our polymers were present as early as 12.5 billion years ago, and there appears to be a gas phase route to their formation, it is possible that this chemistry was and is present throughout the universe,” said author Julie McGeoch.

Preventing terrestrial contamination was a top priority for the researchers. They devised a clean room method using a clean stepper motor with vacuum-brazed diamond bits to drive several millimeters into the meteorite sample before retrieving newly etched material from only the bottom of the hole. Several drill bits were used in a single etch, all being cleaned with ultrasonification.

The resulting micron scale meteorite particles were then placed in tubes and stored at minus 16 degrees Celsius. Polymers were induced to diffuse out of the micron particles via Folch extraction, which involves two chemical phases related to different solvents with different densities.

Mass spectrometry revealed the existence of the polymers, which were composed of chains of glycine, the simplest amino acid, with additional oxygen and iron. They had a very high deuterium-to-hydrogen-isotope ratio that confirmed their extraterrestrial origin.

This research was inspired by observations on a small, highly conserved biological protein that entrapped water. That finding suggested if such a molecule could form in gas phase space, it would aid early chemistry by supplying bulk water.

The researchers employed quantum chemistry to show amino acids should be able to polymerize in space within molecular clouds, retaining water of polymerization. Many experiments followed using meteorites as the source of polymer culminating in 3D structures.

Going forward, the researchers hope to get more detail of the glycine rods via continued X-ray analysis. Other polymers in the same class remain to be characterized and could reveal the energetics of polymer formation.

The article, “Structural organization of space polymers,” is authored by Julie E.M. McGeoch and Malcolm W. McGeoch. The article will appear in Physics of Fluids on June 29, 2021 (DOI: 10 1063/5.0053302). After that date, it can be accessed at https://aip.scitation.org/doi/10.1063/5.0054860.

Featured image: Three layers of hydrogen-bonded edge-to-edge polymer. Each layer has four polymer rods bonded at a central vertex. Atoms are colored as follows: hydrogen white, carbon black, nitrogen blue, oxygen red, silicon pink, and iron green. CREDIT: Julie Elizabeth Mary McGeoch and Malcolm William McGeoch.


Provided by American Institute of Physics

Decline of Dinosaurs Under Way Long Before Asteroid Fell (Paleontology)

Ten million years before the well-known asteroid impact that marked the end of the Mesozoic Era, dinosaurs were already in decline. That is the conclusion of the Franco-Anglo-Canadian team led by CNRS researcher Fabien Condamine from the Institute of Evolutionary Science of Montpellier (CNRS / IRD / University of Montpellier), which studied evolutionary trends during the Cretaceous for six major families of dinosaurs, including those of the tyrannosaurs, triceratops, and hadrosaurs.

The last march of dinosaurs, painting.
© Jorge Gonzalez

Using a novel statistical modelling method that limited bias associated with gaps in the fossil record, they demonstrated that, for dinosaurs 76 million years ago, extinctions outpaced speciations. The impact of a 12-km-wide asteroid 66 million years ago was thus the coup de grâce for an animal group already struggling. 

These findings, published in Nature Communications on 29 June, show that the demise of dinosaurs was probably tied to global cooling towards the end of the Cretaceous,1 when the mean global temperature fell by 7 °C.

According to the researchers, herbivores were particularly affected by the first extinctions of this period, and this may have disturbed the equilibrium of ecosystems, setting off cascading extinctions among the other dinosaur families.

Notes

  1. Changes to oceanic circulation patterns then resulted in a decrease in atmospheric CO2 levels.

Featured image: Graphs showing how speciation rate (blue) dipped and extinction rate (red) rose sharply in the last 10 million years of the age of dinosaurs. Run together, this corresponds to a rapid reduction in the number of species (black) just before the impact of the asteroid 66 million years ago.  © Fabien L. Condamine / ISEM / CNRS


Bibliography

Dinosaur biodiversity declined well before the asteroid impact, influenced by ecological and environmental pressures, Fabien L. Condamine, Guillaume Guinot, Michael J. Benton & Philip J. Currie. Nature Communications, 29 June 2021. DOI: 10.1038/s41467-021-23754-0


Provided by CNRS

Stretching Changes the Electronic Properties Of Graphene (Material Science)

The electronic properties of graphene can be specifically modified by stretching the material evenly, say researchers at the University of Basel. These results open the door to the development of new types of electronic components.

Graphene consists of a single layer of carbon atoms arranged in a hexagonal lattice. The material is very flexible and has excellent electronic properties, making it attractive for numerous applications – electronic components in particular.

Researchers led by Professor Christian Schönenberger at the Swiss Nanoscience Institute and the Department of Physics at the University of Basel have now studied how the material’s electronic properties can be manipulated by mechanical stretching. In order to do this, they developed a kind of rack by which they stretch the atomically thin graphene layer in a controlled manner, while measuring its electronic properties.

Sandwiches on the rack

The scientists first prepared a “sandwich” comprising a layer of graphene between two layers of boron nitride. This stack of layers, furnished with electrical contacts, was placed on a flexible substrate.

The researchers then applied a force to the center of the sandwich from below using a wedge. “This enabled us to bend the stack in a controlled way, and to elongate the entire graphene layer,” explained lead author Dr. Lujun Wang.

“Stretching the graphene allowed us to specifically change the distance between the carbon atoms, and thus their binding energy,” added Dr. Andreas Baumgartner, who supervised the experiment.

Altered electronic states

The researchers first calibrated the stretching of the graphene using optical methods. They then used electrical transport measurements to study how the deformation of the graphene changes the electronic energies. The measurements need to be performed at minus 269°C for the energy changes to become visible.

“The distance between the atomic nuclei directly influences the properties of the electronic states in graphene,” said Baumgartner, summarizing the results. “With uniform stretching, only the electron velocity and energy can change. The energy change is essentially the ‘scalar potential’ predicted by theory, which we have now been able to demonstrate experimentally.”

These results could lead, for example, to the development of new sensors or new types of transistors. In addition, graphene serves as a model system for other two-dimensional materials that have become an important research topic worldwide in recent years.

Featured image: Force from below causes the component to bend. This elongates the embedded graphene layer and changes its electronic properties. (Photo: University of Basel/SNI)


Original publication: Lujun Wang, Andreas Baumgartner, Péter Makk, Simon Zihlmann, Blesson S. Varghese, David I. Indolese, Kenji Watanabe, Takashi Taniguchi, and Christian Schönenberger
Global strain-induced scalar potential in graphene devices
Communication Physics (2021), doi: 10.1038/s42005-021-00651-y


Provided by University of Basel

This Material Could Speed Up Production of New Technologies For Smart Buildings and Robotics (Material Science)

Scientists at Berkeley Lab, UC Berkeley design 3D-grown material that could speed up production of new technologies for smart buildings and robotics

Crystallization is one of the most fundamental processes found in nature – and it’s what gives minerals, gems, metals, and even proteins their structure.

In the past couple of decades, scientists have tried to uncover how natural crystals self-assemble and grow – and their pioneering work has led to some exciting new technologies – from the quantum dots behind colorful QLED TV displays, to peptoids, a protein-mimic that has inspired dozens of biotech breakthroughs.

Now, a research team led by scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley has developed a nanoparticle composite that grows into 3D crystals. The scientists say that the new material – which they call a 3D PGNP (polymer-grafted nanoparticle) crystal in their recently published Nature Communications study – could lead to new technologies that are 3D-grown rather than 3D-printed.

“We’ve demonstrated a new lever to turn, so to speak, to grow a crystalline material into a composite or structured material for applications ranging from nanoscale photonics for smart buildings to actuators for robotics,” said Ting Xu, senior author of the study. Xu is a faculty senior scientist in Berkeley Lab’s Materials Sciences Division and professor of chemistry and materials science and engineering at UC Berkeley.

Xu said that their new method is compatible with the demands of mass manufacturing. “Many smart minds have designed elegant chemistries, such as DNAs and supramolecules, to crystallize nanoparticles. Our system is essentially a blend of nanoparticle and polymers – which are similar to the ingredients people use to make airplane wings or automobile bumpers. But what’s even more interesting is that we didn’t expect our method to be so simple and so fast,” Xu said.

A chance discovery

Lead author Yiwen Qian, a Ph.D. student researcher in the Xu Group at UC Berkeley, discovered the 3D PGNP nanocrystals by chance in an ordinary lab experiment.

A couple of days before, she had left a solution of toluene solvent and gold nanoparticles grafted with polystyrene (Au-PS) in a centrifuge tube on a lab counter. When she looked at the sample under a transmission electron microscope (TEM), she noticed something odd. “Nanoparticles had crystallized quickly. That was not a normal thing to expect,” she said.

Using microscopes at Berkeley Lab’s Molecular Foundry, a world-leading user facility in STEM tomography, Ting Xu and her research team captured crystalline 3D patterns of gold-polystyrene nanoparticles. © Berkeley Lab

To investigate, Xu collaborated with Peter Ercius, a staff scientist at Berkeley Lab’s Molecular Foundry, and Wolfgang Theis and Alessandra DaSilva of the University of Birmingham, all of whom are widely regarded for their expertise in STEM (scanning transmission electron microscopy) tomography, an electron microscopy technique that uses a highly focused beam of electrons to reconstruct images of a material’s 3D structure at high resolution.

Using microscopes at the Molecular Foundry, a world-leading user facility in STEM tomography, the researchers first captured crystalline 3D patterns of the Au-PS nanoparticles.

On the hunt for more clues, Xu and Qian then deployed nuclear magnetic resonance spectroscopy experiments at UC Berkeley, where they discovered that a tiny trace of polyolefin molecules from the centrifuge tube lining had somehow entered the mix. Polyolefins, which include polyethylene and polypropylene, are some of the most ubiquitous plastics in the world.

Qian repeated the experiment, adding more polyolefin to the Au-PS solution – and this time, they got bigger 3D PGNP crystals within minutes.

Xu was surprised. “I thought, ‘This shouldn’t be happening so fast,'” she recalled. “Crystals of nanoparticles usually take days to grow in the lab.”

A boon for industry: growing materials at the nanolevel

Subsequent experiments revealed that as the toluene solvent quickly evaporates at room temperature, the polyolefin additive helps the Au-PS nanoparticles form into 3D PGNP crystals, and to “grow into their favorite crystal structure,” said Qian.

In another key experiment, the researchers designed a self-assembling 100-200-nanometer crystalline disc that looks like the base of a pyramid. From this stunning demonstration of mastery over matter at the nanolevel, the researchers learned that the size and shape of the 3D PGNP crystals are driven by the kinetic energy of the polyolefins as they precipitate in the solution.

Altogether, these findings “provide a model for showing how you can control the crystal structure at the single particle level,” Xu said, adding that their discovery is exciting because it provides new insight into how crystals form during the early stages of nucleation.

“And that’s challenging to do because it’s hard to make atoms sit next to each other,” Ercius said.

The new approach could grant researchers unprecedented control in fine-tuning electronic and optical devices at the nanolevel (billionths of a meter), Xu said. Such nanoparticle-scale precision, she added, could speed up production and eliminate errors in manufacturing.

Looking ahead, Qian would like to use their new technique to probe the toughness of different crystal structures – and perhaps even make a hexagonal crystal.

Xu plans to use their technique to grow bigger devices such as a transistor or perhaps 3D-print nanoparticles from a mix of materials.

“What can you do with different morphologies? We’ve shown that it’s possible to generate a single-component composite from a mineral and a polymer. It’s really exciting. Sometimes you just need to be in the right place at the right time,” Xu said.

Co-authors on the paper include Alessandra da Silva and Wolfgang Theis at the University of Birmingham in the United Kingdom; Emmy Yu, an undergraduate student researcher in the Xu Group at UC Berkeley; and Christopher L. Anderson and Yi Liu at Berkeley Lab’s Molecular Foundry.

The Molecular Foundry is a DOE Office of Science nanoscience user facility at Berkeley Lab.

The work was supported by the DOE Office of Science.

Featured image: STEM tomography image of a 3D-grown 100-200-nanometer crystalline disc grown from 3D gold-polystyrene polymer-grafted nanoparticles © Berkeley Lab


Reference: Qian, Y., da Silva, A., Yu, E. et al. Crystallization of nanoparticles induced by precipitation of trace polymeric additives. Nat Commun 12, 2767 (2021). https://doi.org/10.1038/s41467-021-22950-2


Provided by LBL

RUDN University Chemists Create Substances For Supramolecules’ Self-assembly (Chemistry)

RUDN University chemists derived molecules that can assemble into complex structures using chlorine and bromine halogen atoms. They bind to each other as “velcro” – chlorine “sticks” to bromine, and vice versa. As a result supramolecules are assembled from individual molecules. The obtained substances will help to create supramolecules with catalytic, luminescent, conducting properties. The study is published in Mendeleev Communications.

Supramolecules are the structures made of several molecules. Individual molecules are combined, for example, by self-assembly or without external control. The resulting structure has properties that the molecules did not have individually. That is the way to create new materials, catalysts, molecular machines for drug delivery, conductors, and so on. To get a material with the specified properties, you need to choose the right starting molecules and auxiliary substances that will ensure their unification. One of the ways to control self-assembly is halogen-halogen interactions. These are the chemical bonds forming between two halogens (for example, chlorine, fluorine, bromine). RUDN University chemists have created a molecule with a halogen bond that can form supramolecules by itself or provide the required self-assembly with other substances. They will help to create substances for the chemical industry, medicine, and electronics.

“The possibility of fine control of the local molecular environment is highly desirable to access new properties for substances that function as catalysts, luminescent or conductive materials, etc. 2-4 Halogen bonding has recently emerged as useful instrument for the accurate control of the structural organization of such supramolecular materials. In this context, halogen-halogen interactions received a particular attention and were intensively explored both experimentally and theoretically”, said the authors of the article.

Chemists used 7 types of hydrazones and carbon tetrachloride as starting materials for synthesis. The reaction lasted 1-3 hours at room temperature, with copper chloride as a catalyst. As a result, 7 compounds were obtained, two of them were suitable for the formation of a halogen-halogen bond between themselves or with other substances. RUDN University chemists studied them with X-ray diffraction analysis. Then the scientists built a 3D model of intramolecular interactions and confirmed their observations using topological analysis of the electron density distribution.

Thanks to the ability to form halogen-halogen bonds, new substances can control the self-assembly of molecules or form supramolecules themselves. That is because the new substances contain atoms of two halogens on two sides of the molecules — chlorine and bromine. As a result, they can connect to each other through halogens — chlorine combines with bromine, and vice versa. They can also form halogen-halogen bonds with other substances, thus controlling the assembly of supramolecules.

“Calculations demonstrated that highly polarizable dichlorodiazadiene unit is capable of acting as a relatively strong halogen bond donor. When the dye was decorated with halogen bond-accepting bromine atoms, formation of 3D supramolecular framework was observed”, said the authors of the article.

Featured image: RUDN University chemists derived molecules that can assemble into complex structures using chlorine and bromine halogen atoms. They bind to each other as “velcro” — chlorine “sticks” to bromine, and vice versa. As a result, supramolecules are assembled from individual molecules. The obtained substances will help to create supramolecules with catalytic, luminescent, conducting properties. © RUDN University


Reference: Namiq G. Shikhaliyev, Abel M. Maharramov, Khanim N. Bagirova, Gulnar T. Suleymanova, Biligma D. Tsyrenova, Valentine G. Nenajdenko, Alexander S. Novikov, Victor N. Khrustalev, Alexander G. Tskhovrebov, Supramolecular organic frameworks derived from bromoaryl-substituted dichlorodiazabutadienes via Cl···Br halogen bonding, Mendeleev Communications, Volume 31, Issue 2, 2021, Pages 191-193, ISSN 0959-9436, https://doi.org/10.1016/j.mencom.2021.03.015. (https://www.sciencedirect.com/science/article/pii/S0959943621000699)


Provided by RUDN University