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Category: chemistry – Page 8
Unexpected Resonances Could Boost NMR’s Potency
A radio-frequency field can be resonant with nuclear spins in a sample even if its frequency does not match a spectroscopic transition—a result that could enable new forms of NMR spectroscopy.
Physical systems often have characteristic frequencies. When excited at such a frequency, they start to resonate. The Broughton Suspension Bridge incident on April 12, 1831, showed how this can go wrong. A detachment of 74 riflemen marched in step over the bridge, accidentally matching its resonance frequency. Before they had crossed, the bridge collapsed. At the much-smaller scale of nuclear magnetic resonance (NMR) spectroscopy, resonant excitation is less dramatic yet very useful. Typically, NMR relies on secular resonance, which occurs when the energy of the radio-frequency photons used in a measurement matches the energy required for flipping the magnetic moment of a nucleus in a static magnetic field. This secular resonance occurs at the so-called Larmor frequency. Structure determination of chemical compounds, experimental observation of protein dynamics, and magnetic resonance imaging rely on this matching.
Microscopic imaging reveals how electric double layers form at battery nucleation sites
Electrochemical cells—or batteries, as a well-known example—are complex technologies that combine chemistry, physics, materials science and electronics. More than power sources for everything from smartphones to electric vehicles, they remain a strong motivation for scientific inquiry that seeks to fully understand their structure and evolution at the molecular level.
A team led by Yingjie Zhang, a professor of materials science and engineering in The Grainger College of Engineering at the University of Illinois Urbana-Champaign, has completed the first investigation into a widely acknowledged but often overlooked aspect of electrochemical cells: the nonuniformity of the liquid at the solid-liquid interfaces in the cells.
As the researchers report in the Proceedings of the National Academy of Sciences, microscopic imaging revealed that these interfacial structures, called electrical double layers (EDLs), tend to organize into specific configurations in response to chemical deposition on the surface of the solid. The paper is titled “Nucleation at solid–liquid interfaces is accompanied by the reconfiguration of electrical double layers.”
Programmable 2D nanochannels achieve brain-like memory
Researchers at The University of Manchester’s National Graphene Institute have developed a new class of programmable nanofluidic memristors that mimic the memory functions of the human brain, paving the way for next-generation neuromorphic computing.
In a study published in Nature Communications, scientists from the National Graphene Institute, Photon Science Institute and the Department of Physics and Astronomy have demonstrated how two-dimensional (2D) nanochannels can be tuned to exhibit all four theoretically predicted types of memristive behavior, something never before achieved in a single device.
This study not only reveals new insights into ionic memory mechanisms but also has the potential to enable emerging applications in low-power ionic logic, neuromorphic components, and adaptive chemical sensing.
The First Molecules In The Universe Reveal Surprises After Being Bombarded With Deuterium
In new experiments, the team attempted to recreate the conditions of the early universe, and test whether HeH+ could provide the cooling needed to form the universe’s first stars. The team bombarded the molecule with deuterium at varying temperatures, simulated by varying the relative speed of the beams of particles. To their surprise, and contrary to previous predictions, the reaction rate did not slow as temperatures significantly decreased.
“Previous theories predicted a significant decrease in the reaction probability at low temperatures, but we were unable to verify this in either the experiment or new theoretical calculations by our colleagues,” Dr Holger Kreckel from the Max-Planck-Institut für Kernphysik (MPIK) explained in a statement. “The reactions of HeH⁺ with neutral hydrogen and deuterium therefore appear to have been far more important for chemistry in the early universe than previously assumed.”
These results could have profound implications for our understanding of the early universe, and may even force a bit of reevaluation.
New theory may solve quantum ‘jigsaw puzzle’ for controlling chemical reactions
In the past, chemists have used temperature, pressure, light, and other chemical ways to speed up or slow down chemical reactions. Now, researchers at the University of Rochester have developed a theory that explains a different way to control chemical reactions—one that doesn’t rely on heat or light but instead on the quantum environment surrounding the molecules.
In a paper published in the Journal of the American Chemical Society, the researchers—including Frank Huo, the Dean and Laura Marvin Endowed Professor in Physical Chemistry in Rochester’s Department of Chemistry and graduate students Sebastian Montillo and Wenxiang Ying—argue that traditional theories used to predict how fast chemical reactions occur may not fully capture what happens under certain quantum light-matter interaction conditions.
To address this, they developed a new theory showing how quantum effects —specifically, an effect called vibrational strong coupling (VSC)—can influence chemical reactions.
New physical model aims to boost energy storage research
Engineers rely on computational tools to develop new energy storage technologies, which are critical for capitalizing on sustainable energy sources and powering electric vehicles and other devices. Researchers have now developed a new classical physics model that captures one of the most complex aspects of energy storage research—the dynamic nonequilibrium processes that throw chemical, mechanical and physical aspects of energy storage materials out of balance when they are charging or discharging energy.
The new Chen-Huang Nonequilibrium Phasex Transformation (NExT) Model was developed by Hongjiang Chen, a former Ph.D. student at NC State, in conjunction with his advisor, Hsiao-Ying Shadow Huang, who is an associate professor of mechanical and aerospace engineering at the university. A paper on the work, “Energy Change Pathways in Electrodes during Nonequilibrium Processes,” is published in The Journal of Physical Chemistry C.
But what are “nonequilibrium processes”? Why are they important? And why would you want to translate those processes into mathematical formulae? We talked with Huang to learn more.
The US just got a new X-ray laser toolkit to study nature’s mysteries
With a suite of reimagined instruments at SLAC’s LCLS facility, researchers see massive improvement in data quality and take up scientific inquiries that were out of reach just one year ago.
Some of science’s biggest mysteries unfold at the smallest scales. Researchers investigating super small phenomena—from the quantum nature of superconductivity to the mechanics that drive photosynthesis—come to the Department of Energy’s SLAC National Accelerator Laboratory to use the Linac Coherent Light Source (LCLS).
Like a giant microscope, LCLS sends pulses of ultrabright X-rays to a suite of specialized scientific instruments. With these tools, scientists take crisp pictures of atomic motions, watch chemical reactions unfold, probe the properties of materials and explore fundamental processes in living things.
Frustrated by Design: Chemistry Triggers Exotic Electron Behavior in New Quantum Material
In a striking demonstration of how chemical bonding can engineer exotic physics, researchers at Columbia University have discovered that quantum frustration —a key ingredient for superconductivity and other correlated quantum phases—can be induced not just by geometry, but directly through chemistry. The new material, Pd5AlI2, showcases this unusual electron behavior in a two-dimensional crystal structure with orbital configurations that mimic flat-band lattice geometries.
Maximizing direct methanol fuel cell performance: Reinforcement learning enables real-time voltage control
Fuel cells are energy solutions that can convert the chemical energy in fuels into electricity via specific chemical reactions, instead of relying on combustion. Promising types of fuel cells are direct methanol fuel cells (DMFCs), devices specifically designed to convert the energy in methyl alcohol (i.e., methanol) into electrical energy.
Despite their potential for powering large electronics, vehicles and other systems requiring portable power, these methanol-based fuel cells still have significant limitations. Most notably, studies found that their performance tends to significantly degrade over time, because the materials used to catalyze reactions in the cells (i.e., electrocatalytic surfaces) gradually become less effective.
One approach to cleaning these surfaces and preventing the accumulation of poisoning products produced during chemical reactions entails the modulation of the voltage applied to the fuel cells. However, manually adjusting the voltage applied to the surfaces in effective ways, while also accounting for physical and chemical processes in the fuel cells, is impractical for real-world applications.