Phys.org October 23, 2023 In theoretical models for active particles, it is often assumed that the particles’ swimming speed is always the same. However, this is not so for particles produced in many experiments. An international team of researchers (UK, Germany) used a combination of computer simulations and theoretical derivations, to study the behavior of systems consisting of many active particles whose speed depended on orientation. In the process they discovered a series of new effects. They found that systems consisting of many active particles could spontaneously form clusters—even when the individual particles do not attract one another. The particles […]
Category Archives: Materials science
Nanoscale rust: The future of magnets?
Phys.org October 5, 2023 Multiferroics have tremendous potential to revolutionize logic and memory devices through new functionalities and energy efficiencies. To better understand and enhance their ferroic orders and couplings an international team of researchers (Canada, USA – Lawrence Berkeley National Laboratory, Argonne National Laboratory) used epsilon iron oxide (ϵ-Fe2O3) as a model system with a simplifying single magnetic ion. Using 15, 20, and 30 nm nanoparticles, they found that a modified and size-dependent Fe–O hybridization changed the spin–orbit coupling. However, the size effects disappeared in the high-temperature phase where the strongest Fe–O hybridization occurred. By manipulating hybridization, they could […]
Scientists discover ‘flipping’ layers in heterostructures to cause changes in their properties
Nanowerk October 10, 2023 Assembling different TMD layers into vertical stacks creates a new artificial material called a van der Waals (vdW) heterostructure. By incorporating different materials, it becomes possible to combine the properties of individual layers, producing new optoelectronic devices with tailor-made properties. To understand the unusual stacking sequence, an international team of researchers (South Korea, Germany, USA – Oak Ridge National Laboratory) introduced the excitonic Elliot formula by imposing strain exclusively on the top layer that could be a consequence of the stacking process. They found that the intensity ratio of Q- to K-excitons in the same layer […]
Striking rare gold: Researchers unveil new material infused with gold in an exotic chemical state
Phys.org September 30, 2023 Although Cu2+ is ubiquitous, the relativistic destabilization of the 5d orbitals makes the isoelectronic Au2+ exceedingly rare, typically stabilized only through Au–Au bonding or by using redox non-innocent ligands. An international team of researchers (USA – Stanford University, UC Berkeley, SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory, Canada) have developed the perovskite Cs4AuIIAuIII2Cl12, an extended solid with mononuclear Au2+ sites, which is stable to ambient conditions and characterized by single-crystal X-ray diffraction. The 2+ oxidation state of Au was assigned using 197Au Mössbauer spectroscopy, electron paramagnetic resonance, and magnetic susceptibility measurements, with comparison to paramagnetic […]
Topological materials open a new pathway for exploring spin hall materials
Science Daily September 21, 2023 One of the hallmarks of Magnetic Weyl semimetals (mWSMs) is the emergence of large intrinsic anomalous Hall effect. On heating the mWSM above its Curie temperature, the magnetism vanishes while exchange-split Weyl point pairs collapse into doubly degenerate gapped Dirac states. Researchers in Japan found potential of these Dirac nodes in paramagnetic state for efficient spin current generation at room temperature via the spin Hall effect. They introduced Ni and In to separately substitute Co and Sn in a prototypal mWSMCo3Sn2S2 shandite film and tuned the Fermi level. Composition dependence of spin Hall conductivity for […]
Transistor-inspired ultra-sensitive materials heat up advanced data security
Nanowerk September 26, 2023 Researchers in China proposed a novel strategy for constructing highly sensitive TFMs with tunable emission (450–650 nm) toward multilevel information encryption which employs polarity-sensitive fluorophores with donor–acceptor–donor (D–A–D) type structures as emitters and long-chain alkanes as thermosensitive loading matrixes. The structure–function relationships between the performance of TFMs and the structures of both fluorescent emitters and phase-change molecules were systematically studied. The TFMs exhibited over 9500-fold fluorescence enhancement toward the temperature change, as well as ultrahigh relative temperature sensitivity up to 80% K−1, which were confirmed. The TFMs could be further developed as information-storage platforms within a […]
Plumbing the depths of thermoelectrics in search of novel materials
Phys.org September 18, 2023 Although historically the thermoelectric effect was first discovered in metals, state-of-the-art research focuses on semiconductors. An international team of researchers (Austria, Japan) discovered unprecedented thermoelectric performance in metals and realized ultrahigh power factors in binary nickel and gold alloys, more than twice larger than in any bulk material above room temperature. In metallic NixAu1–x alloys, large Seebeck coefficients originated from electron-hole selective scattering of Au s electrons into more localized Ni d states. This intrinsic energy filtering effect owing to the unique band structure yielded a strongly energy-dependent carrier mobility. While the metastable nature of the […]
Researchers develop high-performance zero thermal expansion composite for precision devices
Phys.org September 14, 2023 Negative thermal expansion (NTE) materials can be applied to suppress thermal expansion of other materials, forming composites with zero thermal expansion (ZTE). However, the shortcomings (e.g., high density, narrow working temperature window) inherited from various NTE materials hinder the applications of corresponding ZTE composites. An international team of researchers (China, Poland) used modified Cu2P2O7 by reducing oxygen deficiencies, which had a relatively low density and strong NTE over a wide temperature range, to composite with 2024Al. When the volume content of modified Cu2P2O7 was about 50%, the composite Cu2P2O7/2024Al showed ZTE effect, and the linear coefficient […]
New laser tweezers allow gentle, efficient manipulation of cells and nanoparticles (w/video)
Nanowerk September 8, 2023 Optical tweezers are used from manufacturing to biotechnology. However, the requirement of refractive index contrast and high laser power results in potential photon and thermal damage to the trapped objects. Optothermal tweezers have been developed to trap particles and biological cells via opto-thermophoresis with much lower laser powers. But the intense laser heating and stringent requirement of the solution environment prevent their use for general biological applications. A team of researchers in the US (UT Austin, UT Dallas) has proposed hypothermal opto-thermophoretic tweezers (HOTTs) to achieve low-power trapping of diverse colloids and biological cells in their […]
Scientists synthesize new organometallic “sandwich” compound capable of holding more electrons
EurekAlert September 5, 2023 The versatility of the metallocenes stems from their ability to stabilize a wide range of formal electron counts. To date, d-block metallocenes with an electron count of up to 20 have been synthesized and utilized in catalysis, sensing, and other fields but, those with more than 20-electron counts have remained elusive because the metal–carbon bonds in d-block metallocenes become weaker with increasing deviation from the stable 18-electron configuration. An international team of researchers (Japan, Germany, Russia) synthesized, isolated, and characterized a 21-electron cobaltocene derivative. The discovery was based on the ligand design that allowed the coordination […]