Phys.org February 18, 2019 Excitons form when intense light shines on solids, kicking negatively charged electrons out of their spots and leaving behind positively charged holes. A team of researchers in the US (Rutgers University, University of Florida, North Carolina State University) has discovered chiral surface exciton on the surface of bismuth selenide. Chiral exiton consists of particles and anti-particles bound together and swirling around each other on the surface of solids. The electrons and holes resemble rapidly spinning tops. The electrons eventually “spiral” towards the holes, annihilating each other in less than a trillionth of a second while emitting […]
Tag Archives: Materials science
Across the spectrum: Researchers find way to stabilize color of light in next-gen material
Science Daily February 11, 2019 Color tunability has always been possible with halide perovskites, but it’s not been stable. While the bandgap can be conveniently tuned by mixing different halogen ions, mixed-halide perovskites suffer from severe phase separation under illumination. A team of researchers in the US (Florida State University, Rensselaer Polytechnic Institute) found that phase separation can be highly suppressed by embedding nanocrystals of mixed-halide perovskites in an endotaxial matrix. The tuned bandgap remains remarkably stable under extremely intensive illumination. The agreement between the experiments and a nucleation model suggests that the size of the nanocrystals and the host-guest […]
Unleashing perovskites’ potential for solar cells
MIT News February 7, 2019 Perovskites have attracted a great deal of attention as potential new solar-cell materials because of their low cost, flexibility, and relatively easy manufacturing process. But much remains unknown about the details of their structure and the effects of substituting different metals or other elements within the material. A team of researchers in the US (MIT, UC San Diego, Georgia Institute of Technology, Purdue University, Argonne National Laboratory) found that adding these alkali metals, such as cesium or rubidium, to the perovskite compound helps some of the other constituents to mix together more smoothly making it […]
Sodium is the new lithium: Researchers find a way to boost sodium-ion battery performance
Science Daily February 1, 2019 Sodium ion batteries meet the demand for large-scale energy storage. By investing ~4300 candidates via a high-throughput computation, researchers in Japan have identified nanotube-type Na2V3O7 as a cathode material because of its fast sodium diffusivity. High-rate performance was confirmed, showing ~65% capacity retention at a current density of 10C at room temperature, despite the large particle size of >5 μm. But they found that Na2V3O7 underwent deterioration in the final charging stages, which limits the practical storage capacity to the half of theoretical one. In their future experiments, the researchers aim to focus on improving the […]
Materials that open in the heat of the moment
Science Daily January 24, 2019 The porous nanomaterials that are currently used for gas separation and storage are not tunable: their pores are persistent and rigid. Researchers in Japan designed a porous coordination polymer with copper atoms linked by butterfly-shaped ligands made from isophthalic acid and phenothiazine-5,5-dioxide. The material was comprised of tiny nanocages with protruding channels. At very low temperatures, the channels were very narrow; as the temperature was increased, the channels opened more and more, allowing gas molecules to move between the cages. A gas could move or become locked within the material depending on the size of […]
Artificial intelligence ARTIST instantly captures materials’ properties
Science Daily January 30, 2019 An international team of researchers (Finland, Denmark, Germany) has developed and trained the architecture ARTIST, made of three different neural network architectures: multilayer perceptron (MLP), convolutional neural network (CNN), and deep tensor neural network (DTNN), to predict molecular excitation using the coordinates and charges of the constituent atoms of each molecule as input. In demonstration they scanned the structures of 10k previously unseen organic molecules and obtained their spectra predictions to identify molecules for potential applications. The research has the potential to speed up the development of flexible electronics, produce better batteries and catalysts and […]
Controllable fast, tiny magnetic bits
Phys.org January 4, 2019 Researchers at MIT present an analytical theory to describe three-dimensional magnetic textures in perpendicularly magnetized magnetic multilayers that arise in the presence of magnetostatic interactions and the Dzyaloshinskii-Moriya interaction (DMI). They demonstrated that domain walls in multilayers develop a complex twisted structure, which persists even for films with strong DMI. The origin of this twist is surface-volume stray field interactions that manifest as a depth-dependent effective field whose form mimics the DMI effective field. They found that the wall twist has a minor impact on the equilibrium skyrmion or domain size but can significantly affect current-driven […]
Physicists uncover new competing state of matter in superconducting material
Science Daily January 2, 2019 Using ultrafast terahertz pump-probe a team of researchers in the US (Iowa State University, University of Alabama) found an unusual out-of-equilibrium Cooper pair nonlinear dynamics and a nonequilibrium state in iron pnictides. They identified long prebottleneck dynamics that are sensitive to both doping and temperature. According to the researchers the buildup of excitonic interpocket correlation between electron-hole quasiparticles quenches superconductivity after photoexcitation leading to a long-lived, many-quasiparticle excitonic state. Findings help create better superconducting electronics and energy-efficient devices…read more. TECHNICAL ARTICLE
A catalytic flying carpet
Nanowerk January 2, 2019 Catalyst-coated, hard particles can spontaneously generate fluid flows, which, in turn, propel the particles through the fluid. If it were a deformable sheet, then the self-generated flows could affect not only the sheet’s motion but also its shape. Researchers at Pittsburgh University developed models that capture the interrelated chemical, hydrodynamic, and mechanical interactions to uncover novel behavior emerging from the previously unstudied coupling between active, soft sheets and the surrounding fluid. The sheets can be tailored by modifying the sheet’s geometry, patterning the sheet’s surface with different catalysts, and using cascades of chemical reactions. The layers […]
New megalibrary approach proves useful for the rapid discovery of new nanomaterials
Nanowerk December 18, 2018 A team of researchers in the US (Northwestern University, AFRL at Wright-Patterson AFB) supports the efficacy of a potentially revolutionary new tool developed at Northwestern University to rapidly test millions (even billions) of nanoparticles to determine the best one for a specific use. The tool utilizes a combinatorial library, or megalibrary, of nanoparticles in a very controlled way. The libraries are created using Mirkin’s Polymer Pen Lithography (PPL) technique, which relies on arrays with hundreds of thousands of pyramidal tips to deposit individual polymer “dots” of various sizes and composition, each loaded with different metal salts […]