Nanowerk April 29, 2020 Controlling the interactions at the interface of a magnetic/topological insulator heterostructure is an outstanding challenge with implications in fundamental science and technology. An international team of researchers (Spain, Switzerland, Italy) has shown that it is possible to tune the interfacial interaction without quenching the molecular spin and the topological surface state of the topological insulator by choosing suitable organic ligands. They found that CoTBrPP and CoPc monolayers (metal-organic molecules) adsorbed on Bi2Te3 (topological insulator) form robust interfaces where electronic interactions can be tuned without strongly perturbing the intrinsic properties of each constituent. Their conclusions are supported […]
Tag Archives: Materials science
Wide-band-gap semiconductors could harvest sunlight underwater
Physics World April 17, 2020 Using detailed-balance calculations researchers at the University of New York have shown that underwater solar cells can exhibit efficiencies from ∼55% in shallow waters to more than 65% in deep waters, while maintaining a power density >5 mW cm −2. They showed that the optimum band gap of the solar cell shifts by ∼0.6 eV between shallow and deep waters and plateaus at ∼2.1 eV at intermediate depths, independent of geographical location. This wide range in optimum band-gap energies opens the potential for a library of wide-band-gap semiconductors to be used for high-efficiency underwater solar […]
New textile could keep you cool in the heat, warm in the cold
Phys.org April 1, 2020 Researchers in China freeze-spun silk and chitosan, a material from the hard outer skeleton of shellfish, into colored fibers with porous microstructures. They filled the pores with polyethylene glycol (PEG), a phase-changing polymer that absorbs and releases thermal energy. The threads were coated with polydimethylsiloxane to keep the liquid PEG from leaking out. The resulting fibers were strong, flexible, and water-repellent. To test the fibers, the researchers wove them into a patch of fabric and put inside a polyester glove. When a person wearing the glove placed their hand in a hot chamber (122°F), the solid […]
Untwisting plastics for charging internet-of-things devices
Science Daily April 16, 2020 To use body heat to charge some types of micro-devices and sensors lightweight, non-toxic, wearable, and flexible thermoelectric generators are required. Japan studied the thermoelectric properties of highly conductive thiophene-based polymer, called PBTTT. They doped the polymer with a thin ion electrolyte gel, which is known to improve conductivity that infiltrates the polymer successfully when a specific electric voltage is applied. They found that, without the electrolyte gel, the PBTTT chain is highly twisted. Doping it with a critical amount of electrolyte untwists the chain and creates links between its crystalline parts, improving electron conductivity. […]
Engineers use metal-oxide nanomaterials deposited on cloth to wipe out microbes
Nanowerk April 8, 2020 As proof of concept researchers at the State University of Iowa grew shape-controlled cerium oxide nanostructures on fluorine doped tin oxide, carbon paper, and carbon cloth as substrates. They found that the cerium oxide nanostructures grown directly on carbon cloth were the most sensitive glucose biosensors. The enhanced performance of these biosensors was related to the increased surface area and high defect concentrations on the surface. These results provide a potential opportunity for flexible substrates like carbon paper and carbon cloth coupled with nanostructures, in a feasible design, to be used as platforms for robust, affordable, […]
Squeezing Light Out of Silicon
IEEE Spectrum April 8, 2020 Cubic Si, Ge and SiGe alloys are all indirect-bandgap semiconductors that cannot emit light efficiently. An international team of researchers (the Netherlands, Germany, Austria) has demonstrated efficient light emission from direct-bandgap hexagonal Ge and SiGe alloys. They have shown that by controlling the composition of the hexagonal SiGe alloy, the emission wavelength can be continuously tuned over a broad range, while preserving the direct bandgap. Their experimental findings are in excellent quantitative agreement with ab initio theory. Hexagonal SiGe embodies an ideal material system in which to combine electronic and optoelectronic functionalities on a single […]
A twist connecting magnetism and electronic-band topology
Phys.org April 6, 2020 There are only very few examples where the topology of the electronic bands is connected in a well-defined manner to the magnetic properties of the materials. One material in which such interplay between topological electronic states and magnetism has been observed is CaMnBi2, but the mechanism connecting the two remained unclear. An international team of researchers (Switzerland, Germany, China, USA – Brookhaven National Laboratory, Stony Brook University) report a comprehensive study providing clear evidence that a slight nudge on the magnetic moments, known as spin canting, provokes substantial changes in the electronic band structure. These findings […]
Graphene-based actuator swarm enables programmable deformation
Nanowerk April 1, 2020 Graphene-based actuators featuring fast and reversible deformation under various external stimuli are promising for soft robotics. However, these bimorph actuators are incapable of complex and programmable 3D deformation, which limits their practical application. Researchers in China fabricated a moisture-responsive graphene actuator swarm that has programmable shape-changing capability by programming the SU-8 patterns underneath with specific geometries and orientations on a continuous graphene oxide film, forming a swarm of bimorph actuators. They achieved predictable and complex deformations including bending, twisting, coiling, asymmetric bending, 3D folding and the combination of them due to the collective coupling and coordination […]
Scientists electrify aluminum to speed up important process
Science Daily March 26, 2020 Researchers at Ohio State University describe how to shorten a process to turn one chemical — triphenylphosphine oxide — into another chemical — triphenylphosphine. They showed that the energy needed for the conversion can be generated by sending an electrical charge through an aluminum container. Doing so provides enough energy to allow aluminum to break one of the chemical bonds in triphenylphosphine oxide — essentially, to strip oxygen away from that molecule — and to leave behind just triphenylphosphine. The finding could make several industrial manufacturing processes cheaper and more efficient, make it easier to […]
Leaf-inspired surface prevents frost formation
Science Daily March 10, 2020 Based on their fundamental understanding of discontinuous frost patterns found on the leaf vein structure on the scale of millimeters, researchers at Northwestern University elucidated the thermodynamic correlation between the frost-free area and two major surface system parameters—macroscopic surface geometry and ambient humidity. This systematic study on the frost formation mechanism allowed them to demonstrate a ∼50% of frost coverage even for superhydrophilic surfaces and provides a quantitative guideline for further reducing frost coverage. The finding could help decrease the amount of energy needed for de-frosting and could potentially result in fewer canceled flights, which […]