(Funded by the U.S. Department of Energy and the U.S. National Science Foundation)
The shape of nanoparticles depends on the choice of solvent and temperature during their growth. But the tiny seed particles that form first and that guide the formation of final nanoparticle shapes are too small to measure accurately. With the help of a supercomputer, Penn State researchers have developed computer simulations to model seed particles with 100 to 200 atoms. They found that the shapes of the tiny particles depend on the solvent composition and temperature in unexpected ways. Surprisingly, in some cases the shape of the seed particle changes dramatically when only a single atom is added or removed.

(Funded by the U.S. National Science Foundation and the National Institute of Standards and Technology)
The fractional quantum Hall effect arises when electrons in two-dimensional materials are subject to a strong perpendicular magnetic field at very low temperatures. Researchers from George Mason University, Brown University, and the National Institute of Standards and Technology have shown that fractional quantum Hall states could be better detected using thermopower measurements than with conventional electrical resistivity. (Thermopower is an electrical voltage generated when charge carriers move from the hot side to the cold side of a conducting or semiconducting material.) The researchers performed thermopower measurements on bilayer graphene and observed new fractional quantum Hall states, which had not been previously reported.

(Funded by the U.S. Department of Defense and the U.S. National Science Foundation)
Researchers from Lehigh University, the U.S. Army Research Laboratory, Arizona State University, and Louisiana State University have developed a nanostructured copper alloy with exceptional thermal stability and mechanical strength, making it one of the most resilient copper-based materials ever created. The breakthrough comes from the formation of copper-lithium precipitates, stabilized by a tantalum-rich atomic bilayer complexion. Unlike typical grain boundaries that migrate over time at high temperatures, this complexion acts as a structural stabilizer, maintaining the nanocrystalline structure, preventing grain growth and dramatically improving high-temperature performance. The U.S. Army Research Laboratory was awarded a U.S. patent for the alloy.

(Funded by the U.S. Department of Defense)
Researchers from The University of Texas at Dallas; Texas State University in San Marcos, TX; and Lintec of America in Plano, TX, as well as international collaborators, have invented a new, inexpensive method in which fibers are coiled to make springlike artificial muscles. What’s unique about this method is that it doesn’t make use of a mandrel – a spindle that serves to support or shape the artificial muscles. The mandrel-free fabrication process involves inserting twist into individual fibers, causing them to coil back on themselves, and then plying the twisted fibers to create springlike coils. The researchers used the mandrel-free method to make high-spring-index carbon nanotube yarns, which could be used to harvest mechanical energy or as self-powered strain sensors.

(Funded by the U.S. National Science Foundation)
In a Perspective article published in Nature Materials, two engineers at the Massachusetts Institute of Technology, Carlos Portela and James Surjadi, discuss key hurdles, opportunities, and future applications in the field of mechanical metamaterials. Metamaterials are artificially structured materials with properties not easily found in nature. With engineered three-dimensional geometries at the micro- and nanoscale, metamaterials achieve unique mechanical and physical properties with capabilities beyond those of conventional materials. Over the past decade, metamaterials have emerged as a promising way to address engineering challenges for which other existing materials have lacked success.

(Funded by the National Institutes of Health)
Researchers from the California NanoSystems Institute at the University of California, Los Angeles, have developed a sensor technology based on natural biochemical processes that can continuously and reliably measure multiple metabolites at once. The sensors are built onto electrodes made of tiny cylinders called single-wall carbon nanotubes. These electrodes use enzymes and other molecules to perform reactions that mirror the body’s metabolic processes. Depending on the target metabolite, the sensors either detect it directly or first convert it into a detectable form through a chain of intermediary enzymatic reactions. The team measured metabolites in sweat and saliva samples from patients receiving treatment for epilepsy and detected a gut bacteria-derived metabolite in the brain that could cause neurological disorders if it accumulates.

(Funded by the National Institutes of Health)
Researchers at the University of Pennsylvania have developed a new process that transports DNA into cells using lipid nanoparticles. Unlike messenger RNA (mRNA), DNA remains active in cells for months, or even years, and can be programmed to work only in targeted cells. But past attempts to use lipid nanoparticles to deliver DNA failed, because DNA can trigger severe immune reactions. The researchers discovered that by adding a natural anti-inflammatory molecule, called nitro-oleic acid, to the lipid nanoparticles, these immune reactions could be eliminated. With this advancement, treated cells produced intended therapeutic proteins for about six months from a single dose – much longer than the few hours seen with mRNA therapies.

(Funded by the U.S. Department of Energy)
Stacking single layers of sub-nanometer-thick semiconductor materials, known as transition metal dichalcogenides, can generate a moiré potential – a “seascape” of potential energy with regularly repeating peaks and valleys. These peaks and valleys were previously thought to be stationary, but now, researchers from the Molecular Foundry, a user facility at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, and the University of California, Berkeley, along with international collaborators, have shown that the moiré potentials that emerge when transition metal dichalcogenides are stacked are constantly moving, even at low temperatures. Their discovery contributes to foundational knowledge in materials science and holds promise for advancing the stability of quantum technologies, because controlling moiré potentials could help mitigate decoherence in qubits and sensors. (Decoherence occurs when interference causes the quantum state and its information to be lost.)

(Funded by the U.S. National Science Foundation and the U.S. Department of Energy)
Scientists from the U.S. Department of Energy’s (DOE) Argonne National Laboratory (ANL) and SLAC National Accelerator Laboratory; the University of Chicago; the University of Vermont; Middlebury College; Brown University; Stanford University; and Northwestern University have observed that when semiconductor nanocrystals called quantum dots were exposed to short bursts of light, the symmetry of the crystal structure changed from a disordered state to a more organized one. The return of symmetry directly affected the electronic properties of the quantum dots by causing a decrease in the bandgap energy, which is the difference in energy that electrons need to jump from one state to another within a semiconductor material. This change can influence how well quantum dots conduct electricity and respond to electric fields. Part of this work was conducted at the Center for Nanoscale Materials, a DOE Office of Science user facility at ANL.

(Funded by the U.S. National Science Foundation)
Researchers at The Ohio State University have developed a new material that, by harnessing the power of sunlight, can clear water of dangerous pollutants. Solar fuel systems that use titanium dioxide nanoparticles can cause significant challenges to implementation, including low efficiency and the need for complex filtration systems. So, the researchers added copper to the nanoparticles, and the new structures, called nanomats, can now absorb enough light energy to break down harmful pollutants in air and water. These lightweight, easy-to-remove fiber mats can float and operate atop any body of water and are even reusable through multiple cleaning cycles. Because the nanomats are so effective, the researchers envision that they could be used to rid water of industrial pollutants in developing countries, turning otherwise contaminated rivers and lakes into sources of clean drinking water.