News from the NNI Community - Research Advances Funded by Agencies Participating in the NNI

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. 

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.

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.

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.

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.  

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. 

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.

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.)

Scientists from The Wistar Institute, the University of Pennsylvania, the Icahn School of Medicine at Mount Sinai, Saint Joseph’s University (Philadelphia, PA), and Inovio Pharmaceuticals (Plymouth Meeting, PA) have described a next-generation vaccination technology that combines plasmid DNA with a lipid nanoparticle delivery system. The team showed that these DNA lipid nanoparticles demonstrate a unique way of priming the immune system compared to mRNA and protein-in-adjuvant formulations and that these DNA lipid nanoparticles induced robust antibody and T-cell responses after a single dose. Importantly, these responses were durable, with memory responses in small animals persisting beyond a year after immunization. 

Researchers from the City University of New York, Yale University, Caltech, Kansas State University, and international collaborators have discovered a new way of generating phonon-polaritons, a unique type of electromagnetic wave that occurs when light interacts with vibrations in a material’s crystal lattice structure. This advance could pave the way for cheaper, smaller long-wave infrared light sources and more efficient device cooling. The researchers made that discovery by using a thin layer of graphene sandwiched between two hexagonal boron nitride slabs. Until now, exciting and detecting phonon-polariton waves has been expensive – typically involving costly mid-infrared or terahertz lasers and near-field scanning probes – but in this study, the researchers used a cheaper alternative: an electrical current generated by applying an electric field to the graphene.