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

A team of U.S. researchers from various academic and research institutions has developed a new additive material that can make an inexpensive iron-nitrogen-carbon fuel cell catalyst more durable. In particular, the additive material, which is composed of tantalum-titanium oxide nanoparticles, scavenged and deactivated unstable atoms, molecules, or ions called free radicals. The researchers showed that when the nanoparticle material was added to the reactions of fuel cell systems, hydrogen peroxide yield was suppressed to less than 2% – a 51% reduction – and current density decay of fuel cells was reduced from 33% to 3%.

Researchers at Brown University have carried out a study investigating superconductivity in magic-angle trilayer graphene to better understand the unusual superconducting behavior observed in this material. The results from this study are similar to results from another study the researchers performed on magic-angle bilayer graphene, which suggests that superconducting phases in these two materials (magic-angle bilayer and magic-angle trilayer graphene) have a common origin. Both materials consist of sheets of graphene stacked together with a rotational misalignment of approximately 1.5 degrees.

With billions of transistors in a single computer chip, their manufacturing tools now operate at the molecular level.  Typically, these tools involve using stencils to selectively pattern or remove materials with high fidelity to form nanoscale electronic devices. As chips fit more and more components to keep up with the digital world's growing computational demands, these nanopatterning stencils are becoming smaller and more precise. Now, researchers from the University of Pennsylvania and the University of Konstanz in Germany have demonstrated how "multiblock" copolymers can produce exceptionally ordered patterns in thin films, achieving spacings smaller than three nanometers.

An international team of researchers has developed a wireless, biodegradable sensor that could offer doctors a way to monitor changes in brain chemistry without requiring a second operation to remove the implant. As a proof of concept, the researchers inserted the device into the deep brain region of a mouse, and the device collected data on levels of dopamine, an important neurotransmitter, as well as pH levels, temperature, and electrophysiology, before dissolving back into the body. The implant is composed of two-dimensional transition metal dichalcogenides, which are considered an emerging class of materials that are increasingly used in nanoelectronics and nanophotonics applications. 

Scientists at Rice University have put forth the idea that growing graphene on a surface that undulates like an egg crate would stress the graphene enough to create a very small electromagnetic field. This phenomenon, which is possible because graphene is pliable enough to adhere to a surface during chemical vapor deposition, could be useful for creating 2D electron optics.

Scientists at the University of Tennessee, Knoxville, have discovered that a form of cellulose obtained from plants can be added to ice cream to control the formation and growth of ice crystals in it – and the additive works better than currently used ice growth inhibitors when temperature fluctuates. The additive consists of cellulose nanocrystals, which are extracted from the plant cell walls of agricultural and forestry byproducts. In a model ice cream – a 25% sucrose solution – the cellulose nanocrystals initially had no effect, but after the model ice cream was stored for a few hours, the researchers found that the cellulose nanocrystals completely shut down the growth of ice crystals, while the crystals continued to enlarge in the untreated model ice cream. 

Quantum dots are lab-grown nanoparticles with special optical properties that are detectable by standard microscopy, tomography, and fluorescence imaging. Now, scientists at the University of Illinois Urbana Champaign have used quantum dots to image macrophages – immune cells present in fat tissue – inside the body. The team created quantum dots coated with dextran, a sugar molecule that also targets macrophages in fat tissue. As a proof-of-concept, the scientists injected these quantum dots into obese mice and compared imaging results against dextran alone, the current standard for imaging macrophages. Quantum dots outperformed dextran alone across all imaging platforms, including simple optical techniques.

Scientists from the University of Chicago, Northwestern University, Arizona State University, the University of California, Berkeley, the U.S. Department of Energy’s Stanford Linear Accelerator Center and Lawrence Berkeley National Laboratory, and Technische Universität Dresden in Germany have laid out design rules to make nanocrystals work together. Scientists can grow nanocrystals out of many different materials, but whenever they try to assemble these nanocrystals together into arrays, the resulting crystals grow with long “hairs” around them. These hairs made it difficult for electrons to jump from one nanocrystal to another. The new method is meant to reduce the hairs around each nanocrystal, so they can be packed more tightly, allowing electrons – the messengers of electronic communication – to move easily along.

As part of an overarching quest to build “skin-inspired” electronics that are soft and stretchy, researchers at Stanford University have shown the proof of principle toward a stretchable, potentially reshapable display. About three years ago, the researchers discovered that a yellow-colored light-emitting polymer, called SuperYellow, not only became soft and pliable but also emitted brighter light when mixed with a type of polyurethane, a stretchy plastic. After adding polyurethane, the researchers saw that SuperYellow formed nanostructures that were connected like a fishnet and made the polymer emit brighter light.

Researchers from Harvard University and the University of Arizona have developed an attachment that can turn just about any camera or imaging system into polarization cameras. The attachment uses metasurfaces of subwavelength nanopillars to direct light based on its polarization and compiles an image that captures polarization. The researchers attached the polarization metasurface to an off-the-shelf machine vision camera, simply screwing it on in front of the objective lens. The attachment could be used to improve machine vision in vehicles or in biometric sensors for security applications.