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

Scientists from the Massachusetts Institute of Technology, Arizona State University, the U.S. Department of Energy’s Brookhaven National Laboratory, Sorbonne University in Paris, France, and Utrecht University in the Netherlands have reported new insights into exotic particles that are key to a form of magnetism that originates from ultrathin materials only a few atomic layers thick. The scientists identified the microscopic origin of these particles, known as excitons, and showed how they can be controlled by chemically “tuning” the material, which is primarily composed of nickel. Also, the scientists found that the excitons propagate throughout the bulk material instead of being bound to the nickel atoms.

The U.S. Environmental Protection Agency (EPA) is seeking applications for research to develop and demonstrate nanosensor technology with the potential to detect, monitor, and degrade per- and polyfluoroalkyl substances (PFAS) in groundwater or surface water that may be used as drinking water sources. Using nanotechnology may help to build better environmental sensors by reducing cost, improving efficiency, and increasing selectivity. Nanotechnology may also be used to degrade PFAS in a way that does not create toxic byproducts.

Researchers from Florida State University, the University of California Santa Barbara, Tsinghua University in China, Leipzig University in Germany, and Stuttgart University in Germany have identified, for the first time, the existence of local collective excitations of #electrons, called #plasmons, in a #Kagome metal – a class of materials whose atomic structure follows a hexagonal pattern that looks like a traditional Japanese basket weave – and found that the wavelength of those plasmons depends upon the thickness of the metal. The researchers also found that changing the frequency of a #laser shining at the metal caused the plasmons to spread through the material rather than staying confined to the surface. “[O]ur research reveals how electron interactions can create these unique waves at the nanoscale," said Guangxin Ni, the scientist who led this study. "This breakthrough is key for advancing technologies in nano-optics and nano-photonics."

Putting 50 billion transistors into a microchip the size of a fingernail is a feat that requires manufacturing methods of nanometer-level precision. The process relies heavily on solvents that carry and deposit materials in each layer – solvents that can be difficult to handle and toxic to the environment. Now, researchers from Tufts University and Istituto Italiano di Tecnologia in Milan, Italy, have developed a nanomanufacturing approach that uses water as the primary solvent, making it more environmentally compatible and opening the door to the development of devices that combine inorganic and biological materials.

Researchers from the University of California San Diego have developed an innovative approach to multispectral photodetection by alternating layers of graphene and colloidal quantum dots. By carefully engineering the material stack, the researchers created photodetectors sensitive to different wavelength bands without additional optical components. The key innovation lies in using graphene monolayers as independent charge collectors at different depths within a quantum dot absorber layer.

Researchers from Penn State and the National Institute for Materials Science in Japan have created a switch that turns on and off the presence of “kink states” – electrical conduction pathways at the edge of semiconducting materials. By controlling the formation of the kink states, researchers can regulate the flow of electrons in a quantum system. Kink states exist in a quantum device built with a bilayer graphene, which comprises two layers of atomically thin carbon stacked together, in such a way that the atoms in one layer are misaligned to the atoms in the other. "The amazing thing about our devices is that we can make electrons moving in opposite directions not collide with one another … even though they share the same pathways," said Ke Huang, one of the scientists involved in this study.

This online post from the U.S. Food and Drug Administration states that “[m]icroplastics and nanoplastics may be present in food, primarily from environmental contamination where foods are grown or raised,” but “[c]urrent scientific evidence does not demonstrate that levels of microplastics or nanoplastics detected in foods pose a risk to human health.”

Caltech engineers have built a metasurface patterned with tunable nanoscale antennas capable of reflecting an incoming beam of optical light to create many channels of different optical frequencies. The work points to a promising route for the development of not only a new type of wireless communication channel but also potentially new range-finding technologies and even a novel way to relay larger amounts of data to and from space. "With these metasurfaces, we've been able to show that one beam of light comes in, and multiple beams of light go out, each with different optical frequencies and going in different directions," says Harry Atwater, one of the engineers involved in this study. "It's acting like an entire array of communication channels. And we've found a way to do this for free-space signals rather than signals carried on an optical fiber."

Researchers from North Carolina State University, the Leibniz Institute of Polymer Research Dresden in Germany, Technische Universität Dresden in Germany, and Otto von Guericke University Magdeburg in Germany have embedded gold nanorods in hydrogels that can be processed through 3D printing to create structures that contract when exposed to light and expand when the light is removed. When the hydrogel structures are exposed to light, the embedded gold nanorods convert that light into heat. This causes the polymers in the hydrogel to contract, pushing water out of the hydrogel and shrinking the structure. When the light is removed, the polymers cool down and begin absorbing water again, which expands the hydrogel structure to its original dimensions. Because this expansion and contraction can be performed repeatedly, the 3D-printed structures can serve as remotely controlled actuators.

Researchers from the University of Maryland and the National Institute of Standards and Technology have engineered a seafood-waste material that removes chemical pesticides and herbicides from produce and extends shelf life. The material, made of a derivative of crab and shrimp shells, is designed to form a thin nanocrystal layer on the treated produce, removing chemical residues. The researchers used a smartphone app to check the chemical residue level. They found that this coating was effective in absorbing the chemical residues, enhanced the fruit's shelf life, and was easily rinsed off.