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

Researchers from the U.S. Department of Energy’s National Renewable Energy Laboratory have developed a trilayer of semiconductors to enable the dissociation of electron-hole pairs, also called excitons – a fundamental process for the performance of photovoltaic systems. The trilayer, which consists of single-walled carbon nanotubes sandwiched between two semiconductors, enables a photo-induced charge transfer cascade, in which electrons move in one direction, while holes move in the other direction. The trilayer architecture appears to facilitate ultrafast hole transfer and exciton dissociation, resulting in a long-lived charge separation.

Researchers from the University of Rochester have outlined a process for mapping heat transfer using luminescent nanoparticles. By applying highly doped upconverting nanoparticles to the surface of a device, the researchers were able to achieve super-high-resolution thermometry at the nanoscale level from up to 10 millimeters away. According to Andrea Pickel , one of the scientists involved in the study, this method could be used by manufacturers to improve a wide array of electrical components.

Researchers from Rice University and the University of Texas MD Anderson Cancer Center have developed ultrasmall, stable gas-filled protein nanostructures that could revolutionize ultrasound imaging and drug delivery. These diamond-shaped, 50-nanometer gas vesicles are believed to be the smallest stable, free-floating structures for medical imaging ever created. They can penetrate tissue and reach immune cells in lymph nodes. This discovery opens up new possibilities for imaging and delivering therapies to previously inaccessible cells. “The research has notable implications for treating cancers and infectious diseases, as lymph-node-resident cells are critical targets for immunotherapies," said George Lu, one of the researchers involved in this study.

Researchers from the U.S. Department of Energy’s Lawrence Livermore National Laboratory, Columbia University, and the University of California, Irvine, have discovered a new mechanism that could boost the efficiency of hydrogen production through water splitting. This process relies on hydrated ion-permeable ultrathin coatings (such as porous oxide materials), which are used to select chemical species. Using advanced simulations, the scientists revealed that water confined within nanopores smaller than 0.5 nanometers shows significantly altered reactivity and proton transfer mechanisms. "This insight could pave the way for optimizing porous oxides to improve the efficiency of hydrogen production systems by tuning the porosity and surface chemistry of the oxides," said Hyuna Kwon, one of the scientists involved in this study.

Scientists from the U.S. Department of Energy’s Pacific Northwest National Laboratory have discovered that reducing graphene oxide membranes with ultraviolet light alters the oxygen functional groups on the graphene oxide surface. This modification results in a novel separation mechanism that is selective for charge rather than size. Exposure to ultraviolet light selectively removed hydroxyl groups from the graphene oxide planes, leading to enhanced interactions of metal cations with functional groups located at the edges of the graphene oxide. This, in turn, resulted in a lower ratio of free mobile lithium cations in solution compared to calcium cations. 

To function, quantum computers need to be kept very cold – just a few degrees above absolute zero. Now, researchers at Northeastern University, the University of California, Berkeley, the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, and the National Institute for Materials Science in Tsukuba, Japan, have shown that one day, it might be possible to run quantum computers at room temperature. The researchers identified novel van der Waals heterostructures (created by combining layers of atomically thin materials, including graphene) that allow control of the coherent movements of atoms out of their equilibrium positions – also called acoustic phonons – at terahertz frequencies. With current quantum computer transistors, the control of acoustic phonons is limited to the gigahertz range. So, increasing the range of these transistors into terahertz frequencies – an increase by a factor of a thousand – opens the possibility of running quantum computers at room temperature.

Researchers from The University of Texas at El Paso and the Connecticut Agricultural Experiment Station have shown that nanoplastics and per- and polyfluoroalkyl substances (PFAS) – commonly known as forever chemicals – can alter proteins found in human breast milk and infant formulas. While nanoplastics originate primarily from the degradation of larger plastic materials, like water bottles and food packaging, forever chemicals are found in various products, such as cookware and clothing.

Researchers from the U.S. Department of Energy’s SLAC National Accelerator Laboratory and Argonne National Laboratory; Stanford University; Harvard University; Columbia University; Florida State University; and the University of California, Los Angeles, have discovered new behavior in an 50-nanometer-thick two-dimensional material, which offers a promising approach to manipulating light that will be useful for devices that detect, control or emit light, collectively known as optoelectronic devices. Optoelectronic devices are used in light-emitting diodes (LEDs), optical fibers, and medical imaging. The researchers found that when oriented in a specific direction and subjected to linearly polarized terahertz radiation, an ultrathin film of tungsten ditelluride circularly polarizes the incoming light.

Researchers from the U.S. Department of Energy's Princeton Plasma Physics Laboratory and the University of Delaware have provided new insights into the variations that can occur in the atomic structure of two-dimensional materials called transition metal dichalcogenides (TMDs). The researchers found that one of the defects, which involves hydrogen, provides excess electrons. The other type of defect, called a chalcogen vacancy, is a missing atom of oxygen, sulfur, selenium, or tellurium. By shining light on the TMD, the researchers showed unexpected frequencies of light coming from the TMD, which could be explained by the movement of electrons related to the chalcogen vacancy.

Researchers from the University of Illinois Urbana-Champaign have identified how gold nanoparticles transfer charge to a connecting semiconductor and quantified how much charge is transferred using different colors of light. The researchers theorized that by using light to excite collective electronic oscillations (also called a plasmon) in gold nanoparticles, they would get a boost in charge transfer to the semiconductor material. And their study confirmed their theory.