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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Towards single-species selectivity of membranes with subnanometre pores

Synthetic membranes with pores at the subnanometre scale are at the core of processes for separating solutes from water, such as water purification and desalination. While these membrane processes have achieved substantial industrial success, the capability of state-of-the-art membranes to selectively separate a single solute from a mixture of solutes is limited. Such high-precision separation would enable fit-for-purpose treatment, improving the sustainability of current water-treatment processes and opening doors for new applications of membrane technologies. In this paper, we introduce the challenges of state-of-the-art membranes with subnanometre pores to achieve high selectivity between solutes. Here, we then analyse experimental and theoretical literature to discuss the molecular-level mechanisms that contribute to energy barriers for solute transport through subnanometre pores. We conclude by providing principles and guidelines for designing next-generation single-species selective membranes that are inspired by ion-selective biological channels.

42 ENGINEERING↗
DOE OSTI2021

Bioorthogonal catalytic patch

The toxicity and complicated administration procedures of transition metal catalysts have hampered the applications of bioorthogonal catalysis in vivo. Here the authors fill the needles of a microneedle array patch with palladium nanoparticles deposited on titanium nanosheets and show that the device, applied locally on the skin of mouse models bearing melanoma, promotes intratumoural conversion of systemically injected caged doxorubicin into the active drug, reducing its toxicity and side effects. Bioorthogonal catalysis mediated by transition metals has inspired a new subfield of artificial chemistry complementary to enzymatic reactions, enabling the selective labelling of biomolecules or in situ synthesis of bioactive agents via non-natural processes. However, the effective deployment of bioorthogonal catalysis in vivo remains challenging, mired by the safety concerns of metal toxicity or complicated procedures to administer catalysts. Here, we describe a bioorthogonal catalytic device comprising a microneedle array patch integrated with Pd nanoparticles deposited on TiO 2 nanosheets. This device is robust and removable, and can mediate the local conversion of caged substrates into their active states in high-level living systems. In particular, we show that such a patch can promote the activation of a prodrug at subcutaneous tumour sites, restoring its parent drug's therapeutic anticancer properties. Finally, this in situ applied device potentiates local treatment efficacy and eliminates off-target prodrug activation and dose-dependent side effects in healthy organs or distant tissues.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Light–matter coupling in large-area van der Waals superlattices

Two-dimensional (2D) crystals have renewed opportunities in design and assembly of artificial lattices without the constraints of epitaxy. However, the lack of thickness control in exfoliated van der Waals (vdW) layers prevents realization of repeat units with high fidelity. Recent availability of uniform, wafer-scale samples permits engineering of both electronic and optical dispersions in stacks of disparate 2D layers with multiple repeating units. In this study, we present optical dispersion engineering in a superlattice structure comprising alternating layers of 2D excitonic chalcogenides and dielectric insulators. By carefully designing the unit cell parameters, we demonstrate greater than 90% narrow band absorption in less than 4 nm of active layer excitonic absorber medium at room temperature, concurrently with enhanced photoluminescence in square-centimetre samples. These superlattices show evidence of strong light–matter coupling and exciton–polariton formation with geometry-tuneable coupling constants. Our results demonstrate proof of concept structures with engineered optical properties and pave the way for a broad class of scalable, designer optical metamaterials from atomically thin layers.

2D Crystals↗
DOE OSTI2022

Bridging Nano- and Microscale X-Ray Tomography for Battery Research by Leveraging Artificial Intelligence

X-ray computed tomography (CT) is a non-destructive imaging technique in which contrast originates from the materials' absorption coefficient. The recent development of laboratory nanoscale CT (nano-CT) systems has pushed the spatial resolution for battery material imaging to voxel sizes of 50 nm, a limit previously achievable only with synchrotron facilities. Given the non-destructive nature of CT, in situ and operando studies have emerged as powerful methods to quantify morphological parameters, such as tortuosity factor, porosity, surface area and volume expansion, during battery operation or cycling. Combined with artificial intelligence and machine learning analysis techniques, nano-CT has enabled the development of predictive models to analyse the impact of the electrode microstructure on cell performances or the influence of material heterogeneities on electrochemical responses. In this Review, we discuss the role of X-ray CT and nano-CT experimentation in the battery field, discuss the incorporation of artificial intelligence and machine learning analyses and provide a perspective on how the combination of multiscale CT imaging techniques can expand the development of predictive multiscale battery behavioural models.

diagnostics↗
DOE OSTI2022

Graphene nanopattern as a universal epitaxy platform for single-crystal membrane production and defect reduction

Heterogeneous integration of single-crystal materials offers great opportunities for advanced device platforms and functional systems. Although substantial efforts have been made to co-integrate active device layers by heteroepitaxy, the mismatch in lattice polarity and lattice constants has been limiting the quality of the grown materials. Layer transfer methods as an alternative approach, on the other hand, suffer from the limited availability of transferrable materials and transfer-process-related obstacles. Here, we introduce graphene nanopatterns as an advanced heterointegration platform that allows the creation of a broad spectrum of freestanding single-crystalline membranes with substantially reduced defects, ranging from non-polar materials to polar materials and from low-bandgap to high-bandgap semiconductors. Additionally, we unveil unique mechanisms to substantially reduce crystallographic defects such as misfit dislocations, threading dislocations and antiphase boundaries in lattice- and polarity-mismatched heteroepitaxial systems, owing to the flexibility and chemical inertness of graphene nanopatterns. More importantly, we develop a comprehensive mechanics theory to precisely guide cracks through the graphene layer, and demonstrate the successful exfoliation of any epitaxial overlayers grown on the graphene nanopatterns. Furthermore, this approach has the potential to revolutionize the heterogeneous integration of dissimilar materials by widening the choice of materials and offering flexibility in designing heterointegrated systems.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Atmospheric emission of nanoplastics from sewer pipe repairs

Nanoplastic particles are inadequately characterized environmental pollutants with significant adverse effects on aquatic and atmospheric systems, causing drastic impacts on human health through inhalation, ingestion, and skin penetration. At present, it is explicitly assumed that environmental nanoplastics (EnvNP) are weathering fragments of microplastic or larger plastic debris discharged into terrestrial and aquatic environments, while atmospheric occurrence of EnvNP is solely attributed to aerosolization by wind and other mechanical forces. However, sources and emissions of unintended EnvNP are poorly understood and are therefore largely unaccounted for in various risk assessments. In this work, we show that large quantities of EnvNP may be directly emitted into the atmosphere as steam laden waste components discharged from a commonly used technology to repair sewer pipes in urban areas. Comprehensive chemical analysis of the discharged waste condensate reveals abundant presence of insoluble colloids, which after drying form solid organic particles with composition and viscosity consistent with EnvNP. We suggest that airborne emissions of EnvNP from these globally used sewer repair practices may be prevalent in highly populated urban areas. Airborne emissions of these EnvNP particles may have important implications on air quality and toxicological levels in large urban areas that need to be mitigated.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Lorentz electron ptychography for imaging magnetic textures beyond the diffraction limit

Nanoscale spin textures, especially magnetic skyrmions, have attracted intense interest as candidate high-density and power-efficient information carriers for spintronic devices. Facilitating a deeper understanding of sub-100 nm to atomic-scale spin textures requires more advanced magnetic imaging techniques. Here, we demonstrate a Lorentz electron ptychography (LEP) method which can enable high-resolution, high-sensitivity magnetic field imaging for widely-available electron microscopes. The resolution of LEP is not limited by the usual diffraction limit of the lens optics, but instead is determined by the maximum scattering angle at which a statistically meaningful dose can still be recorded – this can be an improvement of up to 2 to 6 times depending on the allowable dose. Using FeGe as a model system, we realize a more accurate magnetic field measurement of skyrmions with an improved spatial resolution and sensitivity by also correcting the probe damping effects from the imaging optics via LEP. This allows us to directly resolve subtle internal structures of magnetic skyrmions near the skyrmion cores, boundaries, and dislocations in an FeGe single crystal. Our study establishes a quantitative, high-resolution magnetic microscopy technique that can reveal the nanoscale spin textures, especially magnetization discontinuities and topological defects in nanomagnets. In conclusion, the technique’s high dose efficiency should also make it well-suited for the exploration of magnetic textures in electron radiation-sensitive materials such as organic or molecular magnets.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

A room-temperature polarization-sensitive CMOS terahertz camera based on quantum-dot-enhanced terahertz-to-visible photon upconversion

Detection of terahertz (THz) radiation has many potential applications, but presently available detectors are limited in many aspects of their performance, including sensitivity, speed, bandwidth and operating temperature. Most do not allow the characterization of THz polarization states. Recent observation of THz-driven luminescence in quantum dots offers a possible detection mechanism via field-driven interdot charge transfer. Here, we demonstrate a room-temperature complementary metal–oxide–semiconductor THz camera and polarimeter based on quantum-dot-enhanced THz-to-visible upconversion mechanism with optimized luminophore geometries and fabrication designs. Besides broadband and fast responses, the nanoslit-based sensor can detect THz pulses with peak fields as low as 10 kV cm–1. A related coaxial nanoaperture-type device shows a to-date-unexplored capability to simultaneously record the THz polarization state and field strength with similar sensitivity.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

Tunable interaction between excitons and hybridized magnons in a layered semiconductor

The interaction between distinct excitations in solids is of both fundamental interest and technological importance. One example of such interactions is coupling between an exciton, a Coulomb bound electron-hole pair, and a magnon, a collective spin excitation. The recent emergence of van der Waals magnetic semiconductors1 provides a powerful platform for exploring these exciton-magnon interactions and their fundamental properties, such as strong correlation2, as well as their photo-spintronic and quantum transduction3 applications. Here we demonstrate precise control of coherent exciton-magnon interactions in the layered magnetic semiconductor CrSBr. We show that by controlling the direction of applied magnetic fields relative to the crystal axes, and thus the rotational symmetry of the magnetic system4, we can tune not only the exciton coupling to the bright magnon, but also to an optically dark mode via magnon hybridization. The exciton-magnon coupling and associated magnon dispersion curves can be further modulated by applying a uniaxial strain. At the critical strain, a dispersionless dark magnon band emerges. Our results demonstrate unprecedented control of the opto-mechanical-magnonic coupling, and a step towards the predictable and controllable implementation of hybrid quantum magnonics.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2022

A closer look at spin textures

Here, Lorentz electron ptychography, a coherent diffractive imaging method, unveils magnetization singularities in a skyrmion lattice in FeGe and captures subtle internal structures near the skyrmion cores, boundaries, and dislocations.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Spontaneous assembly of hierarchical phases

We report the grand promise of self-assembly is the creation of target nanostructures through spontaneous molecular organization, a process that is — in principle — simpler and more scalable than laborious top-down nanofabrication methods. Yet self-assembly faces a fundamental challenge: the structures that form thermodynamically tend to minimize surface area and maximize symmetry; the most readily-accessible structures are thus quite simple. Block copolymer (BCP) self-assembly, for example, takes advantage of the chemical incompatibility along a polymer backbone to drive local phase separation; frustrated assembly leads to a nanoscale morphology whose unit cell is dictated by chain architecture. Canonical BCPs (linear chains with two blocks) form alternating lamellae and hexagonally-packed cylinders in a straightforward manner; but more exotic phases require additional control, for example directing the assembly using external forces, such as shear or chemical templates. An elegant alternative is to use synthetic methods to design more sophisticated chain architectures, which may give rise to new morphologies. An outstanding challenge is to achieve morphological control without undue synthetic burden. Sun et al. now report in Nature Nanotechnology the design and synthesis of novel triblock copolymers that give rise to structural order at multiple length scales, thereby forming complex and hierarchical nanoscale phases.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Photocarrier-induced persistent structural polarization in soft-lattice lead halide perovskites

The success of the lead halide perovskites in diverse optoelectronics has motivated considerable interest in their fundamental photocarrier dynamics. Here, in this work, we report the discovery of photocarrier-induced persistent structural polarization and local ferroelectricity in lead halide perovskites. Photoconductance studies of thin-film single-crystal CsPbBr 3 at 10 K reveal long-lasting persistent photoconductance with an ultralong photocarrier lifetime beyond 10 6 s. X-ray diffraction studies reveal that photocarrier-induced structural polarization is present up to a critical freezing temperature. Photocapacitance studies at cryogenic temperatures further demonstrate a systematic local phase transition from linear dielectric to paraelectric and relaxor ferroelectric under increasing illumination. Our theoretical investigations highlight the critical role of photocarrier–phonon coupling and large polaron formation in driving the local relaxor ferroelectric phase transition. Our findings show that this photocarrier-induced persistent structural polarization enables the formation of ferroelectric nanodomains at low temperature, which suppress carrier recombination and offer the possibility of exploring intriguing carrier–phonon interplay and the rich polaron photophysics.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Three-dimensional topological magnetic monopoles and their interactions in a ferromagnetic meta-lattice

Topological magnetic monopoles (TMMs), also known as hedgehogs or Bloch points, are three-dimensional (3D) nonlocal spin textures that are robust to thermal and quantum fluctuations due to the topology protection. Although TMMs have been observed in skyrmion lattices, spinor Bose–Einstein condensates, chiral magnets, vortex rings and vortex cores, it has been difficult to directly measure the 3D magnetization vector field of TMMs and probe their interactions at the nanoscale. Here, we report the creation of 138 stable TMMs at the specific sites of a ferromagnetic meta-lattice at room temperature. We further develop soft x-ray vector ptycho-tomography to determine the magnetization vector and emergent magnetic field of the TMMs with a 3D spatial resolution of 10 nm. This spatial resolution is comparable to the magnetic exchange length of transition metals, enabling us to probe monopole-monopole interactions. We find that the TMM and anti-TMM pairs are separated by 18.3±1.6 nm, while the TMM and TMM, anti-TMM and anti-TMM pairs are stabilized at comparatively longer distances of 36.1±2.4 nm and 43.1±2.0 nm, respectively. We also observe virtual TMMs created by magnetic voids in the meta-lattice. This work demonstrates that ferromagnetic meta lattices could be used as a platform to create and investigate the interactions and dynamics of TMMs. Furthermore, we expect that soft x-ray vector ptycho-tomography can be broadly applied to quantitatively image 3D vector fields in magnetic and anisotropic materials at the nanoscale.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Imaging solid–electrolyte interphase dynamics using operando reflection interference microscopy

The quality of the solid–electrolyte interphase is crucial for the performance of most battery chemistries, but its formation dynamics during operation are not well understood due to a lack of reliable operando characterization techniques. Herein, we report a dynamic, non-invasive, operando reflection interference microscope to enable the real-time imaging of the solid–electrolyte interphase during its formation and evolution processes with high sensitivity. The stratified structure of the solid–electrolyte interphase formed during four distinct steps includes the emergence of a permanent inner inorganic layer enriched in LiF, a transient assembly of an interfacial electrified double layer and a consequent emergence of a temporary outer organic-rich layer whose presence is reversible with electrochemical cycling. Reflection interference microscope imaging reveals an inverse correlation between the thicknesses of two interphasial subcomponents, implying that the permanent inorganic-rich inner layer dictates the organic-rich outer layer formation and lithium nucleation. In conclusion, the real-time visualization of solid–electrolyte interphase dynamics provides a powerful tool for the rational design of battery interphases.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Structure, folding and flexibility of co-transcriptional RNA origami

RNA origami is a method for designing RNA nanostructures that can self-assemble through co-transcriptional folding with applications in nanomedicine and synthetic biology. However, to advance the method further, an improved understanding of RNA structural properties and folding principles is required. Here we use cryogenic electron microscopy to study RNA origami sheets and bundles at sub-nanometre resolution revealing structural parameters of kissing-loop and crossover motifs, which are used to improve designs. In RNA bundle designs, we discover a kinetic folding trap that forms during folding and is only released after 10 h. Furthermore, exploration of the conformational landscape of several RNA designs reveal the flexibility of helices and structural motifs. Finally, sheets and bundles are combined to construct a multidomain satellite shape, which is characterized by individual-particle cryo-electron tomography to reveal the domain flexibility. Together, the study provides a structural basis for future improvements to the design cycle of genetically encoded RNA nanodevices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

High-throughput manufacturing of epitaxial membranes from a single wafer by 2D materials-based layer transfer process

Layer transfer techniques have been extensively explored for semiconductor device fabrication as a path to reduce costs and to form heterogeneously integrated devices. These techniques entail isolating epitaxial layers from an expensive donor wafer to form freestanding membranes. However, current layer transfer processes are still low-throughput and too expensive to be commercially suitable. Here we report a high-throughput layer transfer technique that can produce multiple compound semiconductor membranes from a single wafer. We directly grow two-dimensional (2D) materials on III–N and III–V substrates using epitaxy tools, which enables a scheme comprised of multiple alternating layers of 2D materials and epilayers that can be formed by a single growth run. Each epilayer in the multistack structure is then harvested by layer-by-layer mechanical exfoliation, producing multiple freestanding membranes from a single wafer without involving time-consuming processes such as sacrificial layer etching or wafer polishing. Moreover, atomic-precision exfoliation at the 2D interface allows for the recycling of the wafers for subsequent membrane production, with the potential for greatly reducing the manufacturing cost.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Low-thermal-budget synthesis of monolayer molybdenum disulfide for silicon back-end-of-line integration on a 200 mm platform

Two-dimensional (2D) materials are promising candidates for future electronics due to their excellent electrical and photonic properties. Although promising results on the wafer-scale synthesis (≤150 mm diameter) of monolayer molybdenum disulfide (MoS 2 ) have already been reported, the high-quality synthesis of 2D materials on wafers of 200 mm or larger, which are typically used in commercial silicon foundries, remains difficult. The back-end-of-line (BEOL) integration of directly grown 2D materials on silicon complementary metal–oxide–semiconductor (CMOS) circuits is also unavailable due to the high thermal budget required, which far exceeds the limits of silicon BEOL integration (<400 °C). This high temperature forces the use of challenging transfer processes, which tend to introduce defects and contamination to both the 2D materials and the BEOL circuits. Here we report a low-thermal-budget synthesis method (growth temperature < 300 °C, growth time ≤ 60 min) for monolayer MoS 2 films, which enables the 2D material to be synthesized at a temperature below the precursor decomposition temperature and grown directly on silicon CMOS circuits without requiring any transfer process. We designed a metal–organic chemical vapour deposition reactor to separate the low-temperature growth region from the high-temperature chalcogenide-precursor-decomposition region. We obtain monolayer MoS 2 with electrical uniformity on 200 mm wafers, as well as a high material quality with an electron mobility of ~35.9 cm 2 V -1 s -1 . Finally, we demonstrate a silicon-CMOS-compatible BEOL fabrication process flow for MoS 2 transistors; the performance of these silicon devices shows negligible degradation (current variation < 0.5%, threshold voltage shift < 20 mV). We believe that this is an important step towards monolithic 3D integration for future electronics.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Low Ohmic contact resistance and high on/off ratio in transition metal dichalcogenides field-effect transistors via residue-free transfer

Beyond-silicon technology demands ultrahigh performance field-effect transistors. Transition metal dichalcogenides provide an ideal material platform, but the device performances such as the contact resistance, on/off ratio and mobility are often limited by the presence of interfacial residues caused by transfer procedures. Here, we show an ideal residue-free transfer approach using polypropylene carbonate with a negligible residue coverage of ~0.08% for monolayer MoS 2 at the centimetre scale. By incorporating a bismuth semimetal contact with an atomically clean monolayer MoS 2 field-effect transistor on hexagonal boron nitride substrate, we obtain an ultralow Ohmic contact resistance of ~78 Ω µm, approaching the quantum limit, and a record-high on/off ratio of ~10 11 at 15 K. Further, such an ultra-clean fabrication approach could be the ideal platform for high-performance electrical devices using large-area semiconducting transition metal dichalcogenides.

77 NANOSCIENCE AND NANOTECHNOLOGY↗