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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Evaluation of the cytotoxic and cellular proteome impacts of food-grade TiO2 (E171) using simulated gastrointestinal digestions and a tri-culture small intestinal epithelial model

Engineered nanomaterials (ENMs) are widely used in the food industry; however, regulations for ENMs in food are still in the early stages of development due to insufficient health data. This study investigated the cytotoxicity and changes to the proteomic profile in an in vitro small intestinal epithelium model after exposure to digested food models containing the ubiquitous engineered particulate food additive, TiO2 (E171). TiO2 at 0.75% or 1.5% (w/w) concentrations in either a fasting food model (FFM) or a standardized food model (SFM) based on American diet were digested using an in vitro oral-gastric-small intestinal simulator, and the resulting digestas were applied to a small intestinal epithelium tri-culture cellular model. Effects on cell layer integrity, cytotoxicity, and oxidative stress were assessed. In order to explore impact on cellular processes beyond basic cytotoxicity, mass spectrometrybased quantitative proteomic analyses of control and exposed tri-culture cells was performed. TiO2 in FFM, but not in SFM, produced significant, dose-dependent cytotoxicity, and at the higher dose caused significant oxidative stress, indicative of a food matrix effect. No significant perturbations of the cellular proteome were observed with TiO2 in either FFM or SFM food models. However, proteins involved in the tricarboxylic acid (TCA) cycle, gluconeogenesis, and translation were up-regulated by digestas from SFM compared to those from FFM, also indicative of food matrix effects in the case of food models alone. Interestingly, the differences in profiles between the two food models was more pronounced in the presence of TiO2 indicative of food matrix effects. Together, these results indicate that TiO2 in a fasting diet may be slightly cytotoxic, and that ingested TiO2 does not significantly alter the epithelial proteome, whereas the food matrix alone can have a dramatic effect on the proteome.

Cao, Xiaoqiong↗
DOE OSTI2025

Tailoring Cu-Zr gradient nanoglass structures: Influence of nanoparticle size and cooling rates on glass-glass interfaces

The study of gradient nanoglasses (GNGs) has gained attention due to their unique mechanical properties and potential applications in advanced materials. This study employs molecular dynamics simulations to synthesize a GNG using Cu-Zr metallic glass nanoparticles (NPs) sized from 3 to 15 nm. The NPs were produced by melting and quenching metallic clusters at a relatively slow quench rate of 10 9 K/s. The synthesis of GNG is elucidated along with the characterization of its heterogeneous metallic glass nanostructure. A seamless GNG structure is formed through cold compression of Cu 64 Zr 36 amorphous NPs of varying sizes. The influence of NP size on the GNG structure is investigated, utilizing deeply relaxed NPs, which exhibit a characteristic Cu segregation pattern on their surfaces. The results highlight an increase in structural heterogeneity due to heterogeneous mass transport and the development of local composition and density variations caused by Cu segregation at glass-glass interfaces (GGIs). A reduction in NP size is correlated with decreased Cu atomic displacements and local density at GGIs, suggesting that larger NPs may produce stronger GGIs. This research presents a novel methodology for synthesizing heterogeneous metallic glasses, demonstrating the capacity to control and customize nanostructure heterogeneity through the manipulation of NP sizes and cooling rates. Furthermore, these findings enhance our understanding of structural evolution during nanoglass synthesis and lay the foundation for further exploration in nanomaterial synthesis and characterization.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Giant low-field magnetocaloric effect and refrigerant capacity in reduced dimensionality EuTiO 3 multiferroics

Engineering magnetic materials into a thin film form while preserving its excellent magnetocaloric response is essential in the development of miniature magnetic coolers. We demonstrate how this can be achieved in the case of EuTiO 3 - an emerging multiferroic material. Unlike conventional cases where reduced dimensionality considerably decreased the magnetic entropy change (ΔS M ) and hence the refrigerant capacity (RC), we show the large low-field enhancements of ΔS M and RC in a ~100 nm thick nanocrystalline EuTiO 3 film (ΔS M ~ 24 J kg -1 K -1 and RC = 152 J kg -1 for μ 0 ΔH = 2T) relative to its single crystal counterpart (ΔS M ~ 17 J kg -1 K -1 and RC ~ 107 J kg -1 for μ 0 ΔH = 2T). The nanocrystalline EuTiO 3 film is an excellent candidate for cryogenic magnetic refrigeration. From our study, a new approach for improving both MCE and RC in magnetic nanomaterials is proposed, which will stimulate further research on magnetocaloric thin films and related cooling devices.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Calorimetric metal vapor adsorption energies for characterizing industrial catalyst support materials

Many important catalysts and electro-catalysts for energy and environmental technologies involve late transition metal atoms and nanoparticles dispersed across the surface of high-surface-area support materials, for example, oxide nanoparticles. The surface reactivity and long-term stability against deactivation of these materials depends strongly on the strength of bonding of the metal atom and nanoparticles to the support surface. Here, we introduce a novel calorimetry method that implements a LiTaO 3 crystal for heat detection and extends metal adsorption calorimetry to surfaces of nanomaterials that are deposited from liquid solutions, as is typical when preparing industrial catalyst supports. This allows one to measure the strength of metal atom bonding and the adhesion energy of metal nanoparticles to clean surfaces of technologically relevant catalyst supports. We demonstrate that here by measuring the heat of Ag vapor adsorption onto the clean surfaces of high-surface-area TiO 2 anatase powdered support materials (i.e., 5-nm-diameter nanoparticles). These heats of adsorption show a pulse-to-pulse standard deviation of only 9.3 kJ/mol (3.3%) for pulses containing only 1% of a monolayer of Ag vapor, with potential for a 5-fold reduction in noise if used with another metal evaporator. The calorimeter was also proven to work well measuring heats of Ag adsorption on calcium niobate(001) nanosheets deposited as thin films from liquid solution. Here, this calorimeter opens up the possibility of using metal adsorption calorimetry to screen catalyst support materials for the strengths with which they bind metal atoms and metal nanoparticles, offering new opportunities to discover better support materials or for basic scientific study of structure / function relationships with respect to metal / support bond energies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Designing sequence-defined peptoids for fibrillar self-assembly and silicification

In the biological environment, mineral crystals exquisitely controlled by biomacromolecules often show intricate hierarchical structures and superior mechanical properties. Among these biominerals, spicules, hybrid silica/protein superstructures serving as skeletal elements in demosponges, represent an excellent example for motivating the synthesis of silica materials. Herein, by designing sequence-defined peptoids containing side chains with a strong binding to silica, we demonstrated that self-assembly of these peptoids into fiber structures enables the mimicking of both biocatalytic and templating functions of silicatein filaments for the formation of silica fibers at near-neutral pH and ambient temperature. We further showed that the presence of amino groups is significant for the nucleation of silica on self-assembled peptoid nanofibers. Molecular dynamics simulation further confirmed that having silica-binding of amino side chains is critical for self-assembled peptoid fibers in triggering silica formation. Here, we demonstrated that tuning inter-peptoid interactions by varying carboxyl and amino side chains significantly influences the assembly kinetics and final morphologies of peptoid assemblies as scaffolds for directing silica mineralization to form silica spheres, fibers, and sheets. The formation of silica shell on peptoid fibers increased the mechanical property of peptoid hydrogel materials by nearly 1000-fold, highlighting the great potential of using silicification to enhance the mechanical property of hydrogel materials for applications including tissue engineering. Since peptoids are highly robust and programmable, we expect that self-assembly of peptoids containing solid-binding side chains into hierarchical materials opens new opportunities in the design and synthesis of highly tunable scaffolds that direct the formation of composite nanomaterials.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Effects of particle shape and surface roughness on van der Waals interactions and coupling to dynamics in nanocrystals

The van der Waals interaction between colloids and nanoparticles is one of the key components to understanding particle aggregation, attachment, and assembly. While the ubiquity of anisotropic particle shapes and surface roughness is well-recognized in nanocrystalline materials, the effect of both on van der Waals forces and torques has not been adequately investigated. Here, in this study, we develop a numerical scheme and determine the van der Waals forces and torques between cubic particles with multiple configurations and relative orientations. Our results show that the van der Waals torque due to anisotropic particle shapes is appreciable at nearly all configurations and mutual angles, outcompeting Brownian motion for various materials systems and conditions. The effect of surface roughness increases this shape effect, resulting in stronger van der Waals interactions ascribed to protrusions in the rough surfaces. Moreover, a scaling analysis indicates that the surface roughness alters the separation dependence of the van der Waals force and, more importantly, significantly influences the dynamics of two approaching particles. Our results clearly demonstrate that surface roughness and anisotropic shape play a crucial role in the energetics and kinetics of various particle-scale and emergent phenomena, such as crystal growth by oriented attachment, nanomaterials synthesis and assembly, mud flow rheology, as well as the deposition of natural nanocrystals within the subsurface.

Arbitrary configurations↗
DOE OSTI2022

Crystallization pathways and interfacial drivers for the formation of hierarchical architectures

The development of structural hierarchy on various length scales during crystallization process is ubiquitous in biological systems and is also observed in synthetic nanomaterials. The driving forces for the formations of complex architectures range from local interfacial interactions, that modify interfacial speciation, local supersaturation, and nucleation barriers, to macroscopic interparticle forces. Although it is enticing to interpret the formation of hierarchical architectures as the assembly of independently nucleated building blocks, often crystallization pathways follow monomer-by-monomer addition with structural complexity arising from interfacial chemical coupling and strongly correlated fluctuation dynamics in the electric double layers. Here, the mechanism of the development of structural hierarchy through heterogeneous nucleation, coupled interfacial nucleation and assembly, and oriented attachment of independently nucleated particles is discussed. In this article, the emphasis is made on the discussion of the underlying interfacial forces and chemical coupling that drives crystallization pathways towards the formation of structural hierarchy.

36 MATERIALS SCIENCE↗
DOE OSTI2021

In situ preparation of visible-light-driven carbon quantum dots/NaBiO 3 hybrid materials for the photoreduction of Cr(VI)

Here, different carbon quantum dots (CQDs)/NaBiO 3 hybrid materials were synthesized as photocatalysts to effectively utilize visible light for the photocatalytic degradation of contaminants effectively. These hybrid materials exhibit an enhanced photocatalytic reduction of hexavalent chromium (Cr(VI)) in the aqueous medium. Zero-dimensional nanoparticles of CQDs were embedded within the two-dimensional NaBiO 3 nanosheets by the hydrothermal process. Compared with that of the pure NaBiO 3 nanosheets, the photocatalytic performance of the hybrid catalysts was significantly high and 6 wt.% CQDs/NaBiO 3 catalyst exhibited better photocatalytic performance. We performed the first-principles density functional theory calculations to study the interfacial properties of pure NaBiO 3 nanosheets and hybrid photocatalysts, and confirmed the CQDs played an important role in the CQDs/NaBiO 3 composites. The experimental results indicated that the enhanced reduction of Cr(VI) was probably due to the high loading of CQDs (electron acceptor) on NaBiO 3 , which made NaBiO 3 nanomaterials to respond in visible light and significantly improved their electron-hole separation efficiency.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Superior removal of As(III) and As(V) from water with Mn-doped β-FeOOH nanospindles on carbon foam

Arsenic pollution of water is one of the severest environmental challenges threatening human health. Iron-based nanomaterials have been demonstrated effective in arsenic removal. However, they generally suffer from low removal efficiency towards highly toxic As(III), loss of active sites owing to agglomeration, and poor reusability. Herein, we report a carbonized melamine foam supported Mn(IV)-doped β-FeOOH nanospindles(CF@Mn-FeOOH NSp) for tackling the technical hurdles. The designed CF@Mn-FeOOH NSp appears as a free-standing monolith through a low-cost and straightforward hydrothermal method. The atomic-scale integration of Mn(IV) into β-FeOOH enables an oxidation-adsorption bifunctionality, where Mn(IV) serves as oxidizer for As(III) and Fe(III) acts as adsorber for As(V). The maximal adsorption capacity for As(V) and As(III) can reach 152 and 107 mg g -1 , respectively. Meanwhile, As in simulated high arsenic groundwater can be decreased to below 10 μg L -1 within 24 h. By simple "filtrating-washing", 85% and 82% of its initial adsorption capacity for As(V) and As(III) can be easily recovered even after 5-cycles reuse. Kinetics and isotherm adsorption study indicate that the arsenic adsorption behavior is mainly through chemical bonding during single-layer adsorbing process. The as-prepared CF@Mn-FeOOH offers a scalable, efficient, and recyclable solution for arsenic removal in groundwater and wastewater from mines and industry.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2022

Environmental application of chlorine-doped graphitic carbon nitride: Continuous solar-driven photocatalytic production of hydrogen peroxide

Solar-driven photocatalytic generation of H 2 O 2 over metal-free catalysts is a sustainable approach for value-added chemical production. Here, we synthesized chlorine-doped graphitic carbon nitride (Cl-doped g-C 3 N 4 ) through a solvothermal method to effectively produce H 2 O 2 with a rate of 1.19 ± 0.06 µM min –1 under visible light irradiation, which was improved by 104 times compared to pristine g-C 3 N 4 . Continuous net production of H 2 O 2 was realized at a rate of 2.78 ± 0.10 µM min –1 up to 54 h with isopropanol as the hole scavenger, whereas H 2 O 2 production was only sustained for ~ 6 h without scavengers. Both molecular simulations and advanced spectroscopic characterizations elucidated that the Cl dopant increased the charge transfer rate, decreased the bandgap, and reduced the activation energy of the rate-limiting step of O 2 reduction, all of which favored H 2 O 2 production. Furthermore, this work implemented a novel metal-free photocatalyst for sustainable H 2 O 2 production and elucidated the mechanism for promoting H 2 O 2 production that can guide future photoreactive nanomaterial design.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Thermodynamics and kinetics of 2D g-GeC monolayer as an anode materials for Li/Na-ion batteries

Development of high capacity anode materials is one of the essential strategies for next-generation high-performance Li/Na-ion batteries. Rational design, using density functional theory, can expedite the discovery of these anode materials. Here, we propose a new anode material, germanium carbide, g-GeC, for Li/Na-ion batteries. Our results show that g-GeC possesses both benefits of the high stability of graphene and the strong interaction between Li/Na and germanene. The single-layer germanium carbide, g-GeC, can be lithiated/sodiated on both sides yielding Li 2 GeC and Na 2 GeC with a storage capacity as high as 633 mA h/g. Besides germagraphene’s 2D honeycomb structure, fast charge transfer, and high (Li/Na)-ion diffusion and negligible volume change further enhance the anode performance. These findings provide valuable insights into the electronic characteristics of newly predicted 2D g-GeC nanomaterial as a promising anode for (Li/Na)-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Ingeniously enhanced ferromagnetism in chemically-reduced 2D Ti 3 C 2 T X MXene

Chemical reduction is a facile and cost-effective technique for the modulation of the physical and chemical properties of nanomaterials. In this work, we demonstrate an enhancement of the magnetic behavior of Ti 3 C 2 T x MXene after its chemical reduction via l-ascorbic acid treatment. Small ferromagnetic loops have been observed below 50 K for Ti 3 C 2 T x prepared by hydrofluoric acid (HF) etching of Al layers from Ti 3 AlC 2 . Such a ferromagnetic ordering of spins was significantly enhanced via a chemical reduction of Ti 3 C 2 T x with l-ascorbic acid. Ferromagnetic hysteresis loops were observed for reduced Ti 3 C 2 T x (r-Ti 3 C 2 T x ) up to 150 K indicating a significant upshift of the paramagnetic to the ferromagnetic transition temperature, pushing towards room temperature. The enhancement of ferromagnetism and upshift of the ferromagnetic transition temperature could be attributed to the localized unpaired electron in Ti-3d orbital of the r-Ti 3 C 2 T x crystal and increase in the number of unsaturated Ti atoms upon l-ascorbic acid treatment. Chemical reduction via l-ascorbic acid treatment shows a promising pathway towards the modulation and enhancement of magnetism in various MXene materials for the development of 2D metallic soft ferromagnets and spintronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Widespread opportunities for materials engineering of nanocrystals: Synthetically tailorable effects and methodologies

Since their initial development, semiconductor nanocrystals (NCs) and metal nanoparticles (NPs) have become widely utilized in a variety of applications, including solar energy harvesting, lighting, catalysis, biomedical imaging, and targeted cancer treatments. Because of their reduced dimensionality, NCs and NPs have vastly different optical and electronic properties than their bulk counterparts, and the properties often depend heavily on the NC or NP surface. Surface defects and ligands alter the optoelectronic properties of NCs and NPs and affect their interaction with the environment, allowing tailoring of their properties without changing the overall chemical composition. In this review, we discuss research progress focusing on optoelectronic properties of NPs and NCs and their respective applications. We highlight how different surface treatments and ligand functionalization of nanomaterials can influence these applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A general flame aerosol route to high-entropy nanoceramics

High-entropy ceramics are an emerging class of materials with fascinating characteristics. However, elemental immiscibility and crystal complexity limit the development of a general synthesis strategy, and common methods yield bulk materials. Here, we introduce a transformative non-equilibrium flame aerosol technique for synthesizing high-entropy nanoceramics. This scalable, one-step process enables the production of high-entropy oxide nanoceramics with an unprecedented diversity of crystal structures, including fluorite-phase materials that integrate up to 22 distinct cation elements. The method’s capacity for entropic stabilization and grain refinement significantly improves the thermal stability of these nanostructures. In a representative application, a Pt-(MgCoNiCuZn)O high-entropy single-atom catalyst showed superior activity and long-term stability, maintaining constant CO 2 conversion over 670 h and dramatically outperforming conventional catalysts. Finally, the general approach opens a vast composition and structure space for the creation of high-entropy oxide nanomaterials for application across diverse fields, including catalysis, energy storage, sensing, and thermal management.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Development of carbon nanosensor for vinpocetine at zinc oxide modified carbon matrix with anionic surfactant for clinical application

A nano-level sensing method was formulated for the trace-level detection and determination of vinpocetine (VIN) at a zinc oxide nanomaterial-based carbon matrix with immobilised anionic surfactant sodium dodecyl sulfate (ZnO-SDS/CPE) using cyclic voltammetry (CV) and square wave voltammetry (SWV) approaches. The catalytic properties of ZnO impact the electron rate of VIN activity, resulting in a threefold increase in the VIN peak response with the ZnO-SDS-modified sensor. Here, the effects of several factors, including scan rate, pH, accumulation length, modifier amount, and concentration, were investigated on the VIN peak current. The electro-oxidation of VIN by pH study involves one proton and one electron. The CV method also investigated the effect of scan rate. The charge transfer coefficient (α) is obtained to be 0.58, and the heterogeneous rate constant (k°) is estimated to be 4.46 s⁻¹. The concentration effect of VIN was studied using the SWV method. Specifically, the SWV methodology achieved the lowest detection limit compared to previously published approaches, with estimated values of the Limit of Detection (LOD) and Limit of Quantification (LOQ) being 2.2 × 10⁻⁸ M and 7.7 × 10⁻⁸ M, respectively. The trace level of VIN in tablet and urine samples was determined using the modified sensor. Moreover, the sensor demonstrates particular reproducibility and long-term stability, making it suitable for real-time applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Atomistic insights into the synergistic effects of tensile strain and hydroxyl group on increasing the thermal conductivity of monohydric alcohols as latent heat storage materials

The low thermal conductivity of linear monohydric alcohols significantly limits their performance when used as latent heat storage materials. It was found that imposing certain mechanical strains on nanomaterials with highly ordered structures can lead to appreciable thermal conductivity enhancement. To explore the potential of enhancing the intrinsic thermal conductivity of monohydric alcohols, a simplified ideal crystal model was employed for molecular arrangement in this work. The variation of atomistic heat transfer as a function of tensile strains was exploited by non-equilibrium molecular dynamics simulations. Furthermore, the influence of stretching on the vibration density of states and the corresponding molecular morphology were revealed. The results suggested that the thermal conductivity of monohydric alcohols with such simplified ideal crystalline structures can increase by about 170 % at the strain of 0.1. The distance between neighboring interfaces was found to determine the energy of inter-molecular interactions at the crystal grain boundaries. The hydrogen bonds energy has not reached the critical value when increasing tensile strains from 0 to 0.1. In contrast, the strongest van der Walls interactions for alkanes were obtained at the strain of 0.06 where the interfacial distances of alkanes have achieved their equilibrium distances. In addition, the interfacial heat transfer coefficient of ideal crystal monohydric alcohols at hydroxyl interfaces was found to be threefold than that between methyl interfaces, in consistent with the strength of inter-molecular interactions between functional groups at the interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Enabling a novel approach to a controlled fabrication of 1D crystalline nanowires on suspended microstructures of arbitrary geometries using two direct-writing technologies

Recent progresses in additive manufacturing have inspired new technologies, such as direct laser writing technique, based on two-photon polymerization (2 PP), which complements and further enriches the nanofabrication tools portfolio. Here, we combine 2 PP and our mask-free scanning probe assisted ‘direct-write patterning’ (DWP) method to allow for: a) the fabrication of micro-bridge structures with sub-micrometer resolution, b) selective synthesis of crystalline ZnO nanowires at predefined locations, respectively. This synergistic approach enables cantilever probe patterning of catalysts directly on suspended micro-bridges for in-situ CVD growth of nanoscale material, in a templated manner. The study reported here represents the first proof-of-concept experiments demonstrating versatile and scalable methodology, which can be applied and straightforwardly extended to grow a variety of other nanomaterials, in a controlled and selective fashion, on freestanding micro/nanoscale structures, whose size and geometry can be conveniently varied via templating of sacrificial 2 PP polymeric scaffolds. Furthermore, the demonstration of the possibility to integrate this new approach with the conventional lithography techniques provides a step forward to the development of the novel class of hybrid polymer-silicon-1D or -2D materials, and systems. The quality of the produced ZnO nanowire assemblies was assessed using several physical characterization methods.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Expanding the interlayer spacing of MXene through nanoarchitecture design

MXenes, a diverse class of two-dimensional transition metal carbides and nitrides with distinct surface chem istries, offer remarkable electrochemical and physicochemical properties. Yet, their performance can be hindered by the intrinsic restacking of layers, which restricts surface activity. This review outlines recent advances in interlayer spacing modulation strategies designed to overcome this limitation. A wide range of guest spe cies–including mono- and polyatomic ions, small molecules, low-dimensional nanomaterials, and polymers–are discussed with respect to their intercalation mechanisms, structural effects, and capacity to introduce functional enhancements. These intercalating species interact with MXene via electrostatic forces, hydrogen bonding, redox reactions, or covalent linkages, resulting in stable, expanded nanoarchitectures. The influence of expanded spacing on capacitive behavior is briefly highlighted to illustrate its practical relevance. Although Ti 3 C 2 T x is currently the most extensively investigated MXene, applying these interlayer engineering strategies to other MXene compositions will be essential for accessing a wider range of properties and functionalities.

36 MATERIALS SCIENCE↗