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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Hierarchical ZnO Nanowire Growth with Tunable Orientations on Versatile Substrates Using Atomic Layer Deposition Seeding

The ability to synthesize semiconductor nanowires with deterministic and tunable control of orientation and morphology on a wide range of substrates, while high precision and repeatability are maintained, is a challenge currently faced for the development of many nanoscale material systems. Here we show that atomic layer deposition (ALD) presents a reliable method of surface and interfacial modification to guide nanowire orientation on a variety of substrate materials and geometries, including high-aspect-ratio, three-dimensional templates. We demonstrate control of the orientation and geometric properties of hydrothermally grown single crystalline ZnO nanowires via the deposition of a ZnO seed layer by ALD. The crystallographic texture and roughness of the seed layer result in tunable preferred nanowire orientations and densities for identical hydrothermal growth conditions. The structural and chemical relationship between the ALD layers and nanowires was investigated with synchrotron X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy to elucidate the underlying mechanisms of orientation and morphology control. The resulting control parameters were utilized to produce hierarchical nanostructures with tunable properties on a wide range of substrates, including vertical micropillars, paper fibers, porous polymer membranes, and biological substrates. This illustrates the power of ALD for interfacial engineering of heterogeneous material systems at the nanoscale, to provide a highly controlled and scalable seeding method for bottom-up synthesis of integrated nanosystems.

ALD↗
DOE OSTI2016

Organic–Inorganic Perovskites: Structural Versatility for Functional Materials Design

Although known since the late 19th century, organic–inorganic perovskites have recently received extraordinary research community attention because of their unique physical properties, which make them promising candidates for application in photovoltaic (PV) and related optoelectronic devices. In this review, we will explore beyond the current focus on three-dimensional (3-D) lead(II) halide perovskites, to highlight the great chemical flexibility and outstanding potential of the broader class of 3-D and lower dimensional organic-based perovskite family for electronic, optical, and energy-based applications as well as fundamental research. The concept of a multifunctional organic–inorganic hybrid, in which the organic and inorganic structural components provide intentional, unique, and hopefully synergistic features to the compound, represents an important contemporary target.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Versatile Nature of Oxygen Vacancies in Bismuth Vanadate Bulk and (001) Surface

Bismuth vanadate (BiVO 4 ) has emerged as one of the most promising photoanode materials for solar fuel production. Oxygen vacancies play a pivotal role in the photoelectrochemical efficiency, yet their electronic nature and contribution to n-type conductivity are still under debate. Using first-principles calculations, we show that oxygen vacancies in BiVO 4 have two distinguishable geometric configurations characterized by either undercoordinated, reduced V IV O 3 and Bi II O 7 subunits or a V IV –O–V IV/V bridge (split vacancy), quenching the oxygen vacancy site. While both configurations have similar energies in the bulk, the (001) subsurface acts like an energetic sink that stabilizes the split oxygen vacancy by ~1 eV. In conclusion, the barrierless creation of a bridging V 2 O 7 unit allows for partial electron delocalization throughout the near-surface region, consistent with recent experimental observations indicating that BiVO 4 (001) is an electron-rich surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Polymer Nanoparticle Assemblies: A Versatile Route to Functional Mesostructures

Fabricating macromolecular mesoscale assemblies containing disparate components with targeted molecular order for each of the components on the nanoscale and targeted assembly of the components in the mesoscale is a challenge. In this Perspective, we explore the self-assembly of polymer nanoparticles as a viable route to obtain tunable mesostructured materials. Here, we describe the state-of-the-art methods available for and the challenges to obtain spherical and nonspherical polymer nanoparticles. We discuss the predicted ordered assemblies and disordered assemblies of nanoparticles and the challenges to obtain these assemblies in polymer nanoparticles. We also comment on the rich and future opportunities in the burgeoning field of polymer nanoparticle assemblies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Versatile Synthesis of Amine-Reactive Microgels by Self-Assembly of Azlactone-Containing Block Copolymers

Relations between molecular design, chemical functionality, and stimulus-triggered response are important for a variety of applications of polymeric systems. In this paper, reactive amphiphilic block copolymers (BCPs) of poly(2-vinylpyridine)-block-poly(2-vinyl-4,4-dimethylazlactone) (PVP-b-PVDMA) were synthesized and assembled into microgels capable of incorporating functional amines. The composition of the PVP-b-PVDMA BCPs was varied to control the number of reactive sites in the spherical aggregates created by self-assembly of PVP-b-PVDMA BCPs in a 2-propanol/THF (v:v = 19:1) solvent mixture, which is selective for PVP. PVDMA and PVP segments were selectively cross-linked by 1,4-diaminobutane (DAB) or 1,4-diiodobutane (DIB) to fabricate core- and corona-cross-linked azlactone-containing microgels, respectively. Non-cross-linked aggregates of PVP-b-PVDMA and DIB-cross-linked microgels dissociate when exposed to THF, which is a good solvent for both blocks. However, the DAB-cross-linked BCP microgels swell in THF, suggesting the formation of a stable, three-dimensional network structure. Finally, because of their ability to be reactively modified in ways that allows their stability or disassembly characteristics to be tailored, these azlactone-containing BCP microgels provide an attractive platform for applications in a wide range of fields, including catalysis, imaging, molecule separation, and guest loading for targeted delivery.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A Convenient and Versatile Method To Control the Electrode Microstructure toward High-Energy Lithium-Ion Batteries

Control over porous electrode microstructure is critical for the continued improvement of electrochemical performance of lithium ion batteries. This paper describes a convenient and economical method for controlling electrode porosity, thereby enhancing material loading and stabilizing the cycling performance. Sacrificial NaCl is added to a Si-based electrode, which demonstrates an areal capacity of ~4 mAh/cm 2 at a C/10 rate (0.51 mA/cm 2 ) and an areal capacity of 3 mAh/cm 2 at a C/3 rate (1.7 mA/cm 2 ), one of the highest material loadings reported for a Si-based anode at such a high cycling rate. X-ray microtomography confirmed the improved porous architecture of the SiO electrode with NaCl. The method developed here is expected to be compatible with the state-of-the-art lithium ion battery industrial fabrication processes and therefore holds great promise as a practical technique for boosting the electrochemical performance of lithium ion batteries without changing material systems.

25 ENERGY STORAGE↗
DOE OSTI2019

[(MeCN) 3 Co(C 2 F 5 ) 3 ]: A Versatile Precursor to Cobalt(III) Perfluoroethyl Complexes

The air-stable [fac-(MeCN) 3 Co(C 2 F 5 ) 3 ] (1) was prepared through the reaction of cobalt(II) bromide with [Me 3 Si-C 2 F 5 ] and AgF. Upon reaction of 1 with wet pyridine, the unexpected product [fac-(H 2 O) 3 Co(C 2 F 5 ) 3 ·6 pyridine] (2) was formed in which water coordinates to cobalt instead of pyridine, and the pyridines form short contacts with each of the hydrogen atoms in the bound water molecules. Facile exchange of the bound acetonitrile ligands in 1 with terpyridine (tpy) and bipyridine (bpy) did occur, however, affording [(tpy)Co(C 2 F 5 ) 3 ] (5) and [(bpy)Co(C 2 F 5 ) 3 (MeCN)] (6) in high yields.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Versatile Liquid Crystal Elastomer Formulations Using Amine-Acrylate Chemistry and Processing for Advanced Manufacturing

This study aims to tune rheological properties of liquid crystal elastomers (LCEs) through a strategic approach, leveraging the differing reaction rates of thiols and primary and secondary amines with acrylate monomers or the inclusion of processing additives to enable amenability to advanced manufacturing. We found that varying the time of oligomerization at elevated temperatures of amine-functional monomers with acrylate-functional monomers enabled simple control of rheological properties. Additionally, we could also control rheological properties by introducing reinforcing fillers or organic solvents. By varying the oligomerization conditions, we achieved a broad range of viscosities, from 1.1 Pa s to 560 Pa s as measured at 60 °C. When the rheological properties were varied through the incorporation of various solid and liquid inclusions, viscosities could range from less than 1 Pa s to nearly 1000 Pa s when measured at 60 °C. The shape morphing capabilities that are intrinsic to LCEs and the mechanical properties were also characterized. Here, we find that the oligomerization conditions and the addition of fillers influence shape morphing and energy absorption, as characterized by the stress–strain characteristics, further suggesting their potential to be used in energy dissipation applications where performance can be turned. Last, we demonstrate how the range of accessible rheological properties grants formulations amenable to various advanced manufacturing techniques.

Liquid chromatography↗
DOE OSTI2026

A Versatile Method for Creating Ultrathin Films of Polyzwitterions with Antifouling Properties

Protein repellent (i.e., antifouling) properties of ultrathin polymeric films have been ascribed to the formation of a dense layer of adsorbed polymers, which causes steric hindrance to protein adsorption on underlying substrates. The antifouling properties of the films are hypothesized to be independent of polymer hydrophilicity based on previous studies involving uncharged polymers. Here, to test the hypothesis and extend it to the realm of charged polymers, we have developed a grafting method for creating ultrathin layers of polyzwitterions on solid surfaces. To demonstrate the efficacy of this method, poly[1-(3-sulfopropyl-1)-2-vinylpyridinium betaine] (P2VPPS) was synthesized via free-radical polymerization and immobilized onto surfaces by using a photoreactive benzophenone derivative as the cross-linker, which was covalently bonded to either quartz or Si/SiOx substrates through a silane anchor. We found that ultrathin films with thicknesses of less than 10 nm can be obtained in dry states using 365 nm ultraviolet (UV) cured/cross-linked surface coatings. These films were found to be hydrophilic and undergo structural rearrangements in the presence of water. The antifouling performance of the films was evaluated using Pseudomonas aeruginosa strain PAO1 bacterium as the fouling agent and exhibited antifouling properties with a kinetic control via the coating method (i.e., spin-coating and drop-casting). In particular, the surface area coverages due to the PAO1 cell attachment on the quartz substrates coated with P2VPPS were found to be ∼5% and ∼0% for the spin-coated and drop-casted films, respectively, after 4 h. These results show that the grafting method can be used to generate surfaces with antifouling properties based on ultrathin films of polyzwitterions.

Pseudomonas aeruginosa↗
DOE OSTI2024

Monodisperse Cu Nanoparticles Supported on a Versatile Metal–Organic Framework for Electrocatalytic Reduction of CO 2

Rare-earth metal–organic frameworks (REMOFs) based on polynuclear metal clusters are an emerging class of materials that have shown promise for CO 2 capture and conversion. Here, in this work, copper nanoparticles (CuNPs) were successfully installed on a cluster-based Y(III) MOF to yield a composite material, CuNP-Y-TBAP. The abundance of Cu binding sites on the Y(III) clusters allowed a remarkably high Cu loading to be achieved, and electron microscopy demonstrated that the MOF-supported CuNPs are exceptionally small and monodisperse. CuNP-Y-TBAP was found to be an active heterogeneous catalyst for electrochemical reduction of CO 2 , yielding CO and CH 4 as the primary CO 2 reduction products.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Versatile Ligand-Exchange Method for the Synthesis of Water-Soluble Monodisperse AuAg Nanoclusters for Cancer Therapy

A general-applicable two-phase ligand exchange method is developed to prepare a series of monodisperse water-soluble AuAg nanoclusters. This method relies on the ligand exchange of the water-soluble ligands (e.g., tiopronin, captopril, N-acetyl-l-cysteine, 4-mercaptobenzoic acid, glutathione, and mercaptosuccinic acid) with phenylacetylene and triphenylphosphine co-protected AuAg precursors. Both polyacrylamide gel electrophoresis (PAGE) and transmission electron microscopy (TEM) indicate the monodispersity and ultrasmall size of the prepared water-soluble metal nanoclusters. In addition, the structure has also been characterized by UV–vis absorption spectroscopy, extended X-ray absorption fine structure (EXAFS), electrospray ionization time-of-flight mass spectra (ESI-TOF-MS), etc. The preliminary application of the as-prepared AuAg nanoclusters protected with tiopronin has been explored via the postmodification of the carboxyl groups of thiols with doxorubicin (DOX).

60 APPLIED LIFE SCIENCES↗