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At least 289 records · Page 16

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DOE OSTI2020

Rapid growth of anthropogenic organic nanoparticles greatly alters cloud lifecycle in the Amazon rainforest

Atmospheric nanoparticles can significantly influence Earth’s climate if they grow to sizes large enough to nucleate cloud droplets. While the contribution of extremely low volatility vapors to nanoparticle growth has been discussed extensively, the role of semivolatile organics has been largely overlooked. Here we examine the growth and impacts of air pollution nanoparticles from an isolated metropolis amidst the Amazon rainforest. Although extremely low volatility organics are necessary for the initial growth of nanoparticles, model analysis suggests that dynamic gas-particle partitioning of semivolatile oxidation products of anthropogenic and natural hydrocarbons is predominantly responsible for the observed rapid growth to 50 nm. Furthermore, cloud-resolving simulations demonstrate that the grown particles appreciably modify shallow cloud droplet size distribution, suppress precipitation, and enhance the transition to deep clouds. With condensable semivolatile organics typically formed in greater proportion, similar nanoparticle growth and impacts on clouds could likely occur in heavily urbanized forested regions globally.

Zaveri, Rahul A↗

DOE OSTI2020

DATASET: Rapid growth of anthropogenic organic nanoparticles greatly alters cloud lifecycle in the Amazon rainforest

Zaveri, Rahul A↗

DOE OSTI2025

Signal Differentiation of Moving Magnetic Nanoparticles for Enhanced Biodetection and Diagnostics

Magnetic nanoparticles are extensively utilized as markers/signal labelling in various biomedical applications. Detecting and distinguishing magnetic signals from similarly sized moving magnetic nanoparticles in microfluidic systems is crucial yet challenging for biosensing. In this study, we have developed an original method to detect and differentiate magnetic signals from moving superparamagnetic (SPM) and ferrimagnetic (FM) nanoparticles of comparable sizes. Our approach utilizes a highly sensitive magnetic-coil-based sensor that harnesses the combined effects of giant magnetoimpedance (GMI) and an LC-resonance circuit, offering performance superior to that of conventional GMI sensors. Iron oxide nanoparticles, which have similar particle sizes but differing coercivities (zero for SPM and non-zero for FM) or similar zero coercivities but differing particle sizes, flow through the magnetic coil at controlled velocities. Their distinct effects are analyzed through changes in the complex impedance of the sensing system. Our findings provide a unique pathway for utilizing SPM and FM nanoparticles as innovative magnetic markers to identify specific biological entities, thereby expanding their potential applications.

Hwang, Kee Young↗

DOE OSTI2024

Optimization and Multimachine Learning Algorithms to Predict Nanometal Surface Area Transfer Parameters for Gold and Silver Nanoparticles

Interactions between gold metallic nanoparticles and molecular dyes have been well described by the nanometal surface energy transfer (NSET) mechanism. However, the expansion and testing of this model for nanoparticles of different metal composition is needed to develop a greater variety of nanosensors for medical and commercial applications. In this study, the NSET formula was slightly modified in the size-dependent dampening constant and skin depth terms to allow for modeling of different metals as well as testing the quenching effects created by variously sized gold, silver, copper, and platinum nanoparticles. Overall, the metal nanoparticles followed more closely the NSET prediction than for Förster resonance energy transfer, though scattering effects began to occur at 20 nm in the nanoparticle diameter. To further improve the NSET theoretical equation, an attempt was made to set a best-fit line of the NSET theoretical equation curve onto the Au and Ag data points. An exhaustive grid search optimizer was applied in the ranges for two variables, 0.1≤C≤2.0 and 0≤α≤4, representing the metal dampening constant and the orientation of donor to the metal surface, respectively. Three different grid searches, starting from coarse (entire range) to finer (narrower range), resulted in more than one million total calculations with values C=2.0 and α=0.0736. The results improved the calculation, but further analysis needed to be conducted in order to find any additional missing physics. With that motivation, two artificial intelligence/machine learning (AI/ML) algorithms, multilayer perception and least absolute shrinkage and selection operator regression, gave a correlation coefficient, R2, greater than 0.97, indicating that the small dataset was not overfitting and was method-independent. This analysis indicates that an investigation is warranted to focus on deeper physics informed machine learning for the NSET equations.

Demers, Steven M. E. (ORCID:0000000192213246)↗

DOE OSTI2024

Rapid Prototyping for Nanoparticle-Based Photonic Crystal Fiber Sensors

The advent of nanotechnology has motivated a revolution in the development of miniaturized sensors. Such sensors can be used for radiation detection, temperature sensing, radio-frequency sensing, strain sensing, and more. At the nanoscale, integrating the materials of interest into sensing platforms can be a common issue. One promising platform is photonic crystal fibers, which can draw in optically sensitive nanoparticles or have its optical properties changed by specialized nanomaterials. However, testing these sensors at scale is limited by the the need for specialized equipment to integrate these photonic crystal fibers into optical fiber systems. Having a method to enable rapid prototyping of new nanoparticle-based sensors in photonic crystal fibers would open up the field to a wider range of laboratories that could not have initially studied these materials in such a way before. This manuscript discusses the improved processes for cleaving, drawing, and rapidly integrating nanoparticle-based photonic crystal fibers into optical system setups. The method proposed in this manuscript achieved the following innovations: cleaving at a quality needed for nanoparticle integration could be done more reliably (≈100% acceptable cleaving yield versus ≈50% conventionally), nanoparticles could be drawn at scale through photonic crystal fibers in a safe manner (a method to draw multiple photonic crystal fibers at scale versus one fiber at a time), and the new photonic crystal fiber mount was able to be finely adjusted when increasing the optical coupling before inserting it into an optical system (before, expensive fusion splicing was the only other method).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

Binder-free and carbon-free nanoparticle containing component, methods and applications

A method for forming an adherent metal based nanoparticle material layer upon a substrate includes an electrophoretic deposition method for depositing a metal nanoparticle material layer upon the substrate. The metal nanoparticle material layer may then be treated to form the adherent metal based nanoparticle material layer comprising a material selected from the group consisting of a metal oxide material, a metal nitride material, a metal oxynitride material and a metal chalcogenide material. The method is particularly useful for fabricating a battery electrode comprising a Co3O4 nanoparticle material layer, for use within a lithium ion battery. Other applications include fuel cells, capacitors and catalytic reactors.

Robinson, Richard D.↗

DOE OSTI2020

Copper nanoparticle structures for reduction of carbon dioxide to multicarbon products

This disclosure provides systems, methods, and apparatus related to copper nanoparticle structures for reduction of carbon dioxide to multicarbon products. In one aspect, a method includes providing a plurality of copper nanoparticles. The plurality of copper nanoparticles are deposited on a support. The plurality of copper nanoparticles are transformed to a plurality of copper structures during an operation in which carbon dioxide is reduced. The plurality of copper nanoparticles on the support are used as a working electrode in an electrochemical cell during the operation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Metal nanoparticle-decorated nanotubes for gas sensing

Disclosed herein are methods of producing metal nanoparticle-decorated carbon nanotubes. The methods include forming a reaction mixture by combining a first solution with a second solution, wherein the first solution comprises polymer-coated metal nanoparticles comprising metallic nanoparticles coated with a polymer, and wherein the second solution comprises carbon nanotubes. The methods also include heating the reaction mixture to a temperature greater than a glass transition temperature of the polymer for a time sufficient to cause the polymer-coated metal nanoparticles to bind to the carbon nanotubes forming the metal nanoparticle-decorated carbon nanotubes.

Iftime, Gabriel↗

DOE OSTI2023

X-Ray Absorption Spectroscopy (XAS): Surface Structural Determination of Alloy Nanoparticles

In catalysis since reactions occur on the surface of nanoparticles (NP), it is essential to determine the composition of this structure, rather than that of the nanoparticles, since the two may be, and often are, different. Conventional techniques including X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) are powerful techniques, but these data reflect the average composition of the entire particle. In this chapter, we introduce the method of EXAFS analysis, which isolates the surface atoms of nanoparticles based on its sensitivity to chemical reactions, specifically surface oxidation. As shown in our case studies, if the surface of a Pt-based nanoparticle is contacted by air at room temperature, the surface will selectively oxidize, resulting in the loss of Pt-Pt and Pt-M bonds to the formation of Pt-O bonds. The difference between the completely reduced and surface-oxidized nanoparticle allows for the isolation of signal from the catalytic surface. Although these examples highlight Pt alloys, similar analysis is also possible for other group 8 and IB bimetallic catalysts.

Zhang, Guanghui↗

DOE OSTI2023

Overcoming Barriers Associated with Oral Delivery of Differently Sized Fluorescent Core‐Shell Silica Nanoparticles

Oral delivery, while a highly desirable form of nanoparticle-drug administration, is limited by challenges associated with overcoming several biological barriers. Here, in this study, the authors study how fluorescent and poly(ethylene glycol)-coated (PEGylated) core-shell silica nanoparticles sized 5 to 50 nm interact with major barriers including intestinal mucus, intestinal epithelium, and stomach acid. From imaging fluorescence correlation spectroscopy studies using quasi-total internal reflection fluorescence microscopy, diffusion of nanoparticles through highly scattering mucus is progressively hindered above a critical hydrodynamic size around 20 nm. By studying Caco-2 cell monolayers mimicking the intestinal epithelia, it is observed that ultrasmall nanoparticles below 10 nm diameter (Cornell prime dots, [C’ dots]) show permeabilities correlated with high absorption in humans from primarily enhanced passive passage through tight junctions. Particles above 20 nm diameter exclusively show active transport through cells. After establishing C’ dot stability in artificial gastric juice, in vivo oral gavage experiments in mice demonstrate successful passage through the body followed by renal clearance without protein corona formation. Results suggest C’ dots as viable candidates for oral administration to patients with a proven pathway towards clinical translation and may generate renewed interest in examining silica as a food additive and its effects on nutrition and health.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Plasma catalytic ammonia synthesis on Ni nanoparticles: The size effect

Herein we demonstrate the synthesis of ammonia via atmospheric DBD plasma discharge over nickel nanoparticles supported on silica. We evaluated the performance of nickel nanoparticles with average sizes of 5.6nm and 13.5 nm. The smallest nanoparticle size sample resulted in an ammonia synthesis rate at least 2 times higher than that of the larger nanoparticle size sample and nickel bulk at equimolar composition. This allowed us to observe experimentally, for the first time, the size effect in the area of plasma catalysis. Moreover, the presented results allowed us to investigate a hydrogen sink metal such as nickel under atmospheric plasma conditions and determine the gas composition that resulted beneficial for this surface chemistry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

Annealing-Driven Phase Control Enables Plasmonic Tunability in Alloy Nanoparticles

A critical aspect of designing and realizing useful solid state materials is controlling phase and structure to tailor physical properties. While common for semiconductor and quantum materials, plasmonic materials have inhabited a narrow phase space typically comprising one or two elements, e.g., face-centered cubic metals. While this simplicity has enabled robust use and understanding of Au and Ag nanoparticles, it has also limited the design and manipulation of solid state properties. Here, we show that by tuning the phase and elemental composition of binary Au−Sn nanoparticles, the steady-state absorbance and ultrafast thermalization properties of plasmonic nanoparticles can be controlled. Solid state characterization suggests this is due to the dealloying of Sn and destabilization of the AuSn phase, leading to higher quality Au 5 Sn intermetallic phases alongside Au. Consequently, this work shows that phase control can profoundly influence the properties of plasmonic nanoparticles, providing important tunability for applications in catalysis, photothermal heating, and sensing.

Gold↗

DOE OSTI2020

Selective Lanthanide Sensing with Gold Nanoparticles and Hydroxypyridinone Chelators

The octadentate hydroxypyridinone chelator 3,4,3-LI(1,2-HOPO) is a promising therapeutic agent because of its high affinity for f-block elements and noncytotoxicity at medical dosages. The interaction between 3,4,3-LI(1,2-HOPO) and other biomedically relevant metals such as gold, however, has not been explored. Gold nanoparticles functionalized with chelators have demonstrated great potential in theranostics, yet thus far, no protocol that combines 3,4,3-LI(1,2-HOPO) and colloidal gold has been developed. Here, we characterize the solution thermodynamic properties of the complexes formed between 3,4,3-LI(1,2-HOPO) and Au 3+ ions and demonstrate how under specific pH conditions the chelator promotes the growth of gold nanoparticles, acting as both reducing and stabilizing agent. 3,4,3-LI(1,2-HOPO) ligands on the nanoparticle surface remain active and selective toward f-block elements, as evidenced by gold nanoparticle selective aggregation. Finally, a new colorimetric assay capable of reaching the detection levels necessary for the quantification of lanthanides in waste from industrial processes is developed based on the inhibition of particle growth by lanthanides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Role of Oxidizing Conditions in the Dispersion of Supported Platinum Nanoparticles Explored by Ab Initio Modeling

Achieving fine control over the dispersion of supported platinum nanoparticles (Pt) is a promising avenue to enhancing their catalytic activity and selectivity. Experimental observations suggest that exposing ceria-supported Pt nanoparticles to O 2 at 500 °C promotes their dispersion into smaller particles and eventually single atoms. The exact role of oxygen in this process is not yet well understood. Past density functional theory studies of ceria-supported Pt have typically narrowed their scope to single atoms and clusters of a few atoms. Herein, we combine several approaches and types of models in a consistent atomistic framework to evaluate the relative stability of ceria-supported Pt as a function of the degree of oxidation of Pt and of the particle size, ranging from single atoms to nanoparticles 1.5 nm of diameter. Finally, we find that the largest nanoparticles remain the thermodynamically most stable species on the lowest energy facet of ceria even under oxidizing conditions, suggesting that stronger adsorption sites are required to stabilize smaller clusters and single atoms and promote oxidative dispersion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Electron Radiation-Induced Nickel Nanoparticle Formation in KCl-ZnCl 2 Eutectic Molten Salt Using X-ray Absorption Spectroscopy

Understanding the speciation and local structure of metal solutes in molten salts is essential for predicting thermal properties and the redox and corrosion potentials of molten salts for next-generation nuclear reactors and concentrated solar power plant applications. Here, we employ X-ray absorption spectroscopy combined with electron paramagnetic resonance (EPR) measurements to investigate the effects of electron irradiation on 0.1 wt % NiCl 2 dissolved in molten eutectic KCl-ZnCl 2 salt. Radiation-driven reduction of Ni 2+ leading to nucleation and growth of Ni nanoparticles is studied as a function of electron dose (3–15 MGy) and temperature. Quantitative X-ray absorption near edge structure and linear combination fitting are utilized to investigate the extent of reduction as a function of the electron dose and temperature. A multiple-scattering (MS) approach is used for extended X-ray absorption fine structure analysis to deduce the size of the Ni nanoparticles formed and to understand the effect of the dose on the local structure of the nanoparticles. EPR studies on solidified NiCl 2 dissolved in molten eutectic KCl-ZnCl 2 salt show the formation of magnetic Ni nanoparticles.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Low-Frequency Oscillations in Optical Measurements of Metal-Nanoparticle Vibrations

Time-resolved optical measurements of vibrating metal nanoparticles have been used extensively to probe the ultrafast mechanical properties of the nanoparticles and of the surrounding liquid, but nearly all investigations so far have been limited to the linear regime. Herein, we report the observation of a low-frequency oscillating signal in transient-absorption measurements of nanoparticles with octahedral gold cores and cubic silver shells; the signal appears at the difference of two mechanical vibrational frequencies in the particles, suggesting a nonlinear mixing process. We tentatively attribute this proposed mixing to a nonlinear coupling between a vibrational mode of the nanoparticle and its optical-frequency plasmon resonance. The optimization of this nonlinear transduction may enable high-efficiency opto-mechanical frequency mixing in the GHz-THz frequency regime.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2020

Phase-Selective Epitaxial Growth of Heterophase Nanostructures on Unconventional 2H-Pd Nanoparticles

Heterostructured, including heterophase, noble-metal nanomaterials have attracted much interest due to their promising applications in diverse fields. However, great challenges still remain in the rational synthesis of well-defined noble-metal heterophase nanostructures. Furthermore, we report the preparation of Pd nanoparticles with an unconventional hexagonal close-packed (2H type) phase, referred to as 2H-Pd nanoparticles, via a controlled phase transformation of amorphous Pd nanoparticles. Impressively, by using the 2H-Pd nanoparticles as seeds, Au nanomaterials with different crystal phases epitaxially grow on the specific exposed facets of the 2H-Pd, i.e., face-centered cubic (fcc) Au (fcc-Au) on the (002)h facets of 2H-Pd while 2H-Au on the other exposed facets, to achieve well-defined fcc-2H-fcc heterophase Pd@Au core–shell nanorods. Moreover, through such unique facet-directed crystal-phase-selective epitaxial growth, a series of unconventional fcc-2H-fcc heterophase core–shell nanostructures, including Pd@Ag, Pd@Pt, Pd@PtNi, and Pd@PtCo, have also been prepared. Impressively, the fcc-2H-fcc heterophase Pd@Au nanorods show excellent performance toward the electrochemical carbon dioxide reduction reaction (CO 2 RR) for production of carbon monoxide with Faradaic efficiencies of over 90% in an exceptionally wide applied potential window from –0.9 to –0.4 V (versus the reversible hydrogen electrode), which is among the best reported CO 2 RR catalysts in H-type electrochemical cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Multicomponent Nanoparticle Synthesis for Advanced Manufactured Melt Wire Development

Additive manufacturing (AM) based direct-write technologies have emerged as a predominant enabler for the fabrication of advanced passive sensors in-pile applications. This work continues previous efforts with the modification and optimization of synthesis methods for multi-component nanoparticle systems used to support the development, fabrication and testing of AM sensors for peak temperature detection. For this report, bismuth, bismuth/platinum, tin, tin/silver, tin/zinc, indium, and indium/silver bi-metallic nanoparticles were synthesized using the wet chemical methods. The nanoparticles were then characterized with x-ray fluorescence to evaluate the elemental composition and differential scanning to determine the melting point and mass loss of the samples. Results continue to show that bi-metallic nanoparticles are a viable pathway for the fabrication of high-resolution AM melt wires.

36 MATERIALS SCIENCE↗