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At least 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Colloidal immobilized protein based on stable colloid of TiO 2 nanoparticles at neutral pH for protein microarray

A stable colloid of titanium dioxide nanoparticles was specially prepared at neutral pH so that horse radish peroxidase as a model protein can interact and be immobilized with colloidal titanium dioxide nanoparticles, while usually titanium dioxide colloid is only stable at acidic condition. Colloidal immobilized peroxidase based on titanium dioxide nanoparticles at neutral pH were highly active and stably dispersible in aqueous solution. The resulting colloidal immobilized peroxidase can be readily printed using a standard microarray printer for facile fabrication of protein microarrays. After printing, the colloidal immobilized protein formed uniform membrane of proteinated nanoparticles with 3-dimensional nanoconfiguration. Finally, the protein microarray sensitivity based on peroxidase-titanium dioxide nanoparticles was nearly 20 times as high as that using conventional technology.

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

Hairy nanoparticles by atom transfer radical polymerization in miniemulsion

Polymer nanoparticles with various architectures and functionalities are promising materials in numerous fields. Miniemulsion polymerization is one of the suitable pathways to prepare polymer nanoparticles since each droplet could act as a “nanoreactor”. A “smart” atom transfer radical polymerization (ATRP) catalytic system comprising Cu-TPMA/DS – (TPMA = tris(2-pyridylmethyl)amine, DS – = dodecyl sulfate anion) ion pair catalyst was efficiently applied in miniemulsion ATRP at low catalyst concentrations. Herein, hairy nanoparticles consisting of hydrophobic poly(n-butyl methacrylate) (P(BMA/EGDMA), EGDMA = ethylene glycol dimethacrylate) network “core” and hydrophilic oligo(ethylene oxide) methyl ether methacrylate (OEOMA) chains as “hair” were prepared by miniemulsion ATRP and a successive chain extension by aqueous ATRP from the particle surface. The addition of an inimer, 2-(α-bromoisobutyryloxy)ethyl methacrylate (HEMA-iBBr) to the P(BMA/EGDMA) network introduced more ATRP initiation sites for ATRP of OEOMA, enabling adjustment of the particle size from >400 nm to <150 nm. The miniemulsion system remained stable after the one pot synthesis of P(BMA/EGDMA)-g-POEOMA and P(BMA/EGDMA/HEMA-iBBr)-g-POEOMA, and the resulting polymer nanoparticles were re-dispersed in water for further modification. A zwitterionic monomer, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), was grafted from P(BMA/EGDMA/HEMA-iBBr)-g-POEOMA. The resulting hairy nanoparticles provide an avenue for the design and preparation of novel nanostructured materials.

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

Evaluation of Force Fields for Molecular Dynamics Simulations of Platinum in Bulk and Nanoparticle Forms

Here, understanding the size- and shape-dependent properties of platinum nanoparticles is critical for enabling the design of nanoparticle-based applications with optimal and potentially tunable functionality. Toward this goal, we evaluated nine different empirical potentials with the purpose of accurately modeling faceted platinum nanoparticles using molecular dynamics simulation. First, the potentials were evaluated by computing bulk and surface properties - surface energy, lattice constant, stiffness constants, and the equation of state - and comparing these to prior experimental measurements and quantum mechanics calculations. Then, the potentials were assessed in terms of the stability of cubic and icosahedral nanoparticles with faces in the {100} and {111} planes, respectively. Although none of the force fields predicts all the evaluated properties with perfect accuracy, one potential - the embedded atom method formalism with a specific parameter set - was identified as best able to model platinum in both bulk and nanoparticle forms.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Extraordinary Thermal Stability and Sinter Resistance of Sub-2 nm Platinum Nanoparticles Anchored to a Carbon Support by Selenium

Nanoparticle sintering has long been a major challenge in developing catalytic systems for use at elevated temperatures. Here we report an in situ electron microscopy study of the extraordinary sinter resistance of a catalytic system comprised of sub-2 nm Pt nanoparticles on a Se-decorated carbon support. When heated to 700 °C, the average size of the Pt nanoparticles only increased from 1.6 to 2.2 nm, while the crystal structure, together with the {111} and {100} facets, of the Pt nanoparticles was well retained. Our electron microscopy analyses suggested that the superior resistance against sintering originated from the Pt–Se interaction. Confirmed by energy-dispersive X-ray elemental mapping and electron energy loss spectra, the Se atoms surrounding the Pt nanoparticles could survive the heating. This work not only offers an understanding of the physics behind the thermal behavior of this catalytic material but also sheds light on the future development of sinter-resistant catalytic systems.

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

Magnetic and Optical Properties of Au–Co Solid Solution and Phase-Separated Thin Films and Nanoparticles

The chemical composition and morphology of Au x Co 1–x thin films and nanoparticles are controlled via a combination of cosputtering, pulsed laser-induced dewetting (PLiD), and annealing, leading to tunable magnetic and optical properties. Regardless of chemical composition, the as-deposited thin films and as-PLiD nanoparticles are found to possess a face-centered cubic (FCC) Au x Co 1–x solid-solution crystal structure. Annealing results in large phase-separated grains of Au and Co in both the thin films and nanostructures for all chemical compositions. The magnetic and optical properties are characterized via vibrating sample magnetometry (VSM), ellipsometry, optical transmission spectroscopy, and electron energy loss spectroscopy (EELS). Despite the exceptionally high magnetic anisotropy inherent to Co, the presence of sufficient Au (72 atom %) in the Au x Co 1–x solid solution results in superparamagnetic thin films. Among the as-PLiD nanoparticle samples, an increased Co composition leads to a departure from traditional ferromagnetism in favor of wasp-waisted hysteresis caused by magnetic vortices. Phase separation resulting from annealing leads to ferromagnetism for all compositions in both the thin films and nanoparticles. The optical properties of Au x Co 1–x nanostructures are also largely influenced by the chemical morphology, where the Au x Co 1–x intermixed solid solution has significantly damped plasmonic performance relative to pure Au and comparable to pure Co. Phase separation greatly enhances the quality factor, optical absorption, and electron energy loss spectroscopy (EELS) signatures. The enhancement of the localized surface plasmon resonances (LSPRs) scales with the reduction in Co composition, despite EELS evidence that excitation of the Co portions of a nanoparticle can provide a similar, and in some instances enhanced, LSPR resonance compared to Au. This behavior, however, is seemingly limited to the LSPR dipole mode, while higher-order modes are greatly damped by a Co aloof position. As a result, this observed magneto-plasmonic functionality and tunability could be applicable in biomedicine, namely, cancer therapeutics.

annealing (metallurgy)↗
DOE OSTI2014

Dendritic Assembly of Gold Nanoparticles during Fuel-Forming Electrocatalysis

We report on the dendritic assembly of alkanethiol-capped gold nanoparticles on a glassy carbon support during electrochemical reduction of protons and CO 2 . We discovered that the primary mechanism by which surfactant-ligated gold nanoparticles lose surface area is by taking a random walk along the support, colliding with their neighbors, and fusing to form dendrites, a type of fractal aggregate. A random walk model reproduces the fractal dimensionality of the dendrites observed experimentally. The rate at which the dendrites form is strongly dependent on the solubility of the surfactant in the electrochemical double layer under the conditions of electrolysis. Since alkanethiolate surfactants reductively desorb at potentials close to the onset of CO 2 reduction, they do not poison the catalytic activity of the gold nanoparticles. While catalyst mobility is typically thought to be limited for room-temperature electrochemistry, our results reflect that nanoparticle mobility is significant under conditions at which they electrochemically catalyze gas evolution, even in the presence of a high surface area carbon and binder. A careful understanding of the electrolyte- and polarization-dependent nanoparticle aggregation kinetics informs strategies for maintaining catalyst dispersion during fuel-forming electrocatalysis.

dendrons↗
DOE OSTI2015

Morphology and Activity Tuning of Cu 3 Pt/C Ordered Intermetallic Nanoparticles by Selective Electrochemical Dealloying

Improving the catalytic activity of Pt-based bimetallic nanoparticles is a key challenge in the application of proton-exchange membrane fuel cells. Electrochemical dealloying represents a powerful approach for tuning the surface structure and morphology of these catalyst nanoparticles. We present a comprehensive study of using electrochemical dealloying methods to control the morphology of ordered Cu 3 Pt/C intermetallic nanoparticles, which could dramatically affect their electrocatalytic activity for the oxygen reduction reaction (ORR). Depending on the electrochemical dealloying conditions, the nanoparticles with Pt-rich core–shell or porous structures were formed. We further demonstrate that the core–shell and porous morphologies can be combined to achieve the highest ORR activity. Lastly, this strategy provides new guidelines for optimizing nanoparticles synthesis and improving electrocatalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Covalently integrated silica nanoparticles in poly(ethylene glycol)-based acrylate resins: thermomechanical, swelling, and morphological behavior

Nanocomposites integrate functional nanofillers into viscoelastic matrices for electronics, lightweight structural materials, and tissue engineering. Herein, the effect of methacrylate-functionalized (MA-SiO 2 ) and vinyl-functionalized (V-SiO 2 ) silica nanoparticles on the thermal, mechanical, physical, and morphological characteristics of poly(ethylene glycol) (PEG) nanocomposites was investigated. The gel fraction of V-SiO 2 composites decreases upon addition of 3.8 wt% but increases with further addition (>7.4 wt%) until it reaches a plateau at 10.7 wt%. The MA-SiO 2 induced no significant changes in gel fraction and both V-SiO 2 and MA-SiO 2 nanoparticles had a negligible impact on the nanocomposite glass transition temperature and water absorption. The Young's modulus and ultimate compressive stress increased with increasing nanoparticle concentration for both nanoparticles. Due to the higher crosslink density, MA-SiO 2 composites reached a maximum mechanical stress at a concentration of 7.4 wt%, while V-SiO 2 composites reached a maximum at a concentration of 10.7 wt%. Scanning electron microscopy, transmission electron microscopy, and small-angle X-ray scattering revealed a bimodal size distribution for V-SiO 2 and a monomodal size distribution for MA-SiO 2 . Although aggregates were observed for both nanoparticle surface treatments, V-SiO 2 dispersion was poor while MA-SiO 2 were generally well-dispersed. Finally, these findings lay the framework for silica nanofillers in PEG-based nanocomposites for advanced manufacturing applications.

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

Regulating the Catalytic Activity of Pd Nanoparticles by Confinement in Ordered Mesoporous Supports

Studying structure-sensitive reactions requires the synthesis of catalytic nanoparticles with precisely controlled sizes. Here we demonstrate the facile production of size controlled Pd nanoparticles by confinement in the pores of mesoporous silica nanoparticles (MSN). We show that Pd particles 2.1 nm in size have a higher catalytic activity than larger nanoparticles for the Suzuki-Miyaura cross coupling between 4’-bromoacteophenone and phenyl boronic acid and for the hydrogenation of phenol in aqueous phase. The enhanced activity can be explained in terms of increased number of coordinatively unsaturated sites and higher back donation capacity of the small nanoparticles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Optical and Mechanical Properties of Nanocomposite Films Based on Polymethyl Methacrylate (PMMA) and Fumed Silica Nanoparticles

Nanocomposite polymer films are prepared by using ultrasonic spray deposition (USD) technique through mixing polymethyl methacrylate as matrix and fumed silica nanoparticles as second phase in dimethyl carbonate solvent. Annealing procedure improves the film uniformity and optical transmission. The addition of fumed silica nanoparticles impedes the transmission of the electrolyte films due to agglomeration of fumed silica nanoparticles. Adding surfactant, cetyltrimethylammonium bromide, disperses the fumed silica nanoparticles and retrieves the optical transmission of nanocomposite polymer films to around 90%. The hardness and elastic modulus of the nanocomposite polymer films are better than the commercial bulk. The USD deposited nanocomposite polymer film comprises of PMMA and fumed silica nanoparticles is a promising candidate of solid-state electrolyte for EC windows application.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Sculpting the Plasmonic Responses of Nanoparticles by Directed Electron Beam Irradiation

Spatial confinement of matter in functional nanostructures has propelled these systems to the forefront of nanoscience, both as a playground for exotic physics and quantum phenomena and in multiple applications including plasmonics, optoelectronics, and sensing. In parallel, the emergence of monochromated electron energy loss spectroscopy (EELS) has enabled exploration of local nanoplasmonic functionalities within single nanoparticles and the collective response of nanoparticle assemblies, providing deep insight into associated mechanisms. However, modern synthesis processes for plasmonic nanostructures are often limited in the types of accessible geometry, and materials and are limited to spatial precisions on the order of tens of nm, precluding the direct exploration of critical aspects of the structure-property relationships. Here, the atomic-sized probe of the scanning transmission electron microscope is used to perform precise sculpting and design nanoparticle configurations. Using low-loss EELS, dynamic analyses of the evolution of the plasmonic response are provided. It is shown that within self-assembled systems of nanoparticles, individual nanoparticles can be selectively removed, reshaped, or patterned with nanometer-level resolution, effectively modifying the plasmonic response in both space and energy. This process significantly increases the scope for design possibilities and presents opportunities for unique structure development, which are ultimately the key for nanophotonic design.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Role of Co{sub 3}O{sub 4} Nanoparticles in Dielectric Properties of Cu{sub 0.5}Tl{sub 0.5}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10-δ} Superconducting Phase

Cobalt oxide (Co{sub 3}O{sub 4}) nanoparticles and Cu{sub 0.5}Tl{sub 0.5}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10-δ} (CuTl-1223) superconducting phase were prepared by sol–gel and solid-state reaction methods, respectively. Co{sub 3}O{sub 4} nanoparticles were added in CuTl-1223 superconducting matrix to get (Co{sub 3}O{sub 4}){sub x}/CuTl-1223, x = 0–2.0 wt.%, nanoparticles–superconductor composites. The unchanged crystal structure of the host CuTl-1223 superconducting phase (i.e. tetragonal) revealed that Co{sub 3}O{sub 4} nanoparticles were settled at the grain boundaries. Superconducting properties of the CuTl-1223 phase were overall suppressed due to hole–charge carriers interaction at the grain boundaries. The dielectric properties of (Co{sub 3}O{sub 4}){sub x}/CuTl-1223 composites were investigated by varying the test frequencies from 40 Hz to 100 MHz and operating temperatures from 77 to 298 K. The values of dielectric properties were found maximal at lower frequencies and started to decrease at higher frequencies. So, the dielectric properties of the CuTl-1223 superconducting phase can be tuned by varying the contents of (Co{sub 3}O{sub 4}) nanoparticles, test frequencies as well as operating temperatures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Recovery of Chromium(III) from Tannery Wastewater by Nanoparticles and Whiskers of Chitosan

Chitosan, its nanoparticles and whiskers present an excellent capacity to complex chromium ions. However, this phenomenon is influenced by different parameters. In our search, we determined the appropriate range of pH to form chitosan–Cr(III), nanoparticles Cr(III) and whiskers–Cr(III) complex. We studied also the influence of chromium concentration and nature of chitosan-based materials on complexation process. Our main aim is approximate the optimal conditions to remove chromium(III) from tanning bath, recuperated from tannery wastewater of Marrakech in Morocco. However, the results of adsorption kinetic in tannery wastewater revealed that chitosan, its nanoparticles, whiskers and biocomposites are good sorbent of chromium as well, even if the adsorbed quantity is less compared to chromium solution. Although, according to ICP-OES analysis in this real effluent, nanoparticles are the best complexing ligand, after 24 h of contact nanoparticles can remove 70% of chromium from this tannery wastewater.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Preparation of Avermectin/Grafted CMC Nanoparticles and Their Sustained Release Performance

Avermectin (AVM) is a highly efficient pesticide against a variety of insects and is widely used in agriculture. However, it is susceptible to oxidation and photolysis, resulting in instability under UV irradiation and a short half-life. Herein, sodium carboxymethyl cellulose (CMC) was grafted by styrene (St), Methyl methacrylate (MMA) and butyl acrylate (BA) respectively to prepare grafted polymer nanoparticles in application for AVM sustained released. And the influence of different grafted monomer and the grafted rate on the AVM/grafted polymer nanoparticles performance was discussed. The larger the grafted rate of St was, the larger the particle size of AVM/grafted polymer nanoparticles had with a higher drug loading rate and stronger resistance to ultraviolet light. Besides, the particle size, drug loading rate and the ability of anti-ultraviolet light of grafted CMC emulsion was also influenced by the modifying agent. While the concentration of AVM was kept the same, the acrylic esters (MMA and BA) grafted emulsion have smaller particle sizes with higher drug loading rates and stronger anti-ultraviolet ability comparing to styrene (St) grafted emulsion. The effect of different amount of St and different monomer grafted on the sustained release performance of AVM/grafted polymer was also investigated. As the grafted rate of St increased, the release rate became smaller. The release speed has a sequence of CMC-g-PBA > CMC-g-PS > CMC-g-PMMA when CMC grafted with different monomer. Their sustained release curves can be described by Korsmeyer-Peppas equation. Finally, the insect toxicity test showed that insecticide toxicity against diamondback moth (Plutella xylostella L.) has no apparent difference among the AVM and AVM/grafted polymer nanoparticles indicating that AVM/grafted polymer nanoparticles can reduce the amount of organic solution used for dissolution and prolonged its service life without decreasing its insecticide toxicity.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2017

Preparation and Characterization of Magnetite–Chitosan Nanoparticles and Evaluation of Their Cytotoxicity Effects on MCF7 and Fibroblast Cells

Nowadays, magnetic nanoparticles play a key role in drug treatment. However, if they are uncoated, they might aggregate and cause embolism in drug delivery. To avoid this, they are generally coated with polymers. In this investigation, magnetic nanoparticles (MNPs) were coated with chitosan through in situ co-precipitation process and their properties in addition to their cytotoxicity in MCF7 and fibroblast cells were analyzed. The results showed MNPs–chitosan nanoparticles would contain an average mean diameter of 32 nm and a saturation magnetization (M{sub S}) value of 38.87 emu/g. To characterize the synthesized nanoparticles in terms of structural, morphological and magnetic properties, Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and vibrating sample magnetometry (VSM) studies were used. Toxicity test was also done to investigate whether their presence would cause any toxicity in the body; in addition, antibacterial assay was done to analyze if nanoparticles could be used as an antimicrobial agent.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Enhanced Photocatalytic Degradation of Methylene Blue Dye, Opto-magnetic and Antibacterial Behaviour of Pure and La-doped ZnO Nanoparticles

The different doping concentrations of lanthanum (La)-doped ZnO nanoparticles were synthesized successfully using zinc acetate and lanthanum nitrate via wet chemical method. Characterization of the prepared sample was done by standard analytical techniques such as powder x-ray diffraction analysis (P-XRD), high-resolution scanning electron microscopy (HR-SEM), energy-dispersive spectroscopy (EDS), Fourier transformer-infrared (FT-IR) spectroscopy, photoluminescence (PL) and UV-Vis spectroscopy (UV-Vis), and magnetic studies (VSM). The structural analysis has been carried out by powder x-ray diffraction. X-ray diffraction studies revealed that the nanoparticles are well-crystalline and possess hexagonal wurtzite structure. HR-SEM images showed the homogenous spherical-shaped morphology of the synthesized ZnO nanoparticles. EDS analysis confirmed the presence of La ions into ZnO lattice. The band gap (Eg) energy was determined by UV-Visible spectral data, and it was found that the Eg value decreases with increasing the La concentration into ZnO lattice. PL spectra confirmed that the effective La doping enhance the UV and visible region near band gap emission. The effect of La doping on the photocatalytic activity of ZnO nanoparticles for the degradation of methylene blue dye was studied under solar illumination and the results showed that the La doping kindles appreciable degradation of MB. The optical density measurements of the ZnO nanoparticles against both gram-positive (Bacillus subtilis, Staphylococcus aureus) as well as gram-negative bacteria (Proteus mirabilis, Salmonella typhi) showed better bacterial activity than pure ZnO. Moreover, it showed that higher dopant La in ZnO exhibit efficient antibacterial activity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Transition of Magnetic Characteristics from Paramagnetic State to Ferromagnetic Phase in Ce{sub 1−x}Ni{sub x}O{sub 2} Nanoparticles

Nowadays, oxide-based diluted magnetic semiconductor nanoparticles are the most reliable compounds, wherein they accommodate both spin as well as charge of the electron in single domain, means most preferable for the fabrication of spintronic devices. In this view, we report on new Ce{sub 1−x}Ni{sub x}O{sub 2} (x = 0.00, 0.02, 0.04, 0.06, and 0.08) nanoparticles prepared by precipitation method via polyethylene glycol as a surfactant. XRD analysis revealed that all the synthesized nanoparticles were crystallized in distinct FCC fluorite structure as that of CeO{sub 2} host lattice. Transmission electron microscopy analysis confirmed that all the synthesized samples were in spherical shape with average particle size of 8–10 nm, which is well concord with the grain size estimated from the Scherrer formula. The vibrating sample magnetometer evaluations suggested that pristine host lattice shows signals of paramagnetism; meanwhile, Ni substitution CeO{sub 2} nanoparticles exhibits strong ferromagnetism at room temperature. Particularly, 4% Ni-doped CeO{sub 2} samples shows enhanced ferromagnetism and which is suppressed with raising dopant concentration. The perceived magnetization with respect to the Ni dopant concentration is well anticipated by F-center exchange mechanism. We expect that the observations in this research suggest suitable path for preparing of various oxide-based diluted magnetic semiconductor nanoparticles and their applications in fabrication of spintronic devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Fe Substitution on Microstructure and Magnetic Properties of Ni{sub 1−x}Fe{sub x}O{sub 2} Nanoparticles

Fe-substituted NiO nanoparticles (Ni{sub 1−x}Fe{sub x}O{sub 2}) (x= 0.00, 0.03, 0.05, 0.07, and 0.09) were synthesised using ball-milling method followed by vacuum sintering and studied for their microstructural and magnetic properties. All the samples show a cubic structure with a crystallite size of 17–26 nm. Secondary phases related to Fe{sub 2}O{sub 3} were identified from XRD, indicating that the observed ferromagnetism may be due to the dopants. The doping of Fe ions does not cause any significant variation in the crystal structure. The pure NiO nanoparticles were weak ferromagnetic in nature, and Fe-doped NiO nanoparticles exhibit room temperature ferromagnetism. The strength of magnetization increased from 0.57 to 0.94 emu/g with an increase of Fe concentration from 3 to 7 at.%, respectively. A high coercive field of 173 Oe was observed for the Ni{sub 1−x}Fe{sub x}O{sub 2} nanoparticles at x= 0.09. The results and the process of development of ferromagnetism at room temperature in the Ni{sub 1−x}Fe{sub x}O{sub 2} nanoparticles were presented and discussed in detail.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗