Material Characterization Study of Magnetite Nanocrystals for RF Sensing.

Magnetite nanocrystals show promise for electrically small gigahertz frequency applications, which could lead to miniaturizing transformer cores and new sensing technologies. This work presents a rigorous radiofrequency characterization of these nanocrystals using vector network analyzer (VNA) ferromagnetic resonance (FMR) measurements. For the first time, two different average diameters of FeO nanocrystals are investigated (7.

Linkage Transformations in a Three-Dimensional Covalent Organic Framework for High-Capacity Adsorption of Perfluoroalkyl Substances.

Despite their many advantages, covalent organic frameworks (COFs) built from three-dimensional monomers are synthetically difficult to functionalize. Herein, we provide a new synthetic approach to the functionalization of a three-dimensional covalent organic framework (COF-300) by using a series of solid-state linkage transformations. By reducing the imine linkages of the framework to amine linkages, we produced a more hydrolytically stable material and liberated a nucleophilic amino group, poised for further functionalization.

Effect of manganese substitution of ferrite nanoparticles on particle grain structure.

To investigate the influence of manganese substitution on the saturation magnetization of manganese ferrite nanoparticles, samples with various compositions (Mn Fe O, = 0, 0.25, 0.5, 0.

Templated synthesis enhances the cobalt adsorption capacity of a porous organic polymer.

Divalent transition metals such as Co(II) are important targets for removal from water sources, due to their potential toxicity as well as their high value. In this study, we found that a series of porous organic polymers based on amide-linked tetraphenylmethane units are effective Co(II) ion adsorbents in aqueous solution. To increase the density of Co(II) binding sites, we then developed a templated synthesis in which the branched, rigid monomers are pre-assembled around Co(II) ions prior to polymerization.

Unravelling Magnetic Nanochain Formation in Dispersion for In Vivo Applications.

Self-assembly of iron oxide nanoparticles (IONPs) into 1D chains is appealing, because of their biocompatibility and higher mobility compared to 2D/3D assemblies while traversing the circulatory passages and blood vessels for in vivo biomedical applications. In this work, parameters such as size, concentration, composition, and magnetic field, responsible for chain formation of IONPs in a dispersion as opposed to spatially confining substrates, are examined. In particular, the monodisperse 27 nm IONPs synthesized by an extended LaMer mechanism are shown to form chains at 4 mT, which are lengthened with applied field reaching 270 nm at 2.

Faceted Branched Nickel Nanoparticles with Tunable Branch Length for High-Activity Electrocatalytic Oxidation of Biomass.

Controlling the formation of nanosized branched nanoparticles with high uniformity is one of the major challenges in synthesizing nanocatalysts with improved activity and stability. Using a cubic-core hexagonal-branch mechanism to form highly monodisperse branched nanoparticles, we vary the length of the nickel branches. Lengthening the nickel branches, with their high coverage of active facets, is shown to improve activity for electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF), as an example for biomass conversion.

Magnetic Tunability in RE-DOBDC MOFs via NO Acid Gas Adsorption.

The magnetic susceptibility of NO-loaded RE-DOBDC (rare earth (RE): Y, Eu, Tb, Yb; DOBDC: 2,5-dihydroxyterephthalic acid) metal-organic frameworks (MOFs) is unique to the MOF metal center. RE-DOBDC samples were synthesized, activated, and subsequently exposed to humid NO. Each NO-loaded MOF was characterized by powder X-ray diffraction, and the magnetic characteristics were probed by using a VersaLab vibrating sample magnetometer (VSM).

Antibacterial activity of iron oxide, iron nitride, and tobramycin conjugated nanoparticles against Pseudomonas aeruginosa biofilms.

Background: Novel methods are necessary to reduce morbidity and mortality of patients suffering from infections with Pseudomonas aeruginosa. Being the most common infectious species of the Pseudomonas genus, P. aeruginosa is the primary Gram-negative etiology responsible for nosocomial infections.

Formation of Branched Ruthenium Nanoparticles for Improved Electrocatalysis of Oxygen Evolution Reaction.

Branched nanoparticles are one of the most promising nanoparticle catalysts as their branch sizes and surfaces can be tuned to enable both high activity and stability. Understanding how the crystallinity and surface facets of branched nanoparticles affect their catalytic performance is vital for further catalyst development. In this work, a synthesis is developed to form highly branched ruthenium (Ru) nanoparticles with control of crystallinity.

Soft magnetic materials for a sustainable and electrified world.

Soft magnetic materials are key to the efficient operation of the next generation of power electronics and electrical machines (motors and generators). Many new materials have been introduced since Michael Faraday's discovery of magnetic induction, when iron was the only option. However, as wide bandgap semiconductor devices become more common in both power electronics and motor controllers, there is an urgent need to further improve soft magnetic materials.

Formation of Metal Nanoparticles Directly from Bulk Sources Using Ultrasound and Application to E-Waste Upcycling.

A method for creating nanoparticles directly from bulk metal by applying ultrasound to the surface in the presence of a two-part surfactant system is presented. Implosive collapse of cavitation bubbles near the bulk metal surface generates powerful microjets, leading to material ejection. This liberated material is captured and stabilized by a surfactant bilayer in the form of nanoparticles.

Reversible Magnetic Agglomeration: A Mechanism for Thermodynamic Control over Nanoparticle Size.

We present a method for the synthesis and precise size control of magnetic nanoparticles in a reversible magnetic agglomeration mechanism. In this approach, nanoparticles nucleate and grow until a critical susceptibility is reached, in which magnetic attraction overcomes dispersive forces, leading to agglomeration and precipitation. This phase change in the system arrests nanoparticle growth and gives true thermodynamic control over the size of nanoparticles.

Magnetic Nanocomposites and Their Incorporation into Higher Order Biosynthetic Functional Architectures.

A magnetically active FeO/poly(ethylene oxide)--poly(butadiene) (PEO--PBD) nanocomposite is formed by the encapsulation of magnetite nanoparticles with a short-chain amphiphilic block copolymer. This material is then incorporated into the self-assembly of higher order polymer architectures, along with an organic pigment, to yield biosynthetic, bifunctional optical and magnetically active FeO/bacteriochlorophyll /PEO--PBD polymeric chlorosomes.

Self-Assembled Layering of Magnetic Nanoparticles in a Ferrofluid on Silicon Surfaces.

This article describes the three-dimensional self-assembly of monodisperse colloidal magnetite nanoparticles (NPs) from a dilute water-based ferrofluid onto a silicon surface and the dependence of the resultant magnetic structure on the applied field. The NPs assemble into close-packed layers on the surface followed by more loosely packed ones. The magnetic field-dependent magnetization of the individual NP layers depends on both the rotational freedom of the layer and the magnetization of the adjacent layers.

Phase-sensitive small-angle neutron scattering experiment.

In the work reported herein, we investigate the practicality of a recently introduced variant of a general phase-sensitive method in small-angle neutron scattering that attempts to address the loss of phase-information as well as the orientational averaging simultaneously-through the use of reference structures in conjunction with finite element analysis. In particular, one possible physical realization of this approach is to employ polarized beams together with a magnetic reference connected to the sample object. We report on a first such practical implementation by successfully recovering the structure of a core-shell nanoparticle system.

Non-volatile iron carbonyls as versatile precursors for the synthesis of iron-containing nanoparticles.

The most commonly used method for the formation of well-defined iron and iron-containing heterometallic nanoparticles is the thermal decomposition of iron pentacarbonyl (Fe(CO)). However, iron pentacarbonyl is highly toxic and volatile, which introduces safety concerns and drastically diminishes control over the reaction stoichiometry. Here we alleviate these issues by beginning with an easy-to-handle solid, triiron dodecacarbonyl (Fe(CO)).

Magnetically Recoverable Pd/Fe O Core-Shell Nanowire Clusters with Increased Hydrogenation Activity.

Core-shell nanostructures are promising candidates for the next generation of catalysts due to synergistic effects which can arise from having two active species in close contact, leading to increased activity. Likewise, catalysts displaying added functionality, such as a magnetic response, can have increased scientific and industrial potential. Here, Pd/Fe O core-shell nanowire clusters are synthesized and applied as hydrogenation catalysts for an industrially important hydrogenation reaction: the conversion of acetophenone to 1-phenylethanol.

Sub-Millisecond Response Time in a Photorefractive Composite Operating under CW Conditions.

Extensive study of photorefractive polymeric composites photosensitized with semiconductor nanocrystals has yielded data indicating that the inclusion of such nanocrystals enhances the charge-carrier mobility, and subsequently leads to a reduction in the photorefractive response time. Unfortunately, the included nanocrystals may also act as a source of deep traps, resulting in diminished diffraction efficiencies as well as reduced two beam coupling gain coefficients. Nonetheless, previous studies indicate that this problem is mitigated through the inclusion of semiconductor nanocrystals possessing a relatively narrow band-gap.

Phase Behavior of Ternary Polymer Brushes.

Ternary polymer brushes consisting of polystyrene, poly(methyl methacrylate), and poly(4-vinylpyridine) have been synthesized. These brushes laterally phase separate into several distinct phases and can be tailored by altering the relative polymer composition. Self-consistent field theory has been used to predict the phase diagram and model both the horizontal and vertical phase behavior of the polymer brushes.

Magnetic relaxometry as applied to sensitive cancer detection and localization.

Background: Here we describe superparamagnetic relaxometry (SPMR), a technology that utilizes highly sensitive magnetic sensors and superparamagnetic nanoparticles for cancer detection. Using SPMR, we sensitively and specifically detect nanoparticles conjugated to biomarkers for various types of cancer. SPMR offers high contrast in vivo, as there is no superparamagnetic background, and bones and tissue are transparent to the magnetic fields.

Poly(N-isopropylacrylamide) surfactant-functionalized responsive silver nanoparticles and superlattices.

Metal nanoparticles exhibit unique optical characteristics in visible spectra produced by local surface plasmon resonance (SPR) for a wide range of optical and electronic applications. We report the synthesis of poly(N-isopropylacrylamide) surfactant (PNIPAM-C18)-functionalized metal nanoparticles and ordered superlattice arrays through an interfacial self-assembly process. The method is simple and reliable without using complex chemistry.

Nanoscale patterning of membrane-bound proteins formed through curvature-induced partitioning of phase-specific receptor lipids.

This work describes a technique for forming high-density arrays and patterns of membrane-bound proteins through binding to a curvature-organized compositional pattern of metal-chelating lipids (Cu(2+)-DOIDA or Cu(2+)-DSIDA). In this bottom-up approach, the underlying support is an e-beam formed, square lattice pattern of hemispheres. This curvature pattern sorts Cu(2+)-DOIDA to the 200 nm hemispherical lattice sites of a 600 nm × 600 nm unit cell in Ld - Lo phase separated lipid multibilayers.

Thermally programmable pH buffers.

Many reactions in both chemistry and biology rely on the ability to precisely control and fix the solution concentrations of either protons or hydroxide ions. In this report, we describe the behavior of thermally programmable pH buffer systems based on the copolymerization of varying amounts of acrylic acid (AA) groups into N-isopropylacrylamide polymers. Because the copolymers undergo phase transitions upon heating and cooling, the local environment around the AA groups can be reversibly switched between hydrophobic and hydrophilic states affecting the ionization behavior of the acids.

Development of antibody-tagged nanoparticles for detection of transplant rejection using biomagnetic sensors.

Organ transplantation is a life-saving procedure and the preferred method of treatment for a growing number of disease states. The advent of new immunosuppressants and improved care has led to great advances in both patient and graft survival. However, acute T-cell-mediated graft rejection occurs in a significant quantity of recipients and remains a life-threatening condition.

Iron Oxide Nanocrystals for Magnetic Hyperthermia Applications.

Magnetic nanocrystals have been investigated extensively in the past several years for several potential applications, such as information technology, MRI contrast agents, and for drug conjugation and delivery. A specific property of interest in biomedicine is magnetic hyperthermia-an increase in temperature resulting from the thermal energy released by magnetic nanocrystals in an external alternating magnetic field. Iron oxide nanocrystals of various sizes and morphologies were synthesized and tested for specific losses (heating power) using frequencies of 111.