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 78,556 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Organic-coated superparamagnetic iron oxide nanoparticles (OC-SPIONs) were synthesized and characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. OC-SPIONs were transferred from organic media into water using poly(amidoamine) dendrimers modified with 6-TAMRA fluorescent dye and folic acid molecules. The saturation magnetization of the resulting dendrimer-coated SPIONs (DC-SPIONs) was determined, using a superconducting quantum interference device, to be 60 emu/g Fe versus 90 emu/g Fe for bulk magnetite. Selective targeting of the DC-SPIONs to KB cancer cells in vitro was demonstrated and quantified using two distinct and complementary imaging modalities: UV-visible and X-ray fluorescence; confocal microscopy confirmed internalization. The results were consistent between the uptake distribution quantified by flow cytometry using 6-TAMRA UV-visible fluorescence intensity and the cellular iron content determined using X-ray fluorescence microscopy.
ACS Nano 2008 Apr
PMID:Synthesis, characterization, and in vitro testing of superparamagnetic iron oxide nanoparticles targeted using folic Acid-conjugated dendrimers. 1920 10

Using two-step (air/argon) thermal processing, sol-gel-derived nickel-iron oxide aerogels are transformed into monodisperse, networked nanocrystalline magnetic oxides of NiFe(2)O(4) with particle diameters that can be ripened with increasing temperature under argon to 4.6, 6.4, and 8.8 nm. Processing in air alone yields poorly crystalline materials; heating in argon alone leads to single phase, but diversiform, polydisperse NiFe(2)O(4), which hampers interpretation of the magnetic properties of the nanoarchitectures. The two-step method yields an improved model system to study magnetic effects as a function of size on the nanoscale while maintaining the particles within the size regime of single domain magnets, as networked building blocks, not agglomerates, and without stabilizing ligands capping the surface.
ACS Nano 2008 Apr
PMID:Nickel ferrite aerogels with monodisperse nanoscale building blocks--the importance of processing temperature and atmosphere. 1920 11

The pyrolysis of cylinder-forming samples of the diblock copolymer polystyrene-block-poly(ferrocenylethylmethylsilane) (PS-b-PFEMS) in bulk and in thin films has confirmed that these materials are useful for the generation of semi-ordered arrays of C/SiC ceramics containing Fe nanoparticles which are derived from the organometallic domains. In many cases, the ceramic mass yields were predictable and produced ceramics bearing a monomodal distribution of iron nanoparticles due to the nanoscaled structure of the preceramic PFEMS domains. The pyrolysis of thin films stabilized by cross-linking the PS domains with UV light demonstrated high areal yields, improved shape retention, and the presence of cylinder-centered magnetic nanoparticles.
ACS Nano 2008 Feb
PMID:Nanostructured magnetic thin films from organometallic block copolymers: pyrolysis of self-assembled polystyrene-block-poly(ferrocenylethylmethylsilane). 1920 26

Centrifugation is an increasingly important technique for nanomaterial processing. Here, we examine this process for gold, cadmium selenide, and iron oxide nanocrystals using an analytical ultracentrifuge. Such data provide an accurate measure of the sedimentation coefficients for these materials, and we find that this parameter has a significant dependence on the size and surface coating. Conventional models for particle sedimentation cannot capture the behavior of these nanocrystals unless the density of the nanocrystals is described by a size-dependent term that accounts for both the inorganic core and the organic coating. Using this modification in the particle sedimentation framework, it is possible to estimate sedimentation coefficients from information about the nanocrystal core and surface coating dimensions. Such data are useful in choosing the speeds for a centrifugation process and are particularly important when bimodal nanocrystal distributions are present.
ACS Nano 2008 Feb
PMID:Size-dependent sedimentation properties of nanocrystals. 1920 32

Knowledge of the optical properties and shape of nanoparticles is central to many technological applications including the fabrication of advanced materials and the characterization and formation of ordered films for optoelectronic devices. Measurement of such properties typically involves the independent use of advanced instrumentation such as electron and near field optical microscopy. We propose a simple experimental technique for extracting the optical and geometric properties of dilute suspensions of nanoparticles in situ. A theoretical formalism is developed to determine both the dichroic ratio and aspect ratio from a single measurement of the change in extinction of an incident light beam. The validity of this method is demonstrated for hematite nanorods, for which good agreement with independent measurements is found.
ACS Nano 2008 Feb
PMID:Measurement of the optical properties and shape of nanoparticles in solution using Couette flow. 1920 35

Magnetotactic bacteria produce exquisitely ordered chains of uniform magnetite (Fe(3)O(4)) nanocrystals, and the use of the bacterial mms6 protein allows for the shape-selective synthesis of Fe(3)O(4) nanocrystals. Cobalt ferrite (CoFe(2)O(4)) nanoparticles, on the other hand, are not known to occur in living organisms. Here we report on the use of the recombinant mms6 protein in a templated synthesis of CoFe(2)O(4) nanocrystals in vitro. We have covalently attached the full-length mms6 protein and a synthetic C-terminal domain of mms6 protein to self-assembling polymers in order to template hierarchical CoFe(2)O(4) nanostructures. This new synthesis pathway enables facile room-temperature shape-specific synthesis of complex magnetic crystalline nanomaterials with particle sizes in the range of 40-100 nm that are difficult to produce using conventional techniques.
ACS Nano 2007 Oct
PMID:Cobalt ferrite nanocrystals: out-performing magnetotactic bacteria. 1920 53

Nanostructured metal (Fe, Co, Mn, Cr, Mo) oxides were fabricated under microwave irradiation conditions in pure water without using any reducing or capping reagent. The metal oxides self-assembled into octahedra, spheres, triangular rods, pine, and hexagonal snowflake-like three-dimensional morphologies. Pine-structured nano-iron oxides were studied as a novel support for various catalytic organic transformations.
ACS Nano 2009 Mar 24
PMID:Self-assembly of metal oxides into three-dimensional nanostructures: synthesis and application in catalysis. 1920 27

Star-shaped mesotructures are formed when an aqueous suspension of Au nanorice particles, which consist of prolate hematite cores and a thin Au shell, is subjected to an electric current. The nanorice particles assemble to form hyperbranched micrometer-scale mesostars. To our knowledge, this is the first reported observation of nanoparticle assembly into larger ordered structures under the influence of an electrochemical process (H(2)O electrolysis). The assembly is accompanied by significant modifications in the morphology, dimensions, chemical composition, crystallographic structure, and optical properties of the constituent nanoparticles.
ACS Nano 2009 Feb 24
PMID:Au nanorice assemble electrolytically into mesostars. 1923 60

Nanoparticles composed of magnetic cores with continuous Au shell layers simultaneously possess both magnetic and plasmonic properties. Faceted and tetracubic nanocrystals consisting of wustite with magnetite-rich corners and edges retain magnetic properties when coated with a Au shell layer, with the composite nanostructures showing ferrimagnetic behavior. The plasmonic properties are profoundly influenced by the high dielectric constant of the mixed iron oxide nanocrystalline core. A comprehensive theoretical analysis that examines the geometric plasmon tunability over a range of core permittivities enables us to identify the dielectric properties of the mixed oxide magnetic core directly from the plasmonic behavior of the core-shell nanoparticle.
ACS Nano 2009 Jun 23
PMID:Magnetic-plasmonic core-shell nanoparticles. 1944 94

Tellurium (Te) nanorods have been successfully aligned on a solid substrate via a magnetization-alignment-demagnetization ("MAD") process in the presence of an external magnetic field. Te nanorods carrying a poly(tert-butyl methacrylate) shell were first converted into magnetic nanocylinders by assembling magnetite nanoparticles on their surface via a hydrophobic interaction in THF. We demonstrate that, below a critical concentration of the nanoparticles, this assembly process is able to quantitatively tune the magnetite nanoparticles' density on the nanorods in terms of their stoichiometric ratio. Due to the polymer and surfactant on their surface, the formed magnetic nanocylinders are soluble in THF and aligned when dried on a solid substrate in the presence of an external magnetic field. The demagnetization of the prealigned nanocylinders was achieved via an acid-etching process, leaving Te nanorods in an aligned state. This MAD process can be extended as a general procedure for other nonmagnetic 1-D nanostructures. Additionally, the nonetched magnetic nanocylinders can be potentially applied in field of magnetorheology.
ACS Nano 2009 Jun 23
PMID:Alignment of tellurium nanorods via a magnetization-alignment-demagnetization ("MAD") process assisted by an external magnetic field. 1948 33


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