Biomedical subjects

Philip M Rice

Publications and source records attributed to Philip M Rice.

6 recordsLinked to original sources

PubMed2005

Dumbbell-like bifunctional Au-Fe3O4 nanoparticles.

Dumbbell-like Au-Fe(3)O(4) nanoparticles are synthesized using decomposition of Fe(CO)(5) on the surface of the Au nanoparticles followed by oxidation in 1-octadecene solvent. The size of the particles is tuned from 2 to 8 nm for Au and 4 nm to 20 nm for Fe(3)O(4). The particles show the characteristic surface plasmon absorption of Au and the magnetic properties of Fe(3)O(4) that are affected by the interactions between Au and Fe(3)O(4). The dumbbell is formed through epitaxial growth of iron oxide on the Au seeds, and the growth can be affected by the polarity of the solvent, as the use of diphenyl ether results in flower-like Au-Fe(3)O(4) nanoparticles.

Adsorption↗

PubMed2005

Oriented mesoporous organosilicate thin films.

Coassemblies of block copolymers and inorganic precursors offer a path to ordered inorganic nanostructures. In thin films, these materials combined with domain alignment provide highly robust nanoscopic templates. We report a simple path to control the morphology, scaling, and orientation of ordered mesopores in organosilicate thin films through the coassembly of a diblock copolymer, poly(styrene-b-ethylene oxide) (PS-b-PEO), and an oligomeric organosilicate precursor that is selectively miscible with PEO. Continuous films containing cylindrical or spherical pores are generated by varying the mixing composition of symmetric PS-b-PEO and an organosilicate precursor. Tuning interfacial energy at both air/film and film/substrate interfaces allows the control of cylindrical pore orientation normal to the supported film surfaces. Our method provides well-ordered mesoporous structures within organosilicate thin films that find broad applications as highly stable nanotemplates.

Journal Article↗

PubMed2004

Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers.

Magnetically engineered magnetic tunnel junctions (MTJs) show promise as non-volatile storage cells in high-performance solid-state magnetic random access memories (MRAM). The performance of these devices is currently limited by the modest (< approximately 70%) room-temperature tunnelling magnetoresistance (TMR) of technologically relevant MTJs. Much higher TMR values have been theoretically predicted for perfectly ordered (100) oriented single-crystalline Fe/MgO/Fe MTJs. Here we show that sputter-deposited polycrystalline MTJs grown on an amorphous underlayer, but with highly oriented (100) MgO tunnel barriers and CoFe electrodes, exhibit TMR values of up to approximately 220% at room temperature and approximately 300% at low temperatures. Consistent with these high TMR values, superconducting tunnelling spectroscopy experiments indicate that the tunnelling current has a very high spin polarization of approximately 85%, which rivals that previously observed only using half-metallic ferromagnets. Such high values of spin polarization and TMR in readily manufactureable and highly thermally stable devices (up to 400 degrees C) will accelerate the development of new families of spintronic devices.

Computers↗

PubMed2004

Shape-controlled synthesis and shape-induced texture of MnFe2O4 nanoparticles.

Monodisperse MnFe2O4 nanoparticles with cubelike and polyhedron shapes were synthesized by reaction of Fe(acac)3 and Mn(acac)2 with 1,2-hexadecanediol, oleic acid, and oleylamine. Controlled evaporation of the particle dispersion led to nanoparticle superlattices. The crystal orientation of the particle in the assembly depends on the shape of the particles, with particles in a cubelike shape showing (100) texture and those in the polyhedron shape exhibiting (110) texture.

Journal Article↗

PubMed2004

Monodisperse MFe2O4 (M = Fe, Co, Mn) nanoparticles.

High-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)(3), with 1,2-hexadecanediol in the presence of oleic acid and oleylamine leads to monodisperse magnetite (Fe(3)O(4)) nanoparticles. Similarly, reaction of Fe(acac)(3) and Co(acac)(2) or Mn(acac)(2) with the same diol results in monodisperse CoFe(2)O(4) or MnFe(2)O(4) nanoparticles. Particle diameter can be tuned from 3 to 20 nm by varying reaction conditions or by seed-mediated growth. The as-synthesized iron oxide nanoparticles have a cubic spinel structure as characterized by HRTEM, SAED, and XRD. Further, Fe(3)O(4) can be oxidized to Fe(2)O(3), as evidenced by XRD, NEXAFS spectroscopy, and SQUID magnetometry. The hydrophobic nanoparticles can be transformed into hydrophilic ones by adding bipolar surfactants, and aqueous nanoparticle dispersion is readily made. These iron oxide nanoparticles and their dispersions in various media have great potential in magnetic nanodevice and biomagnetic applications.

Journal Article↗

PubMed2003

Versatile synthesis of nanometer sized hollow silica spherest.

Using the controlled precipitation of silicic acid on functionalized polystyrene latexes, nanometer sized silica-coated spheres could be prepared and subsequently modified to allow dispersion in non-aqueous solvents; removal of the interior polymer by calcination resulted in the formation of hollow silica spheres.

Journal Article↗