High resolution neutron Larmor diffraction using superconducting magnetic Wollaston prisms.

The neutron Larmor diffraction technique has been implemented using superconducting magnetic Wollaston prisms in both single-arm and double-arm configurations. Successful measurements of the coefficient of thermal expansion of a single-crystal copper sample demonstrates that the method works as expected. The experiment involves a new method of tuning by varying the magnetic field configurations in the device and the tuning results agree well with previous measurements. The difference between single-arm and double-arm configurations has been investigated experimentally. We conclude that this measurement benchmarks the applications of magnetic Wollaston prisms in Larmor diffraction and shows in principle that the setup can be used for inelastic phonon line-width measurements. The achievable resolution for Larmor diffraction is comparable to that using Neutron Resonance Spin Echo (NRSE) coils. The use of superconducting materials in the prisms allows high neutron polarization and transmission efficiency to be achieved.

Magnetic virus-like nanoparticles in N. benthamiana plants: a new paradigm for environmental and agronomic biotechnological research.

This article demonstrates the encapsulation of cubic iron oxide nanoparticles (NPs) by Brome mosaic virus capsid shells and the formation, for the first time, of virus-based nanoparticles (VNPs) with cubic cores. Cubic iron oxide NPs functionalized with phospholipids containing poly(ethylene glycol) tails and terminal carboxyl groups exhibited exceptional relaxivity in magnetic resonance imaging experiments, which opens the way for in vivo MRI studies of systemic virus movement in plants. Preliminary data on cell-to-cell and long-distance transit behavior of cubic iron oxide NPs and VNPs in Nicotiana benthamiana leaves indicate that VNPs have specific transit properties, i.e., penetration into tissue and long-distance transfer through the vasculature in N. benthamiana plants, even at low temperature (6 °C), while NPs devoid of virus protein coats exhibit limited transport by comparison. These particles potentially open new opportunities for high-contrast functional imaging in plants and for the delivery of therapeutic antimicrobial cores into plants.

Magnetic nanoparticles with functional silanes: evolution of well-defined shells from anhydride containing silane.

Modification of iron oxide nanoparticles (NPs) synthesized by high temperature solvothermal routes is carried out using two silanes: (i) N-(6-aminohexyl)-aminopropyltrimethoxysilane (AHAPS) where only one end of the molecule reacts with the surface Fe-OH groups and (ii) 3-(triethoxysilyl)propylsuccinic anhydride (SSA) where both ends are reactive with Fe-OH. Depending on the NP synthesis protocol, the amount of surface OH groups on the NPs may differ, however, for all the cases presented here, the comparatively low OH group density prevents a high density of AHAPS coverage, yielding NP aggregates instead of single particles in aqueous solutions. Alternatively, use of SSA containing two terminal functionalities, anhydride and siloxy, which are both reactive towards the NP surface, results in the formation of discrete dense polymeric shells, providing stability of individual NPs in water. The mechanism of the SSA shell formation is discussed. The evolution of the chemical transformations leads to shells of different thickness and density, yet this evolution can be halted by hydrolysis, after which the NPs are water soluble, negatively charged and exhibit excellent stability in aqueous media.

Mixed Co/Fe oxide nanoparticles in block copolymer micelles.

Small iron oxide and Co-doped iron oxide nanoparticles (NPs) were synthesized in a commercial amphiphilic block copolymer, poly(ethylene oxide)-b-poly(methacrylic acid) (PEO 68-b-PMAA8), in aqueous solutions. The structure and composition of the micelles containing guest molecules (metal salts) or NPs (metal oxides) were studied using transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, and X-ray powder diffraction. The enlarged micelle cores after incorporation of metal salts are believed to be formed by both PMAA blocks containing metal species and penetrating PEO chains. The nanoparticle size distributions in PEO 68-b-PMAA8 were determined using small-angle X-ray scattering (SAXS) in bulk. Two independent methods for SAXS data interpretation for comprehensive analysis of volume distributions of metal oxide NPs showed presence of both small particles and larger entities containing metal species which are ascribed to organization of block copolymer micelles in bulk. The magnetometry measurements revealed that the NPs are superparamagnetic and their characteristics depend on the method of the NP synthesis. The important advantage of the PEO 68-b-PMAA8 stabilized magnetic nanoparticles described in this paper is their remarkable solubility and stability in water and buffers.

Hydrophilic Monodisperse Magnetic Nanoparticles Protected by an Amphiphilic Alternating Copolymer.

Iron oxide nanoparticles (NPs) with diameters of 16.1, 20.5, and 20.8 nm prepared from iron oleate precursors were coated with poly(maleic acid-alt-1-octadecene) (PMAcOD). The coating procedure exploited hydrophobic interactions of octadecene and oleic acid tails while hydrolysis of maleic anhydride moieties allowed the NP hydrophilicity. The PMAcOD nanostructure in water and the PMAcOD-coated NPs were studied using transmission electron microscopy, zeta-potential measurements, small-angle X-ray scattering, and fluorescence measurements. The combination of several techniques suggests that independently of the iron oxide core and oleic acid shell structures, PMAcOD encapsulates NPs, forming stable hydrophilic shells which withstand absorption of hydrophobic molecules, such as pyrene, without shell disintegration. Moreover, the PMAcOD molecules are predominantly attached to a single NP instead of self-assembling into the PMAcOD disklike nanostructures or attachment to several NPs. This leads to highly monodisperse aqueous samples with only a small fraction of NPs forming large aggregates due to cross-linking by the copolymer macromolecules.

Syntheses, Structures, and Thermal Behavior of Cu(hfacac) Complexes Derived from Ethanolamines.

A series of novel precursors for MOCVD of metallic copper have been synthesized and structurally characterized. These precursors are composed of Cu(hfacac)(2), which serves as a volatile source of Cu, and amino alcohols, which act as reductants and anchor firmly to the copper center through the amine unit. In some cases, a proton transfer from the coordinated alcohol to the hfacac ligand results in the formation of an alkoxide unit and the release of the free Hhfacac. Metallic copper films can be deposited by MOCVD at 300 degrees C without any external reductant. Crystal data: Cu(hfacac)(2).C(7)H(8) (-103 degrees C), a = 6.510(6) Å, b = 8.594(7) Å, c = 18.478(15) Å, orthorhombic space group Pmnn, Z = 2; Cu(hfacac)(2)(H(2)NCH(2)CH(2)OH) (-158 degrees C), a = 13.145(1) Å, b = 13.418(1) Å, c = 11.245(1) Å, alpha = 110.39(1) degrees, beta = 99.12(1) degrees, gamma = 97.90(1) degrees, triclinic space group P&onemacr;, Z = 4; [Cu(hfacac)(Me(2)NCH(2)CH(2)O)](2) (-153 degrees C), a = 9.259(2) Å, b = 12.011(3) Å, c = 6.304(1) Å, alpha = 91.19(1) degrees, beta = 106.66(1) degrees, gamma = 74.83(1) degrees, triclinic space group P&onemacr;, Z = 1; Cu(hfacac)[N(CH(2)CH(2)OH)(2)(CH(2)CH(2)O)].MeOH (-168 degrees C), a = 10.075(4) Å, b = 8.611(4) Å, c = 19.259(9) Å, beta = 99.82(2) degrees, monoclinic space group P2(1)/m, Z = 4.