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Fe0.8Rh0.2 nanoparticles with an average size of 1.8 nm have been synthesized by simultaneous decomposition of stoichiometric quantities of Fe[N(Si(CH3)3)2]2 and Rh(C3H5)3 in mild conditions of temperature and hydrogen pressure, using hexadecylamine as stabilizer. These nanoparticles display a magnetization of 1.13 μB per iron atom, which is more than two times smaller than the bulk value with the same composition. No surface contamination with iron oxides was detected by Mössbauer spectroscopy. Superconducting quantum interference device and Mössbauer spectroscopy investigations reveal that the origin of this variation may be a core-shell Rh/Fe chemical arrangement. [ABSTRACT FROM AUTHOR]

Self-organization of nanoparticles into two- and three-dimensional superlattices on a large scale is required for their implementation into nano- or microelectronic devices. This is achieved, generally after a size-selection process, through spontaneous self-organization on a surface, layer-by-layer deposition or the three-layer technique of oversaturation, but these techniques consider superlattices of limited size. An alternative method developed in our group involves the direct formation in solution of crystalline superlattices, for example of tin nanospheres, iron nanocubes or cobalt nanorods, but these are also of limited size. Here, we report the first direct preparation in solution of multimillimetre-sized three-dimensional compact superlattices of nanoparticles. The 15-nm monodisperse FeCo particles adopt an unusual short-range atomic order that transforms into body-centred-cubic on annealing at 500 ∘C. The latter process produces an air-stable material with magnetic properties suitable for radiofrequency applications. [ABSTRACT FROM AUTHOR]

Abstract: Nanoparticles (NPs), average size of 2–5 nm, of ruthenium, cobalt, and rhodium have been prepared by an original method, namely the solid-state decomposition under dihydrogen of an organometallic precursor either dispersed in polymer films or directly as nanocrystals. The NPs dispersion, size, and morphology are investigated by transmission electron microscopy, and their structure by wide angle X-ray scattering. Infrared spectroscopy, after adsorption of carbon monoxide on the metal NPs surfaces, evidences a nonoxidized surface of high reactivity. [Copyright &y& Elsevier]

New pyridine containing triAza; 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-triacetic acid (PCTA) ligands presenting pendant carboxylic acid or alcohol functions have been synthesized and used to form diaqua Gd(III) complexes, which have been immobilized onto dense silica nanoparticles. Cytotoxicity studies of these complexes (free or immobilized on the nanoparticles) on normal 1BR3G cells and cancerous HCT 116 cells indicated a dependence on the pendant chemical group for the free complexes. However, this effect disappeared once the complexes were immobilized on the surface of the nanoparticles, leading to non-toxic nanomaterials. The interest of these complexes (free or immobilized on dense silica nanoparticles) as contrast agents in magnetic resonance imaging (MRI) has been evaluated in comparison with DOTAREM® by recording their nuclear magnetic resonance dispersion (NMRD) profiles, measuring their transversal and longitudinal relaxivities as well as recording images on phantoms at 37 °C. This study has evidenced the high potential of these complexes: first it suggested the possibility to reduce the dose to be injected by a factor of 10, second it evidenced their high efficiency in high field T1-weighted MRI (9.4 T), the key towards images of higher resolution and shorter acquisition times. [ABSTRACT FROM AUTHOR]

The reaction of the metal-organic precursor Fe[N(SiMe[sub3])[sub2]][sub2] with H[sub2] in the presence of a long-chain acid and a Long-chain amine in various proportions produces monodisperse zerovalent iron nanoparticles. These Fe particles display magnetic properties that match those of bulk iron as evidenced by magnetic and Mössbauer measurements. The nanoparticles adopt a cubic shape with edges of 7 nanometers and are incorporated into extended crystalline superlattices containing nanocubes in close proximity and with their crystallographic axes aligned. These superlattices are formed in solution, precipitate in high yield, and may be redissolved and redeposited as two-dimensional arrays. [ABSTRACT FROM AUTHOR]

Magnetic nanoparticles can be efficient contrast agents for T2 weighted magnetic resonance imaging (MRI) after tuning of some key parameters such as size, surface state, colloidal stability and magnetization, thus motivating the development of new synthetic pathways. In this paper we report the effects of surface coating on the efficiency of two different types of iron based nanoparticles (NPs) as MRI contrast agents. Starting from well-defined hydrophobic iron oxide nanospheres and iron nanocubes of 13 nm size, we have used three methods to increase their hydrophilicity and transfer them into water: surface ligand modification, ligand exchange or encapsulation. The NPs obtained have been characterized by dynamic light scattering and transmission electron microscopy, and the relaxivities of their stable colloidal solutions in water have been determined. Among all samples prepared, iron nanocubes coated by silica display the highest relaxivity ( r 2 ) value: 628 s −1 mM −1 . [ABSTRACT FROM AUTHOR]

Cobalt nanoparticles with differentsizes and morphologies includingspheres, rods, disks, and hexagonal prisms have been synthesized throughthe decomposition of the olefinic precursor [Co(η3-C8H13)(η4-C8H12)] under dihydrogen, in the presence of hexadecylamine anddifferent rhodamine derivatives, or aromatic carboxylic acids. UV–visspectroscopy, X-ray diffraction, low and high resolution transmissionelectron microscopy, and electron tomography have been used to characterizethe nanomaterials. Especially, the Co nanodisks formed present characteristicsthat make them ideal nanocrystals for applications such as magneticdata storage. Focusing on their growth process, we have evidencedthat a reaction between hexadecylamine and rhodamine B occurs duringthe formation of these Co nanodisks. This reaction limits the amountof free acid and amine, usually at the origin of the formation ofsingle crystal Co rods and wires, in the growth medium of the nanocrystals.As a consequence, a growth mechanism based on the structure of thepreformed seeds rather than oriented attachment or template assistedgrowth is postulated to explain the formation of the nanodisks. [ABSTRACT FROM AUTHOR]

The effectiveness of amine-borane as reducing agent for the synthesis of iron nanoparticles has been investigated. Large (2-4 nm) Fe nanoparticles were obtained from [Fe{N(SiMe3)2}2]. Inclusion of boron in the nanoparticles is clearly evidenced by extended X-ray absorption fine structure spectroscopy and Mössbauer spectrometry. Furthermore, the reactivity of amine-borane and amino-borane complexes in the presence of pure Fe nanoparticles has been investigated. Dihydrogen evolution was observed in both cases, which suggests the potential of Fe nanoparticles to promote the release of dihydrogen from amine-borane and amino-borane moieties. [ABSTRACT FROM AUTHOR]