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Nanostructures are considered as chemical systems of high potential owing to their unusual properties at the interface of those of molecular species and bulk metals. Consequently, they are promising candidates for application in different domains such as catalysis, magnetism, medicine, opto-electronics or sensors. The control of the characteristics of nanostructures is a fundamental prerequisite if one envisages exploring their physical or chemical properties since they vary dramatically with size, shape and surface state. Thus, the development of efficient methods leading to reproducible nanostructures is presently one of the main objectives in the nanochemistry community. Although organometallic chemistry has been early involved, it arises only marginally in the field. Nevertheless, the concepts and techniques of organometallic chemistry appear to be well-adapted for the growth of well-controlled nanostructures. This will be discussed through recent advances in the synthesis of metal and metal oxide nanoparticles in terms of size dispersion, chemical composition, surface state, shape or organization, pointing out the role of ligands. Moreover their characterization at a molecular level and the development of their chemical/physical properties towards applications will be described. This review reflects more than 20 years of efforts of our team to achieve these goals. [ABSTRACT FROM AUTHOR]

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]

A wide range of nano-objects is found in many applications of our everyday life. Recognition of their peculiar properties and ease of functionalization has prompted their engineering into multifunctional platforms that are supposed to afford efficient tools for the development of biomedical applications. However, bridging the gap between bench to bedside cannot be expected without a good knowledge of their behaviour in vivo, which can be obtained through non-invasive imaging techniques, such as positron emission tomography (PET). Their radiolabelling with [18F]-fluorine, a technique already well established and widely used routinely for PET imaging, with [18F]-FDG for example, and in preclinical investigation using [18F]-radiolabelled biological macromolecules, has, therefore, been developed. In this context, this review highlights the various nano-objects studied so far, the reasons behind their radiolabelling, and main in vitro and/or in vivo results obtained thereof. Then, the methods developed to introduce the radioelement are presented. Detailed indications on the chemical steps involved are provided, and the stability of the radiolabelling is discussed. Emphasis is then made on the techniques used to purify and analyse the radiolabelled nano-objects, a point that is rarely discussed despite its technical relevance and importance for accurate imaging. The pros and cons of the different methods developed are finally discussed from which future work can develop. [ABSTRACT FROM AUTHOR]

Presents a selective synthesis, characterization, and spectroscopic studies on a novel class of reduced platinum and palladium particles stabilized by carbonyl and phosphine ligands. Analysis on the stabilization of metal particles by simple classical ligands; Reactivity of colloidal solutions; Synthesis of novel platinum and palladium particles.

Production of hydrogen from a renewable source that is water requires the development of sustainable catalytic processes. This implies, among others, developing efficient catalytic materials from abundant and low-cost resources and investigating their performance, especially in the oxidation of water as this half-reaction is the bottleneck of the water splitting process. For this purpose, NiFe-based nanoparticles with sizes ca. 3–4 nm have been synthesized by an organometallic approach and characterized by complementary techniques (WAXS, TEM, STEM-HAADF, EDX, XPS, and ATR-FTIR). They display a Ni core and a mixed Ni–Fe oxide shell. Once deposited onto FTO electrodes, they have been assessed in the electrocatalytic oxygen evolution reaction under alkaline conditions. Three different Ni/Fe ratios (2/1, 1/1 and 1/9) have been studied in comparison with their monometallic counterparts. The Ni2Fe1 nanocatalyst displayed the lowest overpotential (320 mV at j = 10 mA cm−2) as well as excellent stability over 16 h. [ABSTRACT FROM AUTHOR]

Thecontrol of the metallic nanocrystal shape is of prime importancefor a wide variety of applications. We report a detailed researchwork on metal–organic chemical routes for the synthesis ofa highly symmetrical crystal structure. In particular, this studyshows the key parameters ensuring the anisotropic growth of nickelnanostructures (fcc crystal). Numerous reaction conditions are investigated(precursors, solvents, temperature, reducing agents, reaction time,and types and ratios of surfactants, such as alkyl amines, carboxylicacids, and phosphine oxides), and their effects on the size and shapeof the final product are reported. The role of the growth modifiersand the structuring of the reaction media on the anisotropic growthare demonstrated. This metal–organic approach generates severalnovel anisotropic nanostructures in a wide size range depending onthe reaction conditions. In this way, nanomaterials with reproduciblesize, shape, and composition are obtained with good yield. Transmissionelectron microscopy techniques (TEM and HRTEM) are the principal methodsfor monitoring the morphology. [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]

Phosphonic acid derivatives are suitable compounds for controlling the surface properties of materials and nanomaterials. Here, we present for the first time the use of alkyl phosphonic acid ligands to transfer into water zero-valent iron nanoparticles (FeNP) synthesized by an organometallic approach. The transfer takes place with the formation of an oxide layer at the surface of the iron nanoparticles, beneficial for the coordination of the alkyl phosphonic acid ligands. The nanoparticles are highly soluble in water and present a core–shell structure, with a monocrystalline body-centered cubic iron core of ca. 10 nm in size surrounded by a spinel oxide shell of ca. 2 nm thickness. These hydrophilic nanoparticles display excellent structural stability, magnetization still reaching 70% of that of bulk iron, and a transversal relaxivity r2 of 335 mM−1 s−1 which give them high potential for biomedical applications. [ABSTRACT FROM AUTHOR]

Enhancement of the thermoelectric properties of bismuth due to size reduction has prompted a large body of studies and recent interest in the nanochemistry of this material. The size control at the nanometer scale is complicated because of bismuth's low melting point and little known surface chemistry. We report herein an efficient synthetic method producing bismuth nanoparticles (Bi NPs) of sizes below 10 nm, and of rhombohedral structure based on transmission electron microscopy (TEM) and wide angle X-ray scattering (WAXS) analysis. The nature and dynamics of the ligands at their surface have been investigated by infrared spectroscopy (IR) and nuclear magnetic resonance (NMR) spectroscopy. We demonstrate that alkynyl ligands, seldom used in nanochemistry, efficiently coordinate at the surface and afford stable Bi NPs that can be easily purified, leading to powders with high bismuth payload which can be redispersed into stable colloidal solutions. [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]

A correction is presented to the article "Shape Control of Thermodynamically Stable Cobalt Nanorods Through Organometallic Chemistry" by F. Dumestre and colleagues, published in volume 31, 2002.

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]

Abstract: We have developed a versatile catalyst-assisted chemical vapor deposition (CVD) technique for the synthesis of single-walled carbon nanotubes (SWNTs) from discrete nickel nanoparticles (average diameter of 4.7±1.5 nm). Atomic force microscopy (AFM), transmission electron microscopy (TEM) and electron diffraction are used to characterize these as-grown nanotubes. On a particular sample we found that the SWNTs have an average chiral angle of 25.3°. This result shows that a control of the chiral angle of SWNT with large diameters (mean diameter=1.75 nm) and with a relatively broad diameter distribution (standard deviation=0.5 nm) is achievable to a certain extent. [Copyright &y& Elsevier]

Abstract: We have developed a versatile catalyst-assisted chemical vapor deposition (CVD) technique for the synthesis of single-walled carbon nanotubes (SWNTs) from discrete nickel nanoparticles (average diameter of 4.7±1.4 nm). Atomic force microscopy (AFM), transmission electron microscopy (TEM) and micro-Raman spectroscopy are used to characterize these as-grown nanotubes. Using a conventional set-up, we are able to produce isolated SWNTs with a narrow diameter distribution (1.5±0.5 nm). The advantages of such a versatile CVD method for the study of physical properties at the single nanotube level are illustrated by means of two prospective studies on vibrational and electrostatic properties of SWNTs. [Copyright &y& Elsevier]

The growing concern over the toxicity of Gd-based contrast agents used in magnetic resonance imaging (MRI) motivates the search for less toxic and more effective alternatives. Among these alternatives, iron–iron oxide (Fe@FeOx) core-shell architectures have been long recognized as promising MRI contrast agents while limited information on their engineering is available. Here we report the synthesis of 10 nm large Fe@FeOx nanoparticles, their coating with a 11 nm thick layer of dense silica and functionalization by 5 kDa PEG chains to improve their biocompatibility. The nanomaterials obtained have been characterized by a set of complementary techniques such as infra-red and nuclear magnetic resonance spectroscopies, transmission electron microscopy, dynamic light scattering and zetametry, and magnetometry. They display hydrodynamic diameters in the 100 nm range, zetapotential values around −30 mV, and magnetization values higher than the reference contrast agent RESOVIST®. They display no cytotoxicity against 1BR3G and HCT116 cell lines and no hemolytic activity against human red blood cells. Their nuclear magnetic relaxation dispersion (NMRD) profiles are typical for nanomaterials of this size and magnetization. They display high r2 relaxivity values and low r1 leading to enhanced r2/r1 ratios in comparison with RESOVIST®. All these data make them promising contrast agents to detect early stage tumors. [ABSTRACT FROM AUTHOR]