This paper demonstrates that, by using oil-in-water micelles, nonstoichiometric zinc ferrite nanoparticles are fabricated. Control in size and composition is obtained. The nanocrystals are characterized by a spinel structure with two sublattices in tetrahedral and octahedral sites. Repartition of Fe 3+ in the two sublattices is disordered. The particles are ferrimagnetic with a noncollinear structure (the magnetic moments are not strictly parallel). This is more pronounced with the smallest particles. Zinc ferrite nanocrystals exhibit unusual magnetic properties. The anisotropy constant, K, of nanocrystals differing by their sizes is determined by Mo ¨ssbauer spectroscopy and from zero field cooled (ZFC) curves. The field cooled (FC) curves show a peculiar behavior with a decrease in the magnetization at very low temperature. The ZFC curves are highly sensitive to the applied field, indicating that Langevin law cannot be applied for zinc ferrite nanocrystals. These unusual magnetic properties are attributed to the inclusion of nonmagnetic zinc ions in ferrite nanocrystals, which induces a magnetic disorder.

Zinc nitrate precipitated with NaOH solution at room temperature under double-jet conditions produced micrometric zinc oxide particles with ellipsoid or starlike morphology separated by only a slight variation of pH (9.5 and 10.5, respectively). The formation kinetics of starlike particles was followed by SEM observations, suggesting that they result from a solid-state transformation of the hydroxide matrix. This mechanism involved the nucleation of 30-nm ZnO particles inside the matrix, followed by their aggregation into starlike particles. The introduction of sodium sulfate or sodium dodecyl sulfate in the bath before precipitation led to a drastic size reduction and to a diversity of particle shapes (from half-ellipsoids to full ellipsoids). The presence of these additives provided important hints on particle formation and confirmed that submicronic particles resulted from nanocrystals oriented aggregation.

Syntheses of diluted magnetic semiconductor Cd1- y Mn y S nanoparticles varying in size from 1.9 to 3.5 nm and composition, y, from 0 to 0.3 have been performed in reverse micelles. Size and composition, y, of the particles are controlled independently. The particles are characterized by TEM, EDS, and EPR. Manganese ions are substituted randomly in the CdS matrix. Optical absorption studies show, at fixed composition, a quantum size effect. At fixed size a nonlinear variation of the band gap versus composition is observed. This effect already observed in the bulk phase is more pronounced with quantum dots.

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Cerium oxides (CeO) nanoparticles, also referred to as nanoceria, are extensively used with a wide range of applications. However, their impact on human health and on the environment is not fully elucidated. The aim of this study was to investigate the influence of the CeO nanoparticles morphology on their in vitro toxicity. CeO nanoparticles of similar chemical composition and crystallinity were synthesized, only the shape varied (rods or octahedrons/cubes). Macrophages from the RAW264.7 cell line were exposed to these different samples and the toxicity was evaluated in terms of lactate dehydrogenase (LDH) release, Tumor Necrosis Factor alpha (TNF-α) production and reactive oxygen species (ROS) generation. Results showed no ROS production, whatever the nanoparticle shape. The LDH release and the TNF-α production were significantly and dose-dependently enhanced by rod-like nanoparticles, whereas they did not vary with cubic/octahedral nanoparticles. In conclusion, a strong impact of CeO nanoparticle morphology on their in vitro toxicity was clearly demonstrated, underscoring that nanoceria shape should be carefully taken in consideration, especially in a "safer by design" context.

This article is the first step in the development of a hybrid metrology combining AFM and SEM techniques for measuring the dimensions of a nanoparticle population in 3D space (X,Y,Z). This method exploits the strengths of each technique on the same set of nanoparticles. AFM is used for measuring the nanoparticle height and the measurements along X and Y axes are deduced from SEM images. A sampling method is proposed in order to obtain the best deposition conditions of SiO2 and gold nanoparticles on mica or silicon substrates. Only the isolated nanoparticles are taken into account in the histogram of size distribution. Moreover, a semi-automatic Matlab routine has also been developed to process the AFM and SEM images, measure and count the nanoparticles. This routine allows the user to exclusively select the isolated nanoparticles through a control interface. The measurements have been performed on spherical-like nanoparticles to test the method by comparing the results obtained with both techniques.

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Solid solutions of nonstoichiometric mixed cobalt–zinc ferrite nanoparticles Co0.73yZn0.73(1−y)Fe2.18□0.09O4, were prepared in order to study their magnetic properties as a function of cobalt content y. The saturation magnetization changes with increasing y due to the various occupancies of cations in tetrahedral and octahedral sites and/or to an increase in the disorder of the ferrimagnetic structure. The cobalt content and particle size effects on the coercive field were studied. The increase in the ratio between remanent and saturation magnetizations indicates that, with increasing y, a transition takes place from uniaxial to cubic anisotropy. Field cooled (FC) curves drastically change with the cobalt content. At zero cobalt, this curve is characterized by a well-defined peak that disappears progressively with increasing y. This is attributed to the particles themselves and neither to their interactions nor to experimental procedures. The fit of the zero FC (ZFC) curve indicates an unrealistically high simulated saturation magnetization, consistent with a drastic field-dependent behavior of the ZFC-FC curves.