Properties and suspension stability of dendronized iron oxide nanoparticles for MRI applications

Functionalized iron oxide nanoparticles have attracted an increasing interest in the last 10 years as contrast agents for MRI. One challenge is to obtain homogeneous and stable aqueous suspensions of iron oxide nanoparticles without aggregates. Iron oxide nanoparticles with sizes around 10 nm were synthesized by two methods: the particle size distribution in water suspension of iron oxide nanoparticles synthesized by the co-precipitation method was improved by a process involving two steps of ligand exchange and phase transfer and was compared with that of iron oxide nanoparticles synthesized by thermal decomposition and functionalized by the same dendritic molecule. The saturation magnetization of dendronized nanoparticles synthesized by thermal decomposition was lower than that of nanoparticles synthesized by co-precipitation. The r(2) relaxivity values were shown to decrease with the agglomeration state in suspension and high r(2) values and r(2)/r(1) ratios were obtained with nanoparticles synthesized by co-precipitation by comparison with those of commercial products. Dendronized iron oxide nanoparticles thus have potential properties as contrast agent. Copyright (C) 2010 John Wiley & Sons, Ltd

Oxidation and Reduction Reactions in Spinel Oxides : Influence upon some Physical Properties

In the first part of the paper, a complete model for oxidation and reduction reactions occurring at low temperatures in finely divided spinel oxides such as Mn-Zn, Mo, and V ferrites is presented. When the Fe-based spinel oxides contain more than one oxidizable cation (for instance Fe2+, Mo3+ and Mo4+ in Mo ferrites), it has been demonstrated that each cation oxidizes in a well defined range in temperature in close relation with the cation-oxygen distance of the cation considered. The model involves both thermodynamics and kinetics considerations : thermodynamics involves the minimization of the Gibbs free energy and the kinetics oxidation has been explained on the basis of a diffusion-induced stress effect. Finite element calculations have been developped and applied to compute the features of the reaction in the case of V, Mn-Zn and Mo ferrites. In these materials, the model enables the evolution with time of oxidation to be explained. In the second part of the paper, the influence of the oxidation and reduction reactions occurring during all the stages of sintering upon both physical and mechanical properties is evidenced

Modeling of the DTG curves for oxidation of a nanosized molybdenum ferrite coupling mechanics and diffusion

International audienc

Electron exchanges in nanometric molybdenum ferrites

International audienc

Ultrasmall gadolinium based nanoparticles for multimodal imaging

International audienceMedical diagnostic become more and more reliable by the combination of data issued from multiple assays. Each imaging technique display advantages and disadvantages (sensitivity, resolution…). In this context, new fused instruments have been developed that combine two imaging modalities (PET/MRI, PET/CT…). To accompany the development of these instruments, many multimodal contrast agents have been developed by the scientists, in particular in the field of nanotechnology. Our team has recently developed a new family (AGuIX) of ultrasmall nanoparticles (size < 5 nm) made of a polysiloxane network and surrounded by gadolinium chelates that can be used for multimodal imaging1 and therapy guided by imaging

Ultrasmall gadolinium based nanoparticles for multimodal imaging

International audienceMedical diagnostic become more and more reliable by the combination of data issued from multiple assays. Each imaging technique display advantages and disadvantages (sensitivity, resolution…). In this context, new fused instruments have been developed that combine two imaging modalities (PET/MRI, PET/CT…). To accompany the development of these instruments, many multimodal contrast agents have been developed by the scientists, in particular in the field of nanotechnology. Our team has recently developed a new family (AGuIX) of ultrasmall nanoparticles (size < 5 nm) made of a polysiloxane network and surrounded by gadolinium chelates that can be used for multimodal imaging1 and therapy guided by imaging

Robust universal biotracers based on hybrid GDS (Gold "Dye" Silica) nanosondes

International audienc

Gold nano-antennas for increasing luminescence

Energy transfer between nanoscale particles is demonstrated for a Gold/rare-earth oxide nanocomposite. The gold nanoparticle acts as an antenna, absorbing light that can then be transferred to the bound rare-earth oxide (see Figure), enhancing the oxide luminescence by a factor of 40. This could provide a route to enhanced fluorescence labels for biological systems based on optimized absorber and emitter nanocomposite tags