RESUMO
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.
Assuntos
Compostos Férricos , Imageamento por Ressonância Magnética/métodos , Nanopartículas/química , Meios de Contraste/síntese química , Dendrímeros , Magnetismo , Tamanho da Partícula , SuspensõesRESUMO
The thermochromic phase transition of CuMo(1-x)W(x)O(4) oxide was delayed by the deposit of SiO(2) shells. The phase transition temperature was investigated by optical reflectivity versus temperature. The effect of the shell thickness on the transition temperature is established. The cyclability of the phenomenon is also discussed.
