resumo
Iron oxide nanoparticles with a constant superparamagnetic core coated with a silica shell with a thickness ranging from 0.6 to 71 nm were prepared by a fast and facile soft chemistry approach. The increase of the coating thickness of the gamma-Fe2O3@SiO2 nanoparticles causes a significant decrease of the r(1) and r(2) relaxivities of their aqueous suspensions. The sizes of the nanoparticles obtained by relaxometry are significantly lower than those measured by electron microscopy. Their magnetizations measured by relaxometry also decrease relative to the values obtained by magnetometry, which correspond to the core. However, this "magnetic dilution" is smaller than expected if the entire silica shell was water impermeable. Both results indicate that a significant part of the silica coating is permeable to water. The adequate silica shell thickness may, thus, be tuned to allow for both a sufficiently high response as contrast agent and an adequate grafting of targeted biomolecules.
palavras-chave
IRON-OXIDE NANOPARTICLES; SEMICONDUCTOR QUANTUM DOTS; MAGNETIC NANOPARTICLES; BIOMEDICAL APPLICATIONS; SILICA SPHERES; NANOCRYSTALS; RELAXATION; MRI; PARTICLES; AGENTS
categoria
Chemistry; Science & Technology - Other Topics; Materials Science
autores
Pinho, SLC; Laurent, S; Rocha, J; Roch, A; Delville, MH; Mornet, S; Carlos, LD; Vander Elst, L; Muller, RN; Geraldes, CFGC
nossos autores
João Rocha
Prof. Catedrático
Luís Carlos
Professor CatedráticoProjectos
Nanostructured Photoluminescent rare-earth nanotubes and microporous silicates (PTDC/CTM/73243/2006)
Functionalised Advanced Materials and Engineering of Hybrids and Ceramics - FAME (FAME)
agradecimentos
This work was supported by the Fundacao para a Ciencia e Tecnologia (FCT), Portugal (grants to S.L.C.P. (SFRH/BD/38313/2007), and project PTDC/CTM/73243/2006), the CNRS, the Region Aquitaine France, FEDER, COST Action D38