authors |
Pereira, GA; Ananias, D; Rocha, J; Amaral, VS; Muller, RN; Elst, LV; Toth, E; Peters, JA; Geraldes, CFGC |
nationality |
International |
journal |
JOURNAL OF MATERIALS CHEMISTRY |
keywords |
MRI CONTRAST AGENTS; RELAXATION; PARTICLES; EXCHANGE; COMPLEX; DTPA |
abstract |
A series of zeolite-type silicates containing framework lanthanides and termed Ln-AV-9 have been synthesized. Fundamentally different from conventional zeolites, these materials have the (Na4K2)(Ln(2)Si(16)O(38))center dot 10H(2)O (Ln = Nd, Sm, Eu, Tb, Gd, Dy). Si-29 and Na-23 MAS NMR spectra of Sm-AV-9 indicate the presence of six and two distinct sites, respectively, in agreement with the crystal structure. Gd-AV-9 exhibits a simple Curie paramagnetic behaviour with an effective magnetic moment of 7.97 mu(B), while Eu-AV-9 has a much lower magnetic susceptibility, with a very shallow temperature dependence. The H-1 longitudinal relaxivities of water (r(1)), obtained for aqueous suspensions of several Ln-AV-9 materials with different Ln(3+) ions, are very small (0.04 - 0.09 s(-1) mM(-1)) and almost independent of the Ln(3+) ion, while their transverse relaxivities (r(2)) are much larger (16 - 60 s(-1) mM(-1)) and proportional to mu(4)eff, where mu(eff) is the magnetic moment of the lanthanide ion present. While r(1) of Gd-AV-9 suspensions is very small, the r(2) is substantial and proportional to B-0(2). The dependence of r(2) on mu(eff)(4) and B-0(2) has been fitted using the model of outer-sphere diffusion of water around the particles in the long-echo limit. The results indicate that aqueous suspensions of Ln-AV-9, although inefficient in longitudinal relaxation, are very effective in enhancing transverse relaxation, particularly at high magnetic fields. They are, therefore, attractive as T-2 MRI contrast agents. |
publisher |
ROYAL SOC CHEMISTRY |
issn |
0959-9428 |
year published |
2005 |
volume |
15 |
issue |
35-36 |
beginning page |
3832 |
ending page |
3837 |
digital object identifier (doi) |
10.1039/b504082e |
web of science category |
Chemistry, Physical; Materials Science, Multidisciplinary |
subject category |
Chemistry; Materials Science |
unique article identifier |
WOS:000231563800020
|
ciceco authors
impact metrics
dimensions (citation analysis):
|
|
altmetrics (social interaction):
|
|
|