In:
European Journal of Inorganic Chemistry, Wiley, Vol. 2021, No. 34 ( 2021-09-14), p. 3458-3465
Abstract:
The NMR relaxivities of the decatungstolanthanoate core‐shell nanoparticles, prepared by encapsulating [Ln(W 5 O 18 ) 2 ] 9− polyoxometalates (LnPOM) within amorphous silica shells (K 9 [Ln(W 5 O 18 ) 2 ]@SiO 2 ), were studied along the Ln series. The relaxivity of GdPOM is slightly higher than for Gd‐DTPA due to second‐sphere relaxation effects, but the values for the other paramagnetic LnPOMs are much smaller due to the short T 1e values of their Ln 3+ ‐ions. The NPs have core‐shell spherical structures, with LnPOM‐containing cores with 9.5–28 nm diameters, and 4.0–11.0 nm thick amorphous silica shells. In water suspensions, the NPs have negative zeta potentials (−32.5 to −40.0 mV) and time‐dependent hydrodynamic diameters (31–195 nm) reflecting the formation of aggregates. The relaxivities of GdPOM@SiO 2 NPs suspensions ( r 1 =10.97 (mM Gd) −1 s −1 , r 2 =12.02 (mM Gd) −1 s −1 , 0.47 T, 25 °C) are considerably larger than for the GdPOM solutions, indicating that their silica shell is significantly porous to water. This increase is limited by the agglomeration of the complexes in the NPs core, limiting their access to water to those at the core surface. Replacing half of the Gd 3+ ions by Eu 3+ decreases the NPs r 1 and r 2 relaxivities at 0.47 T to 20 % and 35 % of their initial values, which are still considerable, but does not affect the efficient luminescence properties of the Eu 3+ centers. This indicates that the mixed NPs have potential as dual modality MRI/optical imaging contrast agents.
Type of Medium:
Online Resource
ISSN:
1434-1948
,
1099-0682
DOI:
10.1002/ejic.v2021.34
DOI:
10.1002/ejic.202100445
Language:
English
Publisher:
Wiley
Publication Date:
2021
detail.hit.zdb_id:
1475009-0
