NMR Transversal Relaxivity of Suspensions of Lanthanide Oxide Nanoparticles
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- 作者：Ma
//pubs.acs.org/images/entities/lstrok.gif" border="0">gorzata Norek ; Giovannia A. Pereira ; Carlos F. G. C. Geraldes ; Antonia Denkova ; Wuzong Zhou ; Joop A. Peters
- 刊名：Journal of Physical Chemistry C
- 出版年：2007
- 出版时间：July 19, 2007
- 年：2007
- 卷：111
- 期：28
- 页码：10240 - 10246
- 全文大小：163K
- 年卷期：v.111,no.28(July 19, 2007)
- ISSN：1932-7455
文摘
Aqueous suspensions of paramagnetic lanthanide oxide nanoparticles have been studied by NMR relaxometry.The observed 
e10001.gif"> relaxivities are explained by the static dephasing regime (SDR) theory. The correspondingR2 relaxivities are considerably smaller and are strongly dependent on the interval between the two refocusingpulses. The experimental data are rationalized by assuming the value of the diffusion correlation time, 
D, tobe very long in a layer with adsorbed xanthan on the particle's surface. In this layer, the refocusing pulsesare fully effective and R2 
0. Outside this layer, the diffusion model for weakly magnetized particles wasapplied. From the fit of the experimental relaxation data with this model, both the particle radii (rp) and theradii of the spheres, within which the refocusing pulses are fully effective (rdiff), were estimated. The valuesof rp obtained are in agreement with those determined by dynamic light scattering. Because the value of rdiffdepends on the external magnetic field B and on the magnetic moment of the lanthanide of interest (
eff2), theR2 relaxivity was found to be proportional to B and to eff2.
D, tobe very long in a layer with adsorbed xanthan on the particle's surface. In this layer, the refocusing pulsesare fully effective and R2 0. Outside this layer, the diffusion model for weakly magnetized particles wasapplied. From the fit of the experimental relaxation data with this model, both the particle radii (rp) and theradii of the spheres, within which the refocusing pulses are fully effective (rdiff), were estimated. The valuesof rp obtained are in agreement with those determined by dynamic light scattering. Because the value of rdiffdepends on the external magnetic field B and on the magnetic moment of the lanthanide of interest (eff2), theR2 relaxivity was found to be proportional to B and to eff2.