[show abstract][hide abstract] ABSTRACT: Two samples of ultra small Gd(III) doped iron oxide nanoparticles were prepared to investigate Gd(III) doping effect on longitudinal (r1) and transverse (r2) water proton relaxivities. Gd(III) doping mole percents were 0.2 and 0.4 for samples 1 and 2, respectively. Average particle diameters were 2.5 to 2.1 nm for samples 1 and 2, respectively. Reduced r1 and r2 values were observed in both samples. We attributed this to reduced magnetizations arising from opposing effect of Gd(III) to net magnetizations of Fe(III)/Fe(II) in oxide nanoparticles.
[show abstract][hide abstract] ABSTRACT: A facile one-pot synthesis of a water-soluble MnO nanocolloid (i.e., D-glucuronic acid-coated MnO nanoparticle) is presented. The MnO nanoparticle in the MnO nanocolloid was coated with a biocompatible and hydrophilic D-glucuronic acid, and its particle diameter was nearly monodisperse and ranged from 2 to 3 nm. The average hydrodynamic diameter of the MnO nanocolloid was estimated to be 5 nm. The MnO nanoparticle was nearly paramagnetic down to T=3 K. The MnO nanocolloid showed a high longitudinal water proton relaxivity of r1=7.02 s(-1) mM(-1) with the r2/r1 ratio of 6.83 due to five unpaired S-state electrons of Mn(II) ion (S=5/2) as well as a high surface to volume ratio of the MnO nanoparticle. High contrast in vivo T1 MR images were obtained for various organs, showing the capability of the MnO nanocolloid as a sensitive T1 MRI contrast agent. The suggested three key-parameters which control the r1 and r2 relaxivities of nanocolloids (i.e., the S value of a metal ion, the spin structure, and the surface to volume ratio of a nanoparticle) successfully accounted for the observed r1 and r2 relaxivities of the MnO nanocolloid.
[show abstract][hide abstract] ABSTRACT: Magnetite nanoparticles were synthesized at a wide range of NaCl solutions (c=0.01–3.0M). The particle diameter (d) was reduced from 7.7 to 6.8nm and the colloidal stability dropped with increasing c. The salt effect on the d was successfully elucidated with an aid of a homogeneous nucleation model. The saturation magnetization (Ms) reduction and the lattice contraction (Δa) from −0.015 to −0.038Å with increasing c were observed due to the decrease of the d. From the Δa, the surface tension (γ) enhancement from 0.192 to 0.614N/m with increasing c was estimated.
Colloids and Surfaces A-physicochemical and Engineering Aspects - COLLOID SURFACE A. 01/2010; 367(1):41-46.
[show abstract][hide abstract] ABSTRACT: Paramagnetic ultrasmall gadolinium oxide (Gd(2)O(3)) nanoparticles with particle diameters (d) of approximately 1 nm were synthesized by using three kinds of Gd(III) ion precursors and by refluxing each of them in tripropylene glycol under an O(2) flow. A large longitudinal relaxivity (r(1)) of water proton of 9.9 s(-1) mM(-1) was estimated. As a result, high contrast in vivo T(1) MR images of the brain tumor of a rat were observed. This large r(1) is discussed in terms of the huge surface to volume ratio (S/V) of the ultrasmall gadolinium oxide nanoparticles coupled with the cooperative induction of surface Gd(III) ions for the longitudinal relaxation of a water proton. It is found from the d dependence of r(1) that the optimal range of d for the maximal r(1), which may be used as an advanced T(1) MRI contrast agent, is 1-2.5 nm.
[show abstract][hide abstract] ABSTRACT: We investigated the surface charge effect of surface coating ligands on the colloidal stability of magnetite nanoparticles in a physiological saline solution. We employed the l-lysine and the l-glutamic acid as the surface coating ligands. We investigated the colloidal stability of the l-lysine and the l-glutamic acid coated magnetite nanoparticles by measuring their precipitation times, hydrodynamic diameter distributions, and zeta potentials in a physiological saline solution. From these three measurements, we found that the l-lysine coated magnetite nanoparticles are more stable as colloids than the l-glutamic acid coated magnetite nanoparticles. Based on the bonding structures of the l-lysine and the l-glutamic acid to magnetite nanoparticles, we successfully discussed the colloidal stability in terms of the surface charge effect of the amino acids.
Materials Letters - MATER LETT. 01/2009; 63(3):379-381.