Abstract
The magnetic behavior of Gd2O3 nanoparticles, produced by thermal decomposition method and subsequently annealed at different temperatures, was investigated by magnetization measurements and, at an atomic level, by perturbed γ − γ angular correlation (PAC) spectroscopy measuring hyperfine interactions at 111In(111Cd) probe nuclei. Nanoparticle structure, size and shape were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Magnetization measurements were carried out to characterize the paramagnetic behavior of the samples. XRD results show that all samples crystallize in the cubic-C form of the bixbyite structure with space group Ia3. TEM images showed that particles annealed at 873 K present particles with highly homogeneous sizes in the range from 5 nm to 10 nm and those annealed at 1273 K show particles with quite different sizes from 5 nm to 100 nm, with a wide size distribution. PAC and magnetization results show that samples annealed at 873 and 1273 K are paramagnetic. Magnetization measurements show no indication of blocking temperatures for all samples down to 2 K and the presence of antiferromagnetic correlations.
Highlights
Nanotechnology is nowadays a fast growing field of study with huge potential for medical applications such as tumor detection and treatment.[1,2,3,4,5] As a promising material for these applications, gadolinium nanoparticles (GdNP) currently have been of great interest mainly because their paramagnetic and atomic properties
Results for the X-ray diffraction showed the expected Gd2O3 cubic structure, which belongs to the Ia3 space group, with lattice parameters of a=b=c=10.80481(2) Å for sample 2 and a=b=c=10.80591(3) Å for sample 3, which are quite close to a=b=c=10.82311(20) Å previously reported.[14]
perturbed γ − γ angular correlation (PAC) measurements PAC spectra obtained at different temperatures for samples 2 and 3 along with a spectrum measured at room temperature for sample 1 are shown in Fig. 3, where the solid lines are the best fit of the theoretical functions to the experimental data
Summary
Nanotechnology is nowadays a fast growing field of study with huge potential for medical applications such as tumor detection and treatment.[1,2,3,4,5] As a promising material for these applications, gadolinium nanoparticles (GdNP) currently have been of great interest mainly because their paramagnetic and atomic properties. The high magnetic moment of Gd3+ ion, for instance, resulting in an intense magnetic interaction with external magnetic fields, enable GdNP to be used as magnetic resonance imaging (MRI) contrast agent.[6,7] Besides being developed for MRI contrast enhancement and multimodal imaging, GdNP have been considered as a potential material in tumor therapy by thermal neutrons irradiation.[8] it is important to have a good structural and magnetic characterization of this compound within an atomic scale. Besides magnetization measurements, perturbed-angular-correlation (PAC) spectroscopy was used to measure hyperfine interactions in Gd2O3 nanoparticle samples. This powerful method allows, within an atomic range, the study of magnetic and structural phase transitions, oxidation reactions, and the defect chemistry in oxides.[9] Gd2O3 nanoparticles were produced by thermal decomposition method with the incorporation, during preparation, of radioactive 111In(111Cd) probe nuclei for PAC measurements. Thermal decomposition is considered a good method to produce nanoparticles for medical applications resulting in homogenous nanostructures
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