Magnetic properties of novel superparamagnetic iron oxide nanoclusters and their peculiarity under annealing treatment
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The aim of this work is to present the magnetic properties of novel superparamagnetic-iNANOvative (TM)vertical bar silica nanoparticle clusters. A TEM analysis showed that these nanoparticle clusters, approximately 80 nm in size, contained an assembly of maghemite nanoparticles in the core and an amorphous silica shell. The maghemite nanoparticles in the core were approximately 10 nm in size, whereas the uniform silica shell was approximately 15-nm thick. The number of magnetic nanoparticles that were densely packed in the core of the single nanocluster was estimated to be approximately 67, resulting in a high magnetic moment for the single nanocluster of m(nc) similar to 1.2 x 10(6) mu(B). This magnetic property of the nanoparticle cluster is advantageous for its easy manipulation using an external magnetic field, for example, in biomedical applications, such as drug delivery, or for magnetic separation in biotechnology. The magnetic properties of the iNANOvative (TM)vertical bar sili...ca nanoparticle clusters were systematically studied, with a special focus on the influence of the magnetic interactions between the nanoparticles in the core. For comparison, the nanoparticle clusters were annealed for 3 h at 300 degrees C in air. The annealing had no influence on the nanoparticles size and phase; however, it had a unique effect on the magnetic properties, i.e., a decrease of the blocking temperature and a weakening of the inter-particle interactions. We believe that this surprising observation is related to the thermal decomposition of the organic surfactant on the surfaces of the nanoparticles at the high annealing temperatures, which resulted in the formation of amorphous carbon inside the nanocluster. (C) 2014 Elsevier B.V. All rights reserved.
Keywords:Maghemite / Surface effects / Superparamagnetism (SPION) / Self-assembly nanoparticles / AC susceptibility / Inter-particle interactions
Source:Applied Surface Science, 2014, 322, 255-264
- Magnetic and radionuclide labeled nanostructured materials for medical applications (RS-45015)
- Ministry of Higher Education, Science and Technology of the Republic of Slovenia within the National Research Program