Abstract
Fine Fe2O3 and Gd2O3 magnetic nanoparticles (NPs) with sizes 7 nm and 10 nm embedded into mesoporous silica have been prepared using a wet-impregnation method. A comparative study of the reactant concentration along with the hosting matrix symmetry on mesostructuring and the magnetic properties of the nanocomposites have been investigated. Reactants with four different concentrations of Fe3+ and Gd3+ ions and silica matrices with two different kinds of symmetry (hexagonal and cubic) have been utilized for the study. The structural characterization of the samples has been carried out by the N2 adsorption/desorption method, high-energy X-ray diffraction (HE-XRD), TG/DTA, and high resolution transmission electron microscopy (HRTEM). The magnetic properties of the nanocomposites have been examined by means of SQUID magnetometry. It has been found that a range of different magnetic states (diamagnetic, paramagnetic, ferromagnetic, superparamagnetic) can be induced by the feasible tailoring of the particle concentration, the porous matrix symmetry and the composition. Furthermore, the existence of a “critical concentration limit” for embedding the particles within the body of the matrix has been confirmed. Exceeding the limit results in the expulsion of nanoparticles on the outer surface of the mesoporous matrix. Revelation of the relationships between particle concentration, matrix symmetry and magnetic properties of the particular composite reported in this study may facilitate the design and construction of advanced intelligent nanodevices.
Highlights
Novel magnetic composite materials based on mesoporous silica have found applications in the elds of catalysis, adsorption, chromatography, chemical sensors and biomedicine.[1,2,3,4,5,6] in biomedicine, nanocomposites consisting of mesoporous silica loaded with magnetic NPs and speci c drugs appear very promising for diagnostic and therapeutic applications.[7,8,9,10] The employment of magnetic resonance imaging, hyperthermia treatment or hi-tec stimuli-responsive targeted drug delivery has improved dramatically with the introduction of these kinds of systems
The combination of two different metal ions (Gd3+ or Fe3+), a pair of matrices with 2Dhexagonal or 3D-cubic symmetry and four different nanoparticle concentrations resulted in the preparation of the series of 16 nanocomposite samples
At rst, we studied thermal decomposition of four mesoporous samples SBA-15 and SBA-16 impregnated by Fe(NO3)3$9H2O and Gd(NO3)3$6H2O, Fig. 8(a)
Summary
Novel magnetic composite materials based on mesoporous silica have found applications in the elds of catalysis, adsorption, chromatography, chemical sensors and biomedicine.[1,2,3,4,5,6] in biomedicine, nanocomposites consisting of mesoporous silica loaded with magnetic NPs and speci c drugs appear very promising for diagnostic and therapeutic applications.[7,8,9,10] The employment of magnetic resonance imaging, hyperthermia treatment or hi-tec stimuli-responsive targeted drug delivery has improved dramatically with the introduction of these kinds of systems. One of the most valuable bene ts of these materials is their versatility. It stems from their speci c inner structure and design. J. Safarik University in Kosice, Moyzesova 11, 04054 Kosice, Slovakia bDepartment of Condensed Matter Physics, Faculty of Sciences, P. J. Safarik University in Kosice, Park Angelinum 9, 04054 Kosice, Slovakia. E-mail: adriana.zelenakova@ upjs.sk cDESY-Hasylab, Notkestrasse 85, Hamburg, Germany dFrank Laboratory of Neutron Physics, JINR, Dubna, Russia process. This enables the further introduction of other structures (e.g. nanoparticles, drug molecules) of the desired size into the matrix body. Durability, high thermal stability and low toxicity are the qualities that amorphous silica preserves over a broad range of conditions
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