A.B. Salunkhe

Surface functionalized LSMO nanoparticles with improved colloidal stability for hyperthermia applications

LSMO (La0.7Sr0.3MnO3) magnetic nanoparticles (MNPs) coated with double layer oleic acid (OA) surfactant are prepared to make a water based magnetic nanofluid for hyperthermia application. Various experimental techniques are used for bilayer coating analysis. The effect of the bilayer coating on magnetic properties is studied by superconducting quantum interface device (SQUID). Colloidal behaviour of coated MNPs in aqueous medium is studied by the zeta potential and dynamic light scattering. The effects of pH and ionic strength on the colloidal stability of the MNPs are studied in detail. For the bilayer-coated LSMO MNPs aggregation is not observed even in high ionic strength and at physiological pH (7.4). For making the nanofluid of the bilayer-coated MNPs the colloidal stability is studied in physiological media like phosphate buffer solution. Under induction heating experiment, hyperthermia temperature (42–43 °C) could be achieved by the bilayer-coated sample at a magnetic field of 168–335 Oe and frequency of 267 kHz. The bilayer OA coating can hinder the agglomeration of MNPs significantly and produce stable suspension with improved hyperthermia properties. The bilayer OA coating also improves the specific absorption rate (SAR) of LSMO MNPs from 25 to 40 W g−1.

Low-temperature synthesis of MnxMg1?xFe2O4(x?=?0?1) nanoparticles: cation distribution, structural and magnetic properties

Nanoferrites having composition MnxMg1−xFe2O4(x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) are synthesized by a low-temperature combustion method. The particle size measured from transmission electron microscopy and x-ray diffraction (XRD) patterns confirms the nanosized dimension of the as-prepared powder. From the analysis of XRD data with Scherrers formula, the average crystallite size ranges from 23 to 33 nm and the lattice parameter ranges from 8.385 to 8.468 A. Substitution of Mn2+ in MgFe2O4 causes an increase in the lattice constant, and this moderately distorts the lattice. Magnetic properties such as magnetization (Ms), coercivity (Hc) and remanence (Mr) with increasing Mn2+ concentration are studied at room temperature by a vibrating sample magnetometer. Substitution of Mn2+ for Mg2+ increases Ms from 34.5 to 54.5 emu g−1 and decreases Hc from 51.0 to 45.0 Oe. The results imply that the low-temperature combustion method is an efficient route for synthesis of nanoferrites without any extra calcination step. The as-prepared Mg–Mn ferrites are suitable for memory and switching circuits in digital computers.

Synthesis and magnetostructural studies of amine functionalized superparamagnetic iron oxide nanoparticles

Superparamagnetic iron oxide nanoparticles are synthesized through co precipitation method by using the new generation base diisopropylamine (DIPA) which electrostatically complexes with iron ions, reduces them and subsequently caps the nanoparticle. Coating of DIPA on the surface of the nanoparticles was confirmed through FTIR and TG-DTA. We investigate the effect of reaction time as well concentration of DIPA on the particle size and magnetic properties of Fe3O4 nanoparticles. Effect of concentration of DIPA on particle size reveals that the nanocrystallite size of Fe3O4 nanoparticles increases to its maximum (the increase is nominally 5.2 nm to 8.5 nm) and then reduces (3.2 nm). Particle size and magnetic properties of the synthesized nanoparticles are also influenced by reaction time; in general as the reaction time increases the particle size increases. The lattice parameter of iron oxide nanoparticles varies from ∼8.32 to ∼8.39 A with reaction time. From magnetic measurements, superparamagnetism of the Fe3O4 nanoparticles was confirmed. The results clearly suggest that the magneto-structural properties of Fe3O4 (or any ferrite) can be easily tuned by using DIPA.