Evolution of structural and magnetic properties in iron oxide nanoparticles synthesized using Azadirachta indica leaf extract

The novel superparamagnetic nature of magnetic nanoparticles (MNPs) has received significant attention in the wide variety of fields. However, the prerequisites to use these MNPs, particularly in biomedical applications are biocompatibility and high saturation magnetization (Ms). Thus, the development of a sustainable approach for the synthesis of biocompatible MNPs, which utilizes the redox properties of natural compounds from plant extracts, is highly desired. Herein, we have examined the growth of phase selective MNPs synthesized using Azadirachta indica (Neem) extract as a reducing and capping agent. The physical and biological properties of MNPs synthesized with the modified green hydrothermal method at different reaction times and temperatures were investigated. It was observed that the reaction time and temperature strongly modulated the magnetic and structural characteristics of MNPs. At lower reaction time and temperature of 200 °C for 2 h, primarily iron oxalate hydrate (Fe(C2O4).2(H2O)) was formed. Further, with increasing reaction temperature, the phase transformation from iron oxalate hydrate to pure magnetite (Fe3O4) phase was observed. The MNPs prepared with optimum conditions of 220 °C for 4 h show superparamagnetic nature with improved Ms value of 58 emu g−1. The antibacterial study of MNPs against gram-positive bacteria Staphylococcus aureus showed that the MNPs inhibits the growth of bacteria with the least inhibitory MNPs concentration of 6 μl. Thus, the MNPs obtained by this modified biogenic approach will widen the scope and their applicability in future biomedical applications.

Monolayer grafting of aminosilane on magnetic nanoparticles: An efficient approach for targeted drug delivery system

Magnetic nanoparticles (MNPs) with higher magnetization are highly desirable for targeted drug delivery (TDD) systems, as it helps accumulation of drug at the target site. However, functionalization of MNPs for drug binding reduces the magnetization which affects the efficacy of TDD. Herein we report direct functionalization of MNPs with (3-Aminopropyl)triethoxysilane (APTES) which preserves the magnetization. Grafting density estimated by TGA and BET analysis showed monolayer grafting of APTES on MNP surface. MNPs were comprehensively characterized by XRD, HR-TEM, SQUID-VSM and FTIR. Anti-cancerous drug telmisartan (TEL) was loaded on monolayer APTES grafted MNPs. In-vitro controlled drug release and cytotoxicity study on PC-3 human prostate cancer cell line of TEL conjugated MNPs are also discussed. This functionalization strategy can be extended to other biomedical applications where higher magnetization is desired.

Pulse laser deposited nanocrystalline cobalt ferrite thin films

Cobalt ferrite thin films were pulsed laser deposited on fused quartz substrates at different substrate temperatures and ex-situ annealed at 750 degrees C in air. Grain size of these films was found to be 6-44 nm. Magnetization of these nanocrystalline thin films was found to be dependent on the substrate temperature. Magnetization higher than the cobalt ferrite bulk value was observed in the room temperature deposited film after post deposition annealing at 750 degrees C. This could be explained on the basis of a changed cation distribution in the film caused by quenching during deposition.

RF sputter deposited nanocrystalline (110) magnetite thin film from alpha-Fe2O3 target

Nanocrystalline magnetite thin film was prepared on to fused quartz substrate by sputtering at an rf power of 50 W. X-ray diffraction study showed that the sputtered film was (110) oriented. The stoichiometry in the thin film has been confirmed through a variety of characterization techniques. The room temperature spontaneous magnetization value (4piMs) of the film was 5100 G. This is about 85% of the bulk value. The resistivity of the film showed a sharp change around 120 K, indicative of the Verwey transition.