Current magnetic-nanoparticle technology is challenging due to the limited magnetic properties of iron oxide nanoparticles (IONPs). Increasing the saturation magnetization of magnetic nanoparticles may permit more effective development of multifunctional agents for simultaneous targeted cell delivery, magnetic resonance imaging (MRI) contrast enhancement, and targeted cancer therapy in the form of local hyperthermia. We describe the synthesis and characterization of novel iron-based nanoparticles (FeNPs) coated with biocompatible biscarboxyl-terminated poly(ethylene glycol) (cPEG). In comparison to conventional IONPs similar in size (10 nm), FeNPs particles have a much greater magnetization and coercivity based on hysteresis loops from sample magnetometry. Increased magnetization afforded by the FeNPs permits more effective generation of local hyperthermia than IONPs when subjected to an oscillating magnetic field in a safe frequency range. Furthermore, FeNPs have a much stronger shortening effect on T 2 relaxation time than IONPs, suggesting that FeNPs may be more effective MRI contrast agents. Next-generation FeNPs with a biocompatible coating may

We have designed a potential drug delivery system by combining low-molecular-weight heparin to iron oxide magnetic nanoparticles with an average size of 20 nm. The particles were synthesized by the NaBH4 reduction of FeCl2 and then coated with poly-L-lysine. Heparin was noncovalently conjugated on these nanoparticles via the interactions between the negatively charged sulfate and carboxylate groups of heparin and the positively charged amine group of poly-L-lysine. The nanoparticles were examined by using transmission electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, and zeta potential measurements. The data provide direct evidence that the heparin was immobilized at the surface of poly-L-lysine-coated iron oxide nanoparticles. Magnetic measurements revealed the particles are ferromagnetic with a saturation magnetization of 31 emu/g.

This comprehensive study examines the effect of particle size and atomic ordering on the intrinsic and hysteresis properties of FePt nanoparticles embedded in a carbon matrix formed by annealing sputtered FePt/C multilayer precursors. Structural studies show a transformation from the magnetically soft to the tetragonal FePt phase dependent on the annealing conditions. The magnetic properties scale as a function of particle size. The coercivity depends, in part, on the vol % of carbon and develops with annealing as a result of increased atomic ordering. Under the right conditions a high coercivity of 34 kOe has been achieved. Remanence curves show a variation of interparticles interactions from exchange to magnetostatic with increasing vol % carbon. Time dependent measurements indicate a decrease of the activation volume converging to the actual particle size ͑determined by TEM͒ as the carbon content is increased. The potential for future magnetic recording media is discussed.

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We have used a reductive technique known to produce highly reactive metals to fabricate nickel and nickel-based nanostructured materials. The strong dependence of the magnetic, chemical, electrical, and optical properties of nanostructured materials are intimately correlated with material structure; thus, thorough knowledge of the effect of synthesis parameters on the structure is critical for the refinement of fabrication techniques. X-ray diffraction and electron microscopy are used to determine the effect of the synthetic conditions and subsequent processing on the material structure. Characteristic lengths of these materials range from 3 to 50 nm, depending on synthesis and annealing conditions. Annealing produces a metastable Ni 3 C phase that forms only in the presence of active carbon, suggesting that not only active nickel but also active carbon results from this process. The addition of P(Ph) 3 affects the time and temperature dependence of the nickel crystallite growth, the temperature at which Ni 3 C crystallites are first observed and the maximum temperature to which Ni 3 C can be retained.